Discovery could aid restoration of coral reefs

Penn State Live: Discoveries about tropical coral reefs, to be published on June 23 in the Public Library of Science journal PLoS ONE, are expected to be invaluable in efforts to restore the corals, which are succumbing to bleaching and other diseases at an unprecedented rate as ocean temperatures rise worldwide. The research gives new insights into how the scientists can help to preserve or restore the coral reefs that protect coastlines, foster tourism, and nurture many species of fish. The research, which will be published in the journal PLoS One, was accomplished by an international team whose leaders include Iliana Baums, an assistant professor of biology at Penn State.

The team focused on one of the most abundant reef-building species in the Caribbean, Montastraea faveolata, known as the mountainous star coral. Though widespread, this species is listed as endangered on the Red List of the International Union for the Conservation of Nature because its numbers have declined significantly -- in recent years, up to 90 percent of the population has been lost in some areas.

Discovering how corals respond to ocean warming is complicated because corals serve as hosts to algae. The algae live in the coral and feed on its nitrogen wastes. Through photosynthesis, the algae then produce the carbohydrates that feed the coral. When this complex and delicate symbiosis is upset by a rise in ocean temperature, the coral may expel the algae in a phenomenon known as coral bleaching, which may cause the death of both algae and coral. The challenge is to figure out why some corals cope with the heat stress better than others.

"We decided to focus on coral larvae because the successful dispersal and settlement of larvae is key to the survival of reefs," said Baums. "Also, since free-swimming larvae do not yet have symbiotic algae, we can record the expression of different genes in our samples and know that we are looking at the molecular response of the coral itself to heat stress."

…Baums said she is excited by the clear evidence of local adaptations in populations that this study documented. Previous work by Baums and her colleagues has included experiments in restoring damaged coral reefs by creating larvae from controlled genetic crosses, growing them in captivity until they settle onto ceramic tiles, and then transplanting them into selected areas to replenish damaged reefs. …

Researchers set fine nets over coral just before mass spawning events in order to collect the eggs and sperm as they were broadcast into the water column. Gametes were collected and returned to the lab within an hour to be raised under controlled conditions. From the Penn State Live website