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There
is consensus among scientists who study Narragansett Bay that climate
change is affecting the bay, and could alter the ecology and circulation
of the ecosystem. Bay water temperatures have risen about 2°C in winter and 1°C in summer over the past few decades, and it is predicted that Rhode Island air temperatures could increase 5°C in the coming years. If so, it is projected that the Narragansett Bay ecosystem will approximate coastal ecosystems currently found in South Carolina. Over the last 50 years, the ecosystem of Narragansett Bay has been changed by nutrient loading and overfishing. Nutrients “fertilize” the water, which promotes algal growth and can lead to decreased dissolved oxygen for other aquatic plants and animals. Increases in sea surface temperatures amplify these effects. Nutrient loading to the upper bay is above what is considered acceptable for eelgrass. Increased algae can block sunlight from reaching the eelgrass and diminish water quality. When warming waters due to climate change are added, eelgrass restoration efforts in the upper bay are less than successful. Nuisance algae are becoming more and more common in upper bay areas. The R.I. Department of Environmental Management fisheries trawl surveys were cut back in the upper bay in the mid-1980s due to the trawl nets being choked with algae. In 2004, all trawl survey stations in the upper bay were abandoned for this reason. Climate change also results in shifts in precipitation, and the indication is that precipitation volume is increasing in the Narragansett Bay watershed, which is witnessing as much as a 30 percent increase in precipitation since 1900.
Rainstorms drive nutrients into Narragansett Bay as large quantities
of nitrogen from river and sewage treatment facilities overflow to
bay waters. Increases in impervious surfaces in the watershed, such
as paved roads or parking lots, combined with increased precipitation,
will increase the nutrients that runoff these surfaces to the bay. |
A few degrees’ increase in annual surface
water temperature is significant in shallow water systems such
as Narragansett Bay, exacerbating nutrient impacts to its animal
and plant life. How climate change will fully impact the bay is
nearly impossible to accurately predict, but certainly changes will
occur, and these changes can be unexpected and sometimes startling. For instance, the warming currently affecting the bay has drastically reduced the magnitude of its fundamental food production process—the annual winter-spring phytoplankton bloom. With this link in the food web removed, impacts on other components of the ecosystem, including species declines, are not yet known. The warming of the bay has also increased the abundance of a ctenophore (comb jelly) that has now become abundant earlier in the season. Ctenophores are voracious predators that further affect the food web by consuming zooplankton during summer months, allowing a summer phytoplankton bloom to occur in the upper bay. This bloom might heighten the problem of low oxygen (hypoxia) by providing more organic matter to bottom waters for decomposition—a process that consumes oxygen. An additional concern is that the warming of Narragansett Bay may allow southern species, including invasive species, to move northward and infiltrate the bay ecosystem, further impacting its ecology. For instance, the lionfish, a voracious, invasive predator from more tropical waters, has been noted in waters near Jamestown. There is every indication that this warming trend will continue, and it appears New England will continue to get wetter as well, at least over the near term. Environmental management strategies must incorporate and consider climate change, and they will need to be flexible to respond to the shifts changing climate brings to the Narragansett Bay ecosystem. To do otherwise will be neither productive nor prudent. The Brayton Point plant is a triple threat -- damaging our water and our land as well as poisoning our air. CLF successfully settled a lawsuit against PG&E about its practice of dumping toxic coal waste in unlined pits that leach into surrounding land and water. Following up on that settlement, and forcing a comprehensive cleanup of PG&E's waste disposal practices will not be easy -- but it is essential. Similarly, we need to confront the fact that PG&E continues to discharge heated water into Mount Hope Bay, the easternmost arm of Narragansett Bay, wiping out fish that once thrived there and creating a virtual dead zone. —Barry A. Costa-Pierce is the director of Rhode Island Sea Grant. Alan
Desbonnet is the assistant director of Rhode Island Sea Grant. |
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