2nd Ed. Chapter 7 Ecology

American water lotus beds of Old Woman Creek estuary in 1888 (artist: Charles Courtney Curran).
CHAPTER 1. INTRODUCTION
CHAPTER 7. ECOLOGY
ESTUARY VEGETATION: MACROPHYTES the problem of obtaining adequate oxygen is
exacerbated by the low solubility of oxygen in water
ADAPTATIONS FOR AQUATIC LIFE (generally <10 mg/l) and a much slower rate of oxygen
The dominant plants in the estuary are diffusion in water. Because water-saturated soils of
hydrophytes—plants adapted to life in the water or in coastal wetlands are generally anaerobic, hydrophytes
water-saturated soil. The larger (macroscopic) water have developed anatomical and morphological
plants are collectively known as macrophytes and adaptations to compensate for soil oxygen deficiency,
encompass the vascular plants (those with well- such as: (1) transport systems which supply oxygen to
developed conducting tissue such as aquatic mosses, underground organs from aerial structures, (2)
liverworts, ferns, and flowering plants) as well as metabolic mechanisms which function under anoxic
macroalgae. The evolution of vascular plants from conditions and in the presence of toxic metabolic
simple marine forms involved increasing adaptations products, and (3) detoxifying mechanisms. Aquatic
to terrestrial environments. Thus, hydrophytic vascular plants also differ from upland species in that they must
plants show a reversal in this trend by their absorb nitrogen as ammonium cations (NH4+) because
development of specific adaptations to cope with re- denitrifying micro-organisms (present in anaerobic
invasion of aquatic environments (Arber 1920). Within soils) scavenge nitrate anion (NO3-), the usual source
the estuary exists a spectrum of plants ranging from of this nutrient (Etherington 1983).
those which are normally terrestrial, but which are able
Some vascular aquatic plants have so completely
to endure occasional submergence, to those which are
adapted themselves to a watery environment that they
wholly adapted to an aquatic environment, having lost
have dispensed with roots except in germinating
their capacity for a terrestrial existence.
seedlings. With the exception of Ceratophyllum
Aquatic macrophytes, especially submerged (coontail) and Wolffia (water-meal), all the vascular
forms, have adapted to reduced solar radiation as a plants of the estuary produce some roots. In Lemna
consequence of the light-attenuating and filtering and Spirodela (duckweeds), roots are short and slender
effects of water. Because water loss does not present a organs used to position and stabilize the plant in the
problem as it does with land plants, a dense cuticle is water. Rooted aquatic plants such as Myriophyllum
not required to prevent desiccation except for exposed (water milfoil) and Potamogeton (pondweeds)
surfaces of emergent or floating leaves. Aquatic plants primarily utilize their roots both as an anchoring system
are unusually porous, their tissues containing large and for nutrient uptake (Wetzel 2001).
intercellular spaces that are commonly arranged to
Owing to their hollow center and reduced
form chambers (aerenchyma tissue). This arrangement
vascular bundles, the stems of most monocot
enhances gas exchange and provides leaf buoyancy.
submerged and emergent plants are well adapted to
Most hydrophytes obtain oxygen and carbon dioxide
water movements—numerous, often large, cavities
by direct diffusion between leaf tissues and the water.
supply an abundance of oxygen to all parts of the plant.
The large air channels then provide internal gas
A central canal is present in Potamogeton (pondweeds)
exchange pathways for stem and root tissues which
and in some dicots, as Ceratophyllum (coontail), which
are typically buried in anoxic muds. This mode of gas
functions as the xylem vessel in land plants. For added
exchange is necessary in aquatic plants because unlike
support, the stem is strengthened by thickening of the
terrestrial soil, water-saturated soils and estuarine
cellulose tissue (collenchyma) at the angles of the cell
sediments are generally devoid of gaseous oxygen.
walls.
In addition to dim light and scarce oxygen,
aquatic macrophytes must cope with vertical and
horizontal motion of the water, an absence of
transpiration, and inadequate nutrient-absorbing
capacity of roots (Pieters 1901). For submerged plants
7-1
ECOLOGY OF OLD WOMAN CREEK ESTUARY AND WATERSHED
REPRODUCTION IN AQUATIC PLANTS Most aquatic plants produce fewer seeds than
land plants and in some, seed production is seldom if
Pollen produced by terrestrial plants is transferred
ever seen. Active vegetative propagation and the
from one flower to another by agents such as wind
perennial character of water plants have tended to
and insects. Pollination takes place in the same way
reduce the importance of seed production. Pieters
for aquatic plants having aerial flowers; for those that
(1901) reported that studies of the seeds of aquatic and
live beneath the surface, reproduction presents special
wetland plants show that most seeds are heavier than
problems. Thus, many aquatic plants rely mainly on
water and do not float unless they are adhering in
vegetative reproduction. Others emerge to flower and
masses or have a surface not easily wetted. Some float,
subsequently drop their seeds into the water, revealing
but only for a few days. Seeds of aquatic plants are not
their terrestrial evolutionary ancestry by achieving
well adapted to being spread by animal agents. Thus,
fertilization only in an air medium. Few aquatic plants
most aquatic seed distribution is thought to be local.
are capable of fertilization underwater because most
pollen is not resistant to water; Ceratophyllum
demersum (coontail) is one of the rare plants fertilized ZONATION OF ESTUARY PLANT COMMUNITIES
underwater. Stamens are released at maturity from As with many protected embayments, the cove-
submerged flowers and rise to the surface where pollen like margins of Old Woman Creek Estuary show a great
is discharged and hopefully sinks onto a pistillate regularity in the distribution of aquatic plants. Such
flower (Voss 1985). More commonly however, zonation was first described for European lakes a
reproduction in Ceratophyllum is by simple century ago (Magnin 1893, Arber 1920). Passing into
fragmentation of the rather brittle stem. the estuary from the shore, the following order is
generally observed. First, there is a littoral zone of
Certain submerged plants, such as Potamogeton
plants standing out of the water—Phragmites followed
nodosus (knotty pondweed), produce some floating
by Scirpus or Sagittaria and Sparganium; next, a belt
leaves which serve as a platform for the support of
of submersed plants consisting of Potamogeton and
flowering spikes. In other cases where there are no
Ceratophyllum; and still farther from shore, a zone of
floating leaves and the plant remains totally submerged,
plants with floating leaves, among which Nelumbo
special structures have evolved to bring the flower to
lutea is the dominant species (Whyte 1996).
the surface. Elodea canadensis (common water-weed)
has developed a long, thread-like flower stem (up to Arber (1920) points out that one of the chief
15 cm long), arising from the axil of a leaf, which bears factors determining this zonation is that plants with
a small pink female flower. Rare male flowers are floating leaves can only flourish if guarded from the
produced underwater, the buds of which float to the wind. For this reason they generally do not occur at
surface to liberate pollen which blows along the water great distances from the shore, except in very sheltered
to pollinate the female flowers. This sexual method of basins such as the estuary of Old Woman Creek or
reproduction in Elodea is uncommon—usually this among protective stands of emergent reeds (Pieters
plant reproduces vegetatively by a portion of its stem 1894). Typically, where the water is more exposed to
breaking away to form a new plant (Brown 1971). prevailing winds and moderate wave action, broad-
leaved plants are absent, their place being taken by
Vegetative reproduction is common in most
Myriophyllum, whose highly divided leaves are
aquatic plants and many produce special overwintering
uninjured by wave motion (Matthews 1914). As a rule,
structures known as turions. Turions are specialized
submersed plants form a zone farther from the shore
short stems on which the leaves are closely packed. In
than floating-leaved plants because the latter shades
Elodea, the parent plant persists all winter, but the
the lower layers of the water, reducing sunlight
leaves at the tips of the stems form compact tution buds
penetration to a level insufficient to support a deeper
that do not separate until spring. Potamogeton cripus
flora (Arber 1920). Because much of the estuary is
(curly pondweed) produces turions in the form of side
sheltered, beds of Nelumbo are scattered throughout
shoots which break away from the parent and grow
the open water (Figure 7.1); as a consequence, the most
fresh roots and leaves (Brown 1971). P. pectinatus
favorable habitat for submersed plants is limited to the
(sago pondweed) overwinters by means of tubers
intervening spaces.
produced at the ends of special roots (Pieters 1901).
7-2
CHAPTER 7. ECOLOGY
Figure 7.1. Nelumbo beds in Old Woman Creek estuary

(Lotus Lilies, a painting by Charles Courtney Curran in 1888; courtesy of Terra Museum of American Art).
Zonation within Old Woman Creek estuary—the all parts of these plants are adapted to live under water.
arrangement of taxa in aquatic and marsh plant Stems are weak and the general structure of the plants
communities to form a series of bands more or less is loose since water buoyancy reduces the requirement
parallel to the shoreline—is largely influenced by water of the rigid support needed for plants living in an air
depth and soil moisture. The slope, or gradient, of the environment. Stoma, the pores on the underside of
shore and nearshore bottom controls the width of the leaves used for gas exchange in air, are also reduced
bands; steep gradients yield narrow bands whereas or vestigial.
gentle slopes produce wider bands. Typically four
distinct zone of macrophytes are present in Lake Erie In response to reduced light illumination
coastal embayments and marshes such as Old Woman underwater, photosynthetic pigments (e.g. chlorophyll
Creek Estuary: Zone 1–submerged plants; Zone 2– and carotenoids) are concentrated in surface
rooted, floating–leaved plants; Zone 3–emergent (epidermal) tissue (Wetzel 1983). Submerged plants
plants; and Zone 4–wet shore plants. commonly have numerous and finely divided leaves
and green (photosynthetic) stems to optimize the
reduced light reaching them. These slender and
Zone 1–Submerged Macrophytes
threadlike leaves maximize surface area–to–volume
Plants in this zone grow in water up to several ratios (thereby facilitating gas exchange) and minimize
meters deep and colonize the bottom as long as water resistance to water currents. For example,
clarity permits sufficient sunlight to penetrate for Ceratophyllum leaves are split into many divisions,
effective photosynthesis. The generally turbid while Potamogeton pectinatus leaves are narrow and
condition in the estuary limits the photic zone to a depth elongated. Potomogeton pectinatus also demonstrates
to 0.5 to 0.8 m (Herdendorf and Wilson 1987). The a special adaptation for growth in turbid waters, such
dominant submerged plants in the estuary are as that found in Old Woman Creek estuary. Mostly
Ceratophyllum demersum (coontail) and Potamogeton submerged, this aquatic plant has a crown of leaves on
pectinatus (sago pondweed). Ceratophyllum lives the upper portion of the stem that fan out near the water
suspended in the water column, while Potamogeton is surface (Figure 7.3) to maximize exposure to available
rooted to bottom (Figure 7.2). Except for the flowers, sunlight (Langlois 1954).
7-3
Zone 2–Floating-Leaved Macrophytes

Floating-leaved plants are of two principal types,
those attached to the bottom and those freely floating.
Attached types are primarily flowering plants
(angiosperms) that occur in water 0.5 to a few meters
deep. Freely floating types are not rooted to the bottom
and tend to accumulate in shallow, protected areas.
Because of the generally turbid water and shallow
depths of the estuary, zones 1 and 2 are often
superimposed to form a single zone encompassing most
of the open waters of the estuary. The dominant aquatic
macrophytes in this zone are Nelumbo lutea (American
water lotus), Nymphaea odorata (white water–lily,
Figure 7.4), and to a lesser extent Nuphar lutea advena
WATER SURFACE
Figure 7.2. Sago pondweed (Potomogeton

pectinatus), a submerged plant rooted to the bottom
(Charles E. Herdendorf).
Also in this zone, Elodea canadensis (common

waterweed) was first observed in the estuary in 1995
(Whyte 1996). Although this species was found in Old
Woman Creek above the estuary in 1979, it has very
limited distribution in both habitats. Thin leaves (e.g.
two-cell thickness of Elodea leaves) make the most of
dim light, but they also require adaptations to offset
the turbulent motion of water. For example, ribs in
broad leaves provide needed rigidity (Pieters 1901).
Another plant of this zone, the exotic

