The relationships between the interannual variations of the Levantine intermediate water (LIW) co... more The relationships between the interannual variations of the Levantine intermediate water (LIW) core properties and the corresponding biochemical variations in the euphotic zone were systematically studied in the Southeastern Mediterranean during 2013–2021 and since 2002 based on a previous study. Salinity and temperature interannual fluctuations in the LIW continue to follow the Adriatic–Ionian Bimodal Oscillating System (BiOS) mechanism, with salinity and temperature peaks in the years 2008–2010, 2014–2015, and 2018–2019 coinciding with periods of anticyclonic circulation of the North Ionian Gyre (NIG). During these anticyclonic periods, the transport of Atlantic Water into the Levant is reduced together with the transport of LIW out of the basin. These interannual fluctuations are superimposed on a long-term warming trend clearly evident from previous studies, showing a maximal temperature in 2018–2019, higher than the previously mentioned temperature peaks by ~0.7°C and ~0.4°C. T...
The Eastern Mediterranean Sea (EMS) is a poorly studied ultra-oligotrophic marine environment, do... more The Eastern Mediterranean Sea (EMS) is a poorly studied ultra-oligotrophic marine environment, dominated by small-size phyto- and bacterioplankton. Here, we describe the dynamics of a single annual cycle (2018-19) of phyto- and bacterioplankton (abundances, pigments and productivity) in relation to the physical and chemical conditions in the photic water column at an offshore EMS site (Station THEMO-2, ∼1,500m depth, 50km offshore). We show that phytoplankton biomass (as chlorophyll a), primary and bacterial productivity differed between the mixed winter (January-April) and the thermally stratified (May-December) periods. Prochlorococcus and Synechococcus numerically dominated the picophytoplankton populations, with each clade revealing different temporal and depth changes indicative to them, while pico-eukaryotes (primarily haptophytes) were less abundant, yet likely contributed significant biomass. Estimated primary productivity (∼32 gC m-2 y-1) was lower compared with other well-...
The high variability of coastal waters together with the growing need for assessing the state of ... more The high variability of coastal waters together with the growing need for assessing the state of the marine coastal ecosystem, require continuous monitoring at exceptional resolution and quality, especially during the Anthropocene changing seas. We perform a comprehensive analysis of a decadal (March 2011 to June 2021) thermohaline variability of the East Levantine Basin (LB) coastal waters (continuous measurements), its predominating temporal trends and their linkage with atmospheric forcing and advection. We identify statistically significant long-term warming and salinification trends with yearly rates of 0.048°C and 0.006, respectively. Through the use of the X11-ARIMA method temperature and salinity inter-annual trends are examined and associated with previously published open ocean dynamics as well as model reanalysis. We study the linkage between Northern and Southern coastal locations, and identify the along shore northward current as a primary cause of positive temperature ...
Microbes are key players in marine sediments, yet they are not accessed routinely by monitoring p... more Microbes are key players in marine sediments, yet they are not accessed routinely by monitoring programs. Here, we investigate the spatial and vertical trends in the abundance, activity and diversity of benthic archaea, bacteria and fungi of the southeastern Mediterranean Sea (SEMS), based on ∼150 samples collected by the National Monitoring Program in 2018-2020 in coastal, as well as deep-sea transects across the Israeli exclusive economic zone, using vertical profiles of short sediment cores (0-1, 1-2, 4-5, 9-10 and 19-20 cm below surface). Microbial abundance was usually low (0.01 ×108to 0.21×108cells gr-1sediment), while heterotrophic productivity was the highest in the nearshore stations (12±4 ng C gr-1sediment h-1), as opposed to 0.5±0.9 ng C gr-1sediment h-1at the offshore sites. Using amplicon sequencing of marker genes, we identified the changes in the diversity of microbes along environmental gradients, in the four dimensions (geographic location, seabed depth, distance fr...
