EAST BAY — Chris Deacutis, chief scientist for the Narragansett Bay Estuary Program (NBEP) at the URI Bay Campus, has been working on the issue of excess nutrients (nitrogen) and the low oxygen issue in the upper half of Narragansett Bay for over 10 years.
Today things are better, but Bay advocates are still combating nutrients in the Bay that create algae blooms (which actually create oxygen). But as algae decays it uses oxygen and reduces the oxygen level in the water, often times well below the levels that fish need. This low oxygen level has occurred in Greenwich Bay in the summer as well as in other parts of the Bay.
With a prevailing southwest summer wind in Narragansett Bay, Greenwich Bay (particularly East Greenwich Cove), does not get flushed and low oxygen levels are more prominent there, according to the NBEP, which measures oxygen levels in the Bay. “The famous menhaden fish kill of August 2003 was clearly caused by a sever hypoxia (actually anoxic — no oxygen) events that centered on western Greenwich Bay,” said Dr. Deacutis.
The NBEP eliminated the East Passage, the Mt. Hope Bay and the lower Bay from measurement because oxygen levels in these areas are good. The channel in the east passage acts as a conduit for flushing and mixing. Oxygen levels in deep water off Warwick Neck mix well too, due to the water passing from the east to the west passage and back. Water at Quonset Point and south have good oxygen levels as well.
According to the NBEP blog, “Marine animals breathe oxygen, too, and when oxygen levels drop below 3mg/L there is not enough oxygen to go around. Creatures that live on the bottom of the bay such as oysters, littlenecks and marine worms are at a greater risk during hypoxic events because they cannot move to a different area. Schooling fish such as menhaden are also affected by hypoxia because they are often chased into coves by predators such as striped bass and the school will use up the oxygen faster than it can be produced by photosynthesis or mixed into the water at the surface from the air.”
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