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Michael S Owens - One of the best experts on this subject based on the ideXlab platform.
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Influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics: A laboratory study
2012Co-Authors: Roger I. E. Newell, Jeffrey C. Cornwell, Michael S OwensAbstract:Suspension-feeding eastern oysters, Crassostrea virginica, were once abundant in Chesapeake Bay and may then have exerted top-down control on phytoplankton and also reduced turbidities, thereby increasing light available to Benthic Plants. Alternatively, oysters may have simply recycled inorganic nutrients rapidly back to the water column, with no long-lasting reduction in phytoplankton biomass resulting from oyster feeding activity. To help distinguish between these scenarios, we explored changes in nitrogen fluxes and denitrification in laboratory incubations of sediment cores held under oxic and anoxic conditions in response to loading by pelletized phytoplankton cells, an experimental analog for oyster feces and pseudofeces. When organics were regenerated under aerobic conditions, typical of those associated with oyster habitat, coupled nitrification–denitrification was promoted, resulting in denitrification of �20 % of the total added nitrogen. In contrast, under anoxic conditions, typical of current summertime conditions in main-stem Chesapeake Bay where phytoplankton is microbially degraded beneath the pycnocline, nitrogen was released solely as ammonium from the added organics. We postulate that denitrification of particulate nitrogen remaining in oyster feces and pseudofeces may enhance nitrogen removal from estuaries. In aerobic incubations with sufficient light (70 �mol m�2 s�1), a Benthic microalgal/cyanobacterial community grew that not only absorbed the inorganic nitrogen released from the added organics but also fixed N2. This result suggests tha
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influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics a laboratory study
Limnology and Oceanography, 2002Co-Authors: Roger I. E. Newell, Jeffrey C. Cornwell, Michael S OwensAbstract:Suspension-feeding eastern oysters, Crassostrea virginica, were once abundant in Chesapeake Bay and may then have exerted top-down control on phytoplankton and also reduced turbidities, thereby increasing light available to Benthic Plants. Alternatively, oysters may have simply recycled inorganic nutrients rapidly back to the water column, with no long-lasting reduction in phytoplankton biomass resulting from oyster feeding activity. To help distinguish between these scenarios, we explored changes in nitrogen fluxes and denitrification in laboratory incubations of sediment cores held under oxic and anoxic conditions in response to loading by pelletized phytoplankton cells, an experimental analog for oyster feces and pseudofeces. When organics were regenerated under aerobic conditions, typical of those associated with oyster habitat, coupled nitrification‐denitrification was promoted, resulting in denitrification of;20% of the total added nitrogen. In contrast, under anoxic conditions, typical of current summertime conditions in main-stem Chesapeake Bay where phytoplankton is microbially degraded beneath the pycnocline, nitrogen was released solely as ammonium from the added organics. We postulate that denitrification of particulate nitrogen remaining in oyster feces and pseudofeces may enhance nitrogen removal from estuaries. In aerobic incubations with sufficient light (70 mmol m 22 s 21 ), a Benthic microalgal/cyanobacterial community grew that not only absorbed the inorganic nitrogen released from the added organics but also fixed N 2. This result suggests that an ecosystem dominated by Benthic primary production may develop in shallow waters when reduced turbidity associated with bivalve feeding increases light penetration to a level that can sustain Benthic microalgal production.
