ANNAPOLIS -- Long before eco-anxiety became a national ailment this year, a strong environmental ethic seemed to come naturally to people in Anne Arundel. Looking at a map, it is easy to see why.

With the Chesapeake Bay as its eastern border and four major rivers dividing the county like cracks in a plaster wall, Anne Arundel boasts some 426 miles of shoreline. It's an amount equal to the Pacific coast between Malibu and San Francisco. Creeks, coves, piers and private beaches provide playgrounds for the county.

Little wonder, then, that many of its 430,000 residents are ardent aquaphiles -- boaters, fishermen, skiers -- who moved here to be near the water and commute to high-paying jobs in Washington or Baltimore.

"I wasn't an activist when I moved here. I came for the crabs and the boating and the swimming," said Mary Rosso, president of the Maryland Waste Coalition. "Then the creek near my house was closed for contamination. It smelled and it ran red. And I couldn't believe we had gotten into this mess. So I didn't hesitate to call my council members and ask for answers."

Rosso is one of many residents who have followed an ailing waterway to civic activism, giving Anne Arundel a reputation as one of the most conservation-minded areas in the region.

"I think it's more like places in California and Oregon in terms of environmental awareness," said County Executive James Lighthizer, who credits environmental groups with educating him on the need for measures he pushed in the mid-1980s to control growth and pollution. "These are people who are used to having things happen that they think should happen."

The names of the county's leading civic groups indicate what its citizens care enough to complain about: the Severn River Association, Save Our Streams, Weems Creek Conservancy, Friends of Jug Bay Wetlands Sanctuary, Maryland Waste Coalition, Annapolis Town Meeting on the Environment, Magothy River Association. Nearly every tributary has its own watchdog.

"I used to say that since there is an activist every quarter-mile in Anne Arundel County, it must be something in the water," said Barbara Taylor, an Anne Arundel resident who is director of the statewide Save Our Streams.

The majority of these groups do not make endorsements or campaign contributions, but their presence is nonetheless felt keenly by local officials. For example, they successfully pushed for a strict sediment control law and a requirement that developers replace any trees they remove.

During this election year, the local environmental movement's clout has been vividly evident in the rhetoric of the candidates vying to succeed Lighthizer, who cannot seek a third consecutive term. Suddenly, sediment control, sewage treatment and storm drains are hot issues.

These seemingly mundane topics, ill suited for television sound bites, are not the sort of things politicians usually make the cornerstones of their campaigns. Yet that is exactly what former House of Delegates minority leader Robert R. Neall, a Republican candidate for county executive, did this month.

Neall's first major policy statement, a 12-point plan for protecting the county's streams and rivers, represented a victory for Anne Arundel's "greenies" as Lighthizer calls them, many of whom considered Neall hostile to their cause when he was a legislator. While in the General Assemby, Neall voted against a ban on detergents containing phosphates and a bill strictly limiting development on land near the water.

Now, the environment "is the central issue in this campaign . . . . There is no higher priority among voters in Anne Arundel County," said Neall's campaign manager, David Almy.

When their overtures have been resisted by public officials, county environmentalists have not hesitated to take their case to the news media. "If something is done that we think is not appropriate for the environment, we are not afraid to bring it to the attention of the public," said Cliff Andrew, a past president of the Severn River Association. "We use it as a handle: If this is not taken care of, we will go to the press."

That was the tactic used two years ago to stop the Naval Academy Alumni Association from building a hotel and conference center on the banks of College Creek in downtown Annapolis. The method proved effective again this year when the Severn River Association persuaded the state Department of Natural Resources to restrict water-skiing in two sensitive creeks during the season when underwater grasses that feed aquatic life are sprouting.

Last year Save Our Streams filed a lawsuit charging the State Highway Administration with spoiling Weems Creek during the reconstruction of Route 50. After repeatedly denying wrongdoing, the state agency this summer promised to make amends.

Perhaps the squeakiest of the wheels is the 79-year-old Severn River Association, the nation's oldest organization dedicated to the preservation of a river. With 550 members from some of the county's most exclusive subdivisions, it is the largest civic group in Anne Arundel. Lighthizer and the County Council consistently appoint representatives from the group to advisory committees on major land-use issues, such as the threat posed by an eastern bypass around Washington and the future use of surplus land at Fort Meade.

"They hurt me in the early years politically by being publicly critical of what we were doing," Lighthizer said. A politician who does not heed the environmentalists' concerns "will have hell to pay," he added.

The well-entrenched worry about the environment that these groups represent expresses itself in the unusual hobbies of many Arundel residents. At a day camp sponsored by the Sherwood Forest Community Association this summer, elementary and high school students are learning how to test water in the Severn River for bacteria levels indicative of sewage spills.

The local chapter of Save Our Streams has trained more than 200 residents to serve as "Mudbusters" -- citizen inspectors who monitor construction sites for sediment-control violations that may muddy local creeks. The South County Environmental Commission teaches residents how to spot wetlands in their neighborhoods and to lobby the government to halt their destruction.

Dozens of residents and school groups have obtained kits from the county government for planting sea grasses.

Taylor said Save Our Streams pushes hands-on activism out of fairness to the government agencies it doesn't hesitate to criticize. "If we are not involved in what's happening around us and clear in the messages we send, we can't be upset if the government doesn't respond to the things we are upset about," she said.