Ku’ulei Rodgers says Hawaii’s corals are dissolving

Ku’ulei Rodgers is a coral scientist at the Hawaii Institute of Marine Biology. Dr. Rodgers told us that many sea creatures depend on coral. Her work is to assess the health of Hawaii’s coral reefs, and she said that, because of changes in ocean chemistry, Hawaii’s corals are growing less robust.

Ku’ulei Rodgers: One of the main things that we found is that there will be a net ecosystem calcification loss. And this means that the reefs will be dissolving.

And the reefs will be dissolving faster, she said, than they can build back up. Rodgers explained that’s partly because carbon dioxide is increasing in the atmosphere and being absorbed by the world’s oceans. As a result, the oceans are becoming warmer and more acidic. This acidity, she explained, makes if more difficult for corals to produce the material they use to build their skeletons. Rodgers said this makes reefs more susceptible to stress and disease.

Ku’ulei Rodgers: Once ocean acidification occurs, you’re going to see more fragile coral skeletons. Some of the more sensitive species of corals will be completely eliminated.

She added that, unless drastic measures are taken to curb carbon dioxide emissions worldwide, severe damage to coral beds will almost certainly occur in Hawaii, and worldwide. Rodgers explained that the marine creatures who live in Hawaii’s reefs are truly dependent on coral.

Ku’ulei Rodgers: Some species are obligate coralovores. They eat only coral and can’t survive without it. Other fishes, and other marine organisms, use the reef for protection. And then other species rely on those species. So it’s a cascading effect. Once you get rid of the foundation, you’re going to have a problem with all other trophic levels.

She added that corals are sensitive to changes in the ocean.

Ku’ulei Rodgers: Corals live within 1 to 2 degrees of their summer maximum temperatures. Anything beyond 1 to 2 degrees for extended periods of time, and they begin to bleach, and they eventually die.

Rodgers said that Hawaii’s corals have survived two recent bleaching events due to changes in ocean temperatures – one in 2002 and the other in 2004. During a bleaching event, the corals turn white, because the algae-like organism responsible for giving corals their color and nutrients is expelled from the coral. The Hawaii reefs have recovered from these events, but Rodgers is concerned that increasing temperatures and ocean acidity will permanently damage the reefs.

Ku’ulei Rodgers: When corals are stressed, then they’re more likely to have disease come in. Here in Hawaii, we have located 8 different diseases in the main Hawaiian islands, and another 10 diseases in the northwestern Hawaiian islands. As the corals lose resilience due to bleaching, higher temperatures, and ocean acidification, diseas can come in, although we are seeing them at very low prevalence now.

Our thanks today to NOAA Pacific Services Center – linking culture, science, and people to build resilient Pacific Island communities.

February 15, 2010

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