Myrophyllum spicatum (Eurasian water milfoil), was
first observed in the estuary in 1992 (Whyte 1996) but
as of 2001 it has not firmly established a population in
the estuary. Fragments of this invasive plant have been
observed floating in the lower reaches of the estuary
in each of the years after 1992, but apparently have
been unable to root and form a viable reproducing Figure 7.3. Potomogeton pectinatus (sago pondweed)
population. Since all fragments have been observed showing crown of leaves on the upper portion of the stem
near the estuary mouth, it appears that Lake Erie is the that fan out near the water surface (Fassett 1957).
source of this exotic species.
7-4
CHAPTER 7. ECOLOGY
Figure 7.4. White water-lily (Nymphaea odorata), a rooted, floating-leaved plant of the estuary (Gene Wright).
(spatterdock). Floating Lemna minor (duckweed) often

forms thick mats in the quiet waters among the lotus
beds in early autumn (Figure 7.5).
The structure of floating leaves is strikingly

different from that of submerged leaves in response to
their dissimilar environments. The cells of the upper
epidermis of the floating leaves are smaller, the cell
walls are thicker, and more irregular in outline. Stomata
are confined to the upper surface of the floating leaf,
while they are virtually absent on the submerged leaf.
Floating leaves are of finer texture than submerged ones
and have a waxy covering to protect them from water
injury. In Nelumbo lutea this protection is provided by
numerous papillae (hairs), each arising from an
epidermal cell. These fine projections hold a layer of
air so that water falling on the leaf stands in large drops,
as if on an oiled surface, until it can run off (Pieters
1901). Nelumbo is unique among the floating-leaved
plants in the estuary in that it produces two distinct
cohorts of leaves: the first are floating and emerge in
late May while the second are aerial leaves that appear
in late June or early July (Whyte 1996). The aerial
leaves are generally above the range of seasonal water Figure 7.5. Duckweed (Lemna minor) forms floating
level fluctuations (Figure 7.1). mats in protected coves of the estuary (Linda Feix).
7-5
The boundary layer between air and water is a

challenging environment for aquatic plants, where
temperatures, water levels, current, and clarity vary
from day to day as well as seasonally. The floating
leaves of Nuphar lutea advena and Nymphaea odorata
are well adapted to these conditions with long, bending
stems (flexible petioles) that can alter their position in
the water to keep the leaves on the surface. The leaves
also have a waxy upper surface that resists wetting
and desiccation. Gas exchange pores (stomata) are
distributed on the upper surface instead of the lower
as they are in terrestrial plants.
Zone 3–Emergent Macrophytes

Plants in this zone grow on water-saturated or
shallowly submerged soils, i.e. water table 0.5 m below
the soil surface to sediment covered by up to 1.5 m of
water (Wetzel 1983). Most are perennial with rhizomes
or corms embedded in the soil. In many species,
morphologically different submerged or floating leaves
precede mature aerial leaves. All produce aerial
reproductive organs. Common plants of Old Woman
Creek estuary in this zone include: Leersia orzyoides
(rice cut-grass), Phalaris arundinacea (reed canary–
grass), Phragmites australis (common reed), Scirpus
fluviatilis (river bulrush), Hibiscus moscheutos (swamp
rose-mallow, Figure 6.15), Polygonum amphibium Figure 7.6. Narrow-leaved cattail (Typha angustifolia),
(water smartweed. Figure 6.14), Typha angustifolia an emergent plant that grows at the fringes
(narrow-leaved cattail, Figure 7.6), and various species of the estuary (Gene Wright).
of Carex (sedges).
supply of oxygen. Young, submerged foliage must be
Emergent monocotyledons, such as Phragmites capable of respiring anaerobically until aerial growth
and Scirpus, produce erect, linear leaves from an is attained, since oxygen concentrations in water are
extensive anchoring system of rhizomes. Epidermal very low in comparison to that in air. Once the foliage
cells are elongated parallel to the long axis of the leaf, has emerged, the intercellular spaces increase in size,
which allows flexibility for bending (Wetzel 1983). thus facilitating gaseous exchange between
However, the cell walls are heavily thickened with photosynthetic cells and the atmosphere. Rhizomes are
cellulose, which provides the necessary rigidity. The capable of withstanding prolonged periods (up to a
internal tissue (mesophyll) is generally undifferentiated month) of low oxygen supply (Wetzel 1983).
and contains large air spaces (lacunae). Emergent
dicotyledons, such as Hibiscus moscheutos and The emergent monocot Sparganium (bur-reed)
Polygonum amphibium (water smartweed), produce demonstrates a variety of adaptations to match the
erect, leafy stems which show greater anatomical different conditions experienced by various parts of
differentiation. The internal tissue of the leaves is the plant. Examination of successive cross-sections of
divided into typical upper palisade (elongated cells) the bur-reed shoot shows that the emergent leaf has a
layer and lower spongy (loosely packed cells) layer. tough rigid structure with dense tissue that withstands
the stress at the air-water interface. Farther down the
The roots and rhiozomes of emergent shoot the tissue gets more spongy and full of air, an
macrophytes are permanently embedded in anaerobic adaptation for supplying oxygen to the roots (Angel
sediment and are dependent on the aerial shoots for a and Wolseley 1982).
7-6
CHAPTER 7. ECOLOGY
Production of adventitious “water roots” close Cyperus, Eleocharis, and Scirpus, rushes of the genus
to a seasonally flooded surface is a common strategy Juncus, and grasses of the genera Calamagrostis,
for many water-tolerant species of the swamp forest. Cinna, Echinochloa, Glyceria, Leersia, Phalaris, and
For example, Salix alba (white willow) forms a large Phragmites (Figure 2.12). Herbaceous dicots are
tussock of such roots above the normal flood level. In represented by a wide variety of genera, including
woody plants such as Salix (willows) and Nyssa Ranunculus (buttercups and crowsfoots), Polygonum
sylvatica (black gum), flooding first causes an (smartweeds), Rumex (docks), Lycopus (water
overgrowth of lenticel tissue (hypertrophy) to form a horehounds), Asclepias (milkweeds), Verbena
callus from which adventitious roots then emerge close (vervains), Mentha (mints), Scutellaria (skullcaps),
to the better oxygenated air-water interface. Some Mimulus (monkey-flowers), Galium (bedstraws), and
herbaceous plants behave similarly, for example the composite genera such as Aster, Bidens (beggarticks),
flood-tolerant Epilobium glandulosum (willow-herb) Eupatorium (bonesets), and Solidago (goldenrods).
has hair-like roots for several cm above the stem base
that produce adventitious surface roots on flooding. The wet floodplain adjacent to the south basin of
the estuary also supports many woody plants and can
Emergent plants of the estuary marshes, such as aptly be termed a swamp forest. Typical woody genera
Phragmites australis (common reed), Typha include Acer (maples), Carya (walnuts), Cephalanthus
angustifolia (narrow-leaved cattail), and Scirpus (buttonbushes), Cornus (dogwoods), Corylus
fluviatilis (river bulrush), grow in the most severe of (hazelnuts), Populus (cottonwoods), Quercus (oaks),
all waterlogged environments, their roots and rhizomes Salix (willows), Tilia (basswoods), and Ulmus (elms).
in anaerobic mud and their leaves in a very exposed, Tree species such as these create a canopy that changes
often sunlit environment. Growth habits of the character of wetlands from sunlit marshes with soft-
monocotyledons make such plants well suited to this stemmed plants to shady, woody swamps with
situation, particularly their free adventitous rooting and relatively minor amounts of herbaceous biomass in the
the frequent absence of stem tissue between the leaf understory.
and roots which facilitates the transport of oxygen
(Etherington 1983). Like the emergent zone, wet meadows are highly
productive in terms of biomass and fulfill effective
Wetland plants of the estuary such as Juncus water filtering functions. The juncture of the stems and
effusus (common rush), Sagittaria latifolia roots for plants in this zone is typically just above the
(arrowhead), Scirpus validus (soft-stem bulrush), water table during the growing season. Thus, many of
Sparganium eurycarpum (bur-reed), Typha latifolia the species found in this zone must grow in a wetland
(broad-leaved cattail) are all well supplied with running and are termed obligate hydrophytes. However,
rootstocks. Those of an association of Scirpus or Typha
are particularly strong and wide spreading with each
plant connected to all others of its species by thick
rhizomes.
Zone 4–Wet Meadow and Floodplain

Macrophytes
Lying adjacent to the shoreline of the estuary, this
is a transition zone between estuarine and upland
habitats (Figure 7.7). Plants in this zone grow in soil
that is usually saturated with water to within a few
centimeters of the surface. During wet periods the
nearly flat to gently sloping terrain can be shallowly
flooded and during droughts the water table can drop
tens of centimeters below the surface. The plant
community in this zone is represented by many Figure 7.7. Wet meadow grasses fringe the mudflats
monocots, including sedge genera such as Carex, of the estuary (Charles E. Herdendorf).
7-7
because of this zone’s transition position between the low levels (Figure 7.8). Lake levels remained elevated
estuary and the uplands, other species found in the zone from 1974 through the spring of 1999, with record high
have the ability to live in semi-dry situations and are levels recorded in 1985 and again in 1986. Marshall
termed facultative hydrophytes. (1977) reported five distinct beds of emergent or
floating-leaved species in the estuary in 1974.
TRENDS IN MACROPHYTE POPULATIONS Dominant species included: Peltandra virginica,
Nelumbo lutea, and Polygonum amphibium. Klarer and
Great Lakes coastal wetlands are among the most Millie (1992) examined the changes in macrophyte
dynamic wetland types. This dynamic nature is largely flora from 1974 through 1989. They prepared a map
the result of the variable water levels in the five Great of the different regions of the estuary and a table
Lakes. The impact of seasonal and annual variations recording the changes in flora from Marshall’s original
in water levels on the wetland vegetation can be survey through 1989.
significant. During high lake levels, as much as 50%
of the emergent plant zones can become open water For this site profile, we have employed the same
(Jaworski et al. 1979). Kelley et al. (1985) reported region map developed for the 1992 study (Figure 7.9)
similar results from Pentwater Marsh, Michigan. and a table from that study has been modified (Table
Researchers have also reported this change in aquatic 7.1) to incorporate the more recent floral studies of
flora in Old Woman Creek (Klarer and Millie 1992, Whyte (1996), Whyte et al. (1997), Trexel-Kroll (2002)
Whyte 1996, Whyte et al. 1997, Trexel-Kroll 2002). and Klarer (unpublished data). From 1977 through
1999 Nelumbo lutea dominated the macrophyte flora
The first detailed survey of the aquatic flora of in Old Woman Creek estuary. In 1999 water levels
Old Woman Creek estuary was conducted by John declined to levels similar to those of the 1960s (Figure
Marshall in 1974 (Marshall 1977, Marshall and 7.8). With these declining water levels, the aquatic
Stuckey 1974). At that time, lake levels had risen to macrophyte community underwent a major shift in
very high levels after a 15+year period of moderate to species composition. The dominant Nelumbo, the
Figure 7.8. Mean annual Lake Erie water levels from 1918 to 2000 (NOAA).
7-8
TABLE 7.1. MACROPHYTE DOMINANCE BY AREAS OF THE OLD WOMAN CREEK ESTUARY FROM 1973 TO 2001
NOTES:
Site locations are shown on Figure 7.9. If multiple species are listed for a particular site, they are given in descending order of abundance.
“*” denotes no vegetation reported.
“* Emergents” denotes undifferentiated emergent species including varying proportions of the following taxa: Leersia oryzoides, Echinochloa spp.,
Phalaris arundinacea, Carex spp., Scirpus validus, Typha spp., Sparganium eurycarpum, and Sagitaria latafolia.
1 Nymphaea odorata is the new name of Nymphaea tuberosa as recorded by Marshall (1976), Klarer and Millie (1992), and Whyte (1996)
7-9
CHAPTER 7. ECOLOGY
During the period of Nelumbo dominance, this

species demonstrated two distinct growth patterns: a
general expansion in coverage in the estuary and a
cyclic pattern of expansion and contraction within
individual beds (Whyte et al. 1997). Over this 20+ year
period, the percentage of Nelumbo cover ranged from
5.2% (1977) up to 35.6% (1993) coverage (Table 7.2).
This cyclic expansion and contraction in an individual
bed is readily apparent when examining the yearly
Nelumbo distribution maps in Whyte et al (1997)
(Figure 7.10). The major Nelumbo bed due north of
the island expanded from 1977 to 1984, when it broke
into two separate beds. The northern portion of the
bed continued to migrate northwest in the estuary
toward the mouth, from 1984 through 1989, while the
southern part of the bed gradually disappeared.
TABLE 7.2. PERCENTAGE COVER

