The effect of nitrogen loading on a brackish estuarine faunal community: A stable isotope approach |
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Authors: | Rachel?A?Keats Email author" target="_blank">Laurie?J?OsherEmail author Hilary?A?Neckles |
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Institution: | (1) Department of Biological Sciences and Southeast Environmental Research Center, Florida International University, Miami, FL 33199, USA; |
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Abstract: | Coastal ecosystems worldwide face increased nutrient enrichment from shoreline and watershed development and atmospheric pollution.
We investigated the response of the faunal community of a small microtidal estuary dominated byRuppia maritima (widgeon grass) in Maine, United States, to increased nitrogen loading using an in situ mesocosm enrichment experiment. Community
response was characterized by assessing quantitative shifts in macroinvertebrate community composition and identifying changes
in food web structure using stable carbon and nitrogen isotope ratios of producers and consumers. The community was dominated
by brackish water invertebrates including midge larvae, oligochaetes, damselfly larvae, amphipods, and ostracods. Experimental
nutrient additions resulted in significantly lower densities of herbivorous chironomids and predatory damselflies and greater
densities of deposit feeding oligochaetes. Grazing midge larvae (Chironomidae:Dicrotendipes, Cricotopus) consumed epiphytic algae under both natural and enriched conditions. Deposit feedingChironomus was dependent on allochthonous sources of detritus under natural conditions and exhibited a shift to autochthonous sources
of detritus under enriched conditions. PredatoryEnallagma primarily consumed grazing chironomids under all but the highest loading conditions. Experimental nutrient loading resulted
in an increase in generalist deposit feeders dependent on autochthonous sources of detritus. |
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