SHARKS are vital for the health of coral reefs, a model of the food web in a Caribbean reef suggests.
According to the model, created by Enric Sala of the Scripps Institution of Oceanography in San Diego, California, and colleagues, the removal of top predators allows lesser predators such as groupers to thrive, leading to a reduction in the number of algal feeders such as parrotfish. That makes reefs more vulnerable to disturbances that kill corals, such as disease, pollution and global warming (Proceedings of the National Academy of Sciences, vol 102, p 5443).
The study suggests that the loss of sharks may have contributed to the decline of reefs in the Caribbean, most of which are now dominated by algae. But proving the theory will be difficult, Sala says. 鈥淲e don鈥檛 have a reef where the only thing missing is the sharks.鈥� A few decades ago there was extensive overfishing of all species in the Caribbean, including algae grazers. This was followed in 1982 by a disease that wiped out sea urchins, allowing algae to take over.
Advertisement
The presence of sharks could be important for the recovery of the reefs, Sala says. 鈥淭op predators are very important for maintaining the stability of the system.鈥� To protect sharks, large marine reserves that encompass their entire range must be established, he says.