OF NELUMBO LUTEA IN ESTUARY
Year Percent Coverage
1977 5.2
1978 5.4
1979 12.8
1984 21.5
Figure 7.9. Old Woman Creek estuary map showing
1985 16.6
site locations of aquatic macrophyte beds
1986 17.8
and numbering system (Klarer and Millie 1992).
1988 20.3
1989 10.9
major species in the estuary from the late 1970s through 1993 35.6
1999 (Figures 7.10 to 7.12), was replaced by emergent 1994 34.3
species in both 2000 and 2001 (Trexel-Kroll, 2002). 1995 34 (estimated)
Total vegetation cover rose from 40% in 1999 to greater 1998 29.0
than 70% in 2000 and 2001. The percent cover of 1999 30.4
emergent plants in the estuary rose from less than 10% 2000 22 (estimated)
in 1999 to greater than 45% in 2000 and even slightly 2001 20 (estimated)
greater in 2001. Although the areal extent of the
vegetation did not markedly change between 2000 and Data Sources: Whyte 1999 and Klarer, unpublished
2001, there were noticeable changes in the species
composition. The relative importance of floating- In summary, the aquatic macrophyte
leaved species declined while duckweeds, communities in Old Woman Creek estuary are very
submergents, and particularly emergent species dynamic. The size and locations of the different beds
increased. In the northwest embayment during 2001, change each year. During high water years (1980-1999)
the emergents were nearly equally divided between the vascular flora was dominated by Nelumbo lutea,
grasses—Leersia, Echinochloa, Phragmites (35% of while the emergent vegetation was largely confined to
total vegetation) and non-grasses—Polygonum, Typha, the shoreline edges of the estuary. When Lake Erie
Sparganium, Sagittaria (42% of total vegetation), water levels dropped in 1999, many of the mudflat
while in the major beds south and west of the island, areas that had been underwater from 1980 through 1999
the grasses—particularly Leersia and Echinochloa— were exposed during the spring of 2000. These areas
accounted for 55% of the vegetation and the non- were quickly colonized by emergent vegetation.
grasses only 22%.
7-10
Figure 7.10. Distribution of Nelumbo lutea in Old Woman Creek estuary from 1977 to 1994 (Whyte et al. 1997).
7-11
CHAPTER 7. ECOLOGY
7-12
Figure 7.11. Detail of wetland vegetation distribution in Old Woman Creek estuary for 1993 (Whyte 1996).
Figure 7.12. Distribution of macrophyte vegetation in Old Woman Creek estuary for 1999, 2000, and 2001 (Trexel-Kroll 2002).
7-13
CHAPTER 7. ECOLOGY
INVASIVE SPECIES estuary. In 1994, when no specimens were found in

the estuary, the mouth was open through the barrier
Within Old Woman Creek estuary, three aquatic
beach to Lake Erie only 44% of the year; whereas, in
macrophyte species are deemed invasive species and
1993 and 1995 it was open 58% and 77%, respectively.
have either been eradicated or monitored. Lythrum
salicaria (purple loosestrife) and Myriophyllum Phragmites australis has probably been observed
spicatum (Eurasian water–milfoil) are both non-native, along the Lake Erie shores since before the arrival of
while Phragmites australis (common reed) has been the European explorers. Stuckey (1989) considered this
considered a native species, but perhaps is an alien species a native which had not significantly altered its
variety (Weinstein et al. 2002). distribution for the past 90+ years. This species was
not found by Marshall (1977) in the estuary in the mid-
Lythrum salicaria, a major invasive of Lake Erie
1970s. It was believed to have entered the estuary in
coastal wetlands, was first reported in Old Woman
the mid-1980s and was first observed near the barrier
Creek by Marshall (1977). Although Marshall
beach (Klarer, personal observation). Whyte (1996)
classified this species as common, it has yet to become
reported that small dense stands of Phragmites were
a dominant species in the estuary. A control program
confined to several low relief shoreline floodplain areas
has been in place at Old Woman Creek since the mid-
from 1993 through 1995. Trexel-Kroll reported that in
1980’s. When individual plants are discovered, they
2000 and in 2001 with lowered water levels,
are eradicated—either by physically removing the plant
Phragmites expanded into the newly created emergent
or applying herbicides directly onto the plant. Despite
zones in the wetland. By the end of the 2001 growing
this program, Whyte (1996) and Trexel-Kroll (2002)
season this species was present in scattered beds
both reported this species in their vegetation studies in
throughout the estuary. She considered that this
the estuary. It appears that this species can be
expansion was due in part to direct expansion of
controlled, but not eradicated in the estuary. Only when
existing stands via rhizomes. In five separately
a lake-wide control program is initiated is there any
monitored Phragmites beds in the estuary there was
chance of eradicating this invasive species from the
more than a four-fold increase in the size of the beds
estuary.
from 2000 to 2002 (40.7 m2 in 2000 versus 182.5 m2
Myriophyllum spicatum was first reported in the in 2001). In new non-adjacent beds, translocation of
estuary in 1992 in the northwest embayment (the small rhizome fragments was probably the means of
bay directly south and southwest of the U.S. Route 6 expansion. A Phragmites control program employing
Bridge), although Marshall (1977) reported the cutting and/or direct herbicide application to the stems
presence of the native Myriophyllum exalbescens in has been underway since the late 1990s.
the estuary. Whyte and Francko (2001) reported on
the growth of M. spicatum from its first reported RELATIONSHIP OF AQUATIC PLANTS TO AQUATIC
sighting in 1992 through 1997. Although this species ANIMALS
was found in 1998 and 1999 by Klarer (unpublished), Most of the leafy aquatic plants in Old Woman
Trexel-Kroll (2002) did not report this species in her Creek estuary serve as shade or protection for fish,
detailed study of the flora in this embayment during while some support algae or small animals which serve
2000 and 2001. Whyte and Francko (2001) pointed as food for fish. Krecker (1939) studied the invertebrate
out that the available evidence supports the idea that animal populations associated with aquatic plants in
Lake Erie is the source of this species for Old Woman western Lake Erie. He noted that submerged, leafy
Creek. All sightings have been near the mouth. The types of vegetation are more densely populated than
shallow nature of the wetland, exacerbated by the emergent, hard-surfaced, non-leafy forms.
natural autumn and winter drawdown, frequently Myriophyllum spicatum (water milfoil) and
creates exposed mudflats. This, coupled with the winter Potamogeton crispus (curly pondweed) supported by
periods where freezing temperatures and ice formation far the densest populations (440 and 337 individuals
is common, creates an environment that is detrimental per linear meter), followed by Elodea canadensis
to the successful establishment of M. spicatum. They (common water-weed) and Potamogeton pectinatus
believed that the barrier beach may also play a major (sago pondweed) with lesser, but substantial numbers
role in the dynamics of this invasive species in the (173 and 143/m). Vallisneria americana (wild
7-14
CHAPTER 7. ECOLOGY
celery)—a species not yet reported in the estuary, but The algae of Lake Erie have long been studied,
present in western Lake Erie harbored only negligible with major studies dating back to the beginning of the
numbers of aquatic invertebrates (9/m). Midge larva 20th century and before (Vorce 1880, Pieters 1901,
(Chironomidae) and freshwater annelids (Oligochaeta) Snow 1903). Many of these early workers included
comprised 45 and 44%, respectively, of the adjacent coastal wetland areas in their studies of the
invertebrates living on Potamogeton pectinatus, one lake algae. Although the first study concentrating on
of the most common submersed plants in the estuary. the phytoplankton in the tributaries and coastal areas
The finely divided, narrow leaves of Myriophyllum of Lake Erie was conducted in the 1920’s (Wright et
spicatum and P. pectinatus, are well suited to these al. 1955), very few studies have concentrated on the
animals; midges cling to such leaves with their hook- coastal wetlands of Lake Erie. Sullivan (1953)
bearing appendages and annelids coil about them. examined the plankton in the ten major estuaries along
Conversely, Vallisneria offers a broad, smooth surface. the Ohio shore of Lake Erie. From this work he
The broader leaves of Elodea and P. crispus harbor a concluded that the majority of the phytoplankton in
higher percentage of sessile forms (rotifers, bivalves, the estuaries was of lake origin, being introduced into
hydrozoans, and bryozoans) than narrow-leaved plants. the estuaries by influxes of lake water. Kline (1981) in
a study of the nearshore zone phytoplankton of the
Lake Erie central basin also reported a strong similarity
ESTUARY VEGETATION: PHYTOPLANKTON
between lake and tributary phytoplankton populations.
AND PHYTOBENTHOS However, he did point out that the further the sampling
Plankton consists of the floating organisms in the site was from the lake, the greater the divergence from
estuary and Lake Erie—both plant (phytoplankton) and lake populations. Frederick (1975) examined changes
animal (zooplankton)—whose movements are more in phytoplankton in the East Harbor up through 1974.
or less dependent on currents. While some Only 31% (47 of 151 taxa) of the previously reported
phytoplankters have the ability to rise in the water algal species were still found at East Harbor by 1974,
column and certain zooplankters exhibit active and there were 52 new records for Lake Erie. The
swimming movements that aid in maintaining vertical changes he ascribed to human activities, particularly
position, as a whole, plankton tends to settle and most dredging activities in 1967.
plankters are unable to move against a current. The Taft and Taft (1971) authored a taxonomic survey
phytoplankton of Old Woman Creek, the estuary, and of the algae of the western basin of Lake Erie, which
the nearshore waters of Lake Erie consists of a diverse included various wetland areas on Bass Islands and
taxonomic assemblage of primarily microscopic algae. Catawba Peninsula. The diversity of the algal flora in
A fundamental characteristic of algae is the presence these wetland areas is readily demonstrated by the total
of photosynthetic pigments, such as chlorophyll (a, b, number of species reported from each area (Table 7.3).
c, & d), carotenes, xanthophylls, and chromoproteins The relative high number of Chlorophyceae in the
(phycocyanin and phycoerythrin). Chlorophyll a is the marshes of South Bass Island and Middle Bass Island
primary pigment in all oxygen-evolving photosynthetic is due to the diversity of desmids found in these
organisms, and is present in all algae (Wetzel 2001). marshes, a group that is poorly represented in Old
As discussed in Chapter 6, algal taxonomy at the Woman Creek. The high number of the Euglenophyta
division level is based on the specific combinations of found in Old Woman Creek may be a result of the
other pigments with Chlorophyll a. This results in a transitory nature of phytoplankton populations in this
characteristic color from which the common name of estuary. A complete list of the algae reported from Old
the algal divisions are derived: blue-green algae Woman Creek, its estuary, and the nearshore waters of
(Cyanobacteria), green algae (Chlorophyta), yellow- Lake Erie is presented in Klarer et al. (2001).
green and golden-brown algae and diatoms
(Chrysophyta), euglenoids (Euglenophyta), yellow- The algae in a wetland area such as Old Woman
brown algae and dinoflagellates (Pyrrhophyta), and red Creek estuary occupy a series of overlapping habitats.
algae (Rhodophyta). Many of these groups also Bolsenga and Herdendorf (1993) defined six algal
produce benthic forms associated with sediment, communities in Lake Erie: phytoplankton, epipelon,
sessile on macrophytes, or attached to hard substrates epiphyton, epilithon, epipsammon, and metaphyton
for a portion of their life cycle. (Figure 7.13). The phytoplankton includes all algae
7-15
7-16
TABLE 7.3. RELATIVE ABUNDANCE OF ALGAL SPECIES FOR SEVEN WESTERN LAKE ERIE MARSH AREAS
Data Source: Modified from Herdendorf (1987) with the addition of Old Woman Creek estuary data
CHAPTER 7. ECOLOGY
found in the water column. This community will similar from year to year. Through most of the year,
include many members of the other three communities the phytoplankton was dominated by several small
that have become detached and washed into the Cyclotella species. In the later part of the spring, as
phytoplankton. The epipelon encompasses the algae water temperatures rose toward summer levels, the
that grow in and on the soft sediments. Epipelic algae Cryptophytes: Cryptomonas spp. and Rhodomonas
may be very important in regulating the movement of minuta var. nannoplanctonica became widespread.
nutrients from the anaerobic sediments to the overlying During the summer and autumn Aulacosiera spp.,
water (Wetzel 1996). Many of these algae are motile particularly A. alpigina, were also common in the
flagellates that will also be found in the phytoplankton phytoplankton. Members of the Chlorophyta and
during some part of the year. The epiphyton and Cyanophyta were common in late summer/early fall
metaphyton refer to the algae that grow attached during some years but not others.
(epiphyton) or associated with but not attached
(metaphyton) to the aquatic plants. Epilithic algae grow A study examining the role of storm events on
on rocks while episammic algae grow on sand grains phytoplankton populations in the estuary was
or the intersitial spaces between grains. In Old Woman undertaken in 1984 after it was observed that
Creek, preliminary work has been conducted on all fluctuations in population numbers often coincided
but the epipsammon and metaphyton algal with fluctuations in turbidity. This, coupled with the
communities. paucity of Chlorophyta and Cyanophyta normally
dominant in Lake Erie proper, suggested that storm
runoff events were a major factor in regulating
PHYTOPLANKTON
estuarine phytoplankton (Klarer and Millie 1994b).
Studies of phytoplankton in Old Woman Creek
estuary (Klarer and Millie 1994b, Klarer 1989, Klarer Storm water flowing through the estuary flushed
1983, Klarer unpublished data) demonstrate high out much of the existing populations, but at the same
variability in this community. Multiple peaks were time carried nutrients into the estuary allowing the
observed throughout the year (Figure 7.14). The time surviving populations to rapidly repopulate the estuary.
and duration of these peaks seemed highly erratic. In one of the sampled storms, population numbers in
Despite this variability, the dominant species were the lower estuary increased within two weeks of the
Figure 7.13. Algal communities in Old Woman Creek estuary and watershed (after Bolsenga and Herdendorf 1993).
7-17
Figure 7.14. Phytoplankton populations in Old Woman Creek estuary for 1980 exhibiting multiple peaks
throughout the growing season (after Klarer 1983,1989).
storm’s passage to over four times pre-storm numbers;

