July 14, 2011
Oyster study in Hackensack River shows water still too contaminated to maintain healthy population
By Brian Anderson
Oyster populations introduced to the Hackensack River have either died or had abnormal tissue, according to researchers who have been working on a study. Two officials involved in the study said the oysters that did survive, however, show the riverís health is slowly improving.
Oyster beds were placed in the Hackensack River as a way to study how polluted the water really is and to act as a filtering system. Recently the researchers announced the oysters didnít fare so well in the polluted water.
The study began in 2007 when thousands of oysters were placed in makeshift beds along the river. Beth Ravit, a professor from Rutgers University, headed up the project that introduced oyster to both the Hackensack River and Raritan Bay over the past few years. The study began in 2007 and thousands of oysters were put in the Hackensack River to see if they could help clean up the polluted waterway.
The Hackensack Riverkeeper initiated the study after wild oysters were discovered in the Hackensack River a few years ago. The New Jersey Meadowlands Commission provided start-up funding and volunteers organized by the Riverkeeper have helped with the study as well.
Oysters serve a valuable role in the eco-system of a waterway. Oysters, a bivalve shellfish, are filter feeders and a full-grown oyster has the ability to filter up to 60 gallons of water a day. In the process, they remove organic material like algae and decaying vegetative waste, which helps clear up the water and allows sunshine to hit the bottom of the waterway, allowing sea plants and grass to grow. Oysters also grow on top of each other, which creates a natural reef for other marine creatures and helps prevent shore erosion.
In the fall of 2009, the research team got baby oysters from a hatchery in Long Island, and the oysters were divided into two groupsósome were put in Raritan Bay and the rest in Hackensack River. A year later, the populations were compared.
"Thatís when we started seeing the abnormalities in the Hackensack," Ravit said.
She said the oysters from Raritan Bay were healthy, their tissue was normal, they were ready to reproduce and the population had an even split of male and female oysters. Oysters are all male in infancy. When they mature, some switch sexes.
More oysters were pulled from the Hackensack River about six weeks ago. The oysters from the Hackensack River had tissue abnormalities, tumors, thin shells and none had changed over to females. Many had died off.
Ravit said she is still analyzing what caused the abnormalities and tumors, but her hypothesis is environmental stresses such as pollution and industrial waste.
One spot, at the river bend near the Amtrack Bridge in Kearny where three cages were placed, had the highest number of survivors. The oyster in two cages there thrived, but Ravit said she is still unsure of why.
In cages located along the river, near old industrial sites and landfills, the oyster populations almost completely died. Ravit said of five cages near the Jersey Turnpike near Secaucus and Jersey City, only one had survivors.
"Marine biologists think of the oyster as the canary in the coal mine," she said. "The riverís getting better, but itís just not there yet."
She tells the story of what thin shelled oysters can be up against in the wild. She thinks a small blue claw crabóa natural predator to the oystersógot into one cage when it was young, and feasted on the oysters throughout its life. Because the oysters had thin shells, the crab was able to crack the shells and eat the entire cage of oysters over a long period of time. None of the oysters from the cage survived that blue claw crab.
Riverkeeper Bill Sheehan said although he is saddened that many of the oysters did not survive the entire research period, the data that will come from the project will help further the understanding of the health of the river, and what now needs to be done.
"In a way Iím happy for what we did with these cages, and the research Beth did with it," said Sheehan.
He said the data can also be used to identify what pollutants harmed the oysters. Sheehan said the information provided by the study could be used to get a better understanding of what is polluting the river, and possible locations of where the pollution is entering the water.
Ravit said she doesnít want to conduct another study right away, which would likely kill off thousands more oysters. The next step is trying to identify what contaminants might be causing the thin shells and abnormalities, Ravit said. The biggest problem, she said, is finding funding for another research project. However, she is working with federal and state government officials as well as the United States Navy to continue oyster research in the Raritan Bay.
Last year, after the oil spill in the Gulf of Mexico, the New Jersey Department of Environmental Protection (DEP) required research involving shellfish to stop in coastal and inner harbor waters classified as contaminated due to poaching concerns. Though Ravit said she was required to pull the oysters for the study from the Raritan Bay, she received no directive to pull the cages from the Hackensack River.
The fact that there were survivors of the study is an encouraging sign, said both Sheehan and Ravit. Sheehan said during the height of the pollution of the river, none of these oysters would have been able to survive. But now there are survivors who have grown a few inches since they were introduced into the river, which means the riverís overall health is slowly getting better.
"The river is slowly along the road to recovery," Sheehan said.
Ravit also points to the wild oysters that have been found in the Hackensack. If researchers can figure out how those oysters have evolved to survive, they can breed them to create a stronger, more resilient population of wild oysters.
"Itís disappointing that theyíre not home free yet, but the fact that some of them have lived over three years, thatís a good-news story. It really is," Ravit said.