Frequencies of coral disease in areas suspected of sewage-contaminated groundwater outflow in Bonaire N.A.
Anthropogenically induced stressors are degrading coral reefs globally. Nutrients and bacteria present in wastewater increase the frequency and severity of coral disease. As a result of the lack of sewage treatment and poor sewage containment in Bonaire, N.A., the surrounding coastal marine environment is likely the endpoint of sewage-contaminated groundwater, especially near resort areas where water use is high and only a small portion of sewage is trucked away. This study compared the frequency of coral disease at three sites adjacent to resorts (with >100 beds) with three sites in the same region of the leeward coast that are not adjacent to resorts. Because areas where groundwater is entering the near-shore environment have not been identified; physical parameters of the seawater (temperature, specific conductivity, dissolved oxygen, and pH) at the six sites were measured using a YSI multiparameter probe held directly above the substrate in areas 100 m wide along depths of 3, 6, 9, 12, and 18 m. To detect the presence of enterococci, a fecal indicator bacteria, six water samples were collected at 3, 9, and 18 m isobaths, 0.5 m below the surface and above the substrate. Additionally, water samples were collected twice at 3, 6, 9, 12, and 18 m to determine ammonia concentrations at each site. To determine the frequencies of disease in hard coral (≥20 cm) and soft corals (sea fans, sea rods, sea plumes), three 10 x 1 m transects were surveyed at 3, 6, 9, and 18 m at all sites. The relationship between depth and specific conductivity, temperature, dissolved oxygen, and pH were similar for all sites except 18th Palm. Significantly higher concentrations of ammonia were found at resort sites (p=0.016). Enterococci was detected at the three resort sites in greater concentrations than at non-resort sites. Disease in hard and soft corals did not differ between site types. This study suggests that coral reefs adjacent to resorts have greater concentrations of ammonia and enterococci, common wastewater indicators. Although the frequencies of soft and hard coral disease were not significant between sites, the abundance of hard corals was significantly lower at resort than at nonresort sites (p=0.010). Soft corals were less abundant at resort sites than at non-resort sites, but the difference was not statistically significant (p=0.059).
This student research was retrieved from Physis: Journal of Marine Science VII (Spring 2010)19: 1-11 from CIEE Bonaire.