Maryland Gov. William Donald Schaefer stood morosely on the deck of the Chesapeake Biological Laboratory's research vessel Aquarius one hot morning in June 1988 as he was ferried up St. Leonard Creek, a tributary to Maryland's Patuxent River.

The governor was agitated, and his mood made the scientists and bureaucrats around him uncomfortable. Downriver nearer the Bay, Walter Boynton, a professor at the University of Maryland, had spent some energy trying to explain the significance of environmental monitoring and the relevance of benthic community metabolism to the Chesapeake Bay cleanup effort, which was Schaefer's mandate.

He did not come into office with that mandate in mind. Hard-fisted and tight-minded about waste in government, Schaefer was not initially viewed as a friend of the environment. Upon taking office, he quickly dumped the much-admired Bill Eichbaum, who had ably headed the state's environmental programs throughout the Harry Hughes administration. Eichbaum was replaced by Col. Martin Walsh, an ex-soldier who had just retired from the Army Corps of Engineers. He had a reputation for being brash and difficult, and many in the state's environmental agencies despaired for their careers-and the Bay.

Almost by default, Schaefer had been elected chairman of the Chesapeake Executive Council, titular head of the entire Bay restoration effort, which at the time combined the forces of Maryland, Virginia, Pennsylvania, the District of Columbia and the EPA. Schaefer quickly had sensed the strength of public opinion behind the effort. After his years as mayor of Baltimore, he was, if nothing else, a consummate politician. It made political sense for him to carry that banner.

Months before, I and other citizen-volunteer Bay water quality monitors from the Patuxent had done a show-and-tell for him on the shoreline of South River in Annapolis. He listened as we told him how runoff-either directly by suspended sediments or indirectly through nutrients that grew excess plankton-reduced water clarity and affected the Bay's struggling underwater grass species. We also told him that these beds had once been invaluable wellsprings of habitat-both as nurseries and refuges-for thousands of species that make the Bay their home.

In the governor's comments to the press that day, he referred to some of our insights-a first step, we thought, in converting him to an environmental activist. But as he came up St. Leonard Creek, Schaefer's mood was anything but upbeat, perhaps because he had realized the magnitude of the challenges ahead-and that there was no easy solution to address vexing problems like the Bay's wildly fluctuating dissolved oxygen levels.

The destination was Osborn Cove, where Walsh and his lieutenant, Bob Perciasepe, had set up aerators near Catchall, our home, attempting to raise dissolved oxygen levels in the creek's bottom waters.

The aerators floated over the little relict oyster bed at the foot of our cliffs, directly below an old Woodland Indian site. These modern oysters likely were descendants of ancient oysters eaten here before John Smith came. The shells buried next to pre-historic campfire remains were evidence of how important oysters were in the diet of the early Pawtuxent Indians.

The aerators, run off an electric line run down to Osborn Cove, were the same as those sometimes used on golf course ponds. They are supposed to help when the runoff of turf fertilizers grows so much algae that it decays and consumes oxygen, killing fish and making the ponds smell like rotten eggs.

This same process of excess algal growth, nutrient exhaustion, settling of organic debris and decomposition operates all over the Chesapeake to varying degrees. St. Leonard Creek was no exception.

Dissolved oxygen is necessary for all higher forms of aquatic life. Fish, crabs, worms and mollusks need oxygen in the water to breathe, just like terrestrial creatures. Some oxygen mixes in from the atmosphere with the wind, but a lot comes from photosynthesis by the countless billions of microscopic plant plankton cells that thrive on nutrients entering the water from rivers.

But the Bay ends up with way too much plankton, the result of farms, development and impervious landscapes that too readily leak nutrients. When summer's dry spells occur and river flows slow the input of nutrients, plankton blooms lose steam. They annually run out of nitrogen, in fact, and the expiring cells slowly fall through the water column. There, bacteria break down their organic matter and consume oxygen. A layer of soft organic "floc" often covers the bottom. This can drive oxygen to zero, at which point the worms, clams and crustaceans are stressed-or die outright.

For decades, the Bay states had a dissolved oxygen standard for natural waters, set first at 4 milligrams per liter (mpl), then later at five...an increase that occasioned wide outcries from industry and the wastewater treatment plants that would have to meet it.

I began sampling dissolved oxygen in Osborn cove in 1976 while I was with the Academy of Natural Sciences laboratory in Benedict, about a dozen miles up from the mouth of the Patuxent. My staff and I gathered twice a month to sample sites all over the cove. Back at the laboratory, we chemically analyzed the bottom dissolved oxygen samples, which never showed values less than 4 milligrams per liter.

In 1985, I joined Kathleen Ellett in setting up the Patuxent's volunteer monitoring network (now defunct and unfunded after decades of work), and we began sampling oxygen again. Each summer, we found values down to 1.35 mg/l-darn near lethal. My neighbor, also a volunteer and not a half-mile distant, though in deeper water, sometimes found zero oxygen. This, and the oyster bed, were reasons why Osborn Cove was selected as a trial site for the aerator project.

Occasionally, even in rural St. Leonard Creek, the stress of zero oxygen, for some undefined period in summer's heat, would kill off the whole population of little Baltic clams, a popular food for diving ducks in winter. The clams' putrefying bodies would float up from the sediments and wash ashore in windrows. Sometimes, as water heated up in late spring, mats about a yard square of blackish cyanobacteria-algae that had grown on the bottom from excess nutrients-would float to the surface like pieces of old carpeting.