Coarse mode aerosols influence Earth's climate and biogeochemistry by interacting with long-w... more Coarse mode aerosols influence Earth's climate and biogeochemistry by interacting with long-wave radiation, promoting ice nucleation, and contributing important elements to biogeochemical cycles during deposition. Yet coarse mode aerosols have received less emphasis in the scientific literature. Here we present first efforts to globally synthesize available mass concentration, compositionand optical depth data and modeling for the coarse mode aerosols (<10 \u3bcm) in a new project called "COARSEMAP" (http://www.geo.cornell.edu/eas/PeoplePlaces/Faculty/mahowald/COARSEMAP/). We seek more collaborators who have observational data, especially including elemental or composition data, and/or who are interested in detailed modeling of the coarse mode. The goal will be publications synthesizing data with models, as well as providing synthesized results to the wider communit
ABSTRACTThe marine macroalgae Ulva sp. is considered an ecosystem engineer in rocky shores of tem... more ABSTRACTThe marine macroalgae Ulva sp. is considered an ecosystem engineer in rocky shores of temperate waters worldwide. Ulva sp. harbors a rich diversity of associated microbial epibionts, which are known to affect the algae's typical morphological development and ‘health’. We examined the interaction between airborne microbes derived from atmospheric aerosols and Ulva ohnoi growth and physiological state. Specifically, we measured U. ohnoi growth rates and photosynthetic efficiency (Fv/Fm), alongside its microbial epibionts abundance, activity and diversity following dust (containing nutrients and airborne microorganisms) or UV-treated dust (only nutrients) amendments to filtered seawater. Parallel incubations with epibionts-free U. ohnoi (treated with antibiotics that removed the algae epibionts) were also tested to specifically examine if dust-borne microbes can replenish the epibiont community of U. ohnoi. We show that viable airborne microbes can restore U. ohnoi natural ...
Deep Sea Research Part I: Oceanographic Research Papers, 2021
Abstract The Eastern Mediterranean Sea (EMS), is ultra-oligotrophic with unusual anti-estuarine c... more Abstract The Eastern Mediterranean Sea (EMS), is ultra-oligotrophic with unusual anti-estuarine circulation. It is P depleted and the limited enrichment studies which have been carried out, suggest seasonal changes in nutrient limitation. In this study high sensitivity dissolved nutrients (and associated parameters) were determined monthly over an annual cycle at a pelagic location in the SE Levantine basin. Nitrate & Nitrite (Nox) concentrations were high (300–500 nM) during the winter mixing period and enabled a concurrent phytoplankton increase in which larger picoeukaryotes and eukaryotes were dominant. After the thermal stratification of the water column commenced, Nox decreased through early summer transition period to low values (generally 50 nM or less) in the late summer. DIP remained at low nM concentrations the entire year while DOP decreased from 40 nM in winter to 30 nM in summer.. Prochlorococcus, the smallest picocyanobacteria, that does not typically utilize nitrate, dominated during the summer when both Nox and DIP concentrations were lowest. Ammonium concentrations were low (10–100 nM) with no systematic changes with season or depth. As a result, the DIN:DIP ratios were high (20–825) in winter and low (2–66) in summer, showing that these ratios vary seasonally. The dynamics of nutrient availability combined with the temporal changes in total chlorophyll and the altered dominance of the predominant phytoplankton species (i.e. nitrate-metabolizing Synechococcus during winter versus the smaller Prochlorococcus abundant in summer), leads to our hypothesis that the seasonal change in DIN:DIP indicates a switch from P limitation in winter during the annual phytoplankton increase to N&P or even N limitation in summer. Export Production (172 mmol N m−2 y−1) determined from the calculated loss of Nox from the photic zone, was similar to previous estimates in the EMS. Our results in terms of seasonally changing nutrient dynamics and resulting productivity confirm that the EMS has many of the characteristics found in P starved ocean gyre systems.
Deep Sea Research Part II: Topical Studies in Oceanography, 2019
Abstract The eastern Levantine basin (ELB) is an ultra-oligotrophic, warm and saline marine syste... more Abstract The eastern Levantine basin (ELB) is an ultra-oligotrophic, warm and saline marine system, significantly affected by climate change during the past several decades. The deployment of the first moored station at the ELB (DeepLev), at 1500 m water depth, ~50 km offshore Haifa, Israel, aimed at enhancing synchronized measurements of physical and biogeochemical dynamics. The station carries an array of sediment traps and sensors that measure physical, chemical, and biological attributes along the water column. Here we describe the station and present sediment-flux data from the first 1.5 years of operation (since November 2016). We show that, despite DeepLev's offshore location and the open-sea characteristics of the water column, lateral transport from the continental margin contributes the greatest fraction of particulate flux to the seafloor at this site. This mostly occurs via intermediate nepheloid layer plumes entering the study area between depths of 180 and 800 m. Bottom currents are weak (average ± SD = 3.5 ± 2 cm s−1) and are unlikely to cause significant resuspension. Based on sedimentation rates obtained from nearby sediment cores and sediment particle fluxes sampled in the traps, calculated accumulation rates of total particulate matter and of particulate organic carbon at the seafloor were 95–108 g m−2 y−1 and 0.5–0.6 g m−2 y−1, respectively. Offshore changes in sedimentation rates and in surface sediment elemental ratios indicate that sediment originating from the continental margins is transported at least 100 km offshore.
