Cleaner? Maybe. Depending on where you are on the Potomac River and who you talk to, the river is either getting cleaner or remains threatened by pollution from growing urban and suburban communities along its shores. Office-bound bureaucrats and planners say the Potomac River shows improvement since clean-up programs began in 1969.

Scientists, looking at the same river, say it is too early to tell if clean-up efforts have made any permanent improvements in the Potomac's waters.

All the while, fishermen and oystermen about 100 miles downstream from metropolitan Washington, where the mouth of the Potomac opens on to the Chesapeake Bay, say fishing on the river isn't what it used to be:

"The watermen know something's happening to this river; that the fishing isn't what it once was. They just don't know what that 'something' is yet," said Martin O'Berry, a native of Solomons, Md., located at the mouth of the Patuxent River on the Chesapeake Bay.

O'Berry skippered a day-long cruise recently from the Chain Bridge to the Chesapeake Bay, a span that gradually widens and grows noticeably cleaner with every passing mile. This distance forms the estuary of the Potomac River, a mixture of sea and fresh water that moves more sluggishly than the free-flowing river upstream from Washington. Near the mouth of the river downstream this estuary supports the lifestyles of fishermen and oystermen. In metropolitan Washington, it receives the treated wastes of approximately 3 million people.

O'Berry's passengers on the water research vessel, the Aquarius, included local planners and elected officials, state and federal water control personnel, citizens involved in water issues and staff members of regional planning groups.

These are people who help decide the future of the Potomac River: How much and what kinds of sewage will be dumped into the Potomac; how clean the river should be and how much will be spent to make it clean, and whether the metropolitan area will be able to use the estuary as a source of drinking water.

Most of these people had never been on the river before.

For O'Berry and water researcher Elgin Dunnington of the University of Maryland's Chesapeake Biological Laboratory, the trip was a chance to show the planners that the Potomac has another character besides the wide, murky body of water familiar to Washington area residents stuck in traffic jams on bridges spanning the river.

Some of the passengers were surprised.

"You mean there's fish in this river? "asked a Prince George's County staff member when the Aquarius dredged up a netful of muddy catfish, white perch and brackish water clams near Indian Head, Md., about 40 miles downstream from Alexandria, Va., and Blue Plains, Md., where the Blue Plains regional sewage treatment plant dumps about 275 million gallons of treated sewage into the river daily.

As the river widened from about half a mile wide at Alexandria to about three miles wide 60 miles downstream at the U.S. Rte. 301 bridge, which links King George's County, Va., with Charles County, Md., the water color lightened from amber to a greenish brown. The Aquarius dredged up more fish and clams and less mud, and the salt content of the water increased markedly.

"The river downstream is showing some of the effects of increasing pollution," Dunnington said, as he threw aside several dead clams dredged up near the 301 bridge. "But it is basically a healthy estuary down here. The problem is keeping it that way with the metropolitan area growing as it is upstream."

By the time the river has widened to eight miles at its mouth, it takes on the look of an ocean. The Maryland and Virginia shores are faintly visible from the middle of the stretch. The water is more turbulent. Oystermen are collecting their catch by digging large tongs into the river bottom. Police in motorboats are inspecting catches to make sure only the mature oysters are being taken.

"It's not fair to expect people downstream to live with diluted water conditions as a result of how people are treating the water upstream," he said.

Dunnington was referring to the balance of salt and fresh water in the river estuary, a delicate balance which is upset as pollution changes conditions in the river. Oysters need clean salt water to reproduce, and fish need clean fresh water upstream for spawning grounds.

Spawning grounds for some fish have been shrinking gradually downstream to the point that "we haven't had a good rockfish spawn in five years," according to O'Berry. "It's got to be something, right? Probably pollution."

Fish now go no further to spawn than the 301 bridge, according to Dunnington. O'Berry remembers when they traveled up to Alexandria to spawn.

He noted that the public health service requires Aquarius crew workers to be immunized against tetanus, typhoid and hepatitis when they research waters in the upper Potomac.

"You can't convince me the river in the Washington area hasn't been cleaned up somewhat," said Anne Blackburn, a staff member of the Interstate Commission on the Potomac River Basin, an organization that researches and disseminates information on the Potomac River.

"A scientist or a fisherman compares the river to what it was at its best; we're trying to what it was at its best; we're trying to lift it from when it was at its worst, in the late '60s."

Advance wastewater treatment at Blue Plains, a treatment intended to remove nutrients from the water that use up oxygen needed to support aquatic life, is scheduled to be completed by 1980 at an expected cost of $400 million. Increased chemical treatment is being used in the meantime. Metropolitan Washington jurisdictions on the Virginia side of the river also have upgraded their treatment processes.

Blackburn said few algae blooms, caused by excessive nutrients in treated sewage, were sighted in the river this year. The algae blocks oxygen from reaching aquatic life, sometimes causing fish kills.

"Some say that's not the the result of man's efforts, but to a cold winter last year that cut off the algae's growing cycle," Blackburn said. "They say the lack of rain this year also kept the nutrients that come with stormwater runoff from getting into the river.

"But at the same time, there are better-looking fish being caught in Potomac waters right in the District, where just a few years ago we were seeing fish with ulcers. That means improvement."

Meanwhile, growth continues. John Russell Thomas, director of Blue Plains, says the treatment plant is nearing its capacity. Development is growing near the shores of the river in Maryland and Virginia counties downstream, and with it the increasing incidence of polluted water run-off from paved surfaces and bared construction lots, along with more sewage dischage.

Beyond the metropolitan area downstream, stands of trees dominate the banks of the river for long stretches. What development there is stands out - a Vepco plant, a NASA tracking station, an oil holding depot, sumer camps, luxurious homes, a few subdivisions under construction and old waterfront hamlets.

"Sure the river's changing; it's something that is happening now," Dunnington remarked. "That doesn't mean it has to die."