Diversity of plant-eating fishes may be key to recovery of coral reefs

Washington, Oct 9 (ANI): A new report has suggested that maintaining the proper balance of plant-eating fishes may be critical to restoring coral reefs, which are declining dramatically worldwide.

The conclusion results from a long-term study that found significant recovery in sections of coral reefs on which fish of two complementary species were caged.

The research was conducted at the National Undersea Research Center in Key Largo, Florida.

Coral reefs depend on fish to eat the seaweeds with which the corals compete, and without such cleaning, the reefs decline as corals are replaced by seaweeds.

Different fish consume different seaweeds because of the differing chemical and physical properties of the plants.

"Of the many different fish that are part of coral ecosystems, there may be a small number of species that are really critical for keeping big seaweeds from over-growing and killing corals," explained Mark Hay, the Harry and Linda Teasley Professor of Biology at the Georgia Institute of Technology.

"Our study shows that in addition to having enough herbivores, coral ecosystems also need the right mix of species to overcome the different defensive tactics of the seaweeds," he added.

By knowing which fish are most critical to maintaining coral health, resource managers could focus on protecting and enhancing the highest-impact species.

In situations where local peoples depend on fishing, they might better sustain the reefs on which they depend by harvesting only less critical species.

"This could offer one more approach to resource managers," said Hay. "If ecosystems were managed for critical mixes of herbivorous species, we might see more rapid recovery of the reefs," he added.

Working 60 feet below the surface near the underwater laboratory Aquarius, Hay and co-author Deron E. Burkpile, constructed 32 cages on a coral reef.

Each cage was about two meters square and one meter tall and was sealed so that larger fish could neither enter nor leave.

"For the cages in which we mixed the two species of herbivores, the fish were able to remove much more of the upright seaweeds, and the corals in those areas increased in cover by more than 20 percent during ten months," Hay said. "That is a dramatic rate of increase for a Caribbean reef," he added.

Though the percentage growth was impressive, the actual growth in size of each coral was small, Hay noted.

Prior to the experiment, the coral reef areas studied had just four to five percent coverage of live coral.

After ten months, the corals caged with the two species showed six to seven percent coverage. Corals caged with just one type of fish or no fish lost as much as 30 percent of their cover during the time period. (ANI)