The microscopic alga, Aureococcus anophagefferens, named brown tide for the muddy color it turns the water, first appeared in the Peconic Bay area in 1985. Brown tide blooms can form a thick layer in the water and block sunlight to underwater plants. Without light, the habitat that scallops and other marine life depend on for shelter is destroyed. Brown tide not only blocks sunlight, but also has a severe effect on bivalves, inhibiting their ability to eat, grow, and reproduce. Factors, which contribute to the onset of brown tide, remain subject to speculation. External nutrient loading, water circulation, water use, and meteorological patterns do not appear to be significantly different between the pre-and post-brown tide bloom eras. However, it is known that the land use in the Peconic's watershed has steadily changed and that the estuary receives significant freshwater input from groundwater infiltration. Nitrogen species may be flushed out of bay sediments by groundwater flow. Therefore chemical constituents introduced by groundwater infiltration may potentially have altered the bay's chemistry and biology and promoted brown tide proliferation.

Bioassays were performed by comparing relative growth rates of A. anophagefferens and other common phytoplankters cultured in a dilute seawater medium amended with varying amounts of urea to determine if indeed the expulsion of this nitrogen species into the Peconic causes the onset of brown tide blooms. Six concentrations of urea were added to each of the five cultures of algae creating a total of thirty samples. Daily extractions of 5 ml from each sample were measured for chlorophyll fluorescence. By examining gathered data at the end of an eighteen-day period of testing a trend was observed; the algae flourished under higher concentrations of urea. However, research is still in progress. Further analysis of data and research concerning organic nitrogen species and amino acids such as glutamic acid needs to be performed to gain a better understanding of the cause of detrimental brown tide blooms. A unique opportunity is presented by comparing data and growth rates of past experimentation concerning NO3 and NH4 with current experimentation using urea and glutamic acid. The ability to compare the growth of A. anophagefferens to other algal growth will illustrate what affects competitive advantage in the bays.

The Suffolk County Health Services Grant No. 008459 and Simons Grant 265210 supported this research.