1248 Notes

VON ELERT, E., AND P. STAMPFL. 2000. Food quality for Eudiap- , C. KITAJIMA, AND S. FUJITA. 1983b. Nutritional values of
tomus gracilis: The importance of particular highly unsaturated live organism used in Japan for mass propagation of fish: A
fatty acids. Freshw. Biol. 45: 189–200. review. Aquaculture 34: 115–143.
WACKER, A., AND E. VON ELERT. 2001. Polyunsaturated fatty acids: WORM, J., AND M. SONDERGAARD. 1998. Dynamics of heterotrophic
Evidence for non-substitutable biochemical resources in Daph- bacteria attached to Microcystis spp. (Cyanobacteria). Aquat.
nia galeata. Ecology 82: 2507–2520. Microb. Ecol. 14: 19–28.
WALDOCK, M. J., AND D. I. HOLLAND. 1984. Fatty acid metabolism WRIGHT, D. A., E. M. SETZLER-HAMILTON, J. A. MAGEE, AND H.
in young oysters, Crassostrea gigas: Polyunsaturated fatty ac- R. HARVEY. 1996. Laboratory culture of zebra (Dreissena po-
ids. Lipids 19: 332–336. lymorpha) and quagga (D. bugensis) mussel larvae using es-
WATANABE, T., T. TAMIYA, A. OKA, M. HIRATA, C. KITAJIMA, AND tuarine algae. J. Gt. Lakes Res. 22: 46–54.
S. FUJITA. 1983a. Improvement of dietary value of live foods
for fish larvae by feeding them on v3 highly unsaturated fatty Received: 19 April 2001
acids and fat-soluble vitamins. Bull. Jpn. Soc. Sci. Fish. 49: Amended: 3 March 2002
471–479. Accepted: 24 March 2002

Limnol. Oceanogr., 47(4), 2002, 1248–1255

q 2002, by the American Society of Limnology and Oceanography, Inc.

Avoiding offshore transport of competent larvae during upwelling events: The case of
the gastropod Concholepas concholepas in Central Chile

Abstract—The coast of central Chile is characterized by the tance regarding larval transport (Shanks 1995) and that net
occurrence of coastal upwelling during the austral spring and transport is essentially driven by the interaction of physical
summer seasons, which probably has important consequences oceanic processes and the vertical distribution of larvae in
for the cross-shelf transport of larval stages of many species. the water column (Roughgarden et al. 1988; Shanks 1995).
Three cruises were conducted off the locality of El Quisco
during upwelling-favorable wind periods to determine the sur- Several cross-shelf larval transport processes have been
face distribution of epineustonic competent larvae of the gas- identified on different coasts of the world, including wind
tropod Concholepas concholepas during such events. Contrary drifting, onshore propagating tidal waves and bores, and up-
to the predictions of a traditional model, where neustonic-type welling fronts moving onshore during relaxation. Along
larvae are transported offshore under such conditions, com- eastern ocean boundary conditions, like those found on the
petent larvae of this species were exclusively found in the area Pacific coasts of South and North America and the Atlantic
between the shore and the upwelling front. Two additional coast of Africa, coastal upwelling forced by equatorward
cruises were conducted during calm periods to determine diel winds is a dominant oceanographic feature (Strub et al.
variation in the vertical distribution of C. concholepas com-
petent larvae. The absence of competent larvae at the surface
1998). Thus, it is expected that upwelling conditions will
during early night hours suggests a reverse vertical migration. exert a strong influence on the cross-shelf transport of larval
Thus, the retention of C. concholepas competent larvae in the stages of many species on these coasts. Indeed, simulation
upwelled waters could be the result of the interaction between and field studies have shown the importance of Ekman-driv-
their reverse diel vertical migration and the typical two-layer en circulation on larval transport and their subsequent set-
upwelling dynamics. tlement (Roughgarden et al. 1988; Shanks 1995; Brubaker
and Hooff 2000). The position of larvae in the water column
determines the net transport they undergo. Neustonic larvae
Over the past two decades, oceanographers and marine are first advected offshore by Ekman transport, concentrated
ecologists have dedicated intensive efforts to determining the by the upwelling front, and then driven back toward the
links among physical oceanography, larval distribution, and coast during the relaxation phase of the event, causing a
their dispersal and subsequent recruitment to adult habitats. settlement pulse (Wing et al. 1995; Shanks et al. 2000).
Most of these studies have demonstrated the relationship be- Many holoplanktonic species undergo daily vertical mi-
tween the supply of competent larvae and temporal and spa- grations (Thorson 1964; Mileikovsky 1973; Forward 1988),
tial variability in settlement of invertebrate species (e.g., a pattern also shown by pelagic larval stages of some fish
Roughgarden et al. 1988; Young 1997). Results from these and invertebrate species (e.g., fish, Forward et al. 1996a,b
studies have led to the belief that larval advection mecha- and crustacean, Shanks 1986). The most common diel ver-
nisms are key factors explaining the dynamics of nearshore tical migration type (DVM) corresponds to a deeper distri-
benthic populations of invertebrates with pelagic larval stag- bution of larvae during daytime and surfacing at night (Rich-
es (Roughgarden et al. 1988; Botsford et al. 1994). In this ards et al. 1996). However, in some cases, planktonic
context, and perhaps with the exception of some late larval organisms follow a reverse pattern with nocturnal descent
stages of fish and crustaceans (Luckenbach and Orth 1992; (Ohman et al. 1983 and references therein). Besides DVM,
Stobutzki and Bellwood 1997), it is generally considered that other characteristics such as larval buoyancy and sinking or
larval horizontal swimming capability is of minor impor- swimming behavior can interact with water mass movements
 Notes 1249

