Museum Collections Yield Information on Nitrogen Sources for Coastal Gulf of Mexico, North Carolina, and Caribbean Sea Invertebrates, 1850 to 2004

Abstract

Aconsequence of land-use change and increasing human population in the United States and Central America has been an increase in nitrogen availability to coastal systems. Whereas many studies evaluate the influence of anthropogenically derived nutrients in modern oceans, fewer studies evaluate nutrient sources in coastal environments before the 1960s. This study used stable C and N isotope values of 35 big-claw snapping shrimps (Alpheus heterochaelis) and 48 ivory barnacles (Balanus eburneus) across the Gulf of Mexico, southeast coast of the United States, and the Caribbean over 121 y to examine whether human-derived nitrogen was used by coastal invertebrates. Gulf of Mexico and southeast U.S. collections were divided into preand post-1960 groups for analysis, roughly coinciding with the increase in fertilizer use associated with the “Green Revolution” and large coastal population increases. For B. eburneus, δ15N decreased in the coastal United States after 1960, but that was not the case for A. heterochaelis. 15N-depleted fertilizer would be quickly incorporated by filter-feeding B. eburneus (via plankton). By contrast, the scavenging, omnivorous, A. heterochaelis would obtain more N from heterotrophic organic matter more isolated from the 15N-depleted fertilizer signal. The Caribbean A. heterochaelis incorporated seagrass C and N. Local variation in N sources from the different collection areas was clearly observed. Although anthropogenic N has been making its way into the filter-feeding barnacles, it is not as apparent in the scavengers.