this rapid repopulation was not observed in the upper
reaches of the estuary (Figure 7.15). The researchers
attributed this to a lack of backwater refugia in the
upper reaches of the estuary, which would have
provided the surviving algae necessary for rapid
recolonization.
Circumstantial evidence suggests that the

agricultural chemicals applied in the Old Woman Creek
watershed may be influencing both the numbers and
composition of the phytoplankton. Agriculture is the
dominant land-use pattern within the Old Woman
Creek watershed. The short-and long-term impacts of
agriculturally-derived chemicals on wetlands and their
resident organisms have only recently been addressed
(Krieger 1989, Krieger et al. 1989). Sieburth (1989)
proposed that agricultural chemicals, when introduced
into coastal embayments, potentially raise the growth
ceiling of specific phytoplankton through nutrient input
while killing predators, thereby allowing
phytoplankton to reach maximum growth unrestrained Figure 7.15. Phytoplankton standing crop
by grazing. in response to storm-water inflow through
Old Woman Creek estuary (Klarer and Millie 1994b).
7-18
CHAPTER 7. ECOLOGY
In Old Woman Creek, the flushing of the estuary physical processes are more important than biological
would undoubtedly remove potential predators from ones in regulating the composition of the
the system. However, differential growth of phytoplankton.
phytoplankton taxa in response to agricultural
chemicals might occur. Fertilizers and herbicides In the nearly two decades since the inception of
(particularly triazines) are routinely applied to the monitoring program at Old Woman Creek, Lake
agricultural lands within the watershed during spring Erie has undergone tremendous change, both in nutrient
planting. Although triazine residues are present in the levels and in phytoplankton composition. The massive
estuary throughout the year, storm waters import a mats of the blue-greens Aphanizomenon and Anabaena,
significant chemical load (Krieger 1984). Geographical which were so common in the 1970s, have disappeared.
races of phytoplankton and phytoplankton taxa in Filamentous diatoms and small cryptophytes are more
various physiological states display distinct growth and prevalent. Nutrient levels in the waters of Lake Erie
photosynthetic responses to differing concentrations have declined. With these changes in the receiving lake
of triazine herbicides (e.g. Millie and Hersh 1987; as a backdrop, Klarer (1999) studied the phytoplankton
Millie et al. 1992)—it is highly likely that individual in the Old Woman Creek estuary to determine if similar
taxa display distinct responses as well (Hersh and changes had occurred in the estuary. He reported that
Crumpton 1989). The herbicides introduced by storm the total population numbers were very similar during
waters may alter the water chemistry in Old Woman the two 3-year periods of study (1981-1983 and 1995-
Creek enough to cause changes in the composition and 1997) (Figure 7.16). The relative contribution of the
physiology of the populations that potentially may various algal groups, however, was quite different
recolonize the estuary. This may explain an observed during the two time periods. In both study periods, the
selective increase of Cryptomonas erosa and Cyclotella diatoms, particularly Aulacoseira alpigena and various
spp. after a spring storm event, which closely followed smaller Cyclotella species, was the dominant group
herbicide applications in the watershed. through much of the spring and early summer. In the
early 1980s the diatoms progressively dropped in
Klarer and Millie (1994a) examined summer and relative importance through the year from late spring
autumn phytoplankton populations in the estuary in onward; while in the late 1990s, diatoms remained the
1992, which was a wet year with frequent storm dominant group through the year. In the early 1980s
flushing during the summer and fall, and in 1993, which green algae, primarily chlorococcales such as
was a dry year when the mouth was closed for much Scenedesmus, Didymocystis, Lagerheimia, and
of the summer (Table 5.8). During July, August, and Crucigenia, and the blue-greens, including
September 1992, the phytoplankton was dominated by Merismopedia and various Oscillatoria species, were
diatoms, particularly the smaller Cyclotella species. increasingly more important through the summer and
The Chlorococcales (green algae containing the genera fall (Figure 7.17). This again can be related back to
Scenedesmus, Pediastrum, and other common storm activity in the watershed. During the years 1981-
phytoplankton species) were present only in very small 1983 diminished rainfall in the watershed resulted in
numbers. In 1993, however, when the mouth was the mouth remaining closed for a major part of the
closed for much of this 3 month period, the summer. Rainfall amounts in 1995-1997 were adequate
Chlorococcales formed a significant part of the to keep the mouth largely open through the summer
phytoplankton. The Cyanophyta were also much more growth period. The changes reported in Lake Erie were
common in 1993. The lack of storms influencing the not observed in the estuary. This study again
estuary permitted the estuary to become more highlighted the over-riding importance of physical
physically stable. Under these conditions, biological processes in regulating the phytoplankton in Old
interactions between the various phytoplankton species Woman Creek estuary.
and their grazers would become more significant.
When the mouth was open, there was also a much Wind-induced waves in the lake can push lake
higher proportion of benthic or attached diatoms in water into and up the estuary. Lake water is normally
the phytoplankton. This supports the hypothesis that lower in conductivity, higher in pH, and lower in
periods when the mouth is open correspond to periods metals. In addition, the phytoplankton in Lake Erie is
of increased physical instability in the estuary, in that noticeably different from that in the estuary, therefore,
7-19
Figure 7.16. Total phytoplankton abundance in Old Woman Creek estuary

during two time periods exhibiting relatively consistent numbers.
the presence of certain species such as Stephanodiscus EPIPELON

binderanus or Fragilaria crotonensis is usually a
Jensen (1992) undertook a study of the epipelon
reliable indicator of lake water intrusion.
and factors that might regulate these communities in
In summary, the phytoplankton populations in the Old Woman Creek estuary. During the summer/fall
Old Woman Creek estuary seem to be storm regulated. sampling regime, diatom species dominated the
The waters and the composition of the phytoplankton populations, with Nitzschia spp., particularly N. palea
in the estuary are largely determined by storm activity, (4x105/mm2–August) and N. reversa (1.5xl06/mm2)
either on the lake or in the watershed. Storms and storm being most common. The blue-green filamentous alga
runoff in the estuary largely determine the numbers Oscillatoria sp. (2.9x105/mm2) was also a dominant
and species composition of the phytoplankton. With species at some of the sites during the late summer-
the watershed averaging more than one storm a month early autumn period. The flagellated Euglenophytes
(see Table 4.5), the phytoplankton is normally were present in small to moderate numbers in this
dominated by “pioneer” species including smaller community. Nutrient addition studies were
pigmented flagellates and smaller centric diatoms for inconclusive. Increasing nitrate levels in the overlying
much of the year. Only when storm runoff diminishes waters increased diatom numbers and biovolume, but
and the mouth closes does the physical habitat in the increasing phosphorus levels in the sediments also
estuary become more stable. It is at these times that caused a marked increase in the epipelon. These
biological interactions between the phytoplankton itself contradictory results underline the need for caution
and its grazers may become more important in when interpreting nutrient addition studies. Other
determining species composition and numbers. factors may be influencing this community, and thus
masking nutrient trends. Both shading and turbulence
decreased the numbers and diversity of the epipelon.
7-20
CHAPTER 7. ECOLOGY
Figure 7.17. Percent composition of phytoplankton in Old Woman Creek estuary for 1981-1983 (showing autumn
decline in diatom dominance) and 1995-1997 (showing continued dominance of diatoms in the autumn).
7-21
EPIPHYTON increasing water temperatures. In summary, the

