For 71 years, Daniel Harrison sailed Tangier Sound and the surrounding area in his skipjack, making his living off the Bay’s bounty. But when the 86-year-old Smith Island resident looks at the murky water that surrounds the island today, it bears little resemblance to what he saw as a youth.

“The grasses were everywhere then,” he recalled. In those days, Harrison said, the water was so clear a waterman could see crabs swimming along the bottom in 18 feet of water. “You couldn’t catch them, because you couldn’t reach them.”

Leaning over the side of a boat, Peter Bergstrom lowered a round, black-and-white plate called a Secchi disc into the murky, grassless water of Tangier Sound. Then he measured the depth at which the disc totally disappeared.

At a little more than two feet, it was gone. “To get good grass growth, it should be three feet or more,” said Bergstrom, a biologist with the U.S. Fish & Wildlife Service.

Good grass growth is something Tangier Sound hasn’t been experiencing in the past half-decade. From 1992 through 1998, the beds of underwater grasses which once stretched miles from the shoreline, declined by 63 percent. During that same period, monitoring has shown the water has become increasingly clouded with sediment and algae.

It appears to be a domino effect in the Sound. Submerged aquatic vegetation, or SAV, naturally filter nutrients, which spur algae growth, and sediments, improving water clarity and allowing more grasses to survive. But murky water in Tangier Sound appears to be overwhelming the grass beds.

With fewer grasses to filter the water and buffer shorelines, more sediment is stirred into the water, making it murkier and murkier and causing still more grasses to die off.

Grasses not only filter the water, but provide important habitat for juvenile crabs and fish, as well as food for waterfowl. Studies have found that densities of blue crabs can be 30 times greater in grass beds than in unvegetated bottom. Historically, the lush grass beds of Tangier Sound — the largest remaining beds in the Bay — have been critical for young crabs.

To prove the point, a crab scrape was dropped overboard in an unvegetated area of Tangier Sound, and then pulled aboard. It had a handful of small crabs.

The scraping was repeated in a healthy grass bed. This time, the scrape was teeming with dozens of crabs, grass shrimp, pipefish and small arthropods and isopods — food for crabs, fish and others — as well as two diamondback terrapins. “The number of juvenile crabs in here is amazing,” said Bill Street, a scientist with the Chesapeake Bay Foundation, as he sorted through the contents.

Over the side, Bergstrom dropped his Secchi disc into the grass bed. It hit bottom — at three feet — and was still clearly visible.

Biologists in recent years have increasingly recognized the ecological value of the Bay’s “underwater meadows.” That recognition may soon be translated into action.

The Bay Program, in a new “Chesapeake 2000” agreement to be signed next year, is considering establishing water clarity goals aimed at helping grasses — which now cover only about one-tenth of their historic range — to rebound.

Perhaps more significantly, improving water clarity enough to support underwater grasses is likely to be the aim of a Total Maximum Daily Load — or TMDL — for the Bay. TMDLs are legally required cleanup plans for waterbodies, like the Chesapeake, which are considered “impaired” by pollution. Unlike voluntary Bay Program goals, TMDL goals can be translated into mandatory regulations if the Bay Program fails to accomplish cleanup objectives by 2010.

Both the Bay Program and TMDL process represent a major shift from past policies. Before, cleanup goals such as the Bay Program’s 40 percent nutrient reduction, were aimed more at reducing the amount of pollution entering the water than accomplishing a specific, resource-based objective.

Now — pushed by the legal requirement for TMDLs — the emphasis is on making sure that pollution reductions are making a biological difference in the water, even if that means far greater pollution control efforts than previously envisioned.

In effect, that means a waterbody like the Bay won’t be considered “cleaned up” until resources in the waterbody say the job is done. When managers look for such a biological measuring stick in the Bay, they increasingly see underwater grasses.

About 80 miles north of Tangier Sound, grass beds in the Severn River are on the rebound.

Back in the early 1970s, the river had been filled with redhead grass, which attracted a variety of fish and waterfowl to the river: More than 2,000 tundra swans wintered on the Severn in those days.

“In 1980-81, all the grass died,” said John Page Williams, a senior naturalist with CBF and a longtime resident along the river. “It was like someone throwing a switch.”

As the waterfowl left, so did many of the fish: “For 15 years, there were no pickerel and not many white perch in here,” said Williams, an avid angler. “It was brutal.”

But starting in 1994, the grasses came back a bit more each year. Just a bit of widgeon grass at first, and then more species, until the grass beds covered more than 300 acres.

The Severn is not alone. The Patuxent, Magothy and Bush rivers on Maryland’s Western Shore have all seen grass rebound in recent years, as has the lower Potomac. In a small section of the Gunpowder River, grasses are growing at a depth of 12 to 15 feet.

Williams suggests that the comeback was helped by the state’s Critical Area Law, which restricted development on the shoreline, allowing it to “heal” and revegetate, reducing erosion into the river. At the same time, many homes using septic systems were hooked to public wastewater treatment plants, reducing the flow of nutrients.

Others point to other reasons. In some rivers, wastewater treatment plants have been upgraded to do a better job of removing nitrogen. “We would like to think the improved technology that we’ve applied, and the combination of all the things that we are trying to do, is actually paying off,” Street said. “But knowing how much each of those is actually contributing to the recovery, I don’t think we have the information.”

