STABLE ISOTOPE (CNS) VARIABILITY IN MODERN AND HISTORICAL FAUNA OF BARNEGAT BAY, NJ

Barnegat Bay, New Jersey has experienced long-term nitrogen pollution, resulting in harmful algal blooms and eutrophic conditions. Degraded water quality threatens ecosystems and habitats and weakens local economies. In this study, we aim to assess spatial variability and long-term changes in nutrient pollution to the Bay by analyzing stable isotope (δ¹⁵N, δ¹³C, δ³⁴S) values of modern flora and low-trophic fauna, preserved fish tissues and shell-bound organic material in historical mollusk shells. Historical samples range in collection dates from 1880 to 1980, are spatially separated, and consist of mollusks including: mussels, oysters, clams, mudsnails, as well as Fundulus sp. (fish). Stable nitrogen (N) isotopes reflect natural and anthropogenic sources of N to the environment, such as N derived from upwelling, atmospheric deposition, N fixation, sewage, and chemical and organic fertilizers. Additionally, enhanced nitrogen processing occurs under excess nitrogen loads and can impart a heavy δ¹⁵N signature, regardless of source. Stable carbon and sulfur isotopes also act as tracers of nutrient source and microbial activity. Our initial results suggest somewhat enriched δ¹⁵N in estuarine organisms in comparison with other northeastern estuaries, which was not reflected in a previous analysis of soil profiles. This information provides new perspectives on signatures of eutrophication in Barnegat Bay. Initial measurements of shell-bound organic material from historical mudsnails shows a depletion of ¹⁵N since 1912 by more than 8‰, which if confirmed by additional samples, suggests a radical change in nutrient source to the estuary. Meanwhile, mudsnails collected in 1924 from Cape May Harbor, an estuary 20 miles South of Barnegat Bay, do not contrast significantly from the modern. While surrounding land use differs in each location, this may imply that Barnegat Bay is more heavily impacted by nutrient pollution than other local estuaries. These data will identify spatial patterns in nutrient source and processing that can be used to guide remediation efforts in Barnegat Bay.