COLUMBIA, SC Tiny sea creatures that fish and crabs eat to survive disappeared from parts of the ocean near Charleston after dredges scooped offshore sand from the sea floor to widen erosion-plagued Folly Beach, new research shows.
In what’s considered the first study of its kind in South Carolina, a state scientific report says two beach renourishment projects had a long-lasting effect on bugs, small shellfish and worms that lived in areas where offshore-sand mining occurred at Folly Beach.
Some bottom-dwelling animals were not found on the ocean floor for up to eight years after the areas were mined and the sand pumped ashore to widen the beach, according to the Department of Natural Resources study. In one instance, only eight species were found after sand dredging was completed, the study said. The report said 28 species existed before the project began.
The organisms that vanished were in many cases no bigger than a grain of rice. But they were important in the food chain because fish, crabs and larger marine animals consume them. The DNR study said the loss of small marine creatures could be “deleterious’’ to fish.
Without enough food, fish and crabs might die or move away from some areas, which could be a concern to recreational and commercial anglers.
Published last month, the report provides new insight that could guide the state and federal government on how – and whether – to approve beach renourishment projects in the future.
Renourishment is a major weapon in South Carolina’s fight to keep beaches wide as sea level rises and homes are threatened. But the sand replenishment projects are expensive for taxpayers and have been criticized by those who say the government is paying to protect unwise seaside development.
Taxpayers have spent some $200 million replenishing beaches during the past three decades in South Carolina, past reports have shown.
Rob Young, a coastal geologist at Western Carolina University, said cost is an issue, but the government also needs to look more carefully at the overall environmental impacts of widening beaches. He favors more comprehensive studies of renourishment before projects gain approval.
“We need to be able to quantify those impacts,’’ said Young, who heads the Program for the Study of Developed Shorelines at Western Carolina.
The DNR report looked at sand-mining’s effects on bottom-dwelling sea life for six years at one mined site and eight years at another. The projects occurred in 2005 and 2007 at Folly. The population of bottom-living animals likely dwindled because mud replaced the sand where they thrived, the report indicates.
Mined areas at Folly “showed little evidence of recovering six to eight years later,’’ the study said. Most studies in South Carolina have looked at environmental impacts for no more than a year after sand is mined for renourishment.
The report says the area off of Folly Beach that was mined did not fill back in with as much sand after the dredging. What filled into the holes in the ocean included a substantially greater percentage of mud and silt, according to the DNR study. That indicated the areas mined for sand could not be counted on as sources for future beach renourishment projects.
Denise Sanger, a DNR scientist who co-authored the study, said the study does not mean all areas of the coast will experience the same problems. But it suggests the spots where sand mining occurred might not have been ideal. They appear to receive more silt than some mining sites on other parts of the state’s coast where renourishment has been done.
Folly Beach, a popular resort town of about 2,000 year-round residents, regularly replenishes its beaches with sand because they are eroding so badly. The jetties that keep Charleston harbor open for ships are blamed for cutting off sand that used to naturally replenish the seashore at Folly Beach.
Folly Beach Mayor Tim Goodwin said he had not seen the study, but he doubts his community near Charleston will use the 2005 and 2007 sites for future sand sources. The city now is looking at a nearby river as a future source of sand for beach renourishment.
“I’m sure we won’t go back to those for some length of time,’’ he said