The abundances, distribution and flux of nutrients and chlorophyll a in the New York Bight apex

Abstract

Tidal, spatial and seasonal changes in salinity, temperature and the concentrations of ammonium, nitrite, nitrate, phosphate, silicic acid, chlorophyll a and suspended matter in the waters between Sandy Hook, New Jersey, and Rockaway Point, New York, were measured during five cruises which took place between November 1973 and June 1974. Over this period concentrations of nutrients and chlorophyll a were much greater than those found in the adjacent coastal waters. The main source of the ammonium, nitrite and phosphate is sewage effluent which is discharged into the waters surrounding the New York metropolitan region; nitrate comes mainly from the Hudson River and silicic acid is discharged in large amounts from river and sewage sources. The largest tidal variation in salinity and nutrient and chlorophyll a concentrations occurs near Sandy Hook where the Hudson River discharge has the greatest influence. Near Rockaway Point, nutrient and chlorophyll a concentrations are generally lower and salinities higher than those observed near Sandy Hook because of the inflow of Bight water by non-tidal currents. During the spring freshet nutrient concentrations, especially ammonium, are low along the transect due to (1) dilution by the spring freshet and (2) utilization by the abundant phytoplankton. Flux calculations for the June observations indicate that most of the nutrients and chlorophyll a are being transported from the lower Hudson Estuary into the New York Bight apex.