Michelle brunetti post | Staff writer
DOWNE TOWNSHIP — It takes a special kind of person to wade into a choppy Delaware Bay on a cold, windy day carrying 34-pound blocks of concrete, all in the name of saving the marsh.
But volunteers and staff members from the U.S. Fish and Wildlife Service, the Partnership for the Delaware Estuary and the Nature Conservancy were doing just that last week.
“We call them adult Legos,” said Moses Katkowski, coastal restoration manager for the Nature Conservancy, of the concrete blocks they were moving out into the intertidal zone at its Gandys Beach Preserve.
They were stacked in an interlocking pattern, creating walls about 10 feet to 30 feet long and 3 feet high. The walls are separated by about 5 feet to allow animals, such as horseshoe crabs, access to the beach during spring egg-laying season.
The walls create a barrier to wave action during low- and mid-level tides and become a home for oysters that attach as spat, grow and filter the water.
A little farther down the beach, student volunteers were placing oyster bags in the water to create a different kind of living reef.
“This is largely experimental,” said Nature Conservancy Cape May Preserves Coordinator Adrianna Zito-Livingston, of Cape May.
The idea is that, when the water hits the marsh, it does so with less force and is less likely to cause further erosion, she said. It is also hoped the walls will trap sediment behind them to further fortify the marsh.
Without them, “every wave is acting on the peat, and the vegetation is drowned,” she said. “Once the vegetation dies, there is nothing really holding the marsh in place.”
The marsh they are trying to save has eroded about 500 feet since 1930, said Katie Conrad, of the U.S. Fish and Wildlife Service, which provided an $880,000 grant for the effort.
Marshland not only provides a buffer to human habitation during storms, it is a nursery for countless species of fish, bird and shellfish.
But New Jersey is losing hundreds of acres of marshland each year to erosion, according to government and Rutgers University data.
It’s happening because all the land in South Jersey is subsiding, or sinking, at the same time a warming climate is causing sea levels to rise.
The grant covers the planning, engineering, construction and monitoring of almost 3,000 feet of shoreline to help reduce erosion and provide good habitat for wildlife, according to the U.S. Fish and Wildlife Service.
“Some energy will come through. The goal is not to stop it but to reduce the energy coming through,” Katkowski said.
The important thing is to slow slumping of the marsh, which is undercutting of the base of the grass by wave action, which eventually causes chunks to fall into the water.
Katkowski said data so far show the structures reduce wave action on the marshes overall by about 15 percent through the whole tide cycle. They reduce it by about 50 percent during low and mid-level tides, he said.
The structures are built at about the low-tide line and are completely covered during high tide.
Blocks are delivered by barge on pallets, comes at high tide and offloads them, Katkowski said.
The oyster castles are just one of three types of living shoreline the nonprofit Nature Conservancy is testing here through the grant, which was available as post-Hurricane Sandy funds for strengthening resiliency. Sandy hit the Delaware Bayshore hard, causing serious erosion on many beaches.
Bags of oyster shells are also being used along part of the Bayshore, placed in the intertidal zone to lessen wave action and provide a habitat for oysters to attach and grow.
In Nantunket Creek leading off the bay, the group used coconut fiber coir logs to stabilize the shoreline and allow native marsh grasses to grow to prevent erosion.
Some of the work started last year, but the bulk of it happened this spring and finished with a final push in October.
“We took May and June off for the horseshoe crab season,” Zito-Livingston said. “Then we started again.”
The Delaware Bayshore is a main spawning area for the horseshoe crab, and the eggs they lay are an important food source for migratory birds, such as the threatened and endangered red knot, which stops to feed on its way from South America to the Arctic.
“This is the first time I have built one of these reefs,” said volunteer Murray Rosenberg, an environmental consultant from Philadelphia, as he helped move oyster castle blocks from the beach into the water. “I think it will do a good job of breaking down the wave energy and trapping sediment.”