epiphyton in Old Woman Creek estuary are
Two studies on the epiphyton attached to the
characteristic of a wetland that is eutrophic and slightly
aquatic macrophytes in Old Woman Creek estuary were
alkaline. The numerical dominance of both
conducted in the early 1980s. Millie and Klarer (1980)
Gomphonema parvulum, a facultative nitrogen
surveyed the epiphytic algae growing attached to one
heterotroph, and Nitzschia filiformis, an obligate
algal (Cladophora) and nine different macrophyte hosts
nitrogen heterotroph, suggest a low to moderate level
during June 1980. This study indicated that there was
of dissolved organic compounds in the water, at least
very little evidence of host specificity, but there was
through early to mid-summer.
site specificity. In most areas of the estuary,
Gomphonema parvulum and Nitzschia species (N.
filiformis, N. amphibia, N. dissipata var. media, and EPILITHON
others) dominated the epiphyton flora. In the summer Klarer (1981) also examined the epilithon (algae
of 1999, Reed (1999) studied the epiphyton growing growing attached to rocks) in the creek proper. In many
attached to Nelumbo in several areas of the estuary. river and stream systems, particularly in the faster
She reported that diatoms in the genus Nitzschia still moving portions, the epilithon are the dominant
dominated the epiphyton attached to Nelumbo, but the primary producers. In Old Woman Creek, the creek
species included N. palea, which was not as prevalent bed was dominated by the diatom Gomphonema
in the early 1980s and N. filiformis, which was also a olivaceum in the late winter and early spring. With
dominant in the earlier studies. The very high increasing light levels and water temperatures, the
variability between replicates in the 1999 study green algae Cladophora glomerata became the
suggested that environmental factors and not specific dominant species, primarily due to its size—
interactions between the host macrophyte and the numerically it was never a major component of the
epiphyton seem to regulate the species abundance and population, but the large cell size of this algae made it
diversity in the epiphyton. Reed reported that there was the dominant in biomass. Attached to this algae was
a significant relationship between the sites and the an epiphytic flora that was dominated by diatoms,
populations in July and August of 1983 and July and particularly Rhocosphenia abbreviata and Cocconeis
August of 1999, suggesting that similar conditions placentula.
resulted in similar populations. However, the
populations from June 1983 were not similar to any
other populations in either 1983 or 1999. The cause of
PRIMARY PRODUCTIVITY IN THE ESTUARY
this dissimilarity is not known. In June, just south of In a freshwater wetland system, the
U.S. Route 6 and just south of the railroad phytoplankton is frequently considered a minor
Thalassiosira pseudonana, a brackish water species component of the wetland system, if considered at all
that has become common in Lake Erie, dominated the (Mitsch and Gosselink 1993). In two earlier data
flora. Klarer (1981) studied the epiphyton attached to syntheses on the coastal wetlands of Lake St. Clair
Nelumbo stems, both the dead stems of the previous (Herdendorf et al. 1986) and the coastal marshes of
year and the growing stems of the present year during western Lake Erie (Herdendorf 1987) the
1980. The dead stems remained standing through the phytoplankton were considered a significant, but not
mid-spring. During this early spring period, the diatoms dominant, source of organic carbon. Phytoplankton can
Gomphonema olivaceum and Diatoma elongatum and have a major impact on the food web of the estuary—
the green algae Stigeoclonium sp. dominated the whether the food web is grazer-based or detrital-based
populations growing on the dead stems. As with the (Wetzel 1983,1992). As reported by Reeder (1990),
earlier study by Millie and Klarer (1980), during the the primary source of autotrophic carbon in the Old
June period, the diatoms Gomphonema parvulum and Woman Creek estuary was the phytoplankton. This
Nitzschia species dominated the epiphyton. As the would suggest a grazer-based food web. The method
water temperatures approached summer maximum used by Reeder to determine macrophyte
levels, the green algae Stigeoclonium was replaced by productivity—above ground harvest—tends to
Oedogonium sp. and Spirogyra sp. The blue-green underestimate the net productivity of Nelumbo due to
algae Phormidium sp. also became common with the propensity of these rhizomatous perennials to
7-22
CHAPTER 7. ECOLOGY
translocate a significant part of the photosynthate to from the atmosphere; thus, oxygen levels drop to very
the underground root-rhizome system (Francko and low levels with minimal concentrations occurring just
Whyte 1999). Francko and Whyte (1999), in a later prior to sunrise. At night, respiration releases free
study of Old Woman Creek estuary, concluded that the carbon dioxide back into the water faster than it can
macrophytes were the dominant producers in the diffuse into the atmosphere, thus lowering the pH.
estuary; thus, the food web would be detrital based.
Although these two studies seem to contradict each Data logger data also emphasize the importance
other, it is very likely that each is appropriate for the of storm events in the ecology of the estuary. Figure
particular year being studied. Macrophytes fix more 7-19 is a series of graphs of the data collected over a
carbon per unit area, on the order of 5 to 10 times more two-week period in late August to early September
carbon (Francko and Whyte 1999); so, the relative 1998 from a site in the upper estuary. A storm on August
importance of the two producers is dependent upon 25, 1998 resulted in the influx of storm water, as
the percentage of macrophyte cover (Table 7.1). demonstrated by a rise in water level. This rise
corresponds to both an increase in turbidity and a drop
From the late 1970s through the late 1980s, the in specific conductivity. The dampening of the oxygen
estuary was most likely phytoplankton dominated; but and pH diurnal variations after the passage of the storm
from the early 1990s through 2001, macrophytes were (August 27 to September 1) suggests that the storm
dominant. When considering the food available for the water washed away existing phytoplankton
next level in the food web, production measurements populations. About one week after the storm, the
of Nelumbo—or any other aquatic macrophyte that has previous diurnal variations in both of these parameters
an extensive perennial underground rhizome or root returned, suggesting the re-growth of phytoplankton
system—must consider that a portion of the production in the upper estuary.
will be translocated into the root/rhizome system and
thus will be unavailable to the next food web level. PHYTOPLANKTON—ZOOPLANKTON INTERACTION
Although Reeder’s (1990) macrophyte production rates
underestimated the available food produced because Havens (1991c) examined the role of zooplankton
his method could not account for leaf fall prior to in the food web and energy flow in Old Woman Creek
harvesting, Francko and Whyte’s (1999) macrophyte estuary. His work supports Reeder’s contention of the
production rates probably overestimated the food importance of the phytoplankton in the estuary.
available for the next level for the reason that an Zooplankton community filtration rates here were
unknown portion of the macrophyte production was among the highest reported in the literature with
transferred to the underground rhizome where it was herbivores filtering up to 73% of the water column
unavailable for consumption by the next level of the per hour. Despite this high rate there was no “clear
food web. water” period observed in the estuary. This was
attributed to the very high algal productivity due to
The hypertrophic nature of the estuary is readily continual internal and external nutrient loading through
demonstrated with data obtained from the data loggers. the sampling period. These rapid rates also indicated a
The diurnal changes in oxygen and pH in the estuary rapid energy flow from the phytoplankton to the
(Figure 7.18) are characteristic of a system where zooplankton. In May and June, nauplii and small
production is very high. During the daylight hours, cladocerans dominated zooplankton filtration activity,
oxygen levels in the water rise because high primary but by July rotifers had become the dominant group.
productivity produces oxygen at a greater amount than They maintained this dominance through August. In
respiration can take it up, or it can diffuse into the September the rotifers and small cladocerans were co-
atmosphere. At the same time, free carbon dioxide in dominant. Through the summer and into the autumn,
the water is taken up by the primary producers faster rotifers and the smaller cladocerans dominated the
than it can be replaced by respiration and diffusion zooplankton filtration activity.
from the atmosphere, which causes the pH of the water
to rise. At night, respiration reverses the trend because
photosynthesis has ceased. Oxygen is taken up from
the water faster than it can be replaced by diffusion
7-23
Figure 7.18. Diurnal changes in oxygen (percent saturation) and pH in lower Old Woman Creek estuary.
7-24
CHAPTER 7. ECOLOGY
Figure 7.19. Impact of storm runoff on upper Old Woman Creek estuary during a two week period in late summer 1998.
NOTE: Upper graph—temperature (left vertical scale) and specific conductivity (right vertical scale); middle graph—
dissolved oxygen (left vertical scale) and pH (right vertical scale); and lower graph—turbidity (left vertical
scale) and water level (right vertical scale), water depth increases toward bottom of graph.
7-25
INVERTEBRATE ECOLOGY estuary have previously been described as “pioneer

species”—species that have rapid reproduction rates
OF THE ESTUARY
and can quickly repopulate an area (Hanazato and
Freshwater invertebrates are ubiquitous and often Yasuno 1990, Ferrari et al. 1984; as cited in Havens
abundant members of the benthic, planktonic, 1991d). The dominance of these species of rotifers and
periphytonic, and neustonic communities of Great small cladocerans supports the hypothesis that the
Lakes estuaries and coastal wetlands. They serve an estuary is a storm driven system. The predominance
important role in the transfer of energy and materials of flagellates and small diatoms in the phytoplankton
in these habitats and also provide a major food resource in the estuary should favor the dominance by the larger
for fish and waterfowl (Krieger 1992). Despite their cladocerans, but the larger cladocerans do not have a
apparent importance, comparatively little is known of rapid reproduction rate and so frequent flushing
the distribution and ecology of invertebrates in Great denudes the estuary of these organisms. Although the
Lakes estuaries. However, in recent years a number of storms and other physical forces are critical in
studies have been initiated at Old Woman Creek estuary determining the composition of the zooplankton in the
which address the zooplankton and zoobenthos in a estuary, there appears to be biological interactions also
coastal wetland, including Miller (1982), Havens affecting zooplankton distribution. There were greater
(1991a,b,c,d), Kepner and Pratt (1993,1996), Klarer numbers of the small cladocerans in the vegetated areas
(1989), Krieger (1985,1992), and Krieger and Klarer than in the open water areas. Havens (1993) clearly
(1991,1992,1995). Terrestrial invertebrates in the Old demonstrated the importance of fish predation in
Woman Creek watershed have received even less determining this distributional pattern.
attention, with only three studies of limited scope, Gray
et al. (1997), Phillips (1998), and Phillips and Nemire Community Structure
(1999). The following discussion of invertebrates in
The zooplankton community of Old Woman
the estuary and watershed is based on the results of
Creek estuary was compared with that of the nearshore
these investigations and several specialized studies by
(wave zone) of Lake Erie adjacent to the mouth of the
Bur et al. (1986), Bur and Klarer (1991), Ingold et al.
estuary by Krieger (1985). He found that the crustacean
(1984), and Miller et al. (1984).
zooplankton communities were distinctly different both
in species composition and density between the upper
ZOOPLANKTON estuary and the lake (Table 7.4). Old Woman Creek
While some zooplankters exhibit active estuary is dominated by two cyclopoid copepods
swimming movements that aid in maintaining vertical (Acanthocyclops vernalis and Tropocyclops prasinus
position, as a whole, plankton tends to settle and most mexicaus), a calanoid copepod (Skistodiaptomus
plankters are unable to move against a current. As pallidus), and two cladocerans (Diaphanosoma birgei
animals, zooplankton are not primary producers and and Moina micrura), whereas nearshore Lake Erie is
are either herbivores (phytoplankton feeders), characterized by a cyclopoid copepod (Diacyclops
carnivores (zooplankton feeders), or omnivores thomasi), a calanoid copepod (Eurytemora affinis), and
(phytoplankton and zooplankton feeders). Excluding bosminid and daphnid cladocerans (Bosmina
protozoans, which have been discussed earlier in this longirostris, Daphnia galeata mendotae, and D.
volume (Chapter 6), there are three major groups of retrocurva). The lower estuary represents an ecotone
zooplankton capable of some degree of locomotion: (Odum 1971), in that it possesses a zooplankton
the rotifers, and two microcrustacean forms community intermediate between the lake and the
(cladocerans and copepods). Rotifers are classified as upper estuary. Of 40 crustacean zooplankton species
a distinct phylum (Rotifera), while the other two groups identified in the lake and estuary, only 18 were found
are in the phylum Arthropoda, class Crustacea, and in both the lake and estuary (Krieger 1992).
subclasses Brachiopoda (cladocerans) and Copepoda
The difference in zooplankton communities is
(copepods).
also manifested in terms of the timing of life cycles.
Zooplankton in the estuary are dominated by During early summer Acanthocyclops vernalis and
small cladocerans and rotifers for much of the year. Diacyclops thomasi are the dominant adult copepods
Many of the most important rotifer species in the in the estuary, and the most abundant cladocerans are
7-26
CHAPTER 7. ECOLOGY
TABLE 7.4. MAXIMUM ABUNDANCE OF CRUSTACEAN ZOOPLANKTON SPECIES

