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 Discussion Nitrate levels were consistently poor at Greenwich Bay Marina, which may be due to fuel discharge from boats and the fact that the area is not well flushed (31). These findings are supported by BART, which states that Greenwich Bay is generally polluted with nutrients (29). Storm water runoff, leaking septic systems, and homes with sewage pipes illegally tied into storm drains also introduces nitrogen to the bay. Nitrogen inputs can cause increased growth of algae, causing dissolved oxygen loss which makes it difficult for fish to survive (33). Nitrate fluctuations at URI GSO and East Matunuk could be due to inputs of pollution and nutrients from runoff. Nitrate levels for Greenwich Bay on October 4th and November 15th, URI GSO on October 4th, and East Matunuk on October 4th are rankings of one, which signifies poor water quality. However, a change from a ranking of one on October 4th to a ranking of four on November 15th at both URI GSO and East Matunuk shows that these conditions are not constant. Also, due to the fact that these locations are in more well flushed sections of the bay, it is unlikely that the data obtained signifies a pollution problem. Phosphate levels fluctuate slightly between rankings of "good" and "excellent". Phosphate inputs, like nitrate, can also be from pollution and nutrients from runoff. This slight change does not require special attention, specifically because nitrate is more of a limiting nutrient for plant growth than phosphate in marine systems. The fish kills at the Boys and Girls Club of Pawtucket and Roger Williams University could have been caused by low oxygen levels from algal blooms, poor tidal exchange caused by neap tides, or predation pressure (29). However, these sites are very different in terms of how well flushed they are, so reasons for the kills may vary across the two locations. Water quality data was not very different between the two sites, so I used records from BART to see if there were any differences between the two locations. Unfortunately, RWU data is not up to date. Phillipsdale (above) data for October 4, 2008 shows a change in the percent saturation of dissolved oxygen at the bottom of the river from 84.7% at 4:32am to 28.4% at 8:17am. At 28.4% saturation, dissolved oxygen concentration was 2.32 ppm. Although this shows a significant decline in water quality, and creates conditions in which fish could not survive, the fish at this location appeared to be dead for a long time. I then looked at the BART data for dissolved oxygen levels for the days prior to October 4th, and found consistent dissolved oxygen levels below 50% saturation for each day in the month of September, 2008. In fact, certain dates report percent saturation levels below 10%, which is less than 1ppm. This is extremely low water quality, and would not support fish life. Left: Range of tolerance for dissolved oxygen in fish (http://www.pbs.org/safarchive). Although the RI DEM states that fish kills often occur for natural rather than anthropogenic reasons, the consistently low dissolved oxygen levels in the Seekonk River signify that fish may not even be able to survive in these waters. The 2006-2007 "State of the Bay" report by Save the Bay shows that although some indicators of water quality and ecosystem health are improving, there has been sharp declines in the amount of fish and shellfish, and a "spreading area of low dissolved oxygen and unusually warm water temperatures creating a 'dead zone' on the bottom" (32). This statement correlates with the data collected from the Seekonk River. Save the Bay states that this is proof that improving conditions in the bay requires better  planning and environmental stewardship (32). Save the Bay also states that hypoxia and anoxia are the largest threats to bay health because of the drastic effects these conditions can have on ecosystem function. The decrease in dissolved oxygen levels is mainly due to increasing water temperatures, which has also magnified the affects of  nutrient pollution and has changed species composition away from native species to those that tolerate warmer waters and less oxygen. Increasing temperatures continue to undermine the efforts of policy and management strategies to improve the health of the bay. Unfortunately, mediating the increased temperatures caused by climate change requires efforts on a global scale. Rhode Island can do their part by improving monitoring efforts,  pushing for renewable energy sources, and decreasing emissions (32). The 2006-2007 "State of the Bay" also states that nitrogen levels have been improving in the bay, which supports the data I obtained for nitrogen levels with the exception of Greenwich Bay. Save the Bay recommends that all major wastewater treatment plants in the Narragansett Bay Watershed use systems to remove nitrogen in order to further improve nitrogen levels. This is even more important for the larger cities in the Narragansett Bay watershed such as Providence, East Providence, Worcester and Woonsocket. The CSO abatement program should also decrease point and nonpoint sources of nitrogen pollution from entering the bay. The "State of the Bay" also asses harmful bacteria and pathogens in the bay; something I couldn't test in my water samples because they needed to be frozen. Pollution associated with harmful bacteria and pathogens has declined since 2006, but the CSO abatement program should also improve these conditions as well (32).