in shallow stratified seas, thus affecting their horizontal

transport. Such interactions have been demonstrated through
simulations (Botsford et al. 1994; Hill 1998) and field stud-
ies. The later have mostly been concerned with tidal currents
in estuarine systems (e.g., Forward et al. 1996a) but also
with open coast wind-driven systems (Shanks 1986; Blanton
et al. 1995).
Like other eastern boundary current systems, central Chile
is characterized by the occurrence of coastal upwelling, with
maximum upwelling-favorable winds (south and southwest)
during the austral spring and summer months. Winds are
intermittent, with periods of 3–10 d, producing alternating
upwelling and relaxation conditions (Strub et al. 1998). In
central Chile, upwelling is mostly confined to a narrow ex-
tension from the coast, compared with those found in many
other midlatitudes (Strub et al. 1998).
The gastropod Concholepas concholepas (Bruguière
1789), locally known as ‘‘loco,’’ is the most studied marine
invertebrate species in Chile (Castilla 1988). Because of its
economic value and ecological importance as a top predator,
numerous studies have been conducted to describe the life-
cycle ecology and to understand the population dynamics of
Fig. 1. Grid sampling design off El Quisco. Transects are 1 km
this species. Adults live on rocky bottoms in the intertidal in length. The distance of transects from the shore is 0.5 km for
and subtidal zones down to ;40 m in depth. In central Chile, T1, 1 for T2, 2 for T3, 4 for T4, 6 for T5, 8 for T6, 10 for T7, 12
female C. concholepas lay egg capsules on low intertidal for T8, 14 for T9, and 18 for T10. Broken lines represent the 50,
and shallow subtidal rocky surfaces during austral fall 100, and 200 m isobaths. The dark circle indicates the location of
months (Manrı́quez and Castilla 2001). After ;1 month of moored temperature loggers.
intracapsular development, small planktotrophic veliger lar-
vae (;260 mm) are released and spend the next 3 months
in the water column (DiSalvo 1988). Once the larvae be- ples were preserved in a 5% buffered formaldehyde seawater
come competent, they dwell at the sea surface until they solution and larvae were then identified and counted in the
settle on rocky intertidal and shallow subtidal habitats down laboratory under a dissecting scope. The field sampling
to 30 m deep (Stotz et al. 1991; Moreno et al. 1993; Martı́nez scheme used throughout this study consisted of 1 km long
and Navarrete 2002). Studies elsewhere have shown that epi- transects parallel to the coastline and ranged from 0.5 to 18
neustonic competent C. concholepas larvae are rare com- km from the shoreline (Fig. 1).
ponents of the coastal surface plankton of Chile (Moreno et Three surveys were conducted during strong equatorward
al. 1993; Poulin et al. 2002). wind periods: 5 November 1999 when transects T2, T3, T4,
Although the developmental sequence of C. concholepas T5, T6, T7, and T8 were visited (see Fig. 1), 25 September
larvae is well known, little is known about the distribution 2000 (transects T2, T3, T4, T5, T6, T7, T8, T9, and T10),
and transport processes of the different larval stages, partic- and 6 October 2000 (transects T2, T3, T4, T5, T6, T7, T8,
ularly about the pelagic-benthic transition. Recent studies and T9). Samples were collected by use of a floating neus-
have documented the existence of a positive relationship be- tonic net (700 mm mesh size), specially designed to collect
tween C. concholepas settlement and upwelling intensity in- premetamorphic larvae of C. concholepas in the top few
dex in southern Chile (Moreno et al. 1998) and the possible centimeters of the water column (DiSalvo 1988; Poulin et
influence of upwelling events on the distribution of compe- al. 2002). Because the rectangular mouth of this net (0.8 3
tent larvae in nearshore waters (Poulin et al. 2002). More- 0.4 m) is not totally submerged and because competent C.
over, a recent study showed the absence of competent larvae concholepas larvae are suspended in the first centimeters of
in coastal surface waters during night tows, which contrasted the water column, larval abundance were simply expressed
with their abundance during daylight hours and suggested as number of larvae per kilometer towed. For each transect,
that this larval stage could undergo vertical migration (Pou- towed distance was directly measured from a flow meter
lin et al. 2002). In this study we investigate the spatial dis- attached to the net.
tribution of C. concholepas competent larvae during up- Two extra cruises were conducted to determine diel var-
welling events, characterize diel changes in the abundance iation in the vertical distribution of C. concholepas compe-
of competent larvae in the water column, and propose a tent larvae. These cruises took place during calm periods to
transport model that would allow competent larvae to remain minimize the possible effect of physical mixing of the water
nearshore during upwelling events. column on larval behavior, and consisted of samples every
1.5–2 h along transects T1 and T3 (Fig. 1) during the day-
Study site and sampling grid–Surface zooplankton sam- night transition (from 1300 to 2200 h) on 23 October 2000
ples were collected off El Quisco (33823948.90S, and transects T2 and T3 during the night-day transition
71841940.50W) in the central coast of Chile. Plankton sam- (from 0100 to 1000 h) on 11 November 2000. To look for
1250 Notes

