Evaluation of Nitrogen and Carbon Stable Isotopes in Filter Feeding Bivalves and Surficial Sediment for Assessing Aquatic Condition in Lakes and Estuaries

James L Lake; Jonathan R Serbst; Anne Kuhn; Michael Charpentier; Nathan J Smucker

doi:10.3390/w14223712

Evaluation of Nitrogen and Carbon Stable Isotopes in Filter Feeding Bivalves and Surficial Sediment for Assessing Aquatic Condition in Lakes and Estuaries

Water (Basel). 2022 Nov 16;14(22):1-12. doi: 10.3390/w14223712.

Authors

James L Lake¹, Jonathan R Serbst¹, Anne Kuhn¹, Michael Charpentier², Nathan J Smucker³

Affiliations

¹ US Environmental Protection Agency, Office of Research and Development, 27 Tarzwell Drive, Narragansett, RI 02882, USA.
² General Dynamics Information Technology, 27 Tarzwell Drive, Narragansett, RI 02882, USA.
³ US Environmental Protection Agency, Office of Research and Development, 26 Martin Luther King Drive W., Cincinnati, OH 45268, USA.

Abstract

Excessive inputs of nitrogen from anthropogenic activities in watersheds can cause detrimental effects to aquatic ecosystems, but these effects can be difficult to determine based solely on nitrogen concentrations because of their temporal variability and the need to link human activities to ecological responses. Here, we (1) tested the use of stable isotopes of nitrogen (δ¹⁵N) and carbon (δ¹³C) in benthic organic matter (BOM) as proxies for isotope ratios of filter feeding bivalves in lakes and estuaries, which can be used as indicators but are harder to sample and often spatially sparse, and (2) evaluated if stable isotope ratios in benthic organic matter could be used to assess impacts from anthropogenic land development of watersheds. The δ¹⁵N in BOM isolated from surficial sediment (δ¹⁵N_BOM) was significantly correlated with δ¹⁵N in filter feeding unionid mussels (Elliptio complanata, δ¹⁵N_UN) from lakes and with hard-shell clams (Mercenaria mercenaria, δ¹⁵N_MM) from estuaries. In lakes, δ¹³C_BOM was significantly correlated with δ¹³C_UN, but δ¹³C_BOM was not significantly correlated with δ¹³C_MM in estuaries. Values of δ¹⁵N_BOM and δ¹⁵N_UN were significantly and positively correlated with increasing amounts of impervious surface, urban land cover, and human populations in watersheds surrounding lakes. In estuaries, δ¹⁵N_BOM was only significantly and positively correlated with greater percent impervious surface in the watersheds. Correlations of δ¹³C_BOM in lakes and estuaries, δ¹³C_UN, and δ¹³C_MM with land use and human population were mostly non-significant or weak. Overall, these results show that δ¹⁵N_BOM can serve as a proxy for δ¹⁵N of filter feeding bivalves in lakes and estuaries and is useful for assessing anthropogenic impacts on aquatic systems and resources. Our study area was limited in size, but our results support further studies to test the application of this sediment stable isotope-based technique for assessing and ranking aquatic resources across broad geographical areas.

Keywords: bivalves; impervious surface; nitrogen; nitrogen and carbon stable isotopes; nutrients; sediments; urban; watershed.

Grants and funding

EPA999999/Intramural EPA/United States