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SFS Annual Meeting

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Nutrient enrichment can have strong effects on macroinvertebrate communities, yet the comparative effects of nitrogen and phosphorus is not well understood. Here, we examine relationships between nutrient concentrations and macroinvertebrate communities in streams and reservoirs in the Ohio River Basin. Benthic macroinvertebrates were surveyed and nitrogen, phosphorus, nitrate, and orthophosphate concentrations measured at 37 sites distributed across agricultural, mixed-use, and forested catchments (n= 3). On average, total nitrogen concentrations were higher in agricultural than forested streams and in the mixed-use reservoir than the agricultural and forested reservoirs. Orthophosphate concentrations were higher in mixed-use than forested streams. In streams, preliminary data indicate that macroinvertebrate density and species richness were positively correlated with total nitrogen and nitrate, but not phosphorus. In contrast, density, species richness, and Shannon diversity first increased and then decreased at higher total nitrogen concentrations in reservoirs, thus showing a subsidy-stress response. Density and species richness were also significantly higher in the agricultural vs. the forested reservoir. These results provide initial evidence that nitrogen enrichment may exert stronger effects than phosphorus on macroinvertebrate communities in this system, although we anticipate that stoichiometric relationships will likely be most predictive.

Rebecca Czaja (Primary Presenter/Author), The Ohio State University,;

Krystal Pocock (Co-Presenter/Co-Author), The Ohio State University,;

Kay C. Stefanik (Co-Presenter/Co-Author), The Ohio State University,;

Lauren M. Pintor (Co-Presenter/Co-Author), The Ohio State University,;

S. Ma┼żeika P. Sullivan (Co-Presenter/Co-Author), The Ohio State University,;