IN OLD WOMAN CREEK ESTUARY AND ADJACENT LAKE ERIE
Individuals Per Liter
Upper Lower Nearshore
Estuary Estuary Lake Erie
CYCLOPOID COPEPODS
Acanthocyclops vernalis 44.4 67.0 21.7
Cyclops varicans rubellus 4.1 0.8 0.4
Diacyclops thomasi 7.0 125.5 31.0
Mesocyclops edax 1.2 2.5 8.9
Tropocyclops prasinus mexicanus 4.6 2.5 2.1
CALANOID COPEPODS
Diaptomidae (immature copepodids) 47.3 48.0 23.0
Eurytemora affinis 0.6 2.6 17.1
Leptodiaptomus ashlandi 0.3 1.4 1.3
Leptodiaptomus minutus – 0.3 0.4
Leptodiaptomus sicilis – 0.2 0.6
Leptodiaptomus siciloides 0.3 0.7 0.6
Skistodiaptomus oregonensis 0.1 0.7 1.8
Skistodiaptomus pallidus 9.8 8.8 –
CLADOCERANS
Alona quadrangularis – – 1.1
Alonella setulosa – – 1.4
Bosminidae spp. (mucronate) 19.7 54.6 76.5
Ceriodaphnia recticulata – 0.3 –
Chydorus sp. 1.6 1.3 12.4
Daphnia galeata mendotae 0.7 1.1 20.7
Daphnia parvula 0.4 – –
Daphnia retrocurva 1.6 1.0 15.8
Diaphanosoma birgei 19.7 20.9 2.8
Eubosmina coregoni 1.4 2.9 10.5
Ilyocryptus sordidus 0.4 – 0.5
Moina micrura 21.5 9.6 –
Pleuroxus denticulatus 0.4 0.6 –
Scapholeberis mucronata – 0.4
Data Sources: Krieger (1985); Krieger and Klarer (1991)
7-27
Moina micrura and several species in the family Havens (1991a, l991d) examined the rotifers in
Bosminidae. By late summer the earlier dominant Old Woman Creek estuary in 1990. He also found
species decline and the cladoceran Diaphanosoma marked dissimilarities between the estuary and the
birgei becomes dominant in the estuary. In the wave adjacent Lake Erie. Total population numbers were 2
zone of Lake Erie off the estuary mouth, the early to 3 times greater in the estuary than in the lake. Within
summer dominants also include Diacyclops thomasi the estuary, rotifers were the most abundant group from
and bosminid species, but Diaphanosoma birgei does early July through mid-September; while in the
not become abundant. Bosminids, including Bosmina adjacent lake, they assumed numerical dominance only
longirostris, attain by far the greatest abundance of all for a brief period in late July and early August. The
the cladocerans in the wave zone and the lower estuary most common rotifers in the estuary included
(Krieger (1992). Haven (1991a) found a numerical Polyarthra remata, Brachionus angularis, B.
dominance by rotifers and nauplii in May when the bidentata, B. calyciflorus, and the predatory
estuary mouth was open to Lake Erie, but cladocerans Asplanchna sp. The most common rotifers in the
and nauplii were the most numerous in June after the nearshore lake were Keratella cochlearis cochlearis
mouth was closed by a sand barrier beach. Krieger and Synchaeta kitina.
(1985) noted that the periods when males and ovigerous
females crustacean zooplankters were present, the egg ZOOBENTHOS
ratios were greater in the estuary. This indicates that
secondary productivity is higher in the estuary than in Zoobenthos are those animals living in or on the
the nearshore waters of Lake Erie. He also concluded bed of a water body, be it stream, estuary, or lake
that depending on the number, timing, and severity of (Figure 7.20). Two related groups of animals are the
storm runoff events through the estuary, the seasonal periphytic invertebrates, which live on the submerged
abundances of zooplankters can be strongly reduced surfaces of aquatic plants, and the neuston, the
by flushing out the estuary. community of small animals such as water striders that
Figure 7.20. Life positions of macrobenthos in Old Woman Creek estuary (from Fisher 1982).
NOTE: AMP–amphipods; CHR–chironomids, TO–tubificid oligochaetes; UC–unionid clams
7-28
CHAPTER 7. ECOLOGY
TABLE 7.5. CLASSIFICATION OF BENTHIC INVERTEBRATES OF OLD WOMAN CREEK

ESTUARY AND WATERSHED AND THE ADJACENT NEARSHORE WATERS OF LAKE ERIE
KINGDOM PROTISTA (PROTOZOA) PHYLUM ANNELIDA

Class Hirudinea (leeches)
PHYLUM SARCOMASTIGOPHORA Class Oligochaeta (segmented worms)
Subphylum Mastigophora PHYLUM ARTHROPODA
Class Dinoflagellata Class Arachnida (spiders & water mites)
Class Phytomastigophora Class Crustacea
Class Euglenea Subclass Branchiopoda
Class Zoomastigophora Order Cladocera (water fleas)
Subphylum Sarcodina Subclass Ostracoda (seed shrimp)
Class Lobosa Subclass Copepoda (water-hoppers)
Class Filosa Order Harpacticoida
Class Granuloreticulosa Order Cyclopoida
Class Heliozoa Subclass Branchiura (fish lice)
PHYLUM CILIOPHORA Subclass Malacostraca
Class Kinetofragminophora Order Isopoda (sow bugs)
Class Oligohymenophora Order Amphipoda (scuds)
Class Polyhymenophora Order Decapoda (crayfishes)
Class Insecta
Order Collembola (springtails)
KINGDOM ANIMALIA Order Ephemeroptera (mayflies)
PHYLUM PORIFERA Order Odonata (damselflies & dragonflies)
Class Demospongiae (horny sponges) Order Plecoptera (stoneflies)
PHYLUM CNIDARIA Order Hemiptera (true bugs)
Class Hydozoa (hydras) Order Neuroptera (nerve-wing insects)
PHYLUM PLATYHELMINTHES Order Coleoptera (beetles)
Class Turbellaria (flatworms) Order Diptera (true flies)
PHYLUM GASTROTRICHA Order Trichoptera (caddisflies)
PHYLUM ROTIFERA (rotifers) Order Leptopitera (butterflies & moths)
PHYLUM NEMATODA (roundworms) PHYLUM TARDIGRADA (water bears)
PHYLUM MOLLUSCA PHYLUM BRYOZOA (bryozoans)
Class Gastropoda (snails)
Class Bivalvia (clams)
live in association with the surface film of water bodies. Community Structure and Species Richness
Because the benthic invertebrate community represents Altogether 144 taxa of benthic invertebrates
a major food resource for fishes, impacts the plankton (Table 7.5) were identified from Ekman dredge and
community through various feeding activities, 7.5 cm diameter core samples of sediment obtained
participates in the decompositional pathways, and in throughout the estuary as well as from leaves, stems
turn is influenced by the presence of hydrophyte beds, and tubers of aquatic plants. Samples were taken
this community is a major link in the overall ecology approximately every two months for a period of one
of the Old Woman Creek estuary. A zoobenthos study year. Of the nine phyla found in the estuary, 38% were
was undertaken by Krieger and Klarer (1992,1995) insects, 22% were crustaceans, and 20% were
with two objectives: (1) to determine the relative oligochaete worms. The number of taxa found in
species richness of benthic and periphytic invertebrates samples taken within the American lotus beds
in open water and in aquatic plant beds within the (Nelumbo lutea) exceeded the number of taxa present
estuary and (2) to compare the benthic community of in open water samples by about 1.5 times at the end of
the estuary with that of the upland creek and the the growing season. Invertebrate densities on lotus
adjacent nearshore of Lake Erie. The results of their stems were somewhat less than 20,000 individuals/m2,
investigations are summarized in the following whereas sediments typically had 100,000 or more
sections. individuals/m2.
7-29
The most widespread species was the naidid below the surface film and feed on decaying leaves
worm Nais variabilis, which was found both in the and other vegetation. The epiphytic invertebrate
sediment and on lotus plants. Immature tubificid worms community living on a lotus stem in October consisted
were widespread throughout the estuary sediments, but of six taxa: the chironomid larvae Glyptotendipes sp.
were not found on plant surfaces. Although never (9,944/m2) and Cricotopus sp. (5,136/m2); naidid
abundant, turbellarian flatworms were widespread in oligochaetes Nais variabilis (1,964/m2), Nais pardalis
the sediments and on plants. The overwintering stage (927/m2), and Dero nivea (55/m2); and ceratopogonid
of bryozoans (statoblast) was very abundant in many fly larvae (55/m2).
samples as was the ephippium capsule of cladocerans.
Seasonally, the neuston comprises a highly
The cladoceran Ilyocryptus sordidus was widely
visible component of the Old Woman Creek estuary
distributed and abundant during the fall and spring,
invertebrate fauna. Krieger and Klarer (1992) found
but infrequent in the winter. Nematode roundworms
large aggregations of gyrinid and hydrophylid beetles,
were found in most habitats, at times in considerable
as well as corixid water boatmen, in the late summer
abundance.
and autumn.
Among the insects, ceratopogonid flies were the Because of seasonal life cycles, several benthic
most widespread in sediments, but not usually very taxa are only present or especially abundant during a
abundant. The chironomid Glyptotendipes sp. occurred particular season. Among the oligochaete worms,
in sediments and on plants, but only in the fall and several species of Pristina were found only in the fall,
winter; whereas, Tanytarsus sp. was widespread in whereas two species of Vejdovskyella were present only
sediments mainly in the winter and spring. Corixid in the spring. Likewise, leeches were only collected in
water boatmen were common in all habitats during the the fall and tardigrade water bears were only abundant
summer and fall, but absent in winter and spring. during the winter and spring. Some midges were also
Dragonfly and damselfly nymphs were found seasonal: Dicrotendipes sp. was found only in the fall,
throughout the estuary, but in low numbers. Young Glyptotendipes sp. in the fall and winter, and
nymphs of capniid stoneflies were particularly Hydrobaenus sp. in the winter.
common in the open water sediments and in the flooded
creek channel comprising the upstream end of the On an annual basis, the benthic community of
estuary. Old Woman Creek estuary is dominated numerically
by nematodes, tubificid and naidid worms, tardigrades,
Other relatively common taxa that were restricted ceratopogonids, cladocerans (particularly Ilyocryptus
entirely or primarily to particular benthic habitats sordidus), and chironomids. Overall, the plant beds
include all the snails—with the exception of the large contained a greater species richness than the open water
Japanese snail (Cipangopaludina japonica) which areas. Essentially, the sediment within the plant beds
always associate with aquatic plants. Only two live contained almost all of the taxa found in the open water
zebra mussels (Dreissena polymorpha) were collected, sediment as well as several species associated
one in a sediment sample and the other on a lotus leaf, specifically with hydrophytes.
and only in the fall. Krieger and Klarer (1992)
speculated that this may indicate that they do not Comparison of Estuary, Creek, and Lake
survive over winter in the shallow habitat of the estuary. Communities
Unionid clams, although widespread, were sparse and
restricted to the sediments. Krieger and Klarer (1992) concluded that the
benthic community of Old Woman Creek estuary is
Three relatively rare insects, the microcaddisfly distinct from the benthic communities of the upland
Agraylea sp. and two beetle larvae (a chrysomelid and creek and adjacent Lake Erie. They found the presence
a scirtid), were found only in the sediments of lotus of an ecotone (a narrow and fairly sharply defined
beds. These taxa typically live on or near vascular transition zone between two communities) at the upper
hydrophytes. Agraylea feeds on attached filamentous end of the estuary where the zone is restricted to the
algae; chrysomelid larvae pierce the lotus plant to flooded Old Woman Creek channel. In this channel
obtain air directly from the inside air spaces (lacunae); the larvae of the riffle beetle Dubiraphis sp., which
and scirtid marsh beetle larvae typically remain just was characteristic of the upland creek bed, were present
7-30
CHAPTER 7. ECOLOGY
throughout the year in relatively small numbers, variations never reached limits to survival and
whereas, these larvae were essentially absent in the reproduction of the major invertebrates in the open
remainder of the estuary. Likewise the early instars of estuary. Strong water currents during periods of storm
capniid stoneflies were frequent in the upstream pools runoff, however, may be responsible for the ecotonal
and the flooded upper channel of the estuary, but were nature of the flooded creek channel comprising the
rare elsewhere in the estuary. Ilyocryptus sordidus, upper end of the estuary. Under these conditions,
which was dominant in the open estuary, was present invertebrates are most likely washed from their typical
in low numbers in the upper end of the estuary and stream habitats and deposited downstream where the
was usually absent in the upland creek bed. water velocity is lower.
Correspondingly, the nearshore wave zone of The interactions of the many benthic invertebrate
Lake Erie along the barrier beach at the mouth of Old taxa with each other and the vertebrates, aquatic plants,
Woman Creek estuary possesses a distinct and decompositional communities constitute an
macroinvertebrate community. Here, the shifting sands important aspect of the Old Woman Creek estuary
create a harsh environment resulting in a smaller ecology. Knowledge of the seasonal distribution and
abundance of the same groups which dominate the abundance of these taxa is an essential foundation for
more offshore, less sandy, softer sediments of the understanding these interactions. The study by Krieger
nearshore zone of the lake. The dominant members of and Klarer (1992) suggests that a complex food web
the lake community include the tubificid oligochaetes, exists in the estuary. However, few benthic
especially Limnodrillus spp.; chironomid larvae, invertebrates appear highly specialized in their food
primarily Procladius sp., Chironomus spp., and habits. Most carnivores feed on a variety of prey,
Cryptochironomus sp.; sphaeriidae clams; ostracods; detritivores often ingest microinvertebrates and algae
and nematodes. Each of these taxa were at least along with detritus, and many invertebrate “scrapers”
occasionally found in the estuary, except sphaeriidae and “grazers” are omnivores, nonselectively ingesting
clams which were absent. whatever is present on the substrate and unable to
escape. Table 7.6 lists the trophic categories of the
Ecological and Tropic Interactions major benthic invertebrates identified from Old Woman
Creek estuary. Unfortunately, knowledge of
Krieger and Klarer (1992) also tested the
invertebrate energetics and materials cycling in Great
hypothesis that differences in the benthic invertebrate
Lakes estuaries and coastal wetlands is limited and
community were the result of differences in water depth
determining the exact pathways of energy and material
and thus the frequency of subaerial exposure of the
flow through the food web of Old Woman Creek
estuary bed (i.e. water level lowered to the point where
estuary can only be ascertained by further observations.
sediments were exposed to the air). Their study showed
no evidence of differences in community structure
along the depth gradient in the estuary, even though
FISH AND REPTILE ECOLOGY
some of the sampling sites were exposed up to 31% of OF THE ESTUARY
the time. However, during these periods of dewatering
FISH COMMUNITY
the sediments appeared to remain moist. Despite
occasional freezing at the sediment surface in winter, The diversity of species present in Old Woman
the invertebrate community apparently survived the Creek reflects typical fish populations of estuarine
conditions without demonstrable effect. The areas along Lake Erie’s southern shore. The importance
investigators speculated that the invertebrate of these coastal areas for the production of commercial,
community may have been adversely affected by recreational, and forage fishes has been documented
exposure, but recovery via recolonization or hatching by Trautman (1957,1981) and Hartman (1973). About
of eggs or cysts may have been too rapid to be detected. 40 species of Lake Erie fish need “marsh-like” habitat
to spawn and raise young (Johnson 1989). Hoffman
Also, physical and chemical differences in the (1985) found that the large numbers of young of the
water column and sediments appear to have little year (YOY) and juvenile fishes captured in the estuary
influence on the benthic community structure in the with test nets reflect the importance of the Old Woman
broad expanse of the estuary; physiochemical Creek estuary as a nursery and spawning area.
7-31
7-32
TABLE 7.6. TROPHIC CATEGORIES OF BENTHIC INVERTEBRATES FOUND IN OLD WOMAN CREEK ESTUARY
Carnivores Detritivores Herbivores Omnivores Parasites
Ciliophora Oligochaeta: Nais Ciliophora Rotifera Dtera: Parachironomus

