Smart Choice

Picky corals are better at weathering environmental stress

Corals that are choosy about which organisms they associate with may have a better chance of withstanding stresses such as ocean acidification and bleaching, scientists say.

Corals have symbiotic relationships with organisms called dinoflagellates. In the past, researchers assumed corals that could host many types of dinoflagellates were better-equipped to handle changes in their environment. Corals that were less flexible in their symbiotic partners, on the other hand, would be more vulnerable to stress.

To test this idea, researchers collected 132 samples of coral from reefs around Moorea, an island in the South Pacific. Next, they analyzed DNA from the samples to determine the types of dinoflagellates present. Finally, the team combed the scientific literature for information on how well each type of coral dealt with environmental changes.

Surprisingly, the corals that hosted many diverse dinoflagellates were less resilient and “often described as ecological ‘losers,’” the authors write in Proceedings of the Royal Society B. For example, flexible corals such as Acropora and Pocillopora fared the worst after a mass bleaching at Moorea in 1994. Corals that were picky about their symbiotic partners dealt with challenges more successfully.

The study suggests that being flexible isn’t always a good thing. While “generalist” corals can add or shuffle dinoflagellates more easily, they might be better off with a stable partner. — Roberta Kwok | 29 August 2012

Source: Putnam, H.M. et al. 2012. Endosymbiotic flexibility associates with environmental sensitivity in scleractinian corals. Proceedings of the Royal Society B doi: 10.1098/rspb.2012.1454.

Image © chrisho | iStockPhoto.com