Fig. 2. North-south wind speed (top panels) and 3 and 12 m depth temperature (bottom panels)
registered during the three upwelling-favorable wind episodes corresponding to (A) 11 November
1999, (B) 25 September 2000, and (B) 6 October 2000 cruises. Arrows indicate the beginning of
equatorward wind periods. Sampling hours are highlighted by dark lines.

the presence of competent larvae in subsuperficial waters, observed a descent of ;38C in the temperature of the water
two nonclosing conical nets (0.7 m diameter and 350 mm column at El Quisco (Fig. 2).
mesh size) were towed at 5 and 15 m depth along with the The SST from satellite images for the period between 1
neustonic net described above. and 15 November 1999 showed the evolution of this partic-
ularly strong upwelling event. During the first 2 d of the 7-
Hydrography—Wind speed and direction data were re- d-long southerly wind episode, cold water surged in front of
corded as vector averages every 10 min by a Campbell me- the upwelling centers of Punta Curaumilla and Punta To-
teorological station located onshore at the Estación Costera pocalma, north and south of El Quisco, respectively (Fig.
de Investigaciones Marinas of Las Cruces, 15 km south of 3A). The following days were marked by a progressive ex-
El Quisco. Sea water temperature was measured at 30-min pansion of the coastal area affected by colder waters. The
intervals, at 3 and 12 m deep with temperature loggers (Stow cruise conducted on 5 November 2000 corresponded to the
Away Tidbits, 0.28C precision) moored at ;150 m from the fifth day since the beginning of strong southerly wind con-
shoreline off El Quisco (Fig. 1). During all surveys, surface ditions and by then colder water right in front of El Quisco
to 25-m deep profiles of water column variables (tempera- was clearly visible in the AVHRR images. The superficial
ture, dissolved oxygen, and salinity) were conducted at the
cold water tongue extended ;8 km offshore on this date,
beginning and at the end of each transect by use of a con-
and the cruise transect extended beyond the visible thermal
ductivity-temperature-depth meter with an incorporated ox-
front (see transect line in Fig. 3B).
ygen meter (Seabird-19). Advanced very high resolution ra-
diometer (AVHRR) satellite images of the study area (32.5– Profiles of water column temperature obtained during the
348 S and 74–718 W) were inspected to observe, over a three cruises showed that the system was characterized by
larger scale, the daily variation in sea surface temperature the presence of colder water below 10–15 m, which reached
(SST) corresponding to one of the upwelling-favorable wind the surface near the shore (Fig. 4). In all cases, it was pos-
episodes (1–7 November 1999). sible to identify the presence of a thermal front separating
offshore warmer surface water from inshore colder and more
Distribution of Concholepas competent larvae during up- saline upwelled water, located at about 8, 6, and 10 km from
welling events—Three cruises took place within periods shoreline during each of the respective cruises (Fig. 4). Al-
characterized by the occurrence of strong upwelling favor- though variable in abundance from cruise to cruise, C. con-
able winds. Wind patterns showed the typical diurnal cycle cholepas competent larvae were found only in recently up-
observed in central Chile, with maximum intensity after welled waters, between the thermal front created by the
midday and a relatively calm period in the morning. After upwelling and the shore (Fig. 4). This pattern was particu-
2 or 3 d after the intensification of equatorward winds, we larly evident on the 25 September 2000 cruise, when sam-
 Notes 1251

