Ranston, Emma R.; Webber, Dale F.
Author Affiliation, Ana.
Department of Life Sciences
Phytoplankton distribution in a highly eutrophic estuarine bay, Hunts Bay, Kingston Harbour, Jamaica
Bulletin of marine science
Date of Publication
The phytoplankton community composition, abundance and size fractionated biomass (chlorophyll a) along with various physical, chemical and biological parameters were assessed monthly from December 1993 to February 1995 at two sampling depths at each of nine stations throughout Hunts Bay, Jamaica. The objective of the study was to investigate the distribution of the phytoplankton community within Hunts Bay in order to identify the major sources of stratification and ecological zones of Hunts Bay. Results indicated highly significant differences between surface and deep waters in physical, chemical and biological parameters, particularly during the wet season. This suggested a stratification, or vertical zonation of the Bay into two layers, an upper 0.5 m deep, fresh-brackish water (0-18 salinity) layer, and a deeper 0.5-2.5 m, more saline (24-30) layer. Horizontal variation in physical variables from station to station was low; thus, these variables were of little value in designating horizontal zonation of the Bay. Chemical and biological variables, however, were highly variable and along with community analyses, were quite valuable in designating the horizontal zones of the surface and deep-water layers of the Bay into four general regions: the North Bay, Middle Bay, South Bay and Outer Bay. Both surface and deep-water layers had the same zonation pattern and each zone (except for the Outer Bay) was dependent on, and influenced by, the nearest fresh water inflows. The Outer Bay was influenced more by close proximity to the saline water of Kingston Harbour. At North Bay stations, results of nutrient concentrations (PO4 = 0.73 ÁM), phytoplankton abundance (7.5 x 107 cells L-1), and biomass (18.69 mg chl a m-3) were all significantly (MANOVA, P <0.0001, df = 9) higher compared to the remaining stations of the bay. Therefore, the North Bay was classified as the most eutrophic area of Hunts Bay. There was an eutrophication gradient in the other zones from North to South Bay, followed by the Middle then Outer Bays. This confirms that Sandy Gully and the Duhaney River are the major sources of eutrophication to the Hunts Bay. The Rio Cobre may have significant effect on Hunts Bay; however, the volume of fresh water from this source dilutes the nutrient concentrations and flushes pollutants out of the Bay.....