7 Chesapeake Bay factors


Rising waters may drown coasts

When the effort to restore the bay began in the mid-1980s, "global warming" was an obscure phrase -- seldom spoken except by a few climatologists, many of whom were skeptical to the point of savagery.

Now "climate change" is the politically correct term, and the basic idea -- that humans have changed the atmosphere in ways that are making Earth warmer -- is accepted by most mainstream scientists.

The notion that climate change could have a major effect on Chesapeake Bay restoration hasn't hit the mainstream. But in January, two top ecologists -- the head of Maryland's main environmental research center and his Virginia counterpart -- urged everyone who cares about the bay to pay attention to the issue.

Climate change "constitutes a 'sleeper' issue that has gotten little attention but could have profound consequences for our efforts to manage and restore the bay," wrote Donald F. Boesch, president of the University of Maryland Center for Environmental Science, and L. Donelson Wright, director of the Virginia Institute of Marine Science.

"We are convinced that the bay of the 21st century will be different from the bay of the 20th century in important ways as a result of climate change."

Because of climate change, bay waters are warming and rising; erosion is increasing; and rainfall patterns, which control the mix of fresh and salt water, may already have begun to shift. These factors will affect the success of bay restoration efforts -- but right now, they aren't being taken into account.

Experts predict that sea levels will climb 1 to 3 feet over the next 100 years. At the same time, the land surrounding the Chesapeake is slowly settling, so University of Maryland geologist Michael Kearney estimates bay water levels will rise 2 to 4 feet. That might not sound like much, but in some low-lying areas, waters might intrude a mile inland from today's shoreline.

With the rising waters comes more erosion, which makes bay waters murkier. Marsh plants may not be able to move inland as fast as the waters are rising; their disappearance would further hasten erosion.

One likely effect of climate change is an increase in the amount of rainfall, and thus the fresh water flow, into the bay. With that rainfall will come more nutrients, making it harder to reduce nitrogen and phosphorus levels.

Warmer bay waters may make it harder for important bay plants, such as eelgrass, to produce seeds, according to ecologist J. Court Stevenson of the University of Maryland Center for Environmental Science. And temperature changes may change the mosaic of bay life.

For example, toxic Pfiesteria piscicida likes warm water; the bay may become more hospitable to it. Other creatures, like the Baltic clam, an important food source for diving ducks, prefer cooler water; the bay may lose those, Boesch says.


Area's growth taxes resources

For roughly the first decade of the bay restoration effort, the impact of the Chesapeake region's growing population was like the fable of the emperor's new clothes: Those who saw a problem didn't dare mention it.

That is changing, as bay scientists begin to talk about the increased pollution that more people inevitably bring.

"It's going to be really, really touch-and-go to keep ahead of the increased demands that increased development and population are going to put on the bay," says veteran Maryland Department of Natural Resources biologist Nick Carter.

The Chesapeake Bay region has about 15 million residents. Some bay scientists think its "carrying capacity" -- the number of people the land can support without grave environmental harm -- is roughly 12 million, a level passed almost two decades ago.

And by 2020, more than 17.7 million people are expected to call Bay Country home.

Most of the new residents will be Virginians: Between 1995 and 2020, the portions of Virginia that drain into the Chesapeake will add about 1.3 million people, according to projections by the Chesapeake Bay Program.

Maryland is expected to add about 1 million residents over that 25-year span.

More people mean more sewage that ends up, after treatment, in the bay. More houses mean fewer forests and fields, which act as natural pollution filters.

More cars and longer commutes mean more smog, some of which settles on the water as nitrogen, fueling the bay's lethal algae blooms. According to a bay program estimate, residents of the bay region now drive a combined total of 150 billion miles a year.

The easiest way to reduce nutrients flowing into the bay is to improve sewage treatment. That's already being done. As more people arrive, governments will have to do more.

Some options: new land-use restrictions, better public transportation, economic penalties to discourage driving, better septic tanks, state-of-the-art sewage treatment systems.

But those steps would cost billions -- and some run afoul of long-standing American rights and values.

"It's extremely difficult because people don't want to talk about where people should or shouldn't be allowed to live," says Jack Greer, assistant director of the Maryland Sea Grant College program.