Fig. 3. AVHRR images of sea surface temperature showing the evolution of the November 1999 upwelling event: (A) beginning of the
upwelling event showing upwelled cold water around upwelling centers, (B) day when the cruise took place (transects location correspond
to the yellow line), (C) maximum extension of the cold upwelled water, and (D) relaxation phase.

pling extended up to 18 km offshore and no larvae were welling of cold water within the spatial and temporal domain
found beyond the front (Fig. 4B). of our observations. These upwelling events are common in
this region and have been studied from different perspectives
Day-night variation—The day-night transition cruises (Johnson et al. 1980; Strub et al. 1998), but so far few stud-
conducted in October and November 2000 showed important ies had shown upwelling activity in waters so close to the
variation in the larval distribution at the surface during the shore. Surface temperature from satellite images showed that
course of the day. In the case of the day to night sampling upwelling usually initiates around southern and western ends
conducted on 23 October 2000, peak larval abundance was of capes, where the coastline is oriented in a predominantly
found in late afternoon, ;1600 and 1700 h in transects T1 north-south direction (see also Johnson et al. 1980; Strub et
and T3, respectively (Fig. 5A). Although larval abundance al. 1998).
varied during the course of the day, the presence of larvae During upwelling events, C. concholepas competent lar-
during daylight hours contrasted with their absence in night vae were exclusively found in the recently upwelled cold
samples. A similar pattern was observed during the night to waters, between the upwelling front and the shore. Larvae
day sampling conducted on 11 November 2000, when com- were not concentrated at the cold side of the front but were
petent larvae were absent from the surface at night, between
distributed rather homogeneously within the upwelled wa-
0130 and 0300 h, but started to appear at the surface before
ters. This pattern is not in accordance with the general model
sunrise (Fig. 5B). After sunrise, the abundance of larvae at
proposed by other authors for epineustonic larvae of inver-
the surface continuously increased during the course of the
tebrates and fish along the Pacific and Atlantic coasts of
morning, reaching a maximum between 0800 and 1000 h,
when the cruise was terminated. North America (Fig. 6A) (Wing et al. 1995; Brubaker and
Only two competent larvae were found in all the subsur- Hooff 2000; Shanks et al. 2000). Those studies have shown
face tows (5 and 15 m deep) that were simultaneously per- that epineustonic larvae are usually advected offshore by the
formed during the night-day transition surveys. Both larvae displaced surface mixed layer and are therefore found in the
were found on the 11 November 2000 cruise at 15 m deep warm side of the upwelling front. Considering the poor hor-
and around 0200 h in the morning along transect 2. izontal swimming capability of C. concholepas larvae, it is
unlikely that they would be able to cross the upwelling front,
Discussion—Wind patterns, water column structure and swimming against the Ekman surface current along the sur-
satellite images confirmed the occurrence of wind-driven up- face. Therefore, it is possible that vertical positioning (e.g.,
1252 Notes

Fig. 4. Water column section showing the distribution of isotherms (bottom panels) and corresponding spatial distribution of competent
larvae found at the sea surface (top panels) on (A) 11 November 1999, (B) 25 September 2000, and (C) 6 October 2000.

