Biotic communities

Benthic algal species receive elevated nitrogen (N) and phosphorus (P)
availability as anthropogenic activities increase the loading of nutrients into coastal
waters. Pelagic species could also be responding to this nutrient enrichment. This study
compared the tissue nutrient content and productivity of three benthic and two pelagic
species of Sargassum. We hypothesized that the benthic species would have a higher
tissue nutrient content and productivity than the pelagic species and the pelagic species
would have a higher tissue nutrient content and productivity than historic data. The tissue
nutrient content and net productivity of the benthic and pelagic species were not
significantly different indicating that the pelagic species are receiving high levels of
nutrient availability comparable to that of the benthic species. Pelagic species in the
current study exhibited significantly higher N:P ratios and net productivity than the
historic data, suggesting a shift from N to P limitation and increased productivity.

Little Lake Worth (LLW) (800 m x 200 m x 8« m) is an artificially deep, monomictic marine basin. Pigments and other water quality parameters (O2, pH, T, S, NO3 -. etc.) were utilized to characterize phototrophic communities and water quality. The water column is dominated by diatoms except in the hypolimnon during stratification events (late Summer) when strong anoxia and H2S favors abundant Chlorobium sulfur bacteria. Results indicate nitrate-enriched freshwater baseflow indicative of septic tank seepage during the wet season. This also appears to lead to the accumulation of concentrated organic matter in the sediment. LLW is a potential threat to the health of the ecosystem and the humans using it recreationally. More research is required to verify the effectiveness of restoration options. The spatial and temporal distribution of Chlorobium (phaeovibiroides tent.) and their Bacteriochlorophyll-e homologues is described and compared to similar studies.