Maryland's Smart Growth program tries to do that, channeling state money for development away from suburban and rural areas. Gov. Parris N. Glendening has suggested including "smart growth" ideas in a new multistate Chesapeake agreement.

Scientists say environmentally sound land use has to go further -- not just preserving some forests, for example, but preserving the forests that provide the greatest environmental benefits.

"It's not just smart growth," says bay ecologist Donald Boesch, president of the University of Maryland Center for Environmental Science. "It's really smart growth."


A tattered web of life

The plight of the bay's rockfish may be a textbook example of the law of unintended consequences.

Fishermen and scientists were thrilled when striped bass populations rebounded in the mid-1990s after a five-year fishing moratorium. But last summer, about 10 of every 100 rockfish caught in the bay had skin rashes or sores. Many were startlingly thin.

Some scientists think the sores are linked to a shortage of food. Striped bass like to eat menhaden. There didn't seem to be many of those silvery bait fish in the bay this year, and there definitely are fewer young menhaden along the Atlantic coast.

Because menhaden eat algae, the pollution cleanup work they do might also be lost.

Why aren't young menhaden thriving? No one knows.

Some researchers think there's been a change at the bottom of the food chain: The single-celled plants menhaden prefer are being replaced by different types of algae and bacteria that tolerate pollution but make poor fish food.

That's still unproven, says ecologist Donald Boesch of the University of Maryland Center for Environmental Science, "but there's no question that over the long term there have been fundamental changes in the bay's food chain."

"More of its productivity ends up in bacteria and jellyfish rather than the organisms we care about," he says.

Some watermen are convinced there's a link between the shortage of menhaden and last year's poor crab harvests. Maybe rockfish are turning to young crabs for sustenance, harming the crab supply. But there are no scientific studies of the striped bass diet, so it's hard to know.

It may take more than just removing nutrients to restore fisheries, says scientist Kent Mountford of the EPA's Chesapeake Bay Program.

When a complicated web of life has been radically changed, "it resists returning to the original state, and when it does come back it may be different. You may not like what you come back to as much as you think you will."

Bay scientists say state and federal committees that set fishing limits need to stop aiming for the largest possible catch of each kind of fish. Instead, they say, the goal should be learning about and conserving the natural relationships among bay creatures.

The discovery of some unhealthy rockfish "has taught us that when a species comes back, it not only has effects on other species, but it's affected by the species that it depends on," says William Matuszeski, director of the Chesapeake Bay Program.

"We are not managing with this broader view in mind," Matuszeski says. "We're managing fisheries and we're managing harvests, but we're not managing species in the context of the health of the larger bay."


Lush underwater meadows only a memory

The news about the bay's underwater grasses is mixed: The operation has been a success, but the patient may be getting worse.

Underwater grasses are so important to the Chesapeake's health that scientists have always known there's no way to save the bay without them. Now, it turns out, not only does the bay need more grasses, it needs them in the right spots.

The grasses provide shelter for young fish and shellfish, especially blue crabs, and food for the bay's flocks of wintering ducks and geese. Their roots hold the silty bottom in place, preventing erosion and helping clarify the water. They use nutrients such as nitrogen and phosphorus, improving water quality.

No one knows how extensive the grasses once were, but many bay residents remember river bottoms covered with lush underwater meadows. Once there may have been as many as 600,000 acres of grasses, but by 1984 that had dwindled to only 29,800 acres.

The multistate bay agreement has set a target for the grasses' restoration: 114,000 acres baywide by 2005. That may be within reach.

Grasses had been recovering, reaching 69,000 acres in 1997. That trend reversed in 1998, with the meadows' expanse declining 8 percent baywide, to 63,495 acres.

That's because of staggering losses in Tangier Sound, the bay's most important underwater meadow. Young crabs settle in the sound as they start their migration up the bay. If they find no shelter there, they may not survive. When young crabs suffer, so do other bay denizens that rely on them -- including watermen.

Tangier's grasses have been declining since 1992, from a high of 18,106 acres to 6,609 in 1998. In Maryland's portion, the loss has been even worse -- more than 80 percent in six years.

"It is a big mystery," says Robert Orth, an expert on underwater grasses.

Part of the problem: the five Lower Eastern Shore rivers that flow into Tangier Sound have some of the region's highest nitrogen and phosphorus levels. Those nutrients fuel algae blooms that cloud bay waters -- and grasses can't survive without light.