Turbellaria Tubificdae Naididae Bryozoa Hirudiea: Helobdella &
Naididae:Chaetogaster Hirudinea: Glossiphoniidae Tubificidae Coleoptera: Plaobdella
Hirudinea: Glossiphoniidae Turbellaria Bryozoa Elmidae Hdrachnidia larvae
Bryozoa Bryozoa Nematoda Hydrophillidae: Tropisternus
Nematoda Nematoda Rotifera Scirtidae: Cyphon
Rotifera: Asplanchna Coleoptera: Tardigrada Diptera:
Coleptera: Scirtidae: Cyphon Coleoptera: Ephydridae
Dytiscidae Hydrophilidae: Helophorus Chrysomelidae Chironomidae:
Gyrinidae Halipiidae: Peltodytes adults Hydrophillidae: Loccobius & Chironomus
Tropisternus larvae Diptera: Tropisternus adults Cladoplema
Halipiidae: Peltodytes adults Ephydridae Scirtidae: Cyphon Dicrotendipes
Diptera: Tipulidae Halipiidae: Peltodytes adults Endochironomus
Ceratopogonidae Chironomidae: Diptera: Glyptotendipes
Chaoboridae Chironomus Ephydridae Parachironomus
Ephydridae Endochironomus Tipulidae Polypedilum
Chironomidae: Glyptotendipes Chironomidae: Stictochironomus
Cryptochironomus Polypedilim Endochironomus Tribelos

Parachironomus Stictochironomus Glyptotendipes Tanytarsini
Polypedilum Tribelos Corixidae: Sigara Hydrobaenus
Coelotanypus Plecoptera: Capniidae Trichoptera: Agraylea Procladius
Procladius Amphipoda Tanypus
Tanypus Cladocera: Chydoridae & Heterotrissocladius?
Hemiptera: Belostoma Macrothricidae Ephemeroptera
Corixidae: Trichocorixa Copepoda: Cyclopoida & Corixidae:
Neuroptera: Sialis Harpacticoida young Trichocorixa
Odonata Isopoda Sigara
Copepoda: Cyclopoida Ostracoda Trichoptera, Agraylea
Hydrachnidia: Gastropoda Amphipoda
deutonymphs, adults Bivalvia Cladocera
Copepoda: Calanoida,
Cyclopoida &
Harpacticoida?
Isopoda
Ostracoda
Gastropoda
Bivalvia
Data Sources: Balcer et al. (1984), Merritt and Cummins (1984), Pennak (1989), Thorp and Covich (1991), Krieger and Klarer (1992)
CHAPTER 7. ECOLOGY
Environmental changes, both natural and man- coast and are so readily destroyed or degraded, that
made have resulted in changes in fish species controlled marshes may represent the last high quality
occurrence over the past decade. Siltation, turbidity, coastal marsh resource remaining on the lake. Thus,
wave action, changing water levels, toxic substances, the fate of northern pike, and other species sensitive to
and increased development have all contributed to the environmental changes is tenuous. From 1970-1980,
demise of coastal marshes along Lake Erie (Raphael 327 black bullheads and 45 brown bullheads were
and Jaworski 1978). Likewise, Old Woman Creek has captured in fyke nets set by the Division of Wildlife.
experienced some of these changes—particularly Sampling conducted in Old Woman Creek by Thibault
during high water years—which were especially (1985) in 1983 and 1984 shows a complete reversal in
detrimental to emergent plants. Agricultural activities the species ratio, with 111 brown bullheads captured
throughout the watershed and removal of upland forests and only 10 black bullheads recorded. Trautman (1981)
have contributed to the increased turbidity and siltation found that black bullhead tend to use small, silty
in streams, resulting in unfavorable conditions for impoundments, while brown bullhead tend to prefer
fishes that require clear water and clean sand or gravel deeper waters similar to those of the Ohio River and
substrates for spawning (Trautman l957). western Lake Erie. Old Woman Creek does not follow
this trend. The shallow, heavily silted, turbid waters of
Northern pike populations of Old Woman Creek the estuary appear to favor the brown bullhead. Perhaps
in the 1950s were productive enough to permit the Ohio the estuary’s close proximity to Lake Erie and seasonal
Division of Wildlife to remove some for stocking in access may have permitted the brown bullhead to
other areas of Ohio. Old Woman Creek was reportedly establish an abundant resident population.
one of the most productive fishing spots for crappie
and largemouth bass as well as northern pike along The orangespotted sunfish was first taken in the
Lake Erie (Miller 1957). Although the more tolerant tributaries of the Sandusky Bay in 1948 (Trautman
crappie and largemouth bass still are quite numerous, 1981b). This invader from the west is becoming
few northern pike have been captured in recent times. abundant in the marshes and small streams of southern
Seining has produced no northern pike. However, Lake Erie due to their tolerance to high silt and
electroshocking in the 1984 season produced two turbidity. The first record for orangespotted sunfish in
juvenile pike, and one adult was captured in a gill net. Old Woman Creek was in 1981, and this species of
sunfish has been captured in each successive year.
Ohio Division of Wildlife surveys from 1970- Numbers have increased, and the orangespot is now
1980 recorded 4 pike captured in fyke nets set in Old very common in the estuary (Hoffman 1985). Another
Woman Creek. Although the entire Lake Erie northern invading species, the white perch, was first captured
pike population is low (Trautman 1981b), the only in Old Woman Creek estuary in July, 1980.
obvious reason for such a drastic decline in abundance Considerable numbers were recorded at the mouth of
over 30 years seems to be loss of appropriate habitat. the estuary in the company of white bass during
Old Woman Creek was historically in the “prairie” type spawning months. YOY and 1st year white perch were
marshlands of Ohio, and its once heavily vegetated numerous in late summer months. Trautman (1981)
waters offered ideal spawning and rearing habitat that suggests that new invaders first become overly
attracted great numbers of pike during their early spring abundant, then experience a decline as the species
spawning runs. The pike is not the only species of fish becomes a part of the resident fish fauna.
to succumb to habitat changes in Old Woman Creek.
Hoffman (1985) reported abundant populations of The gizzard shad is an important forage fish in
bowfin, smallmouth bass, buffalofish, longnose gar, Lake Erie (Bodola 1966). The shad, while playing an
and Northern fathead minnows. Recent sampling has important role as food for many sport and commercial
not produced any buffalofish and very few gar, bowfin species, grows to a large size so rapidly that they
and fathead minnows. The low numbers of these become unusable to predators (Scott and Crossman
species suggest some type of environmental change 1973). Gizzard shad captured from 1981-1984 in Old
not favorable to these species. Woman Creek were about 95% YOY and 1st year class
fishes (Hoffman 1985, Thibalt 1985). The protected,
Johnson (1989) suggested that natural wetlands shallow waters of the estuary and the abundance of
cover such a relatively small area along the Lake Erie
7-33
phytoplankton and algae offer a nursery situation which Thibault (1985) found that the estuary of Old
is very favorable for shad. Gizzard shad in the larval Woman Creek appears to have a fish fauna of its own
and juvenile stages make up the largest percentage of and is probably an established environment for a
the diet in piscivorous fishes in Old Woman Creek number of species of fish. A gradient in environments
estuary. During the time immediately following a major sustains a gradient in fish species varying from more
storm event large numbers of shad are killed and are open water (lacustrine) to more flowing water (riverine)
carried out into the lake. Researchers have noted on forms. Traditional Lake Erie fishes of commercial
several occasions that during these times, predatory importance frequent the estuary erratically and are not
fish such as the white bass, and several species of gulls a significant component of the fauna. However, these
congregate offshore to feed (Hoffman 1985). fishes episodically reproduce in the estuary or use it
for a nursery.
Little is known about the effects of the shifting
barrier beach at the mouth of the estuary on Thoma (1999) concluded that Old Woman Creek
anadromous species such as trouts and salmons. estuary was severely impacted by sedimentation from
Continued monitoring may show whether seasonal the watershed, especially that resulting from highway
opening and closing of the estuary mouth hampers fish construction. He found that the estuary was
attempts to enter spawning habitat. In nearby Cranberry characterized by a fish community of pollution-tolerant
Creek, where the mouth remains open year around, taxa and non-indigenous species. The low density of
steelhead trout and coho salmon are frequently caught the fish community was in contrast to the historic fish
by sport fishermen during spring spawning runs communities which contained significant populations
(Hoffman 1985). of northern pike, largemouth bass, other sunfish, and
native minnows.
Figure 7.21. Aquatic food chain in Old Woman Creek estuary (ODNR).
7-34
CHAPTER 7. ECOLOGY
SNAPPING TURTLES Research Reserve (Figure 7.22). His model emphasizes