The relationships between the interannual variations of the Levantine intermediate water (LIW) co... more The relationships between the interannual variations of the Levantine intermediate water (LIW) core properties and the corresponding biochemical variations in the euphotic zone were systematically studied in the Southeastern Mediterranean during 2013–2021 and since 2002 based on a previous study. Salinity and temperature interannual fluctuations in the LIW continue to follow the Adriatic–Ionian Bimodal Oscillating System (BiOS) mechanism, with salinity and temperature peaks in the years 2008–2010, 2014–2015, and 2018–2019 coinciding with periods of anticyclonic circulation of the North Ionian Gyre (NIG). During these anticyclonic periods, the transport of Atlantic Water into the Levant is reduced together with the transport of LIW out of the basin. These interannual fluctuations are superimposed on a long-term warming trend clearly evident from previous studies, showing a maximal temperature in 2018–2019, higher than the previously mentioned temperature peaks by ~0.7°C and ~0.4°C. T...
The Eastern Mediterranean Sea (EMS) is a poorly studied ultra-oligotrophic marine environment, do... more The Eastern Mediterranean Sea (EMS) is a poorly studied ultra-oligotrophic marine environment, dominated by small-size phyto- and bacterioplankton. Here, we describe the dynamics of a single annual cycle (2018-19) of phyto- and bacterioplankton (abundances, pigments and productivity) in relation to the physical and chemical conditions in the photic water column at an offshore EMS site (Station THEMO-2, ∼1,500m depth, 50km offshore). We show that phytoplankton biomass (as chlorophyll a), primary and bacterial productivity differed between the mixed winter (January-April) and the thermally stratified (May-December) periods. Prochlorococcus and Synechococcus numerically dominated the picophytoplankton populations, with each clade revealing different temporal and depth changes indicative to them, while pico-eukaryotes (primarily haptophytes) were less abundant, yet likely contributed significant biomass. Estimated primary productivity (∼32 gC m-2 y-1) was lower compared with other well-...
The high variability of coastal waters together with the growing need for assessing the state of ... more The high variability of coastal waters together with the growing need for assessing the state of the marine coastal ecosystem, require continuous monitoring at exceptional resolution and quality, especially during the Anthropocene changing seas. We perform a comprehensive analysis of a decadal (March 2011 to June 2021) thermohaline variability of the East Levantine Basin (LB) coastal waters (continuous measurements), its predominating temporal trends and their linkage with atmospheric forcing and advection. We identify statistically significant long-term warming and salinification trends with yearly rates of 0.048°C and 0.006, respectively. Through the use of the X11-ARIMA method temperature and salinity inter-annual trends are examined and associated with previously published open ocean dynamics as well as model reanalysis. We study the linkage between Northern and Southern coastal locations, and identify the along shore northward current as a primary cause of positive temperature ...
Microbes are key players in marine sediments, yet they are not accessed routinely by monitoring p... more Microbes are key players in marine sediments, yet they are not accessed routinely by monitoring programs. Here, we investigate the spatial and vertical trends in the abundance, activity and diversity of benthic archaea, bacteria and fungi of the southeastern Mediterranean Sea (SEMS), based on ∼150 samples collected by the National Monitoring Program in 2018-2020 in coastal, as well as deep-sea transects across the Israeli exclusive economic zone, using vertical profiles of short sediment cores (0-1, 1-2, 4-5, 9-10 and 19-20 cm below surface). Microbial abundance was usually low (0.01 ×108to 0.21×108cells gr-1sediment), while heterotrophic productivity was the highest in the nearshore stations (12±4 ng C gr-1sediment h-1), as opposed to 0.5±0.9 ng C gr-1sediment h-1at the offshore sites. Using amplicon sequencing of marker genes, we identified the changes in the diversity of microbes along environmental gradients, in the four dimensions (geographic location, seabed depth, distance fr...
