Stable isotope analyses (δ15N and δ13C) of the trophic relationships of Callinectes sapidus in two north Carolina estuaries

The present study focused on detecting variations in trophic relationships among blue crab (Callinectes sapidus) consumers according to water quality along two estuaries in North Carolina. Stable isotope (delta N-15 and delta C-13) analyses of particulate organic matter and bivalve (Rangia cuneata and Corbicula fluminea) food sources were examined in combination with an Isosource mixing model. Results suggest that blue crab delta C-13 values increased significantly with increasing salinity from upper to lower sites along the Neuse River estuary (NRE; R-2 = 0.87, p < 0.01) and Alligator River estuary (R-2 = 0.92, p < 0.01). There was a positive relationship between blue crab delta N-15 values and nitrate concentrations for the NRE (R-2 = 0.48, p = 0.12). This study found that blue crab delta C-13 values increased with salinity from upper to lower regions along both estuaries. Results suggest that blue crab production may have used alternative food sources that were isotopically (delta C-13) depleted, especially in the upper NRF, and enriched sources in the mid to lower regions of both estuaries. Consumers sampled from the upper NRE may be influenced by higher nitrogen input from urban land use and municipal wastewater.