Ecology of Atlantic Shores Erin Miller, 2008

Home -------------------------- Nahant -------------------------- Narragansett Bay: Introduction Water Quality Methods Observations Results Discussion -------------------------- Bermuda: Introduction Water Quality Coral Disease Aspergillosis Hypothesis and Methods Results Discussion -------------------------- Conclusions -------------------------- References

Narragansett Bay Water and Sewage Treatment Rhode Island’s sewage management programs began in 1901 with the Providence Sewage Treatment System, a chemical treatment plant at Field’s Point. This system proved to be inadequate due to Providence’s rapid growth, and much sewage went untreated in the early 1900s. By the mid-1900s the facility was being continuously renovated. In the 1970s, due to lack of a maintenance program, the facility at Field’s Point was discharging 65 million gallons of partially treated sewage into the bay per day. In 1979 the United States EPA addressed this issue, stating that it violated the Clean Water Act and ordering the city of Providence to tackle the problem. The Narragansett Bay Water Quality District Commission was established in response, developing an 87.7 million dollar  bond to make improvements at the Field’s Point facility (22). Rhode Island's combined sewer overflows (CSOs) were recognized to violate the Clean Water Act in the 1990s, and in March 1993 the Narragansett Bay Commission (NBC) developed a Combined Sewer Outflow Abatement Program. The three phase twenty year program plans for the construction of six miles of underground storage tunnels, two sedimentation/disinfection treatment facilities, and one wetland treatment system. Phase one of the project was initiated in 2002 and completed on time in 2008. Completion of the first phase could reduce outflow volume by about 40 percent, and may reopen shell fishing areas that have been closed for decades. Currently, sewer outflow causes over 11,000 acres of the bay to be temporarily closed for shell fishing when there is more than one-half inch of rainfall (22). Above: How CSOs work: during relatively dry periods the sewer system works as intended. During heavy rainstorms, sewer flows exceed the system capacity and water overfows into local rivers and the Narragansett Bay. This is called "combined sewer overflow" (22). Below: The completed section of the CSO underground storage tunnel (http://www.savebay.org). The Narragansett Bay Commission monitors the Field’s Point facility in Providence and the Bucklin Point facility in East Providence. Plant performance is evaluated on the basis of flow, total suspended solids (TSS), biochemical oxygen demand (BOD), and fecal coliform levels. The NBC’s permit requires no more than 30ppm TSS, 30ppm BOD, and 200MPN/100mL fecal coliform in the plant’s effluent (MPN is an abbreviation for “most probable number”, a statistical convention for measuring fecal coliform).Activated sludge and chlorination techniques are used at both facilities to clean the wastewater. Activated sludge refers to bacteria and other microorganisms that break down organic materials in the wastewater and are filtered out. Harmful bacteria are killed via chlorination, and dechlorination ensures that chlorine is removed before being released. At the Bucklin Point facility disinfection occurs by ultraviolet light instead of chlorination (22). ________________________________________________________________________________________________ Shell fishing Closures The Rhode Island Department of Environmental Management (DEM) identifies 21 growing areas (GAs) that are individually assessed to determine if shellfish in these locations are safe for human consumption (25). These areas are reclassified annually, and regulations are effective from a date around Memorial Day through Columbus Day each year (26). Evaluations are made and locations are placed on a permanent closure list or a seasonal closure list. Locations can also be placed on a conditional closure list whenever the DEM deems necessary due to changes in water quality. GA categories are often divided up into smaller subunits; maps of these regions and closures as of May 2008 can be accessed by the DEM classification map (25). The maps indicate that typically closed locations are coves, inlets, and river tributaries of the bay, due to their proximity to sewage overflow, runoff, and other sources of pollution (27). ________________________________________________________________________________________________ Other Water Quality Concerns In 2004 the Rhode Island DEM developed the Bay Assessment and Response Team (BART) in order to receive reports, assess impacts, develop solutions, and provide information and advice regarding environmental incidents (29). BART works with a number of agencies to collect data on water quality in Narragansett Bay through fixed water quality monitoring stations. The network and information they provide are an essential component of Rhode Island's monitoring strategy for the bay. Currently, there are 13 active stations which are distributed in order to represent the diversity of water quality in the bay. Most locations record data every fifteen minutes from spring to fall, collecting information on temperature, salinity, chlorophyll, and dissolved oxygen levels. Generally, water quality is worse in the northern parts of the bay near the bay's tributaries, and conditions improve as the bay opens into Rhode Island sound. In the summer months the locations with better water quality will report lower temperatures and chlorophyll levels, and higher salinity and dissolved oxygen levels(29). Left: Combined sewer overflow on the Woonasquatucket River Providence, and a heavy algal bloom (http://ian.umces.edu/imagelibrary). The DEM uses BART's data to assess the overall water quality of the bay as required by the Clean Water Act. Researchers and scientists also use this data to understand the ecological conditions of the bay, often in order to predict when and where water quality will "crash" and have detrimental effects on the bay ecosystem. These "crashes" refer to events such as hypoxia and anoxia, algal blooms, and fish kills (29). Hypoxic and anoxic waters are typically warm and sheltered areas with weak currents that hold low amounts of oxygen. Algal blooms are aided by pollution such as sewage, agricultural runoff, and erosion due to the nutrients that these events add to the waters. Warm, sheltered, and polluted waters are often located close to the shore, so low dissolved oxygen levels are often associated with algal blooms. Algal blooms are an ecological threat because they form dense mats that shadow flora below, further depleting dissolved oxygen and producing toxic hydrogen sulfide. Fish kills are most commonly caused by sudden low levels of dissolved oxygen which often occurs in sheltered, warm, and shallow waters (29). Recent fish kills in Narragansett Bay have been attributed to a variety of factors, such low oxygen levels caused by algal blooms, poor tidal exchange caused by neap tides, and predation pressure. Predatory fish may chase large schools of prey into shallower areas of the bay, causing more fish to draw oxygen from the water. This creates low dissolved oxygen levels which can stress fish and cause massive die offs (30). Right: A fish kill of juvenile menhaden in Greenwich Bay, August 2003 (http://ian.umces.edu/imagelibrary).