Whatever the reason, pickerel and other fish are coming back to the river. Williams dipped a blue crab out of the water: “That’s what happens when you get grasses back.”

In some respects, some scientists suggest that the stories in Tangier and the Western Shore tributaries have similarities. Both were systems that were “on the edge” of meeting water quality conditions needed by grasses. In the Severn and other rivers, the water quality teetered enough to the good side to give grasses a toehold. Then, as they recovered, they began modifying local conditions enough to allow more grasses — and more species of grasses — to return.

“It’s a feedback loop,” said Bob Orth, a seagrass expert with the Virginia Institute of Marine Science. “You just need to get the beds to a certain size and density, and that is when they begin influencing the water clarity.”

In Tangier Sound, water quality tottered enough to the bad side to trigger a cycle of worsening water quality which led to fewer grasses filtering the water and stabilizing shorelines, which contributes to more erosion and even worse water quality — a vicious downward spiral.

The Tangier situation could be compounded by sea level rise, which increases erosion, and the rapid growth of the poultry industry on the Eastern Shore, which has increased nutrients in the water.

While the exact causes of water quality improvements in some areas and declines in others isn’t always certain, the bottom line factor affecting grass is perfectly clear: Like all plants, they need sunlight to survive.

“You can argue about the details, but in the big picture, there is just no doubt that improving water clarity is going to help SAV,” said Robert Magnien, head of the Tidewater Ecosystem Assessment Division of the Maryland Department of Natural Resources. “It’s about as good as you get in terms of scientific evidence in support of environmental management.”

Research shows that in most of the Bay, a minimum of 22 percent of the light that strikes the water surface must reach the grasses for them to survive. In fresh water areas, plants need about 13 percent of the available light.

Historically, at least that much light was penetrating the Bay surface to support about 600,000 acres of SAV. Water clarity adequate to grow grasses at depths of two meters was common.

The Bay has a long way to go before such expanses of grass beds are seen again.

An analysis by Peter Bergstrom, of the USF&WS, shows that only about two-thirds of the 70 “segments” the Bay and its tributaries are divided into for monitoring purposes have enough water clarity to support grass growth at one-quarter meter — a bit less than 1 foot.

“I was kind of shocked,” Bergstrom said. “There is no segment meeting the light requirement at two meters. There are only nine meeting it at one meter.”

Although figures aren’t available, field observations report a strong comeback for grasses throughout the Bay this year. That follows the beating grasses took last year, declining 10 percent Baywide to 63,496 acres.

Just as Mother Nature got most of the blame for the 1998 decline — spurred largely by record high river flows in the first six months of the year — she gets most of the credit for the apparent 1999 comeback.

This year’s drought turned off the tap that flushes large amounts of nutrients and sediments into the Bay, where they cloud the water.

The good news extends even to Tangier Sound. Initial surveys show grasses back in many areas. But, Bergstrom cautioned, many returning grass beds appear to be sparse. Also, they are composed mostly of widgeon grass, a species that comes and goes more rapidly than the more stable eelgrass which once dominated the area.

Unlike the Western Shore rivers, which offer more shelter to recovering grass beds, the Tangier Sound beds are less protected should the high flows seen in many recent years return.

Research has been under way this summer to better understand what is going on in Tangier Sound. How much of the problem is caused by nutrients? How much from sediment? And where is the sediment coming from: eroding islands, eroding marshes on the mainland, or is it being flushed in from up the Bay?

No one believes that all the questions will be answered without more research in the future, but as potential causes are narrowed, potential management options will become clearer. Some recommendations could come by early next year.

But Tangier isn’t the only place in need of research. What, for example, triggered water clarity to improve enough on the Severn River to spur a grass comeback, while water quality hasn’t significantly rebounded in the adjacent South River?

“If we really want to know what is going on, we really ought to spend additional resources looking at some of these areas like the Severn,” said Orth, of VIMS. “Why are these areas so unique that we are seeing such a dramatic recovery? From those areas, maybe we will learn what needs to be done elsewhere.”

While those details are sorted out, scientists agree that the future of the Bay’s underwater meadows can’t be left to the whims of nature. Successful grass restoration efforts mean controlling the things people can control — nutrients and sediments — to the point that large, stable grass beds can withstand year-to-year storm events.

“We need some resilience in the system so we aren’t vulnerable to every storm that hits the Bay,” said Ryan Davis, who oversees underwater grass restoration efforts for the Alliance for the Chesapeake Bay. He noted that many Western Shore tributaries may have begun showing some resilience, with grasses increasing last year despite record flows. “You can’t worry about every event that happens.”

Jessie Marsh recalled how up to 200 skiffs could be seen scraping in the lush grass beds off South Marsh Island, which borders Tangier Sound, in years past. “This whole cove was covered with crabs,” he explained.

The crabs seem to have disappeared with the grasses, Marsh said. And some of the population on his native Smith Island, no longer able to make a living, are disappearing, too. Of the 20 kids he went to school with, only two remain on the island.

Marsh is employed — he operates boats for CBF. “Nobody’s scraping. Not one,” he said, scanning the horizon off South Marsh Island. It’s been that same story here for about seven years.”