sewage discharge

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.

Coral reef environments are diverse and productive ecosystems that supply a variety of benefits to marine species and humans alike. Unfortunately, these same reefs, including Bonaire’s, are under increased stress from anthropogenic activities such as nutrient and bacteria groundwater runoff. With poor sewage control, nutrients and bacteria can leech into the groundwater and flow directly into our reefs and thus increase the frequency and intensity of coral disease and bleaching. Enterococci, a common bacteria found in the intestines of humans, is used as an indicator of fecal contamination in water sources. In this study, 10-m transects and Enterococci water samples were taken at three high human impact (HHI) sites and two low human impact (LHI) sites. Although Enterococci was present in the water column at four of the sites, there was no correlation between increased Enterococci and abundance of coral disease. The Enterococci concentration levels at one site were higher than what the Environmental Protection Agency deems a healthy recreational water concentration. Coral disease was present at each site, with frequencies ranging from 12.4-19%. LHI sites had 4.2% more diseased coral than HHI sites. The direct cause of many coral diseases is unknown, although there are a variety of factors that likely contribute to their outbreak and spread. Tourism, terrestrial runoff and nutrient overload all affect coral disease abundance in Bonaire. Since coral disease was present at each site, further protection and prevention must be implemented to reduce the outbreak and spread of diseases before the coral reef is degraded past repair

This student research was retrieved from Physis: Journal of Marine Science XIV (Fall 2013)19: 41-48 from CIEE Bonaire.

Seagrass beds are globally declining due to human activities in coastal areas. We here aimed to identify threats from eutrophication to the valuable seagrass beds of Curaçao and Bonaire in the Caribbean, which function as nursery habitats for commercial fish species. We documented surface- and porewater nutrient concentrations, and seagrass nutrient concentrations in 6 bays varying in nutrient loads. Water measurements only provided a momentary snapshot, due to timing, tidal stage, etc., but Thalassia testudinum nutrient concentrations indicated long-term nutrient loads. Nutrient levels in most bays did not raise any concern, but high leaf % P values of Thalassia in Piscadera Bay (0.31%) and Spanish Water Bay (0.21%) showed that seagrasses may be threatened by eutrophication, due to emergency overflow of waste water and coastal housing. We thus showed that seagrasses may be threatened and measures should be taken to prevent loss of these important nursery areas due to eutrophication.