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Influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics: A laboratory study. Limnol
2002Co-Authors: Roger I. E. Newell, Jeffrey C. Cornwell, Michael S OwensAbstract:Suspension-feeding eastern oysters, Crassostrea virginica, were once abundant in Chesapeake Bay and may then have exerted top-down control on phytoplankton and also reduced turbidities, thereby increasing light available to Benthic Plants. Alternatively, oysters may have simply recycled inorganic nutrients rapidly back to the water column, with no long-lasting reduction in phytoplankton biomass resulting from oyster feeding activity. To help distinguish between these scenarios, we explored changes in nitrogen fluxes and denitrification in laboratory incubations of sediment cores held under oxic and anoxic conditions in response to loading by pelletized phytoplankton cells, an experimental analog for oyster feces and pseudofeces. When organics were regenerated under aerobic conditions, typical of those associated with oyster habitat, coupled nitrification–denitrification was promoted, resulting in denitrification of �20 % of the total added nitrogen. In contrast, under anoxic conditions, typical of current summertime conditions in main-stem Chesapeake Bay where phytoplankton is microbially degraded beneath the pycnocline, nitrogen was released solely as ammonium from the added organics. We postulate that denitrification of particulate nitrogen remaining in oyster feces and pseudofeces may enhance nitrogen removal from estuaries. In aerobic incubations with sufficient light (70 �mol m�2 s�1), a Benthic microalgal/cyanobacterial community grew that not only absorbed the inorganic nitrogen released from the added organics but also fixed N2. This result suggests tha
Jeffrey C. Cornwell - One of the best experts on this subject based on the ideXlab platform.
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Influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics: A laboratory study
2012Co-Authors: Roger I. E. Newell, Jeffrey C. Cornwell, Michael S OwensAbstract:Suspension-feeding eastern oysters, Crassostrea virginica, were once abundant in Chesapeake Bay and may then have exerted top-down control on phytoplankton and also reduced turbidities, thereby increasing light available to Benthic Plants. Alternatively, oysters may have simply recycled inorganic nutrients rapidly back to the water column, with no long-lasting reduction in phytoplankton biomass resulting from oyster feeding activity. To help distinguish between these scenarios, we explored changes in nitrogen fluxes and denitrification in laboratory incubations of sediment cores held under oxic and anoxic conditions in response to loading by pelletized phytoplankton cells, an experimental analog for oyster feces and pseudofeces. When organics were regenerated under aerobic conditions, typical of those associated with oyster habitat, coupled nitrification–denitrification was promoted, resulting in denitrification of �20 % of the total added nitrogen. In contrast, under anoxic conditions, typical of current summertime conditions in main-stem Chesapeake Bay where phytoplankton is microbially degraded beneath the pycnocline, nitrogen was released solely as ammonium from the added organics. We postulate that denitrification of particulate nitrogen remaining in oyster feces and pseudofeces may enhance nitrogen removal from estuaries. In aerobic incubations with sufficient light (70 �mol m�2 s�1), a Benthic microalgal/cyanobacterial community grew that not only absorbed the inorganic nitrogen released from the added organics but also fixed N2. This result suggests tha
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Eutrophication of Chesapeake Bay: Historical trends and ecological interactions
Marine Ecology Progress Series, 2005Co-Authors: W M Kemp, J. E. Adolf, W. C. Boicourt, T. R. Fisher, D. F. Boesch, G. Brush, Patricia M. Glibert, Jeffrey C. Cornwell, Walter R Boynton, James D. HagyAbstract:This review provides an integrated synthesis with timelines and evaluations of ecological responses to eutrophication in Chesapeake Bay, the largest estuary in the USA. Analyses of dated sediment cores reveal initial evidence of organic enrichment in similar to 200 yr old strata, while signs of increased phytoplankton and decreased water clarity first appeared similar to 100 yr ago. Severe, recurring deep-water hypoxia and loss of diverse submersed vascular Plants were first evident in the 1950s and 1960s, respectively. The degradation of these Benthic habitats has contributed to declines in Benthic macro-infauna in deep mesohaline regions of the Bay and blue crabs in shallow polyhaline areas. In contrast, copepods, which are heavily consumed in pelagic food chains, are relatively unaffected by nutrient-induced changes in phytoplankton. Intense mortality associated with fisheries and disease have caused a dramatic decline in eastern oyster stocks and associated Bay water filtration, which may have exacerbated eutrophication effects on phytoplankton and water clarity. Extensive tidal marshes, which have served as effective nutrient buffers along the Bay margins, are now being lost with rising sea level. Although the Bay's overall fisheries production has probably not been affected by eutrophication, decreases in the relative contribution of demersal fish and in the efficiency with which primary production is transferred to harvest suggest fundamental shifts in trophic and habitat structures. Bay ecosystem responses to changes in nutrient loading are complicated by non-linear feedback mechanisms, including particle trapping and binding by Benthic Plants that increase water clarity, and by oxygen effects on Benthic nutrient recycling efficiency. Observations in Bay tributaries undergoing recent reductions in nutrient input indicate relatively rapid recovery of some ecosystem functions but lags in the response of others.
