Reef Macrobenthos Adjacent to a Major Navigational Inlet: Port Everglades, Florida

The reefs off Broward County, Florida, are non-accreting, lie near the northernmost limits of tropical coral reefs, and are now being affected by human influences including physical damage and pollution. Port Everglades may be a source of many anthropogenic contaminants, discharging freshwater, sediments, hydrocarbons, pesticides, heavy metals, and nutrients in a plume that sweeps over the coastal reef. These reefs should be considered fragile, and therefore warrant careful investigation, monitoring and management. This study surveyed the reef community immediately to the north and south of the Port Everglades inlet to determine if the inlet effluent plume produces a water quality gradient and associated biological gradient. Species composition and percent cover of corals, sponges and macroalgae were surveyed adjacent to the inlet using quadrat sampling, point-plotless and line-intercept transects. In addition, water quality parameters were measured from samples taken from the inlet plume including nitrites and nitrates, Total Kjeldahl nitrogen (TKJN), chlorophyll and specific conductivity, in order to delineate the plume and compare with benthic coverage. Live scleractinian coral cover was less than five percent at most sites and appeared to follow substrate variability rather than influence by water quality, and showed no significant correlation with distance from the inlet. However, coral mortality appeared to increase near the inlet, though not significantly. Fleshy macroalgae also showed notable increases at sites nearest the inlet, though no significant linear trend could be shown. Sponges showed no significant change in abundance with proximity to the inlet; however, sponge morphology appears variable in the nearshore environment, and measuring the size and shape of sponges rather than point-plotless estimates may give a more accurate picture of sponge cover. Chlorophyll levels over the reef were positively correlated with levels of nitrites and nitrates coming from the inlet, and coral cover was negatively correlated with chlorophyll concentrations, indicating an indirect correlation between coral cover and nitrites and nitrates. Coral cover was also negatively correlated with phosphorus at sites south of the inlet, and positively correlated with specific conductivity at all sites. Though macroalgae cover was not significantly correlated with any factor, fleshy macroalgae height was positively linked with levels of TKJN, but negatively linked with levels of phosphorus coming from the inlet. Sponge abundance was negatively correlated with nitrites and nitrates, and TKJN, and positively correlated with conductivity at sites south of the inlet. Of the transect methods used, point-plotless transects were fastest and most convenient. However, corals are sparse in the nearshore environment and the distance between each coral colony can increase the likelihood that point-plotless transects will miss coral colonies along a transect line. Sparse benthic cover also produced results with high variation using the quadrat analysis. Line-intercept transects record all cover of a benthic group being assessed along a transect, and thus seem more appropriate in an area of highly variable substrate and resulting biotic cover. This study concluded that Port Everglades affects the health and composition of the adjacent reef. Some biological categories appear to reflect water quality, though further assessment on a larger portion of the reef is recommended