Suppertime Signal

A CHEMICAL SIGNAL released by plankton feeding along coral reefs can be artificially deployed to make hungry fish flock to the scene, a new study shows (Science 2008, 319, 1356). The chemical cue, dimethylsulfoniopropionate (DMSP), has an established role in global climate change, but the study suggests it also may function as a signal in marine food webs.

Jennifer L. DeBose and Gabrielle A. Nevitt of the University of California, Davis, and Sean C. Lema of the University of North Carolina, Wilmington, uncovered DMSP's new role by releasing the chemical at concentrations that fish encounter in nature. Coral-reef-dwelling algae naturally produce DMSP, which is released into the ocean when plankton feed on the algae. Marine microbes break DMSP down into dimethyl sulfide (DMS), a gas that contributes to cloud formation and thus to climate cooling.

At coral reefs off the coast of Curaçao, the team reproduced the sulfurous trail that feeding plankton leave behind. They suspended large plastic containers that would release a plume of either DMSP or distilled water along the reef edge. Their DMSP solutions lured several species of plankton-eating fish to the reef.

Rafel Simó of the Institute of Marine Sciences, Barcelona, an expert on marine sulfur compounds, notes that the work doesn't verify whether fishes sensed DMSP or DMS. DeBose tells C&EN that DMSP is more water-soluble than DMS, and "fish noses respond to water-soluble compounds." However, DeBose agrees that additional experiments could better confirm the identity of the signal.

"Fish, like other predators, probably use a combination of chemical cues to home in on prey," says Gordon V. Wolfe, who studies chemical signaling in marine microbes at California State University, Chico. Anything that helps us understand the dynamic of coral-reef systems is useful, he says, because of global warming and other threats these habitats face.