Relationships between Nutrient Enrichment and Benthic Function: Local Effects and Spatial Patterns |
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| Authors: | Mohamed A Abdelrhman Giancarlo Cicchetti |
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| Institution: | (1) Atlantic Ecology Division, US Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, 27 Tarzwell Drive, Narragansett, RI 02882, USA |
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| Abstract: | Eutrophication-induced changes to benthic faunal activities are problems of significant ecological impact, affecting global
nutrient budgets as well as local trophic connections. We address the question of how nitrogen loads to estuarine embayments
alter the bioturbation activities of benthic fauna. Specifically, we related local benthic activities to calculated local
nitrogen concentrations for 22 northeastern US estuaries. These local nitrogen concentrations were derived from the calculated
nitrogen loading for the embayment together with the spatial distribution of the local flushing time. Our results showed a
maximum bioturbation rate at intermediate nitrogen concentrations or a “hump-shaped” pattern of response. This behavior was
evident in all embayments that had a range of concentrations including low, intermediate, and high values. Embayments where
sampling did not include this full range did not show this behavior. This work provides methods and guidance to help managers
make decisions concerning the effects of nitrogen loading on the activities and well-being of benthic fauna in coastal embayments.
The novelty of this approach lies in identifying the response of bioturbation to nitrogen loading in many systems, without
costly and time-consuming speciation of benthic fauna, and also in rapidly identifying embayments and aquatic areas with vulnerable
fauna. These results are ecologically significant in supporting the hypothesis that benthic organism abundance and activity
will peak at mid-levels of nitrogen due to the interplay of food availability and oxygen levels, noting that the critical
levels of these factors differ among water bodies. |
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