MYRTLE BEACH -- In the mid-August heat, fishermen began pulling in flounder after flounder on Springmaid Pier. But the fish weren't fighting.

Susan Libes could see bottom- dwelling flounder in the surf below the pier. The marine science chemist was out on the Myrtle Beach pier to test for stormwater runoff contamination. It was, she said, "dumb luck" that she happened on the strange scene with equipment to test for oxygen levels in the water.

"I was shocked," she said about those tests in 2004. In a surf zone that roiling water should be keeping well-mixed with air, there was almost no dissolved oxygen in the deeper water. The flounder were suffocating.

Libes had stumbled on a situation so alarming that she would drop her research to devote the next six years to researching and educating about it. She helped form the ad hoc Long Bay Working Group among marine scientists at Coastal Carolina University, where she works, and four other marine science agencies.

The water was hypoxic -- the condition that's called a "dead zone," an area in the water where fish and other marine organisms simply can't survive. The zones can be a consequence of pollution in developed areas.

A dead zone would be a kiss of death in the heart of the beachgoer-swarmed, happy fishing grounds of Myrtle

Beach, the cash cow of a $600 million per year beach tourism industry.

Even worse is what that could mean for the rest of the developing coast.

Dominoes

The kids are whining on a hot afternoon out on Myrtle Beach's brand new, $6 million, boardwalk promenade. They don't care about the sun, sand or the good surf out on the beach. They don't care about the para sailers, the banner planes jostling with the vintage biplane overhead, the Gay Dolphin and the Coppertone Fun Plaza Gift Shop. They just want to go to the Mirror Maze at Ripley's Believe It or Not.

From the edge of the boardwalk, the high-rise hotels look like huge dominoes stacked one after another until they fade in mist.

To lure tourists anymore, sea and sand are not enough. On Ocean Boulevard there's a towering Slingshot bungee ride. The largest Ferris Wheel east of the Mississippi has been proposed on the oceanfront. One of the most popular Myrtle tourist draws, Broadway at the Beach, is an entertainment center almost a mile inland.

These not-so-beach attractions help pack millions of people per year into the tiers of hotel rooms looming above the surf. Myrtle can't develop fast enough to keep up with the swarm. Meanwhile, the permanent population in the town alone grew more than 40 percent in the past 10 years, according to the U.S. Census. The area has remained one of the fastest growing places in the country during the recession.

It's the poster child of tourism for the coast, the venue that other places watch for ideas.

Under the boardwalk are catch basins and pipes that collect rain runoff from the street, part of an ongoing overhaul of a system to drain the streets through pipes that disgorge out at sea. The town's old system drained Ocean Boulevard out onto the beach and into the surf. A few miles down from the boardwalk, some of those outfalls are still there, with signs that read "Caution: following rainfall this area may have elevated levels of bacteria due to storm water run off."

The beaches along there are the worst in the state for the frequency of health warnings issued to swimmers.

Triggers

Hypoxia can happen naturally. It can be caused or exacerbated by pollutants from stormwater runoff and other discharges. Research hasn't determined yet what's causing it at Myrtle Beach.

The most recognized form of hypoxia is an algal bloom, such as the green scum that forms on the surface of ponds during the summer.

Warm waters in the Lowcountry can be prone to hypoxia. A few hundred fish died last week in a tide-washed retention pond on James Island, in what's become a chronic problem for the marshside pond.

Nobody expected to see hypoxia in the circulating ocean off Myrtle Beach. The conditions when it occurred don't fit into either of the two known categories. This was something different, and the researchers have been scrambling to figure out its triggers. Meanwhile, hypoxia occurred along the same stretch of beaches last summer.

"We don't know, it could be a natural phenomenon," said Rich Viso, Coastal Carolina University assistant director for the Center for Marine and Wetlands Studies. "It might be the area is ready to go hypoxic any time."

But two sewage spills in the area and several periods of heavy rain preceded the 2004 hypoxia event. Periodic swimmer warnings or winter oyster bed closings for bacteria are a fact of life along Myrtle Beach, as well as the Lowcountry.

"There is enough evidence to tell us we'd better find out," Libes said.

The city of Myrtle Beach isn't waiting. It's begun aggressive mitigation and control measures, like the new piping. Its recently updated comprehensive plan calls for low impact development that limits solid surfaces where water runs off.

Trouble spots

Charleston's beaches aren't too likely to face hypoxia problems any time soon, said Denise Sanger, S.C. Sea Grant Consortium assistant research director. "Long range, we don't know."

Trouble signs are already here. Testing by the S.C. Natural Resources Department in Charleston Harbor has found spots in feeder creeks in developed areas where the water quality is considered "fair to poor" for supporting marine life.

With the potential threat, you'd think that the Long Bay group's study and testing would be well funded. But the original state monitoring station at Springmaid Pier was removed after a few years for lack of funds.

Federal funds have gone to higher priority "dead zone" research in areas like the Gulf.

The only monitoring station now is at Apache Pier on the north end of the beach, where the owners help maintain it and help pay to keep it operating. The working group keeps the research effort going piecemeal, Sanger said.

"Susan has continued to cobble money sources together," Sanger said. "We've done a lot of the work with almost no money. It runs on the drive of the scientists and resource managers involved."

Meanwhile, under the highrise wall on Myrtle Beach, right in front of a stormwater caution sign, bathers plunked down their beach chairs on a recent cloudless afternoon and kicked back. A few read the sign; almost nobody paid any mind.

Shannon Cage, of Kokomo, Ind., was on vacation with her family. They had booked in Panama City, Fla., then canceled because of worries about the Gulf oil spill pollution. They find they love Myrtle Beach. And no, the sign didn't bother them.

"We just assumed if they were letting people swim it was safe," she said.

Reach Bo Petersen at 937-5744 or bpetersen@postandcourier.com.