Global warming may be a factor. As the bay gets warmer, water levels rise, and marshes at the nearby Blackwater National Wildlife Refuge are drowning. As the marshes disappear, bottom sediments are set loose, muddying the waters.

Even an overabundance of some animals -- the nutria chewing up Eastern Shore marshes, the swans and geese uprooting underwater grasses -- may play a role.

"We really haven't gotten to the heart of the matter," Orth says. "Is it a single bullet or a variety of causes, or is it just natural fluctuation?"

Ecologist Donald Boesch says the grasses' conflicting signals point to an underlying problem: numerical goals such as the 114,000-acre target are really just stand-ins for the true goal of restoring the bay's natural functions and balance. In theory, the bay program could meet all its goals without saving the bay, he says.

"If we just take a single focus, that we're going to restore submerged aquatic vegetation or striped bass without dealing with the underlying biological processes, then we're going to fail," Boesch says.


Ally in bay cleanup falls victim to disease

If the Chesapeake is getting healthier, why have its once-abundant oysters been so decimated that the harvest has plummeted, from about 3 million bushels a year in the 1970s to fewer than half a million bushels today?

"The question is why, after thousands of years of successfully fighting off diseases, are oysters being killed now?" says Jack Greer, assistant director of the Maryland Seagrant College. "The answer is, we don't know."

Most of the bay's oysters were killed by two diseases, MSX and dermo, just as the bay restoration effort began in the 1980s. Suddenly, a stout ally in the cleanup was gone.

Oysters are the Chesapeake's most powerful natural pollution cleansers; a large adult oyster can filter 50 gallons of water a day. Scientists are working to breed disease-resistant strains, and the past two years' worth of natural reproduction has been good in some key spots like Eastern Bay. Experts say this year's harvest may be the best of the '90s.

But the rebound is minuscule compared with what's been lost. The possible culprits include pollution, climate change and the shipping trade:

  • The bay's algae overload may clog oyster tissues, causing them to die or fail to reproduce.

  • Warmer water may overtax them.

  • Ships' ballast water may carry exotic diseases they can't fight off.

  • Persistent low oxygen levels kill off the oyster bars in deep water. Sediment smothers some shallow-water survivors.

    Scientists used to think pesticides and industrial metals had little effect on local oysters, because the bay has only a few toxic "hot spots." Now some researchers are finding low levels of these pollutants may make it tougher for the shellfish to fight off diseases, Greer says.

    Subtler changes may be going on.

    Scientists know some types of algae can tolerate contamination better than others; maybe the algae thriving in a polluted bay make good food for other creatures but not for oysters, Greer says.

    Two centuries of oyster dredging haven't helped. Before European settlement, oysters grew in reefs -- dense colonies where they bred more efficiently because they were close together.

    The reefs also provided nooks where young oysters were hidden from predators. They did the same thing for a wide variety of fish hatchlings.

    But dredging has virtually eliminated the reefs. The effect of that change on other creatures isn't clear, but ecologists don't think it was a change for the better.

    It's as though a mountaintop were bulldozed into a grassy valley, scientists say. You wouldn't expect high-altitude pines and meadow wildflowers to thrive on the muddy new plain.

    So there are at least a half-dozen possible explanations for the oysters' woes. Most likely, all play a role, Greer says. That may mean a half-dozen different problems to tackle before oysters rebound.

    "Oyster restoration is critical" to the bay restoration effort, says Donald Boesch, president of the University of Maryland Center for Environmental Studies, "but we've been working at the bare margins. It's going to have to be a much smarter, more intensive process."


    Pollution overdose looms on the horizon

    Twenty years -- or a couple of big storms -- stand between the Chesapeake Bay and a potentially disastrous pollution overdose.

    Every year, the mile-long Conowingo Dam, which lies across the mouth of the Susquehanna River at the bay's upper reaches, catches and holds back about 2.2 million tons of sediment -- silt carried from the farm fields and parking lots of New York and Pennsylvania.

    The muck is potentially lethal to bay plants and animals.

    "It covers oyster bars and smothers oysters and destroys their habitat," says William Goldsborough, a senior scientist with the Chesapeake Bay Foundation.

    "It also is a problem for grass beds. It coats the leaves and reduces the light getting to the plants and can cause them to die."