In the early 1970s, scientists didn't have a clear understanding of how dissolved oxygen actually varied in the environment. If one measured it at 5.0 mg/l on a monitoring cruise, than that's what it was. It was known that there were variations between daytime, when the sun was out and phytoplankton was producing new oxygen, and night, when the respiration-oxygen consumption-of all plant and animal species would drive it downward. We began to learn things were otherwise.

In 1987, while I was a scientist working at the Chesapeake Bay Program, I deployed a buoy developed by EPA scientist Al Wastler near the Bay Bridge. It was equipped with an oxygen sensor suspended deep in the water column and a radio transmitter at the surface that broadcast data directly to my desk in Eastport, Annapolis.

I was amazed at what I saw. Oxygen levels swung wildly from reasonable to zero, changing with the stage of tide, date and time of day. Water with higher oxygen values from near-surface photosynthesis moved slowly downward by natural mixing in the water column. This process might take 10 or more hours. This meant that deep in the Bay, the highest oxygen values of the day often occurred, incongruously, in the wee hours of morning, when photosynthesis was zero and decay processes consuming oxygen were at their greatest.

Other scientists, like Larry Sanford and Bill Boicourt at the University of Maryland's Horn Point Laboratory, were finding similar results elsewhere in the Bay. Together, we began revealing yet another layer of this ecosystem's complexity. It became clear to a lot of us that the single-number approach to a dissolved oxygen standard simply was not going to work.

For one thing, the original standard contained provisions for being waived. If there were natural conditions which violated the standard, like the blackwater streams emanating from some wet forests, the standard didn't have to apply.

The dissolved oxygen monitor set up at Osborn Cove showed oxygen regularly but unpredictably dropping at or near zero almost 100 times in the months sampled. The stress, while usually not lethal to well-adapted oysters, surely made life hard in the exhausted time after they'd spawned, especially as they labored under the pressure of diseases that have ravaged the species Baywide.

We'd had no idea about the complexity of oxygen change in this single creek. It seemed that in addition to changes that occurred with time of day, there might be lenses (patches) of oxygen-deficient water drifting about on the tide, sweeping over the oxygen measuring sensor-and adjacent living organisms.

It must be stressful to be a tiny creature on the turbid creek floor: an unpredictable struggle for life, unable to tell when (to each worm) an infinitely large mass of uninhabitable, even deadly, waters might sweep over.

Bob Diaz at the Virginia Institute of Marine Sciences said that when organisms like small clams and the many species of bottom-dwelling worms were stressed by low oxygen, they would stick their heads out of the sediments-where they were secure from predators-trying to get oxygen to survive. Predator fish in Virginia's York River had learned about this, Diaz said, and began sacrificing pain for gain, diving through the low-oxygen water to bite off parts of these unfortunate creatures.

The aerator buoys were designed to address this problem-to see if the mechanical introduction of new oxygen from the atmosphere could improve conditions and eliminate the stress over a significant area of bottom.

With them was lost some of the Cove's natural element. Although from a distance they were not loud, one always heard their noise against the background of rustling leaves, summer insect noises and lapping wavelets.

At this point, Maryland had invested a couple hundred thousand dollars into the project in St. Leonard Creek, yet it was not producing results. Months of aerator operation, together with the careful monitoring of oxygen levels and a spectrum of other environmental data, had produced only a barely detectable change in bottom dissolved oxygen levels.

Yet in Rock Creek-a much more polluted tributary to the Patapsco River-aerators connected to a network of perforated pipes on the bottom of the estuary added enough oxygen to end the rotten egg smell of hydrogen sulfide bubbling out of sediments with zero oxygen. This greatly pleased local residents, who had complained bitterly about the smell.

I have never been a fan of engineering solutions to environmental problems, but I do root for environmental progress. As such, I rowed out in my skiff and met Schaefer to put as good a face on this project as I could on behalf of all the people who had worked so hard.

Colonel Walsh had drove there that day. Later, as we walked up the steep path from Osborn Cove to his vehicle, he bounded ahead of me up the bank, then turned to say, "I'm a tough guy."

He went on, "In training for combat, they had us march into a swimming pool with a full field pack and weapons. I went the length of that pool and marched out the other end." It is not a trivial accomplishment pushing through dense water over that distance-presumably on one breath of air. I found myself wondering how much empathy for the Bay's species that experience had given him.

The aerators cranked on until the scheduled end of the study, pretty much confirming that this was not an economical solution to low oxygen in Chesapeake Bay or its tributaries.

Every year since then, without fail, some wag is quoted in the press again proposing a (never inexpensive) scheme for aerating the Bay. Although it has been more than two decades since the original experiments, no plausible schemes have come forward, for either aerating the Bay or really solving its nutrient problems. Perhaps this is because we haven't figured out how to stem the constant population growth that is at the root of it all.

The aerator project was by no means a waste of time. Together with similar continuous monitoring adventures, it provided a significant base upon which EPA scientist Rich Batiuk, NOAA statistician Marcia Olson and their many colleagues built dissolved oxygen goals for the entire Chesapeake.

Perhaps the aerator's greatest achievement, though, took place in the political environment. By the end of his tenure in 1995, Schaefer considered that making Chesapeake Bay even a little better was one of the chosen legacies of his administration.