HISTORY OF HUMAN IMPACTS ON ECOLOGY OF NORTH CAROLINA ESTUARIES

Paleoecological methods make it possible to quantify historical ecological impacts of human settlement and development on estuaries. For this research, sediment cores were collected from the Neuse and Pamlico River estuaries of North Carolina at seven sites, and sample data show strong anthropogenic influence on water quality. The sediments were dated using 210Lead, 137Cesium, radiocarbon and pollen horizon techniques. Water quality parameters investigated include eutrophication (concentrations of nitrogen, phosphorus, sulfur, biogenic silica), selected trace metal flux, sedimentation rates, and benthic vs. pelagic habitat quality (diatom assemblages). Dominant algal groups in the Neuse and Pamlico include diatoms, dinoflagellates, and cryptophytes. Diatoms are particularly useful for paleoecological research because of their silica shell that is preserved in sediments, the morphology of which is species specific. Principal components analysis was performed on the data to summarize trends in diatom community assemblages, as well as the influence of environmental variables. The greatest increases in sedimentation, nutrient and metal flux, and change in diatom assemblages have occurred in the past ~60 years in the Pamlico and Neuse estuaries. Heavy metal concentrations exceed EPA Threshold Effects Levels at more than one site. Diatom diversity has decreased over time, and small planktonic forms have become dominant, most likely due to eutrophication and increased sedimentation. Overall trends are similar between the two estuaries, with some interesting differences that may be related to salinity and nutrient ratios. The North Carolina estuaries are experiencing similar, but more recent, water quality issues related to anthropogenic sources as compared to Chesapeake Bay.