    Right now, the big dam is doing some of the bay restoration work, by trapping about 2 percent of the nitrogen, 40 percent of the phosphorus and 70 percent of the sediment flowing down the Susquehanna.

    But not for long.

    Every dam eventually fills up with silt, and the 71-year-old reservoir behind the Conowingo is filling fast. Scientists at the U.S. Geological Survey estimate that in 20 years it will be full, and all those stored-up pollutants will have to go someplace else. That place will be the bay -- unless bay managers come up with something creative.

    Just to keep up with the incoming supply of sediment, engineers would have to remove enough muck to fill eighty 100-ton railroad cars each day, says USGS hydrologist Michael Langland.

    Where would they put it? No one knows. Certainly no one is asking for it. "Maybe you'd just be moving a problem from one area to another area," says Langland, co-author of a 1998 study on the Conowingo issue.

    The 20-years-capacity estimate is based on the assumption that the area will not get what meteorologists call a "50-year storm" -- a flood so severe that the region sees its equal only twice in 100 years.

    "Of course, since 1972 we've had three 100-year storms, so that could happen any time," Langland says.

    In 1972, Tropical Storm Agnes scoured out the Conowingo's reservoir, forcing a huge slug of sediments, nitrogen and phosphorus through the dam's floodgates and into the bay. Tens of thousands of acres of underwater grasses and shellfish beds were smothered. Longtime bay-watchers say the Chesapeake has never really recovered.

    "We don't need another Agnes," says Bill Matuszeski, director of the EPA's Chesapeake Bay Program. "Either way it goes, it's no good. So we've got to come up with a solution to the problem. And we don't have a lot of time."

    Within the next six months, scientists and bay policy-makers will hold their first formal meeting "to take a look at the possibilities," Langland says. "We're not even going to try to talk about what they might cost."

    7 OXYGEN

    Gasping for breath

    When scientists set their sights on reducing polluted runoff into the bay, one of their main goals was to restore life-giving oxygen to "dead zones" in the bay's depths that once were havens for oysters and rockfish. The pollution is down, and oxygen levels in some rivers have improved.

    But in the bay itself, the airless zones stubbornly persist.

    The phenomenon is partly natural, but pollution has vastly expanded the extent of the oxygen-starved waters.

    Every summer about one-tenth of the bay's bottom has oxygen levels so low that oysters die or fail to reproduce, fish and crabs swim away and fish eggs fail to hatch. In an additional fifth of the bay, oxygen levels are low enough to be unhealthy. Variations in the weather make it hard to see whether there's a subtle improvement, but it doesn't look that way, according to Kent Mountford, a senior scientist at the Environmental Protection Agency's Chesapeake Bay Program.

    Large, persistent oxygen-starved zones probably are a factor in fisheries' decline. Even full-grown rockfish can be harmed.

    Like humans, fish breathe harder when they're hot; they try to seek refuge in the cooler depths. If there's no oxygen in deep water, they'll stay close to the surface, burning up so much energy that they stop growing.

    "They kind of get squeezed," says William Goldsborough, a senior scientist for the Chesapeake Bay Foundation, a conservation group.

    Oxygen-starved water also affects oysters and crabs that are trapped in pots -- oysters most severely, says Goldsborough. "Those that are mobile, like crabs, can usually get out of the way," he says. "Oysters can't."

    Low oxygen levels have helped wipe out the bay's deep-water oyster beds -- a problem for the health of the entire bay, since oysters perform vital pollution-filtering work.

    EPA maps show that the dead zones -- which have so little oxygen that only some rare bacteria can last more than a few days -- follow the deepest water from the Bay Bridge to the Maryland-Virginia line.

    Oxygen-poor zones -- where aquatic life suffers but can survive so long as nothing else goes wrong -- occupy much of the western bay from Baltimore to the mouth of the Rappahannock and beyond.

    Why haven't oxygen levels improved yet?

    Perhaps because there's so much old pollution stored on the bay bottom. Scientists know that when nitrogen and phosphorus levels in the water go down, a natural chemical reaction causes those nutrients to flow out of the sediment and into the water, where they can trigger algae blooms that eat up oxygen.

    Even with new runoff controls, it may take years until all those stockpiled nutrients are used up and the cycle is broken for good.

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