Hawaiian Coral Abundance And Distribution Modeled
May 22, 2013

Researchers Predict Coral Distribution Around Hawaii

Lee Rannals for redOrbit.com - Your Universe Online

Researchers from the University of Hawaii say they have predicted the abundance and distribution of coral around the island state by using a computer model.

The team said they found the order of coral abundance around the main Hawaiian Islands to be Porites lobata, Montipora patula, Pocillopora meandrina, Montipora capitata, Porites compressa, and Montipora flabellata. This is the first study to systematically examine the influence of these factors on the distribution and abundance of coral species across the entire seascape of shallow reefs in the main Hawaiian Islands (MHI).

"Average wave height and maximum wave height were the most influential variables explaining coral abundance in the Hawaiian Islands," reported Erik Franklin, lead author of the study and Assistant Research Professor at the UHM Hawaii Institute of Marine Biology. "Our models also identified relationships between coral cover and island age, depth, sunlight, rugosity, slope, and aspect (direction a slope faces)."

Researchers said they were able to predict coral cover to the highest in primarily wave-sheltered coastlines and embayments. Reefs with the highest cover were concentrated in Kaneohe Bay on Oahu; reefs of Molokai, Lanai, Maui, and Kahoolawe; and the Kohala coast of Hawaii.

The team integrated field surveys for corals with environmental data of wave exposure benthic geomorphology, and sunlight from 2000 to 2009. Regional-scale mapping of coral species from these models provide a framework for population modeling and marine spatial planning of Hawaiian coral reefs.

The geographic characterization of coral reefs could benefit greatly from the improved coral distribution and abundance information generated from coral distribution models. The researchers say data from these models could be used in marine conservation plans or for threat assessments to reefs.

"For example, our results were recently used in the management plan review process of the Hawaiian Islands Humpback Whale National Marine Sanctuary as they considered the distribution and abundance of animals other than whales," Franklin says.

An advantage of this modeling approach is that scientists can consider a broader range of areas than field surveys alone. This could help provide a larger picture of total abundance.

"We were most surprised at the high relative abundance of Montipora patula which is currently under consideration for listing as a threatened or endangered species," reported Franklin.

The team is in the process of extending the modeling approach to include additional marine species in Hawaii, such as reef fish and include additional environmental variables to try to improve the predictive capacity of the models.

Coral reefs across the globe are being threatened by the climate change. However, the fight to save the ocean's colorful structures is not over. Researchers wrote in the journal Geophysical Research Letters that limiting global warming could help buy coral reefs more time. They said restricting greenhouse gases to just 50 – 100 parts per million carbon dioxide would avoid large-scale reductions in reef habitat.

Research findings are published in Marine Ecology Progress Series.