Despite all the sins visited upon the Chesapeake Bay over the years by man, scientists are finding to their relief that the bay is more forgiving than they had thought.
New data emerging from the first long-term study of water quality in the Chesapeake Bay indicate that Maryland's largest body of water will, if given the chance, bounce back from reduced pollution in a matter of years, and not decades as had previously been thought.
Scientists working on the five-year Land Margin Ecosystem Research project will present some of their findings this week at the biennial Chesapeake Bay Conference, which starts tomorrow Baltimore.
Though preliminary, their findings could prove helpful to those interested in cleaning up the bay -- both here and around the world. U.S. Sens. Paul S. Sarbanes and Barbara A. Mikulski of Maryland are scheduled to speak at the conference.
"All our research is supporting the view that in terms of nutrients coming from pollution, the bay has a pretty short memory. That's fairly new," said Walter Boynton, a professor at the University of Maryland's Center for Environmental and Estuarine Studies in Solomons.
Mr. Boynton and 12 other scientists are halfway through the $2.5 million ecosystem research project using long-term water measurements and computers that they hope will become a model for study of coastal bay systems worldwide. Similar, but smaller, studies are being conducted in California, Washington and Massachusetts. All are funded by the National Science Foundation.
Using a fleet of ships from the foundation and sophisticated monitoring devices, the scientists in Maryland have been
tracking the amounts of "nutrient loading" in the bay -- that is, the amounts of organic and inorganic wastes loaded with nitrogen and phosphorus, the same chemicals used in fertilizers. The main sources of this pollution are runoff from farms and %o discharges from sewage treatment plants.
For years, the conventional wisdom was that the massive amounts of these nutrients pouring into the Chesapeake were permanently harming the bay. First, they helped to smother the bay by fertilizing huge blooms of algae that robbed other marine plants of light and oxygen.
Moreover, scientists thought a large percentage of these nutrients then settled into sediment on the bay floor, where they could be used by algae over and over again, keeping the water in a vicious cycle of oxygen starvation and darkness.
Without oxygen and light, neither fish nor plants can live.
As late as 1988, the Chesapeake Bay Commission gloomily reported that this "nutrient trapping" would exacerbate the effects of runoff from farms and sewage plants.
Today, though, scientists' data are beginning to challenge this pessimistic viewpoint, said Michael Kemp, coordinator of the project headquartered at a lab in Cambridge. By repeatedly taking water samples at various depths in different locations, they began to discern that nutrient levels in the bay fluctuated greatly from year to year depending on rainfall.
That was the first data showing that nitrogen and phosphorus were somehow being cycled out of the Chesapeake within a one-year period.
The scientists have found smaller amounts of nitrogen and phosphorus on the bay bottom than they expected.
They theorize that bacteria converted about 35 percent of the nitrogen into nitrogen gas that simply diffused into the atmosphere. Nitrogen also is used by algae and plankton, accounting for another proportion removed from the bay's waters.
Calculating the amounts of water that leave and return to the bay with the tides, the researchers theorize that some nutrients are discharged into the open ocean.
But the most surprising calculation was that fish may be "flushing" another 10 percent of the nitrogen, by eating nitrogen-bearing plants and animals as they grow and then swimming out to the Atlantic, where they die.
All told, perhaps up to 90 percent of the nitrogen in the bay is cycled out of the water each year, the data show.
Scientists also have been surprised by a dramatic drop-off in phosphorus that has run into the bay since the state banned the use of phosphate detergents in 1985.
Like nitrogen, phosphorus is thought to be flushed out of the bay by bacteria, plants, fish and the movement of water.
The new research is good news for Maryland and other signatories of the Chesapeake Bay Agreement, which commits bay states to a 40 percent reduction in nutrient runoff by 2020.
Mr. Kemp and other scientists think that if the bay can be flushed as quickly as the preliminary data show, any decline in nutrients will be reflected in improved water quality within a year or two.
"It makes the scenario a bit more optimistic," Mr. Kemp said.