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Beach replenishment may have long-term ecological consequences

"How frequent and widespread should efforts to replenish beaches be?" asked researcher Tyler Wooldridge.

By Brooks Hays
Beach replenishment may have long-term ecological consequences
Researchers found fewer ringed worm species at beach sites that had been replenished with offshore sand. Photo by UC-San Diego

SAN DIEGO, March 29 (UPI) -- A beach isn't really a beach without sand. Unfortunately, over time, beaches lose their sand to the wind and waves.

One way to battle beach erosion is take offshore sand and dump it on the shrinking beach, a process called beach replenishment. New research suggests the strategy may have long-term negative effects on coastal ecosystems.

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Scientists at the University of California, San Diego found replenished beaches had significantly diminished invertebrate populations 15 months later. Populations of polychaetes, a class of ringed worms, were especially hard hit by replenishment.

"Such reductions may have far reaching consequences for sandy beach ecosystems, as community declines can reduce prey availability for shorebirds and fish," researchers wrote in a new paper on the subject, published in the journal Estuarine, Coastal and Shelf Science.

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Researchers at UC-San Diego measured biodiversity and abundance at eight beaches in Southern California. Each beach featured a control plot and a beach replenishment plot. Scientists then measured four, 12 and 15 months later.

"In San Diego there are multiple species of tiny worms called polychaetes," Heather Henter, a biologist and academic coordinator of the UC Natural Reserve System, said in a news release. "Little bean clams, Donax gouldii, are sometimes on our beaches by the thousands and there are various crustaceans such as amphipods, or sandhoppers, and mole crabs, Emerita analoga, that stick their feathery antennae up above the sand to filter food out of the waves in the swash zone."

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Most animal types suffered initial losses, but many rebounded. The tiny worms, however, failed to recover within 15 months.

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Researchers say additional studies need to be conducted to determine how long these negative effects last.

"Another key question is how frequent and widespread should efforts to replenish beaches be?" asked Tyler Wooldridge, a graduate student at UC-San Diego. "Are there times of the year when it is more or less disruptive for the animals that live in the sandy beach? To answer those questions, we need more studies."

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