Sea nettle (left) and its favorite prey, comb jelly Photo: Becca Morris

This story first appeared in the SERC quarterly Newsletter Winter 2006/2007

Oysters and Jellies

A diminished oyster population in the Chesapeake Bay may be causing a decline in the number of sea nettles, those reviled stinging jellyfish. Welcome news perhaps to summer beachgoers, the recent findings by Denise Breitburg and Richard Fulford may not be such good news to the oysters, or to the fish larvae and other small creatures who depend on sea nettles to eat their predators.

The researchers recently published a study in Estuaries and Coasts revealing a strong correlation between declining oyster populations, a reduction in the abundance of sea nettles, and a subsequent increase in sea nettle's favorite prey.

Previous assertions blamed sea nettle decline on shifts in climate and freshwater river discharge into the Bay, but Breitburg's study which compared data from a variety of sources suggests it was more likely to have been caused by the decline in oysters. Looking more like tiny sea anemones than the familiar bell-shaped jelly fish, juvenile nettles spend the winter months as young polyps attached to hard surfaces. Oyster reefs provide the perfect nursery ground for those polyps. Without them, fewer young nettles survive to adulthood.

The irony for the oysters is that, without adult sea nettles, fewer young oysters may survive. That's because adult nettles are the dominant predator of another gelatinous bay dweller, the comb jelly or ctenophore which preys on oyster larvae. The new study also revealed a correlation between a drop in sea nettles and increased ctenophore populations. This work brings the complex interplay between oyster, sea nettle, and ctenophore into better focus, and suggests another complication in the efforts to assist oyster recovery in the Bay.

For more information, or to reach Dr. Breitburg, please contact SERC science writer Kimbra Cutlip .