THE ECOLOGY OF PHYTOPLANKTON BLOOMS IN MORICHES BAY AND GREAT SOUTH BAY, LONG ISLAND, NEW YORK

Abstract

1. The phytoplankton bloom in Great South Bay and Moriches Bay during the spring, summer, and early fall of 1952 consisted of the Chlorophyta, Nannochloris atomus and Stichococcus sp., to the virtual exclusion of other species. These organisms persisted throughout the year, but were accompanied by minor diatom blooms during the winter and early spring.2. Growth rates of Nannochloris, Stichococcus, and the diatom, Nitzschia closterium were determined from laboratory cultures grown under various conditions of temperature, salinity, and nutrients which are peculiar to the Great South Bay-Moriches Bay area.3. Nannochloris and Stichococcus grew well in nitrogen present as nitrate, nitrite, ammonia, urea, uric acid, cystine, asparagin, and glycocoll. Nitzschia grew equally well in nitrate and nitrite, but showed poor growth in ammonia and the organic N compounds.4. Nannochloris and Stichococcus grew approximately twice as fast in media containing an N:P ratio of 5:1 as they did in media with a 15:1 ratio of these elements. The growth rate of Nitzschia was the same in both media.5. Nannochloris and Stichococcus appear to be brackish water forms with salinity optima of about 170/00, but both species grew well within a salinity range of 3-340/00. Nitzschia, a typical marine form, was unable to grow in low salinity water.6. Nannochloris and Stichococcus grew at temperatures of 10-30° C., with very slight growth at 10° and an optimum range of 15-25°. Nitzschia grew within a temperature range of 5-25° with its best growth at 15°.7. Pollution from duck farms bordering Moriches Bay heavily enriches the bay waters with plant nutrients. The presence of organic nitrogen compounds and the low ratio of nitrogen to phosphorus in the pollutants favor the growth of Nannochloris and Stichococcus over that of the more typical estuarine phytoplankton.8. The peculiar nature of the pollutants together with low salinities and high water temperatures occurring at the time and place of maximum enrichment of the bay waters are factors which may explain the persistent dominance of the Nannochloris-Stichococcus community in the annually recurring plankton blooms in Great South Bay and Moriches Bay.