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influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics a laboratory study
Limnology and Oceanography, 2002Co-Authors: Roger I. E. Newell, Jeffrey C. Cornwell, Michael S OwensAbstract:Suspension-feeding eastern oysters, Crassostrea virginica, were once abundant in Chesapeake Bay and may then have exerted top-down control on phytoplankton and also reduced turbidities, thereby increasing light available to Benthic Plants. Alternatively, oysters may have simply recycled inorganic nutrients rapidly back to the water column, with no long-lasting reduction in phytoplankton biomass resulting from oyster feeding activity. To help distinguish between these scenarios, we explored changes in nitrogen fluxes and denitrification in laboratory incubations of sediment cores held under oxic and anoxic conditions in response to loading by pelletized phytoplankton cells, an experimental analog for oyster feces and pseudofeces. When organics were regenerated under aerobic conditions, typical of those associated with oyster habitat, coupled nitrification‐denitrification was promoted, resulting in denitrification of;20% of the total added nitrogen. In contrast, under anoxic conditions, typical of current summertime conditions in main-stem Chesapeake Bay where phytoplankton is microbially degraded beneath the pycnocline, nitrogen was released solely as ammonium from the added organics. We postulate that denitrification of particulate nitrogen remaining in oyster feces and pseudofeces may enhance nitrogen removal from estuaries. In aerobic incubations with sufficient light (70 mmol m 22 s 21 ), a Benthic microalgal/cyanobacterial community grew that not only absorbed the inorganic nitrogen released from the added organics but also fixed N 2. This result suggests that an ecosystem dominated by Benthic primary production may develop in shallow waters when reduced turbidity associated with bivalve feeding increases light penetration to a level that can sustain Benthic microalgal production.
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Influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics: A laboratory study. Limnol
2002Co-Authors: Roger I. E. Newell, Jeffrey C. Cornwell, Michael S OwensAbstract:Suspension-feeding eastern oysters, Crassostrea virginica, were once abundant in Chesapeake Bay and may then have exerted top-down control on phytoplankton and also reduced turbidities, thereby increasing light available to Benthic Plants. Alternatively, oysters may have simply recycled inorganic nutrients rapidly back to the water column, with no long-lasting reduction in phytoplankton biomass resulting from oyster feeding activity. To help distinguish between these scenarios, we explored changes in nitrogen fluxes and denitrification in laboratory incubations of sediment cores held under oxic and anoxic conditions in response to loading by pelletized phytoplankton cells, an experimental analog for oyster feces and pseudofeces. When organics were regenerated under aerobic conditions, typical of those associated with oyster habitat, coupled nitrification–denitrification was promoted, resulting in denitrification of �20 % of the total added nitrogen. In contrast, under anoxic conditions, typical of current summertime conditions in main-stem Chesapeake Bay where phytoplankton is microbially degraded beneath the pycnocline, nitrogen was released solely as ammonium from the added organics. We postulate that denitrification of particulate nitrogen remaining in oyster feces and pseudofeces may enhance nitrogen removal from estuaries. In aerobic incubations with sufficient light (70 �mol m�2 s�1), a Benthic microalgal/cyanobacterial community grew that not only absorbed the inorganic nitrogen released from the added organics but also fixed N2. This result suggests tha
Karen J Mcglathery - One of the best experts on this subject based on the ideXlab platform.