Fig. 5. Temporal variation in the distribution of competent larvae along the surface during (A) day-night and (B) night-day cruises.
 Notes 1253

in light intensity. A change in daylight is a well-known stim-

ulus for DVM in many marine invertebrate and fish larvae
(e.g., Forward 1988; Richards et al. 1996). However, other
factors such as chemical cues from predators (Forward and
Rittschof 2000) or endogenous rhythms (Forward et al.
1996b) cannot be ruled out. In contrast, the appearance of
larvae at the surface was observed a few hours before sun-
rise (see Fig. 5), which suggests that light might not be the
factor triggering the upward migration of C. concholepas
larvae. The mechanisms by which competent larvae remain
at the surface during the day, migrate to deeper waters
around sunset, and ascend again before daylight are not yet
well understood. However, laboratory and field observations
suggest some of the mechanisms that could aid larvae com-
plete DVM. Competent larvae of C. concholepas have been
reported to use surface water tension to float at the surface
and also adhere to floating objects (DiSalvo 1988; authors’
pers. obs.). This behavior, as well as the existence of a byssal
thread (DiSalvo 1988), could explain their location at the
surface during daytime, probably even in the face of mod-
erate to strong wind mixing. Larval distribution under dif-
ferent sea conditions should be further investigated. Recent
studies have shown that the development of large chromato-
phores on larval structures provides an efficient protection
against ultraviolet radiation in epineustonic invertebrate lar-
vae (Miner et al. 2000). In addition to their dark and thick
larval shell, chromatophores are well developed in the foot
of C. concholepas competent larvae (DiSalvo 1988), which
might help protect competent larvae from harmful UV ra-
diation. The disappearance of competent C. concholepas lar-
vae from the surface at sunset may be the result of active
downward swimming or rapid sinking by the retraction of
the foot and the velum. Free-falling behavior has been ob-
Fig. 6. (A) General model for neustonic larval transport during served in C. concholepas competent larvae (DiSalvo 1988),
upwelling: neustonic larvae located at the surface (panel 1) are first
advected offshore by Ekman transport, concentrated by the upwell-
echinoderms (Pennington and Emlet 1986), fish (Forward et
ing front (panels 2 and 3), and then driven back towards the coast al. 1996b), and bivalve larvae (Manuel et al. 2000). Given
during the relaxation phase (panel 4). (B) Two-layer model that the large and thick larval shell, C. concholepas larvae most
integrates reverse vertical migration of C. concholepas competent likely drop at sunset by simply retracting the velum and foot.
larvae, which explains their observed distribution off El Quisco Active swimming and a bubble capture mechanism (DiSalvo
during upwelling. 1988) would permit competent C. concholepas larvae to
reach surface again in the morning.
Reverse DVM can represent a way of circumventing the
vertical migration) in the water column could allow larvae potentially high mortality rates on settling grounds if pred-
to avoid offshore advection during upwelling events. atory invertebrates and especially fishes predominate on suit-
Although only two competent larvae were collected in the able benthic habitat during daylight hours (Ohman et al.
subsurface tows, the absence of larvae along the surface in 1983; Morgan 1995). In shallow waters, reverse DVM in C.
early night tows suggests that competent larvae of C. con- concholepas competent larvae may thus reduce predation at
cholepas can undergo reverse DVM. These results agree settlement, which might be particularly important consider-
well with those of a previous study that covered a larger ing that this species exhibits bottom-searching behavior
spatial extent in the same region (Poulin et al. 2002). In that (Disalvo 1988). Because of the high frequency of upwelling
study, the absence of competent larvae on the surface during events affecting the central coast of Chile during the months
night cruises contrasted with their presence in the same area when competent larvae are found in the water, it is expected
during daylight hours. Alongshore horizontal transport be- that the DVM would have important consequences on cross-
yond the sampling area, as an alternative explanation for the shelf transport of C. concholepas competent larvae. We pro-
disappearance of larvae from the surface, is unlikely given pose a two-layer model to explain the surface C. conchole-
the stability of the water column through the course of the pas larval distribution observed during upwelling events,
repetitive tows. which in Fig. 6 is contrasted with the transport model de-
On the 23 October 2000 cruise, the disappearance of lar- scribed elsewhere for epineustonic larvae. When upwelling-
vae from the surface coincided with sunset, which suggests favorable winds begin to intensify, larvae would be first ad-
that larval sinking behavior may be a response to variation vected offshore as a consequence of Ekman transport of the
1254 Notes

