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Nitrogen-sensitive estuarine and coastal waters that experience rapid changes in nutrient status can be affected by large and frequently harmful algal blooms. Such symptoms of eutrophication have been seen in the Neuse River Estuary, NC. A new study investigates the annual cycles of phytoplankton bloom dynamics and community structure in the estuary. Significant variability in phytoplankton productivity, biomass and abundance were noted over a three-year period. It is suggested that meteorological conditions provide general control of phytoplankton dynamics.

Increase in nitrogen levels in the coastal waters and estuaries in North Carolina is caused by atmospheric nitrogen decomposition and determined from bioassays of microcosms. Intake of isotopically light nitrogen particulates to nitrogen by primary productivity. Increase in nitrogen is attributed to phytoplankton productivity, which increases during rainy seasons, indicating that rain increases nitrogen levels in the rivers of North Carolina.

Microbial mats swell on mud flat and marshy surface sediments and display high nitrogen fixation rates during the day. Denitrification rates for the mats increase in the dark. Nitrification rates for both the sites reach a peak in summer and the denitrification rates assume highest values in fall.

Natural rainwater was found to increase chlorophyll a (chl a) production in the Gulf Stream water off North Carolina, while synthetic rainwater caused less stimulation for chlorophyll production. Rainwater possesses phytoplankton stimulants and nitrate and ammonium compounds which enhance chlorophyll growth.