Natural World: Seaweed a symptom in Hempstead Bay?

On a recent crisp November day, a boatload of scientists rounded Point Lookout to find the beach there covered with a thick layer of emerald seaweed.

It was the first time some had seen the seaweed explosion for themselves - sheet upon sheet of an algae called ulva lactuca that many consider the main symptom of pollution afflicting Hempstead Bay.

"Two to three feet deep of ulva - that's crazy," said Anne Cooper Doherty, a graduate student who works with Stony Brook University associate professor Bruce Brownawell, an environmental chemist and water quality expert.

Mats of the bright green ulva stretched several hundred feet between jetties. As it dried, the seaweed formed a gray moonscape-like blanket on much of the beach. On warm days when the wind blows toward nearby homes, neighbors complain the stench is unbearable. Some, such as activist Morris Kramer, worry that hydrogen sulfide produced as it decays could be harmful.

Residents and environmental advocates believe nitrogen and other nutrients in sewage from several nearby plants have triggered overgrowths of ulva that smother the bay bottom and wash up onshore near Jones Inlet. Responding to those concerns, Doherty, Brownawell and several other researchers on the boat are embarking on an intense study of Hempstead Bay to determine what exactly ails this fragile complex of channels and marsh islands.

New York State considers Hempstead Bay "impaired" by pathogens swept into the bay via contaminated runoff. More recently, nitrogen was also listed as a suspected contaminant because of the seaweed growth; potential sources include four municipal sewage treatment plants that discharge to Hempstead Bay, as well as stormwater runoff.

"Every time I've been out in spring or summer the ulva has been here," said Larry Swanson, associate dean of Stony Brook's School of Marine and Atmospheric Sciences. "It's been a decade-long discussion."

Ulva tends to thrive in nutrient-heavy waters and is sometimes used as an indicator species to monitor pollution trends. In large quantities, ulva can harm marine life, sucking oxygen from the water as it decomposes, but it's not clear if that has happened here. And little evidence exists so far linking the ulva to sewage because nitrogen levels in Hempstead Bay have not been measured for nearly 30 years.

That's where the scientists come in. To help plan their research, they got an expert tour of the waterways from marina owner Tom Doheny, a former conservation commissioner with the Town of Hempstead.

"This is where the two tides from Rockaway and Jones Inlet meet," Doheny said as his 21-foot motor boat cut through Reynolds Channel, past the Lido Beach Golf Club.

Doheny piloted the scientists past delicate wetland hassocks, up into the back bays and past industrial waterfronts off East Rockaway and Oceanside.

Of prime interest: the underwater sewage outfalls that each day discharge at least 58 million gallons of treated effluent to Hempstead Bay.

Local concerns about sewage reached new heights this fall, as the seaweed piled up high and smelly off Point Lookout and suspicious plumes of brown water were spotted near the outfall pipe for Nassau County's Bay Park treatment plant. Last month those fears were confirmed when state officials said the plant - which treats nearly half of Nassau's sewage - had been illegally dumping sludge into Reynolds Channel since March.

To get a better idea of how water and contaminants flow through the back bays, Stony Brook professor Roger Flood plans to map out the area's underwater topography. On this run, he sat in the back of the boat and tapped away at a sturdy laptop, testing programs and collecting basic GPS information on the various marsh islands. More precise measurements will be plugged into computer models later to help scientists understand how quickly sewage and other pollutants are swept out to the Atlantic.

Brownawell, who has studied sewage-related contaminants in nearby Jamaica Bay, said he was surprised at the lack of academic attention to Hempstead Bay given the large volume of sewage that ends up there. He and Doherty plan to track where the effluent ends up by testing sediment for traces of hair conditioner, fabric softeners and other products commonly found in sewage.

He plans to sample sediments in the northern portions of the bay to check if effluent gets stuck back there instead of flushing out on the tides.

"We'll be looking away from the outfalls," said Brownawell. His prediction: "We'll see a sewage signal all the way out to the Great South Bay."