surface layer. At night, active or passive downward migra- References

tion would allow larvae to cross the thermal front (located
no deeper than 20–25 m, see Fig. 4) and enter into the cold BLANTON, J. O., E. WENNER, F. WERNER, AND D. KNOTT. 1995.
water being upwelled shoreward. The following day, and Effects of wind-generated coastal currents on the transport of
blue crab megalopae on a shallow continental shelf. B. Mar.
depending on their initial position, larvae would reach the
Sci. 57: 739–752.
surface again, on either side of the front. During the course BOTSFORD, L. W., C. L. MOLONEY, A. HASTINGS, J. L. LARGIER, T.
of the upwelling event, the repetitive occurrence of the 24- M. POWELL, K. HIGGINS, AND J. F. QUINN. 1994. The influence
h migration cycle would lead to a progressive incorporation of spatially and temporally varying oceanographic conditions
of larvae in the upwelled water and the retention of larvae on meroplanktonic metapopulations. Deep-Sea Res. II 41:
between the upwelling front and the shore. The rate at which 107–145.
larvae cross from the warm waters into the cold upwelled BRUBAKER, J., AND R. HOOFF. 2000. Demonstration of the onshore
waters will vary depending on the surface and bottom cur- transport of larval invertebrates by the shoreward movement
rent velocities. Considering a general case, when surface off- of an upwelling front. Limnol. Oceanogr. 45: 230–236.
shore current velocity is faster than onshore flow of the bot- CASTILLA, J. C. 1988. Una revisión bibliográfica (1980–1988) sobre
Concholepas concholepas (Bruguière 1789) (Gastropoda: Mur-
tom layer (e.g., Lentz 1994; Strub et al. 1998), the net
icidae): Problemas pesqueros y experiencias de repoblación.
displacement of larvae will also be offshore but at a slower Biol. Pesq. (Chile) 17: 9–19.
rate than that of the front because of the time that larvae DISALVO, L. H. 1988. Observations on the larval and post-meta-
spent at the bottom layer during night hours. Thus, larvae morphic life of Concholepas concholepas (Bruguière, 1789) in
would be progressively incorporated into the upwelled zone, laboratory culture. Veliger 30: 358–368.
but the effectiveness of the mechanism will depend on the FORWARD, R. B., JR. 1988. Diel vertical migration: Zooplankton
offshore surface current velocity, the time spent in each lay- photobiology and behavior. Oceanogr. Mar. Biol. Annu. Rev.
er, and their initial position. In the case of a faster onshore 26: 361–392.
flow of the bottom layer (e.g., Ramp and Abbott 1998), lar- , J. S. BURKE, D. RITTSCHOFT, AND J. M. WELSH. 1996a.
vae will undergo a net onshore transport, would be retained Photoresponses of larval Atlantic menhaden (Brevoortia tyr-
annus Latrobe) in offshore and estuarine waters: Implications
between the upwelling front and the coast and would be
for transport. J. Exp. Mar. Biol. Ecol. 199: 123–135.
concentrated near the shore. Thus, the proposed two-layer , AND D. RITTSCHOF. 2000. Alteration of photoresponses in-
model and reverse DVM should therefore result in the pres- volved in diel vertical migration of a crab larva by fish mucus
ence of larvae between the front and the shore under most and degradation products of mucopolysaccharides. J. Exp. Mar.
upwelling conditions, which corresponds well with the ob- Biol. Ecol. 245: 277–292.
served surface distribution of C. concholepas competent lar- , R. A. TANKERSLEY, AND J. S. BURKE. 1996b. Endogenous
vae on the fourth and fifth days of each of the three up- swimming rhythms of larval Atlantic menhaden, Brevoortia
welling events studied here. tyranus Latrobe: Implications for vertical migration. J. Exp.
In summary, the interaction between the reverse DVM and Mar. Biol. Ecol. 204: 195–207.
upwelling circulation may serve C. concholepas larvae to HILL, A. E. 1998. Diel vertical migration in stratified tidal flows:
Implications for plankton dispersal. J. Mar. Res. 56: 1069–
avoid loss of competent larvae by large-scale offshore ad-
1096.
vection, restricting their distribution to a coastal zone delim- JOHNSON, D. R., T. FONSECA, AND H. SIEVERS. 1980. Upwelling in
ited by the upwelling front. Under particular circumstances the Humboldt Coastal Current near Valparaiso, Chile. J. Mar.
(see above), this basic mechanism could produce net larval Res. 38: 1–15.
transport onshore, but this effect is expected to be localized LENTZ, S. J. 1994. Current dynamics over the Northern California
and it should vary geographically along with changes in bot- inner shelf. J. Phys. Oceanogr. 24: 2461–2478.
tom topography (Ramp and Abbot 1998). In most cases, LUCKENBACH, M. W., AND R. J. ORTH. 1992. Swimming velocities
when a two-layer model dominates local upwelling circula- and behavior of blue crab (Callinectes sapidus) megalopae in
tion, larvae undergoing DVM (normal or reverse) would be still and flowing water. Estuaries 15: 186–192.
retained in upwelled waters. MANRÍQUEZ, P. H., AND J. C. CASTILLA. 2001. Significance of ma-
rine protected areas in central Chile as seeding grounds for the
Elie Poulin, Alvaro T. Palma,1 Germán Leiva, gastropod Concholepas concholepas. Mar. Ecol. Prog. Ser.
Diego Narvaez, Rodrigo Pacheco, Sergio A. Navarrete, and 215: 201–211.
Juan C. Castilla2 MANUEL, J. L., C. M. PEARCE, D. A. MANNING, AND R. K. O’DOR.
2000. The response of sea scallop (Placopecten magellanicus)
Departamento de Ecologı́a and Estación Costera de Inves-
tigaciones Marinas Las Cruces
Acknowledgments
Center for Advanced Studies in Ecology and Biodiversity We thank the enthusiastic field assistance of F. Veliz, A. Rosson,
P. Universidad Católica de Chile E. Hernández, and M. Andrade, skipper of the Barracuda, for their
Alameda 340, Casilla 114-D disposition and expertise. Comments by Alan Shanks and three re-
Santiago CP 6513677, Chile viewers helped improved this paper. This research was supported
by Proyecto Italia-Chile (CICS-Eula Genova-PUCCH), an Andrew
Mellon grant to J.C.C and S.A.N., and FONDAP O. & B.M. grant
1
Present address: Departamento de Ecologı́a Costera, Facultad to S.A.N. A.T.P. also acknowledges additional financial support
de Ciencias, Universidad Católica de la Santı́sima Concepción. Pai- from postdoctoral grant FONDECYT 3990032. The paper was com-
cavi 3000, Casilla 297. Concepción CP 4073978, Chile. pleted during the tenure of FONDAP-FONDECYT grant 1501-0001
2
Corresponding author (jcastill@bio.puc.cl). to the Center for Advanced Studies in Ecology and Biodiversity.
 Notes 1255

