Big enough to be clearly seen from space, a massive algae bloom off the Jersey Shore is painting 100 miles of ocean a striking blue-green but currently poses no danger to marine life, scientists say. That could change if die-offs and decay of the microscopic plants called phytoplankton rapidly deplete dissolved oxygen in near-shore pockets of the ocean. So scientists are tracking the bloom from space, air and sea, sending robotic submarine probes to sample the water and keep tabs on the oxygen levels.
Most of the bloom off southern New Jersey is associated with weeks of ocean upwelling, as prevailing winds pushed
warm surface water away from land and drew up colder water laden with nutrients that phytoplankton thrive on, said assistant professor Josh Kohut, an oceanographer with the Rutgers University Institute of Marine and Coastal Sciences. “It’s not something completely out of the ordinary, but it is unusual for its size.”
Kohut said upwelling is the same wind-driven phenomenon of summer that pushes warm surface water away from the beach, leaving swimmers shivering at the nip of colder waters in August.
It also drives biological productivity in the ocean, where phytoplankton are a base of the food web that links microorganisms larger animals and fish. “It’s along about two-thirds of the New Jersey coastline, from the southern end of Monmouth County to Cape May, and it’s going offshore 20 to 30 miles,” he said.
While satellite imagery shows the vast bulk of the bloom off southern New Jersey and being spread offshore before southwesterly winds, there also appears to be a northern component that may be fueled by nutrients washing out of New York Harbor from last weekend's heavy rains, said Heather Saffert, staff scientist with the Sandy Hook-
based environmental group Clean Ocean Action.
“It seems to be two oceanographic events going on at once,” Saffert said. “It seems the upwelling process started in mid-July, and this latest bloom started after the rains.” Heavy rains over northern New Jersey and New York dumped a report 4 to 10 inches of rain in some places, enough to push waste out of combined sewer overflows in urban areas and flush pollution off streets, she said.
A 2004 study by Rutgers oceanographers documented how pulses of storm water-borne nutrient pollution regularly surge out of the Hudson River and feed algae blooms outside the harbor and down along the Monmouth County coastline. Ever since the disastrous 1987 and 1988 summer season were marred by sewage leaks and trash washups, federal and state government have been working to reduce combined sewer overflows and their impact
on the ocean environment.
But urban New Jersey and the lower Hudson are still dotted with combined overflows, some 1,220 in all, according to a recent report by the U.S. Environmental Protection Agency. “Hopefully all this will just dissipate and nothing will happen,” Jeff Tittel of the Sierra Club said of the bloom. “But it is a clear signal to New Jersey and the region about nutrients” in coastal waters, he said.
Algae blooms get close monitoring from environmental and public health agencies, in case they are toxic organisms like the infamous red tides of New England. This bloom is benign, but scientists are keeping an eye on dissolved oxygen levels in the bloom, because those can drop as the plants die and decay.
A robot probe from the Rutgers fleet of Slocum electric gliders is already cruising in the bloom and transmitting water quality data back to the New Brunswick control center, and a second underwater glider will be launched soon, Kohut said. “We’re seeing lower oxygen values,” but nothing dangerous for fish, Kohut said. Oxygen in the bloom offshore is around 8 parts per million, with pockets of 4 ppm close to shore, but “things don’t get critical for fish until you get below 2” ppm, he said.
While the oxygen levels are not dangerous yet, levels of 4 to 5 parts per million can begin to stress aquatic life, particularly shellfish and other species that cannot swim on to other areas, said Cynthia Zipf, executive director of Clean Ocean Action. In an email, Zipf recalled a 1976 bloom that triggered a widespread oxygen depletion, wiping out much life on the sea floor off New Jersey.
“Fishermen should be looking for fish floating on the surface or in their nets. Divers should look for lobsters, crabs and fish that usually hide in crevices, but are now in the open and lethargic,” Zipf wrote. “Also look for fish that are located higher on the wrecks and/or breathing with difficulty. If divers know how to use dissolved oxygen kits, they should take samples.”
Zipf and Saffert said they are asking the EPA and other agencies to take a close look at the potential causes of the bloom. But officials with the state Department of Environmental Protection said they do not expect any impact on beachgoers from the bloom.
“Large blooms such as these result from extended periods of offshore winds that cause upwelling of cold water that is rich in nutrients to come closer to the coastline,” Jill Lipoti, director of the DEP's Division of Water Monitoring Standards, said in a news release. “They are a natural phenomenon.”