WASHINGTON – Scientists say this summer’s drought may have been a blessing in disguise for the Chesapeake Bay, blunting the record spring rains that flooded the bay with freshwater and pollutants.
“They just kind of canceled each other out,” said Bill Goldsburrough, senior scientist for the Chesapeake Bay Foundation.
Without the drought, the salinity of the bay would be way down, causing terrible conditions for oyster reproduction and limiting crabs to those high-salt areas of the bay, he said.
The drought also slowed the flow of pollutants and runoff into the bay, giving it a chance to flush itself out after the intense spring rains left poor water quality.
“This year has been very unusual,” said Goldsburrough.
He said the stream-flow reached record highs, bringing nutrients and sediments pouring into the bay and lowering salt levels. It was still flowing heavily in July, which marked the beginning of this summer’s drought.
But scientists note that too much drought, without the benefit of the heavy spring rains to balance it out, would also have been bad for the bay.
Lack of rain lowers river flows, which leads to high salt concentrations in the bay.
When salt levels rise, largemouth bass, catfish and other freshwater fish are restricted to a smaller part of the bay, said Harley Speir, of the Maryland Department of Natural Resources.
But most denizens of the Chesapeake can cope with the wide range in salinity, from ocean to freshwater, that makes the bay such a productive fishery.
Since white perch, striped bass and toadfish easily adapt to changing salinity, for example, they are not affected by the increased salt concentration, said Speir.
Crabs are also adaptable, although “they do like a touch of salinity,” Speir said. Increased salt levels throughout the bay allow crabs to expand their usual habitat.
The drought brings good news and bad news for oysters, the scientists agreed. While higher salinity is better for reproduction, the parasites that feed off oysters also flourish in salty waters.
“It’s kind of a two-edged sword for oysters,” Speir said.
And because of the increased salinity, Speir said skiers and swimmers in the bay “are going to see more jellyfish.”
Stinging jellyfish were not as prevalent in the beginning of the summer, but they did appear later on.
Goldsburrough said it is hard to predict what will happen next year because “jellyfish are pretty much a one-year phenomenon.” But if it is as dry next spring as it was at the end of this summer, jellyfish could be a problem.
The wild swings in the bay’s salinity can be at least partly attributed to human influences, Goldsburrough said.
In natural conditions, a groundwater reserve would slowly filter water into the bay, keeping salt concentrations at a fairly even level. But human development has increased the runoff that, in turn, brings more pollutants into the bay and decreases salinity.
Dirt and fertilizers that run into the bay are suspended in the water, causing increased cloudiness. The nutrients stimulate algae growth, which gives the water a “pea soup” density, Goldsburrough said.
The biggest problem caused by increased bay pollution, according to Goldsburrough, is lack of sunlight to oxygen- producing grasses. The murky water prevents next year’s sea grasses from storing energy. It also leads to low and sometimes nonexistent levels of oxygen at the bottom of the bay.