the importance of sediment–water interactions owing
The snapping turtle (Chelydra serpentina) is the
to the shallowness of the estuary. Microbial activity in
largest freshwater turtle in the Great Lakes region,
the water column, at the sediment–water interface, and
growing to lengths of over 70 cm (average shell 28 cm
within the sediment is considered intense because of
long) and weights of more than 20 kg (average 5 to 16
the high temperatures resulting from the shallowness.
kg). Conant and Collins (1991) describe them as “ugly
The water column is treated without vertical structure
both in appearance and disposition.” They have a large
because complete mixing is frequent, providing
head, heavy neck, stout legs, and a long, saw-toothed
sediment resuspension and wide diurnal variations in
tail that are not covered by the rough, dark brown
dissolved oxygen at the sediment surface (Figure 5.13).
carapace (upper shell). The small, cross-shaped
plastron (lower shell) allows free action of the legs The model is designed to represent the estuary
and head, and is dark brown to yellow in color (Morgan during a period of relatively low flow, as occurs after
1930). Snapping turtles inhabit permanent marshes and formation of the barrier beach. The model is also built
embayments of Lake Erie and its tributary streams. on the assumption that after formation of the barrier
Bernhardt (1985) reported them as common in Old beach biotic nutrient assimilation becomes
Woman Creek estuary, particularly south of Star Island. progressively more significant during the passage of
Of 21 specimens noted in his survey (82% females), incoming nutrients through the estuary wetlands;
the carapace length ranged from 18 to 40 cm, with although sedimentation may also represent a major sink
two individuals exceeding 15 kg in weight. One female for incoming nutrients. When the barrier beach is open
was extremely pale in color and had a length of 31 cm and flow through the wetlands occurs, nutrient loss
and a weight of 11 kg (Figure 1.7). from the water column is largely due to sorption on
sediment particles.
In addition to their aquatic habitat, snapping
turtles are commonly found on land near a water body Mitsch and Reeder (1991) and Mitsch (1992b)
or exploring adjoining fields (Morgan 1930). They developed a series of hierarchical models to simulate
rarely bask on logs as do most other freshwater turtles; ecological processes in Old Woman Creek estuary.
in shallow water they often burrow under the mud with Figure 7.23 shows a model of the estuary with details
only their eyes and nostrils showing (Conant and of some of the processes in a wetland which contribute
Collins 1991). However, snapping turtles are good to its nutrient retention capability. Plant uptake, both
swimmers, capable of covering 3 km in several hours by plankton and macrophytes, sedimentation, and
(Behler and King 1979). When catching food, the head resuspension are probably the most significant
darts forward, mouth often agape, and powerful jaws processes involved in the wetland retaining and
snap suddenly (Figure 7.21). Although their releasing phosphorus. This conceptual model was
movements are normally slow, the head can strike with developed into a simulation model based on knowledge
lightning speed. Snapping turtles are seldom ill- of the cycling of phosphorus and energy in wetland
tempered when encountered in the water, although on ecosystems. Unique to this wetland model is the
land they are aggressive and sometimes vicious. Their interaction of Lake Erie with the wetland. The model
musk-like odor is also offensive (Klots 1966). They was divided into three submodels for simulation
are omnivorous and seek food both night and day. Food purposes.
items include fish, reptiles, frogs, insects, crayfish,
ducklings, small mammals, carrion, and large quantities A hydrology submodel of the simulation model
of aquatic plants (Buck 1955). In winter, snapping is designed to depict the hydrologic budget of Old
turtles hibernate in the mud bottom of the estuary, Woman Creek wetland with the only stated variable
emerging from their retreats in April. for this submodel being the volume of water in the
estuary. Factors affecting the volume of water in the
marsh include rainfall, watershed inflow,
ECOLOGICAL MODELS evapotranspiration, and exchange with Lake Erie. The
Heath (1992) constructed a conceptual model of availability of inflow data, fairly good data on
nutrient dynamics for Old Woman Creek based on a evaporation, and knowledge of the hydrologic forcing
synthesis of research investigations conducted at the functions in the wetland allowed the development of
7-35
an accurate hydrologic budget and model. An important a as a calibration variable, the model and field data
part of the hydrodynamics is the timing of an ephemeral were found to be in agreement (within one standard
barrier beach on the wetland outflow. deviation) 78% of the time. Given the differences in
the two field measurements and the variability of
A primary productivity submodel includes the energy/chlorophyll ratios in aquatic systems
state variables macrophyte biomass and plankton (Vollenweider 1974), the model accurately predicted
biomass. These are both a function of sunlight, with seasonal patterns of productivity and biomass.
the major losses being respiration and sedimentation.
The productivity submodel is linked to the hydrology A phosphorus submodel was coupled with both
submodel in two ways. First, plankton are exported to the hydrology and primary productivity submodels and
Lake Erie when water from the wetland flows into the is incapable of running simulations without input from
lake and the beach is open. This assumption is these submodels. This submodel utilizes one
consistent with the field data. Second, macrophytes phosphorus storage in the waters of the wetland and
are assumed to be more abundant when water levels another in the sediments, with linear pathways between
are lower, and less abundant when water levels are the two. The phosphorus submodel includes a
higher. This is based on observations of other Lake sedimentation pathway as defined for shallow lakes
Erie coastal marshes (Herdendorf 1987). Field by Henderson-Sellers (1984) with an average settling
measurements of gross primary productivity as velocity of 0.03 m d-1. Calibration was done by varying
measured in Old Woman Creek estuary were in general the resuspension coefficient until the model predicted
agreement with model simulations. Using chlorophyll phosphorus concentration results similar to field data.
Figure 7.22. Conceptual model of nutrient dynamics in Old Woman Creek estuary.
NOTE: Nitrogen flux in solid arrows; phosphorous flux in open arrows; particulate quantities in boxes; dissolved
quantities unboxed; SUSP SED—suspended sediment; SEDS—sediments, aerobic sediments above dashed
line and anaerobic sediments below; water column above heavy solid line; MP—rooted macrophytes;
DETR—detritus; N–OXID—nitrogen oxidizing bacteria; DENIT—denitrifying bacteria (Heath 1992).
7-36
CHAPTER 7. ECOLOGY
Figure 7.23. Conceptual model of ecological processes in Old Woman Creek estuary (Mitsch and Reeder 1991).
Hydrology, productivity, and phosphorus field the rate for the remainder of the year, when very little
data enabled model calibration and preliminary allochthonous inflows are experienced, is around 10
estimations to be made of the role of phosphorus mg P m-2d-1. The simulated rates of sedimentation and
sedimentation and phosphorus resuspension in the resuspension translate to a total net sedimentation of
shallow estuary. Simulations show high levels of 0.8 g P m-2 for the 9-month study period. This contrasts
sedimentation in the early spring, with resuspension to an estimated annual retention of 5-7 g P m -2
exceeding sedimentation through the remainder of the predicted a few years earlier using a simple empirical
year. This excess of phosphorus resuspension over model (Mitsch 1989a). Because the model is based on
sedimentation in the model simulations is surprising the year 1988 which had a significant drought, the net
at first, but the productivity estimates throughout the sedimentation rate can be expected to be well below
year clearly illustrate that there is insufficient average. Thus, it is not unreasonable to suggest that
phosphorus in the inflow to support the high level of the model predicted less than 20% of normal
productivity and the generally high phosphorus sedimentation because the calibration year was a period
concentrations experienced in the wetland from May of extreme drought and the model was based on nine
through November. months instead of twelve. Subsequent simulations
(Mitsch and Reeder 1991) show that higher inflows
The model also predicts the total phosphorus for the same 9-month period lead to proportionately
sedimentation rate, including contributions from higher net retention of phosphorus, approximately 1.3
plankton and macrophytes. Sedimentation rates as high to 3.3 g P m-2, respectively, for normal and wet years.
as 40 mg P m-2d-1 are simulated for the spring, while
7-37

2nd Ed. Chapter 7 Ecology

Uploaded by

Copyright:

Available Formats

2nd Ed. Chapter 7 Ecology

Uploaded by

Document Information

Original Description:

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

2nd Ed. Chapter 7 Ecology

Uploaded by

Copyright:

Available Formats

American water lotus beds of Old Woman Creek estuary in 1888 (artist: Charles Courtney Curran).

Figure 7.1. Nelumbo beds in Old Woman Creek estuary

Zone 2–Floating-Leaved Macrophytes

Figure 7.2. Sago pondweed (Potomogeton

Also in this zone, Elodea canadensis (common

Another plant of this zone, the exotic

(spatterdock). Floating Lemna minor (duckweed) often

The structure of floating leaves is strikingly

The boundary layer between air and water is a

Zone 3–Emergent Macrophytes

Zone 4–Wet Meadow and Floodplain

During the period of Nelumbo dominance, this

TABLE 7.2. PERCENTAGE COVER

INVASIVE SPECIES estuary. In 1994, when no specimens were found in

storm’s passage to over four times pre-storm numbers;

Circumstantial evidence suggests that the

Figure 7.16. Total phytoplankton abundance in Old Woman Creek estuary

the presence of certain species such as Stephanodiscus EPIPELON

EPIPHYTON increasing water temperatures. In summary, the

INVERTEBRATE ECOLOGY estuary have previously been described as “pioneer

TABLE 7.4. MAXIMUM ABUNDANCE OF CRUSTACEAN ZOOPLANKTON SPECIES

Data Sources: Krieger (1985); Krieger and Klarer (1991)

TABLE 7.5. CLASSIFICATION OF BENTHIC INVERTEBRATES OF OLD WOMAN CREEK

KINGDOM PROTISTA (PROTOZOA) PHYLUM ANNELIDA

Carnivores Detritivores Herbivores Omnivores Parasites

Ciliophora Oligochaeta: Nais Ciliophora Rotifera Dtera: Parachironomus

Cryptochironomus Polypedilim Endochironomus Tribelos

SNAPPING TURTLES Research Reserve (Figure 7.22). His model emphasizes

You might also like