In Bermuda, there is no national sewer system and limited sewage treatment facilities, so most sewage is disposed of 'on site' where it ultimately leaches into the sea. In other areas of the island, sewage is pumped into boreholes or directly into the ocean, with visiting cruise ships contributing significantly to this waste stream in the summer months. Sewage from the City of Hamilton and surrounding areas, including cruise ships, is disposed of at the Seabright Point submarine sewage outfall. At peak flow, 500,000 to 1,000,000 gallons of raw sewage is discharged every day. This sewage, as well as seepage from boreholes, represents a potentially significant source of pollution to Bermuda's inner reef environment.
The Coral Reef Ecology and Optics Lab (CREOL) is funded by the Corporation of Hamilton to conduct a five-year assessment (begun in 2012) of the marine environment and coral reef ecosystem near the Seabright Point sewage outfall. The two main project objectives are:
- to determine the fate of sewage discharge in the environment;
- to determine the impact, if any, of sewage discharge on the reef ecosystem.
Usually, horizontal mixing by currents and waves is much more rapid than the relatively slow sinking of dissolved nutrients and small particulates to the bottom. The implication is that sewage discharge in high energy environments, such as the Seabright Point area, quickly dilutes to ambient levels and that because of its exposure to the open sea, eutrophication is highly unlikely at the Seabright Point outfall. Objective (1) is intended to identify patterns of discharge transport, thereby indicating spatial gradients of potential impact.
The primary influence of sewage on reef ecosystems is increased water turbidity, either through direct discharge of particulates or through nutrient-enhanced stimulation of phytoplankton growth (eutrophication). Less common influences include burial of the seafloor by discharged particulates and death of benthic organisms due to discharged toxins. The long-term effect of these chronic disturbances can be observed by a shift in benthic community structure, from coral-rich to coral-poor. Any negative impact of the Seabright Point sewage outfall on the nearby reef ecosystem should manifest as lower coral abundance/cover relative to unimpacted areas. Objective (2) is intended to identify patterns of reef community structure, thereby indicating spatial gradients of actual impact.