Thursday, Nov 27, 2014
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It’s almost summer beach wrack season


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CLEARWATER BEACH — Scattered masses of marine debris that line the shore particularly during the summer storm season may be an unsightly, smelly annoyance to some sun worshippers enjoying a day at the beach.

But that line of debris has a name — beach wrack — and is an essential part of that ecosystem, according to Florida Fish and Wildlife Conservation Commission biologists. It also offers one of the best places to find shells and other seaborne treasures.

Seaweed, surfgrass, wood and other organic matter that drifts out in the water eventually gets pushed ashore by tides and especially by storms.

While it may appear to be dried and dying, the seaweed, reeds, marine algae and kelp that make up wrack is very much alive and filled with organisms like sponges, soft corals, snails, egg cases and worm tubes that are essential to beach life and the creatures that live there, according to the wildlife commission.

Wrack provides an important ecological link between the land and the sea. Beach animals rely largely upon sources of food, like wrack, that drift onto shore. It also provides essential nutrients for the surrounding ecosystems.

As wrack ages, it facilitates the growth of fungi and other organisms. Beetles, beach-hoppers, ghost crabs and other small animals feed on the fungi and marine creatures that wash ashore.

The smaller animals in the wrack provide shorebirds like sandpipers, snowy plovers, flycatchers and terns with food that fuels their long-distance migrations. Small wading birds called dunlins, for example, migrate more than 6,000 miles each year between their feeding and breeding areas. Without wrack and the organisms that live in it, the birds would starve.

Beach wrack also is the first stage in forming sand dunes, according to biologists. The dunes are natural barriers against wind and water, and they prevent erosion.

Clumps of old wrack provide wind shadows where wind-blown sand and tumbling plant seeds collect on the upper beach. Sprouting plants grow more quickly through their vulnerable period thanks to nutrients in decaying wrack.

Although most wrack clumps and the plants they foster disappear with time, some grow into low dunes on the upper beach. If left undisturbed, these small dunes can grow into substantial mounds capable of protecting upland property from storm erosion.

Wrack also provides a safe haven for many animals that escape predators by hiding under it or blending in with it. A shorebird can “disappear” while resting among the similarly colored shades of brown and gray seaweed, for example.

Over time wrack decomposes, releasing essential nutrients and acting as rich fertilizer for surrounding ecosystems. One study found that land plants near wrack grow 70 percent faster than those without wrack nearby. Another study determined that decomposing wrack also provides nutrients for surfgrass and other plants that grow just offshore in the shallows.

Wrack often is cleared away from public swimming areas in a process called beach grooming. While that leaves flat, clean expanses of sand, it also removes all the benefits that wrack provides to the beach ecosystem. Crustacean species like beach hoppers and roly polies decline dramatically along with the shorebirds that prey upon them. Removing wrack also causes the number of hummocks and dunes to decline along with the number of dune-based plants.

Beach wrack isn’t just icky seaweed that sits along the shore. It is an ecosystem important to the beach and beach life, as well as a place to experience nature and satisfy curiosity.

jane@clearwatergazette.com

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