Seaweed Bodyguards Coral Against Bullying Sea Stars
(Click to enlarge) Researcher Cody Clements places bottle caps into the rocky sea floor off of the Fiji Islands. The caps are used to anchor small colonies of coral for experimentation and allow them to be removed for accurate weighing. (Credit: Cody Clements/Georgia Tech)
Warmer, more acidic oceans are already damaging corals in the South Pacific. But the corals also have more visible foes: such ascrown-of-thorns sea stars. “It’s an underwater swarm of locusts with a stomach that can be turned wrong side out and digest you as it walks across.” Mark Hay, a marine ecologist at Georgia Tech. “You just look in front of them and there’s good corals, and you look behind them and there’s these white skeletons.”
(From Scientific American / by Christopher Intagliata) — Hay says the corals in Fiji’s marine protected areas are particularly vulnerable to attack. So he and his colleague Cody Clements took a closer look at the underwater ecosystem there. And they discovered something weird. Neighboring seaweeds usually compete for resources with corals to the point where they will whip corals with their fronds and poison them with toxins. But the researchers found that, in this case, the seaweeds were saving the corals, blocking the marauding sea stars. “And so these competitors were really acting as kind of bodyguards for the corals, once things got bad.” Hay and Clements replicated those observations in underwater experiments, in which even fake seaweed did the trick—suggesting that seaweed is simply passively blocking the predators. The findings appear in the Proceedings of the Royal Society B.
Read the full story »