Posted by: leahbiery | December 23, 2009

Why So Many Seashells?

Olivia Frejka searches for treasures at Lighthouse Beach.

Sanibel Island is world-renowned for its abundance of seashells, and if you look hard enough on any day of the year you are bound to find a few good-looking gastropod specimens.  Our island’s curved shape causes it to act like a shovel, scooping up shells from the Gulf of Mexico.  In fact, Sanibel Island is the result of thousands of years of accumulation of ocean deposition.  If you’ve strolled along the beach on Sanibel over the last few days, you probably noticed that there is an even higher than normal abundance of usually hard-to-find shells. It’s tempting to write this plenitude off as an early holiday gift from nature, but we biologists are always looking for more plausible answers.

So many seashells.

Often, shells accumulate on the beach in large quantities after large-scale natural events like harmful algal blooms and hurricanes, but shell pile-ups can also occur in the wake of a typical winter storm. Mollusks in the ocean die from predation and other natural causes, leaving their exoskeletons behind. These exoskeletons accumulate on the ocean floor, and when storms blow across the Gulf, the shells are washed up on the beach from far out at sea. Biologists dub these deposits “death assemblages” – a fairly morbid name for such a treasure trove from the depths.  When there is a long time period between storms, more shells accumulate, waiting to be pushed to shore. Before Saturday, Sanibel hadn’t seen heavy wind and rain for many weeks, so to the delight of beach-combers, collectors, and ocean enthusiasts, the storms brought in piles of fabulous Lace Murexes, Alphabet Cones, Fighting Conchs, Olives and Turbans among other bivalves and gastropods.

Today was the first day of our Holiday Peace Camp, and excited campers returned from Lighthouse Beach with pockets, nets, hats and buckets full of spectacular shells.  We gathered 28 gallons of the beautiful white Lucine bivalve to use in art projects during camp and throughout the year.

Our Lucine Mosaic.

If you haven’t visited the beach this week, you should grab your shell bag and head for the nearest beach access. You’re guaranteed to return with a wealth of great seashells, and this is an excellent opportunity to find that long-coveted Junonia. Happy shelling!

Fabulous finds.

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