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spatially explicit feedbacks between seagrass meadow structure sediment and light habitat suitability for seagrass growth
Advances in Water Resources, 2016Co-Authors: Karen J Mcglathery, Joel A Carr, Paolo Dodorico, Patricia L WibergAbstract:In shallow coastal bays where nutrient loading and riverine inputs are low, turbidity, and the consequent light environment are controlled by resuspension of bed sediments due to wind-waves and tidal currents. High sediment resuspension and low light environments can limit Benthic primary productivity; however, both currents and waves are affected by the presence of Benthic Plants such as seagrass. This feedback between the presence of Benthic primary producers such as seagrass and the consequent light environment has been predicted to induce bistable dynamics locally. However, these vegetated areas influence a larger area than they footprint, including a barren adjacent downstream area which exhibits reduced shear stresses. Here we explore through modeling how the patchy structure of seagrass meadows on a landscape may affect sediment resuspension and the consequent light environment due to the presence of this sheltered region. Heterogeneous vegetation covers comprising a mosaic of randomly distributed patches were generated to investigate the effect of patch modified hydrodynamics. Actual cover of vegetation on the landscape was used to facilitate comparisons across landscape realizations. Hourly wave and current shear stresses on the landscape along with suspended sediment concentration and light attenuation characteristics were then calculated and spatially averaged to examine how actual cover and mean water depth affect the bulk sediment and light environment. The results indicate that an effective cover, which incorporates the sheltering area, has important controls on the distributions of shear stress, suspended sediment, light environment, and consequent seagrass habitat suitability. Interestingly, an optimal habitat occurs within a depth range where, if actual cover is reduced past some threshold, the bulk light environment would no longer favor seagrass growth.
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wind driven sediment suspension controls light availability in a shallow coastal lagoon
Estuaries and Coasts, 2007Co-Authors: S E Lawson, Karen J Mcglathery, Patricia Wiberg, David C FugateAbstract:Light availability is critically important for primary productivity in coastal systems, yet current research approaches may not be adequate in shallow coastal lagoons. Light attenuation in these systems is typically dominated by suspended sediment, while light attenuation in deeper estuaries is often dominated by phytoplankton. This difference in controls on light attenuation suggests that physical processes may exert a greater influence on light availability in coastal lagoons than in deeper estuaries. Light availability in Hog Island Bay, a shallow coastal lagoon on the eastern shore of Virginia, was determined for a summer and late fall time period with different wind conditions. We combined field measurements and a process-based modeling approach that predicts sediment suspension and light availability from waves and currents to examine both the variability and drivers of light attenuation. Total suspended solids was the only significant predictor of light attenuation in Hog Island Bay. Waves and currents in Hog Island Bay responded strongly to wind forcing, with bottom stresses from wind driven waves dominant for 60% of the modeled area for the late fall period and 24% of the modeled area for the summer period. Higher wind speeds in late fall than in summer caused greater sediment suspension (41 and 3 mg l−1 average, respectively) and lower average (spatial and temporal) downwelling light availability (32% and 55%, respectively). Because of the episodic nature of wind events and the spatially variable nature of sediment suspension, conventional methods of examining light availability, such as fair-weather monitoring or single in situ recorders, do not adequately represent light conditions for Benthic Plants.