veligers to a weak thermocline in 9-m deep mesocosms. Mar. tical migration: Modeling light-mediated mechanisms. J.
Biol. 137: 169–175. Plankton Res. 18: 2199–2222.
MARTÍNEZ, P., AND S. A. NAVARRETE. 2002. Temporal and spatial ROUGHGARDEN, J., S. GAINES, AND H. POSSINGHAM. 1988. Recruit-
variation in settlement of the gastropod Concholepas concho- ment dynamics in complex life cycles. Science 241: 1460–
lepas in natural and artificial substrata. J. Mar. Biol. Assoc. 1466.
UK. 82: 257–264. SHANKS, A. L. 1986. Vertical migration and cross-shelf dispersal of
MILEIKOVSKY, S. A. 1973. Speed of active movement of pelagic larval Cancer spp and Randallia ornata (Crustacea: Brachyu-
larvae of marine bottom invertebrates and their ability to reg- ra) off the coast of southern California. Mar. Biol. 92: 189–
ulate their vertical position. Mar. Biol. 23: 11–17. 199.
MINER, B. G., S. G. MORGAN, AND J. R. HOFFMAN. 2000. Postlarval . 1995. Mechanisms of cross-shelf dispersal of larval inver-
chromatophores as an adaptation to ultraviolet radiation. J. tebrates and fish, p. 323–367. In L. McEdward [ed.], Ecology
Exp. Mar. Biol. Ecol. 249: 235–248. of Marine Invertebrates. CRC Press.
MORENO, C. A., G. ASENCIO, W. E. DUARTE, AND V. MARTIN. 1998. , J. LARGIER, L. BRINK, J. BRUBAKER, AND R. HOFF. 2000.
Settlement of the muricid Concholepas concholepas and its Demonstration of the onshore transport of larval invertebrates
relationship with El Niño and coastal upwellings in southern by the shoreward movement of an upwelling front. Limnol.
Chile. Mar. Ecol. Prog. Ser. 167: 171–175. Oceanogr. 45: 230–236.
, , AND S. IBÁÑEZ. 1993. Patrones de asentamiento STOBUTZKI, I. C., AND D. R. BELLWOOD. 1997. Sustained swimming
de Concholepas concholepas (Bruguière) (Mollusca: Murici- abilities of later pelagic stages of coral reef fishes. Mar. Ecol.
dae) en la zona intermareal rocosa de Valdivia, Chile. Rev. Prog. Ser. 149: 35–41.
Chil. Hist. Nat. 66: 93–101. STOTZ, W. B., P. DE AMESTI, D. J. MARTINEZ, AND E. PEREZ. 1991.
MORGAN, S. G. 1995. The timing of larval release, p. 157–192. In Lugares de asentamiento y desarrollo de juveniles tempranos
L. McEdward [ed.], Ecology of marine invertebrates. CRC de Concholepas concholepas (Bruguière, 1789) en ambientes
Press. inter y submareales de la IV Region, Coquimbo, Chile. Rev.
OHMAN, M. D., B. W. FROST, AND E. B. COHEN. 1983 Reverse diel Biol. Mar. Valparaiso 26: 339–350.
vertical migration: An escape from invertebrate predators. Sci- STRUB, P. T., J. M. MESIAS, V. MONTECINO, J. RUTLLAND, AND S.
ence 220: 1404–1407. SALINAS. 1998. Coastal ocean circulation off Western South
PENNINGTON, J. T., AND R. B. EMLET. 1986. Ontogenetic and diel America, p. 273–313. In A. R. Robinson and K. H. Brink
vertical migration of a planktonic echinoid larvae, Dendraster [eds.], The sea, vol. 11. John Wiley & Sons.
excentricus (Eschschlotz): Occurrence, causes, and probable THORSON, G. 1964. Light as an ecological factor in the dispersal
consequences. J. Exp. Mar. Biol. Ecol. 104: 69–95. and settlement of larvae of marine bottom invertebrates. Ophe-
POULIN, E., A. T. PALMA, G. LEIVA, E. HERNÁNDEZ, P. MARTÍNEZ, lia 1: 167–208.
S. A. NAVARRETE, AND J. C. CASTILLA. 2002. Temporal and WING, S. R., L. W. BOTSFORD, J. L. LARGIER, AND L. E. MORGAN.
1995. Spatial structure of relaxation events and crab settlement
spatial variation in the distribution of epineustonic competent
in the northern California upwelling system. Mar. Ecol. Prog.
larvae of Concholepas concholepas (Gastropoda: Muricidae)
Ser. 128: 199–211
in the central coast of Chile. Mar. Ecol. Prog. Ser. 229: 95–
YOUNG, C. M. 1997. Novelty of ‘‘supply-side ecology.’’ Science
109.
235: 415–416.
RAMP, S. R., AND C. L. ABBOTT. 1998. The vertical structure of
currents over the Continental Shelf off Point Sur, CA, during Received: 11 September 2001
Spring 1990. Deep-Sea Res. II 45: 1443–1470. Accepted: 19 February 2002
RICHARDS, S. A., H. P. POSSINGHAM, AND J. NOYE. 1996. Diel ver- Amended: 2 April 2002

