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Barnegat Bay eelgrass faces danger


News Source:  Asbury Park Press

May 13, 2011



TOMS RIVER — Ocean County lost more forested land faster than any other New Jersey county before the 2008 financial collapse and recession, a period when Barnegat Bay researchers saw more algae blooms and shrinking eelgrass beds, scientists said Thursday.

“Since 2007 and the recession, you can see the rate of development has dropped from 1,700 acres a year to 600 acres a year,” Richard Lathrop, the director of the Center for Remote and Spatial Sensing at Rutgers University, told a science conference hosted by the Barnegat Bay Partnership at Ocean County College.

“At present, a little more than a third of the watershed is developed,” Lathrop said. “Most of it is coming from upland forest. … Ocean County had the highest rate of upland forest loss of any county in New Jersey” until 2007, he said.

Scientists think increasing ground coverage of houses and pavement in the bay watershed has increased the nutrients flushing to the bay — essentially overdosing the estuary with fertilizer that fans explosive growth of algae and weeds like sea lettuce, as well as with tiny plants called phytoplankton that darken the waters and shut out sunlight to eelgrass on the bottom.

Stressed-out eelgrass meadows in Barnegat Bay and around the world might be in danger of renewed disease or population collapse, says professor Mark Campanella, a Montclair State University ecologist.

“You’re talking about an organism that is critical to dozens of sea creatures,” Campanella told the audience at a daylong science conference hosted by the Barnegat Bay Partnership at Ocean County College.

“When you start to reduce population size, you start to reduce genetic diversity,” Campanella said. “You reduce the ability of the plant to adapt.”

The afternoon session focused on the health of Barnegat Bay’s eelgrass beds, important habitat for fish and crabs that have shrunken dramatically over the years. Montclair State researchers estimate eelgrass coverage has retreated by 62 percent over three decades.

“The plants that are found in Barnegat Bay are small,” probably limited by those environmental conditions, Campanella said. eelgrass grows three to four times as large in Maine and Alaska, he noted.

Genetic analysis of Barnegat Bay eelgrass — which is now 75 percent of the eelgrass left in New Jersey coastal bays — shows that the plants have signs of inbreeding because of the shrinking population and distances between surviving eelgrass areas on the East Coast, he said.

From 2004 to 2010, eelgrass blade length has declined by one-third, and the mass of sampled grass blades is down by 87 percent, said research professor Michael Kennish of Rutgers University.

“Seagrass is the most important bioindicator of nutrients in our estuaries,” Kennish said. That is because underwater grasses thrive in clear water and suffer when the bay is clouded by blooms of microscopic plants and large algae like sea lettuce, he said.

“Seagrass needs very bright light compared to algae, and algae outcompetes the eelgrass,” Kennish said.

Nearly two-thirds of the nutrients flowing to Barnegat Bay come from Ocean County’s northern suburban region, and researchers found markedly higher levels when they sampled rivers during 2010 rainstorms.

“Together the Toms River and Metedeconk account for more than 60 percent of the total load,” said Christine Wieben of the U.S. Geological Survey, which has been revising and updating its picture of how excessive nutrients get into the bay and overfertilize the waters.

Those flows of nitrogen compounds were a major subject of Thursday’s State of the Bay 2011 conference. When those nutrients hit the bay, they get taken up so quickly by algae and microscopic plants that chemical measures are fleeting, Kennish said.

“We have got to take into account the nitrogen is being converted to particulate form,” said Kennish, who heads a team working to develop biological measures of nutrient impact. Water samples can show low levels for dissolved nitrogen, “and the algae blooms are all around you,” he said.

Barnegat Bay has so little daily tidal turnover of water that “essentially it’s a basin, a giant bathtub,” Kennish said. Nitrogen is taken up by plants and sediment of the bay bottom, so it cycles through the system and keeps it overenriched, he said.

That in turn helps algae outcompete native eelgrass that is important habitat for fish and crabs.

This afternoon, Kennish is presenting findings that show eelgrass has declined to the lowest levels observed in a decade.

Meanwhile his group has documented increasingly frequent algae blooms since 2008, so “something has gotten worse in that time,” he added.

The algae blooms are fertilized by nutrients coming into the bay, estimated by the U.S. Geological Survey at around 1.4 million pounds of nitrogen per year. The USGS has been revising its estimates and most notably downgraded the contribution from air pollution fallout.

Whatever the total, Kennish said, “I can tell you one thing: We’re above the threshold for eutrophication,” a state of overenrichment that changes the bay’s ecosystem.

Older atmopsheric data had been drawn from a sampling station at Washington Crossing on the Delaware River — close to Trenton, Pennsylvania power plants and the Interstate 95 transport corridor.

But with data from a newer station close to the bay near Brigantine, the estimate for airborne nitrogen compounds from power plants and car exhausts has dropped by 42 percent, Wieben of the USGS told the conference.

“It doesn’t look like there’s anything substantial at that station,” said Robert Nicholson, who heads environmental programs for the USGS New Jersey office.

One unknown is how much nitrogen emissions are laid on the watershed by traffic on local roads and highways, Nicholson said.“The situation is complicated because you have this local signal superimposed on a regional signal.”

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