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macroalgae mediation of dissolved organic nitrogen fluxes in a temperate coastal lagoon
Estuarine Coastal and Shelf Science, 2001Co-Authors: Anna Christina Tyler, Karen J Mcglathery, Iris C AndersonAbstract:The activity of the benthos, including Benthic Plants, is important in driving the overall system dynamics in shallow lagoons, due to the high ratio of sediment surface area relative to water volume. In Hog Island Bay, Benthic macroalgae appear to be a key regulator of DON dynamics, both while alive and following senescence. We investigated the role of macroalgae in mediating water column concentrations and sediment-water column fluxes of DON across a nutrient gradient in Hog Island Bay, a shallow macroalgal-dominated back-barrier lagoon located on the Virginia Coast. Sediment-water column exchanges of DON, urea and DIN were measured in sediment cores with and without macroalgae (Ulva lactuca) at three subtidal sites from the mainland to the barrier islands in the fall of 1997 and the spring and summer of 1998. The summer sampling dates bracketed a large macroalgal bloom in the mid-lagoon. Dissolved organic nitrogen was an important component (52-98%) of the total dissolved nitrogen pool in Hog Island Bay waters and made up the majority of the sediment N flux to the water column. Macroalgae impacted Benthic-pelagic coupling by preventing diffusion of DIN from the water column to the sediments and by intercepting urea fluxes from the sediment to the water column. Closest to the mainland and closest to the barrier islands, at sites with low macroalgal biomass, sediment-water column fluxes of DIN and urea-free DON were negligible or directed into the sediments. Fluxes of urea from the sediment to the water column were significant at both sites, and may play an important role in satisfying macroalgal N demand, especially at the low N island site. Overall, urea was 32% of the mean DON flux from the sediments to the water column. Fluxes of urea-free DON were highest in the mid-lagoon, where macroalgal biomass was highest. The highest overall flux rates of DON (>38 mmol m−2 d−1) and DIN (>33 mmol m−2 d−1) were measured following an isolated crash of a large macroalgal mat. These release rates were not sustained for long, however, and we estimated that the majority of the N contained in the decomposing macroalgal tissues disappeared in <2 weeks. In addition to release of organic N following senescence, macroalgae ‘ leak ’ DON into the water column during active growth; release of DON increased by 250% in cores incubated with U. lactuca relative to cores with sediment only. These algae function as a conduit whereby water-column DIN and sediment urea are taken up and released to the water column as DON over relatively short (hours) time scales. This conversion of bioavailable dissolved N to PON and DON by macroalgae is likely to be important to overall system metabolism and to the retention of N within the lagoon.
Roger I. E. Newell - One of the best experts on this subject based on the ideXlab platform.
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Influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics: A laboratory study
2012Co-Authors: Roger I. E. Newell, Jeffrey C. Cornwell, Michael S OwensAbstract:Suspension-feeding eastern oysters, Crassostrea virginica, were once abundant in Chesapeake Bay and may then have exerted top-down control on phytoplankton and also reduced turbidities, thereby increasing light available to Benthic Plants. Alternatively, oysters may have simply recycled inorganic nutrients rapidly back to the water column, with no long-lasting reduction in phytoplankton biomass resulting from oyster feeding activity. To help distinguish between these scenarios, we explored changes in nitrogen fluxes and denitrification in laboratory incubations of sediment cores held under oxic and anoxic conditions in response to loading by pelletized phytoplankton cells, an experimental analog for oyster feces and pseudofeces. When organics were regenerated under aerobic conditions, typical of those associated with oyster habitat, coupled nitrification–denitrification was promoted, resulting in denitrification of �20 % of the total added nitrogen. In contrast, under anoxic conditions, typical of current summertime conditions in main-stem Chesapeake Bay where phytoplankton is microbially degraded beneath the pycnocline, nitrogen was released solely as ammonium from the added organics. We postulate that denitrification of particulate nitrogen remaining in oyster feces and pseudofeces may enhance nitrogen removal from estuaries. In aerobic incubations with sufficient light (70 �mol m�2 s�1), a Benthic microalgal/cyanobacterial community grew that not only absorbed the inorganic nitrogen released from the added organics but also fixed N2. This result suggests tha
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influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics a laboratory study
Limnology and Oceanography, 2002Co-Authors: Roger I. E. Newell, Jeffrey C. Cornwell, Michael S OwensAbstract:Suspension-feeding eastern oysters, Crassostrea virginica, were once abundant in Chesapeake Bay and may then have exerted top-down control on phytoplankton and also reduced turbidities, thereby increasing light available to Benthic Plants. Alternatively, oysters may have simply recycled inorganic nutrients rapidly back to the water column, with no long-lasting reduction in phytoplankton biomass resulting from oyster feeding activity. To help distinguish between these scenarios, we explored changes in nitrogen fluxes and denitrification in laboratory incubations of sediment cores held under oxic and anoxic conditions in response to loading by pelletized phytoplankton cells, an experimental analog for oyster feces and pseudofeces. When organics were regenerated under aerobic conditions, typical of those associated with oyster habitat, coupled nitrification‐denitrification was promoted, resulting in denitrification of;20% of the total added nitrogen. In contrast, under anoxic conditions, typical of current summertime conditions in main-stem Chesapeake Bay where phytoplankton is microbially degraded beneath the pycnocline, nitrogen was released solely as ammonium from the added organics. We postulate that denitrification of particulate nitrogen remaining in oyster feces and pseudofeces may enhance nitrogen removal from estuaries. In aerobic incubations with sufficient light (70 mmol m 22 s 21 ), a Benthic microalgal/cyanobacterial community grew that not only absorbed the inorganic nitrogen released from the added organics but also fixed N 2. This result suggests that an ecosystem dominated by Benthic primary production may develop in shallow waters when reduced turbidity associated with bivalve feeding increases light penetration to a level that can sustain Benthic microalgal production.