Limnol. Oceanogr., 47(4), 2002, 1255–1260

q 2002, by the American Society of Limnology and Oceanography, Inc.

Ultrasonic in situ measurements of density, adiabatic compressibility, and stability

frequency

Abstract—An in situ density profile has been measured with formulations (‘‘equations of state’’), the ultrasonic approach
an ultrasonic density probe in the mining lake Merseburg-Ost has the potential to become a reliable reference for density
1b. From the acquired measurements of sound speed and measurements in limnic waters, when chemical conditions are
acoustic impedance, the important physical properties of in complex or spatial or temporal variation of dissolved sub-
situ density and adiabatic compressibility could be calculated. stances becomes relevant for the stability of the water column.
It was also shown that these two properties sufficed to deter-
mine the stability frequency, which hence becomes a directly
observable physical magnitude. Measurements of all magni-
tudes are presented. Currently the accuracy only suffices to Owing to the variable composition of the dissolved sub-
provide new insight in the density structure of natural water stances, density measurements in inland waters are still hard
bodies in cases of unusual composition of dissolved sub- to acquire at the required accuracy (Schimmele and Herz-
stances. However, as all required data are acquired in situ and sprung 2000). The oceanographic approach of calibrating
density is measured directly, i.e., without need of empirical temperature and electrical conductivity (via salinity) against