Being stationary, seagrass populations respond markedly and cumulatively to continued eutrophication over both time and space. Six seagrass meadows located within and near the eutrophic Kingston Harbour were investigated from October 1995 to June 1996 to determine the effects of increased
eutrophication on seagrass population dynamics. The stations were sited at Fort Augusta, Old Coal Wharf (eutrophic, harbor sites), Hellshire coast (mesotrophic) and Port Royal Cays (oligotrophic). Aerial productivity, leaf turnover rate, leaf area, shoot density and total biomass of Thalassia
testudinum were assessed during the period. In addition, the water quality at all the sites was monitored, using phytoplankton biomass as the primary index of water quality. These data were supplemented with water temperature, salinity, dissolved oxygen content, nutrients (nitrates + nitrites
and phosphates), and light extinction coefficient data at these sites. Although there were no significant differences in labile nutrient data at the six sites, the significant difference in phytoplankton biomass confirmed previous observations of a range of water qualities. Water quality ranged
from the eutrophic Kingston Harbour (>2.0 mg m−3 chl a), to mesotrophic Hellshire Bays (0.57±0.02 mg m−3 chl a), and the oligotrophic Port Royal Cays (0.21±0.01 mg m−3 chl a). Thalassia testudinum
populations exhibited an increase in leaf productivity rates (3.64±0.39 g dwt m−2 d−1 at South East Cay to 5.46±1.11 g dwt m−2 d−1 at Old Coal Wharf) and an increase in leaf area (11.64± 1.2 cm2
at South East Cay to 22.85 ± 2.87 cm2 at Fort Augusta) with increasing eutrophication. Conversely, there was a reduction in shoot density (917.25 ± 199.92 m−2at South East Cay to 459.62±65.35 m−2 at Old Coal Wharf) and total
biomass (972.68±88.39 g dwt m−2 at Rackhams Cay to 406.24±62.16 g dwt m−2 at Fort Augusta) with increasing eutrophication stress. Comparisons with previous studies from ten years before indicated that Thalassia testudinum shoot biomass
and density decreased at all sites, while leaf productivity rates increased at oligotrophic sites and decreased at eutrophic sites during this period.
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