Fabulous Food Chain Phenomenon

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A chemosynthetic clam living in sea grass. Researchers are not sure how lobsters dig them up. Credit Nicholas Higgs

Thanks to the Science section of the New York Times for this article, The Freaky Food Chain Behind Your Lobster Dinner, by Steph Yin:

If you’ve ever ordered a lobster tail from Red Lobster, there’s a good chance some of your meal can be traced back to swamp gas.

Let me explain.

Red Lobster is a major purchaser of Caribbean spiny lobster, a species that lives in coral reefs in the western Atlantic Ocean. In the 1980s, lobster fishers started constructing artificial reefs in sea grass beds throughout the Caribbean to attract these lobsters.

Before long, the fishers noticed something peculiar. They were finding “piles and piles of clams” outside their makeshift lobster shelters, said Nicholas D. Higgs, a marine biologist at Plymouth University in Britain who comes from generations of lobster fishermen in the Bahamas.

These clams, Dr. Higgs confirmed in a recent study, form a significant portion of the lobsters’ diet at these reefs. In a paper published on Thursday in Current Biology, Dr. Higgs and colleagues report that sea-grass-dwelling lucinid clams make up 20 percent of what Caribbean spiny lobsters eat in artificial reefs. What’s unusual about this situation (and where swamp gas comes in) is the way these clams get their food.

Most food chains, we learn in grade school, start with life-forms that make their own food using light. Through photosynthesis, plants, algae and some bacteria are able to convert carbon dioxide and water into organic carbon. This magical process ultimately sustains almost all life on Earth. But it’s not the only way organisms make food from scratch.

Lucinid clams get nourishment from symbiotic bacteria living in their gills. These bacteria use an alternative food-producing strategy, called chemosynthesis. Instead of relying on sunlight for fuel, they use the energy released from decomposing leaf litter in sea grass beds to turn carbon dioxide and hydrogen sulfide — the rotten-egg-smelling ingredient in swamp gas — into organic carbon.

This “dark carbon,” so named because it is produced in the absence of light, then makes its way up the food chain, from clams, to lobsters and then to predators like sharks, turtles and you and me as we tuck into our lobster dinner on a Saturday night.

This research fills in gaps from photosynthesis-based measurements of sea grass productivity, which fail to account for all the fisheries production that sea grass systems generate, said Brian R. Silliman, a professor of marine conservation biology at Duke University who was not involved in the research…

Read the whole article here.

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