Study finds how sea urchins affect coral reefs’ growth

WASHINGTON - An 18-year-old study has found that overfished reef systems have more sea urchins-organisms that in turn eat coral algae that build tropical reef systems.

According to the study of Kenya’s coral reefs by the Wildlife Conservation Society and the University of California at Santa Cruz, reef systems closed to fishing have fewer sea urchins because predatory fish keep their growth in check, thereby encouraging higher coral growth rates.

Jennifer O’Leary of the University of California at Santa Cruz and Tim McClanahan of the Wildlife Conservation Society found that reefs with large numbers of grazing sea urchins reduced the abundance of crustose coralline algae, a species of algae that produce calcium carbonate.

The study found that sea urchins were the dominant grazer in the fished reefs, where the predators, triggerfish and wrasses were largely absent.

“This study illustrates the cascading effects of predator loss on a reef system and the importance of maintaining fish populations for coral health,” said McClanahan.

However, these herbivorous fish also removed fleshy algae that compete with coralline algae.

The findings suggest that managing coral reef fisheries can affect coral reef growth and improving the management of tropical fisheries can help these reefs to grow and persist in a changing climate.

“This study demonstrates the importance of improving fisheries management on reefs so that corals can thrive, safeguarding some of the world’s most fragile marine biodiversity and strengthening coastal economies,” concluded Dr. Caleb McClennen, Director of WCS’s Marine Program.

The paper appears in the December 2010 issue of the scientific journal Ecology. (ANI)