Thursday, June 29, 2006

When Rains... It Pollutes

Since the beginning of June, Narragansett Bay's watershed has received nearly 9 inches of rain. While that's short of the record, the wet weather affecting the East is already having a severe impact on Narragansett Bay.

Wastewater bypasses have been common from treatment plants, Combined Sewer Overflows (CSO's), and storm sewers. Polluted runoff has been pouring into the Bay's tributary rivers. Many shellfishing areas and public beaches are already closed due to high bacteria levels (see the RIDOH Beaches Site).

We're already seeing major algae blooms and low dissolved oxygen in the Upper Bay from all the nitrogen being flushed in, and if we get hot, still weather in the coming weeks, we may be in for some serious water quality problems around the Bay. We'll be monitoring the situation closely.

Today's Warwick Beacon did a great story on this:

Warwick Beacon
Rain could mix lethal cocktail for bay

Written by HOWELL, JOHN
Thu, Jun 29 06

Near monsoon conditions this month have done more than wreak havoc with family barbecues, sporting events and vacation plans. It could also be the prelude to a major fish kill in Greenwich Bay and sections of Narragansett Bay.

That’s what people who monitor bay conditions fear.

The heavy and persistent rains are seen as the cause for a spike of nutrients – nitrogen – in bay waters resulting in algae blooms. The blooms are responsible for the water coloration, which in sections of the bay is currently a tea-brown but may also be yellow, red or green according to Joseph Migliore, principal environmental scientist with the Department of Environmental Management office of water resources.

But more important to the creatures living in the water, the blooms of plankton deplete the level of dissolved oxygen. And when the dissolved oxygen falls below 1 milligram per liter, finfish and shellfish start dying.

Migliore says whether Greenwich Bay experiences another massive fish kill like that of 2003 depends on a variety of factors. Winds and tides have an impact on the level of dissolved oxygen as well as the “flushing” of bay coves and inlets. Wave action, the result of wind, serves to restore oxygen to the water. Temperature also plays a role. Warmer water loses its ability to retain oxygen, so a spate of sunny weather that would spell relief for those of us on land could be the death knell for some aquatic organisms.

Signs are pointing to the potential for a lethal cocktail, especially for Greenwich Bay that doesn’t get the tidal activity of Narragansett Bay.

John Williams of Warwick Cove Marina and the Greenwich Bay Watershed Group, which monitors bay water quality on a weekly basis, started seeing the alarming indicators last week. The group measures water temperature, dissolved oxygen and salinity at several assigned locations under a program financed by the Narragansett Bay Estuary Program and the New England Grass Roots Environmental Fund. Samples taken the morning of June 24 found dissolved oxygen levels at 3.5 to 7.2 at a meter below the surface. At a meter from the bottom, however, conditions deteriorated. The readings read from a high of 3.9 at middle ground to 1.1 at Sally Rock.

“This is a wake-up call more than a proclamation of death,” Williams said yesterday, “we’ll leave that to the coroner.”

John Torgan, BayKeeper for Save the Bay, is concerned by the reports and what he is seeing on the bay.

“Unfortunately the conditions are similar to those that led up to the fish kill of 2003,” he said. He added that water conditions are particularly poor in the East Passage and “we are seeing major algae blooms.” Torgan said conditions are setting up “for periods of low dissolved oxygen” and for “dead zones in the bay.”

While the inability of the Providence wastewater treatment plant to process the loads it receives during periods of heavy rain – a condition that is being addressed with the construction of underground tunnels that will enable the retention of water until it can be treated – is seen as a major contributor of nutrients into the bay, it is not the only source. “It’s not just Providence that’s causing this,” said Torgan. He cites how storm runoff washes fertilizers into the bay as well as untreated water from failing septic systems and cesspools.

“When it rains, it [nutrients] pour into the bay,” he said.

Scientists believe there may be more factors at work.

Christopher Deacutis, chief scientist with the Narragansett Bay Estuary Program based at URI, says the introduction of fresh water, which is lighter than salt water, sets up a layering of waters within the water column. In effect, he said, the rain “seals off the bottom” from the mixing that occurs from wave activity. Further, Deacutis said, wind direction is thought to have a significant impact on Greenwich Bay water quality. It is thought that a westerly wind pushes the more sedentary waters on the Cowesett shoreline out into the bay where they are carried back again by the tide.

Finfish can escape by leaving areas that are low in dissolved oxygen, but shellfish are stuck.
Fortunately some shellfish can wait out the period of low to no levels of dissolved oxygen. Deacutis said mussels are among the most vulnerable and can last about a week. Soft shell clams can make it about two weeks and older mature quahogs can go for a month.
“Quahogs clam up, go into hibernation,” said Deacutis.

The next two weeks would appear to be especially critical. Deacutis notes that tides at this time are weak and that next week we will have a neap tide when the rise and fall of the tide is at its least variation.

Migliore says the “bay is very nutrient rich right now and the runoff is washing additional amounts of nutrients.” In this potent concoction, he said, is a number of competing plankton “some good and some not so good.”

The condition is not much different than a home aquarium.

“If you put too much fish food in the tank all of a sudden it goes green,” he said.
The difference, of course, is that reducing the nutrients flowing into the bay takes years to upgrade wastewater treatment plants and get residents to tie into sewer systems. Other actions such as wetland restoration also have an impact.

But for now, Migliore says, “there’s nothing we can do about it.”

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