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Influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics: A laboratory study. Limnol
2002Co-Authors: Roger I. E. Newell, Jeffrey C. Cornwell, Michael S OwensAbstract:Suspension-feeding eastern oysters, Crassostrea virginica, were once abundant in Chesapeake Bay and may then have exerted top-down control on phytoplankton and also reduced turbidities, thereby increasing light available to Benthic Plants. Alternatively, oysters may have simply recycled inorganic nutrients rapidly back to the water column, with no long-lasting reduction in phytoplankton biomass resulting from oyster feeding activity. To help distinguish between these scenarios, we explored changes in nitrogen fluxes and denitrification in laboratory incubations of sediment cores held under oxic and anoxic conditions in response to loading by pelletized phytoplankton cells, an experimental analog for oyster feces and pseudofeces. When organics were regenerated under aerobic conditions, typical of those associated with oyster habitat, coupled nitrification–denitrification was promoted, resulting in denitrification of �20 % of the total added nitrogen. In contrast, under anoxic conditions, typical of current summertime conditions in main-stem Chesapeake Bay where phytoplankton is microbially degraded beneath the pycnocline, nitrogen was released solely as ammonium from the added organics. We postulate that denitrification of particulate nitrogen remaining in oyster feces and pseudofeces may enhance nitrogen removal from estuaries. In aerobic incubations with sufficient light (70 �mol m�2 s�1), a Benthic microalgal/cyanobacterial community grew that not only absorbed the inorganic nitrogen released from the added organics but also fixed N2. This result suggests tha
Roberta A Townsend - One of the best experts on this subject based on the ideXlab platform.
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Records of the Western Australian Museum Supplement No. 77: 50–87 (2009). Marine Benthic Plants of Western Australia’s Shelf-Edge Atolls
2016Co-Authors: John M Huisman, Frederik Leliaert, Heroen Verbruggen, Roberta A TownsendAbstract:Abstract – One hundred and twenty-one species of marine algae, seagrasses and cyanobacteria are reported from the offshore atolls of northwestern Western Australia (the Rowley Shoals, Scott Reef and Seringapatam Reef). Included are 65 species of Rhodophyta, 40 species of Chlorophyta, nine species of Phaeophyceae, three species of Cyanophyta and four species of seagrasses. This report presents the first detailed account of marine Benthic algae from these atolls. Twenty-four species are newly recorded for Western Australia, with four species (Anadyomene wrightii, Rhipilia nigrescens, Ceramium krameri and Zellera tawallina) also newly recorded for Australia
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marine Benthic Plants of western australia s shelf edge atolls
Records of the western Australian Museum, 2009Co-Authors: John M Huisman, Frederik Leliaert, Heroen Verbruggen, Roberta A TownsendAbstract:One hundred and twenty-one species of marine algae, seagrasses and cyanobacteria are reported from the offshore atolls of northwestern Western Australia (the Rowley Shoals, Scott Reef and Seringapatam Reef). Included are 65 species of Rhodophyta, 40 species of Chlorophyta, nine species of Phaeophyceae, three species of Cyanophyta and four species of seagrasses. This report presents the first detailed account of marine Benthic algae from these atolls. Twenty-four species are newly recorded for Western Australia, with four species (Anadyomene wrightii, Rhipilia nigrescens, Ceramium krameri and Zellera tawallina) also newly recorded for Australia.