Coarse mode aerosols influence Earth's climate and biogeochemistry by interacting with long-w... more Coarse mode aerosols influence Earth's climate and biogeochemistry by interacting with long-wave radiation, promoting ice nucleation, and contributing important elements to biogeochemical cycles during deposition. Yet coarse mode aerosols have received less emphasis in the scientific literature. Here we present first efforts to globally synthesize available mass concentration, compositionand optical depth data and modeling for the coarse mode aerosols (<10 \u3bcm) in a new project called "COARSEMAP" (http://www.geo.cornell.edu/eas/PeoplePlaces/Faculty/mahowald/COARSEMAP/). We seek more collaborators who have observational data, especially including elemental or composition data, and/or who are interested in detailed modeling of the coarse mode. The goal will be publications synthesizing data with models, as well as providing synthesized results to the wider communit
ABSTRACTThe marine macroalgae Ulva sp. is considered an ecosystem engineer in rocky shores of tem... more ABSTRACTThe marine macroalgae Ulva sp. is considered an ecosystem engineer in rocky shores of temperate waters worldwide. Ulva sp. harbors a rich diversity of associated microbial epibionts, which are known to affect the algae's typical morphological development and ‘health’. We examined the interaction between airborne microbes derived from atmospheric aerosols and Ulva ohnoi growth and physiological state. Specifically, we measured U. ohnoi growth rates and photosynthetic efficiency (Fv/Fm), alongside its microbial epibionts abundance, activity and diversity following dust (containing nutrients and airborne microorganisms) or UV-treated dust (only nutrients) amendments to filtered seawater. Parallel incubations with epibionts-free U. ohnoi (treated with antibiotics that removed the algae epibionts) were also tested to specifically examine if dust-borne microbes can replenish the epibiont community of U. ohnoi. We show that viable airborne microbes can restore U. ohnoi natural ...
Deep Sea Research Part I: Oceanographic Research Papers, 2021
Abstract The Eastern Mediterranean Sea (EMS), is ultra-oligotrophic with unusual anti-estuarine c... more Abstract The Eastern Mediterranean Sea (EMS), is ultra-oligotrophic with unusual anti-estuarine circulation. It is P depleted and the limited enrichment studies which have been carried out, suggest seasonal changes in nutrient limitation. In this study high sensitivity dissolved nutrients (and associated parameters) were determined monthly over an annual cycle at a pelagic location in the SE Levantine basin. Nitrate & Nitrite (Nox) concentrations were high (300–500 nM) during the winter mixing period and enabled a concurrent phytoplankton increase in which larger picoeukaryotes and eukaryotes were dominant. After the thermal stratification of the water column commenced, Nox decreased through early summer transition period to low values (generally 50 nM or less) in the late summer. DIP remained at low nM concentrations the entire year while DOP decreased from 40 nM in winter to 30 nM in summer.. Prochlorococcus, the smallest picocyanobacteria, that does not typically utilize nitrate, dominated during the summer when both Nox and DIP concentrations were lowest. Ammonium concentrations were low (10–100 nM) with no systematic changes with season or depth. As a result, the DIN:DIP ratios were high (20–825) in winter and low (2–66) in summer, showing that these ratios vary seasonally. The dynamics of nutrient availability combined with the temporal changes in total chlorophyll and the altered dominance of the predominant phytoplankton species (i.e. nitrate-metabolizing Synechococcus during winter versus the smaller Prochlorococcus abundant in summer), leads to our hypothesis that the seasonal change in DIN:DIP indicates a switch from P limitation in winter during the annual phytoplankton increase to N&P or even N limitation in summer. Export Production (172 mmol N m−2 y−1) determined from the calculated loss of Nox from the photic zone, was similar to previous estimates in the EMS. Our results in terms of seasonally changing nutrient dynamics and resulting productivity confirm that the EMS has many of the characteristics found in P starved ocean gyre systems.
Deep Sea Research Part II: Topical Studies in Oceanography, 2019
Abstract The eastern Levantine basin (ELB) is an ultra-oligotrophic, warm and saline marine syste... more Abstract The eastern Levantine basin (ELB) is an ultra-oligotrophic, warm and saline marine system, significantly affected by climate change during the past several decades. The deployment of the first moored station at the ELB (DeepLev), at 1500 m water depth, ~50 km offshore Haifa, Israel, aimed at enhancing synchronized measurements of physical and biogeochemical dynamics. The station carries an array of sediment traps and sensors that measure physical, chemical, and biological attributes along the water column. Here we describe the station and present sediment-flux data from the first 1.5 years of operation (since November 2016). We show that, despite DeepLev's offshore location and the open-sea characteristics of the water column, lateral transport from the continental margin contributes the greatest fraction of particulate flux to the seafloor at this site. This mostly occurs via intermediate nepheloid layer plumes entering the study area between depths of 180 and 800 m. Bottom currents are weak (average ± SD = 3.5 ± 2 cm s−1) and are unlikely to cause significant resuspension. Based on sedimentation rates obtained from nearby sediment cores and sediment particle fluxes sampled in the traps, calculated accumulation rates of total particulate matter and of particulate organic carbon at the seafloor were 95–108 g m−2 y−1 and 0.5–0.6 g m−2 y−1, respectively. Offshore changes in sedimentation rates and in surface sediment elemental ratios indicate that sediment originating from the continental margins is transported at least 100 km offshore.
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