Those large waves that arrive every winter in Hawaii are doing more than bringing thrills to surfers from around the world. They are actually helping to determine the abundance of corals in the 50th state. University of Hawaii at Manoa researchers are using computer models to predict the distribution and abundance of corals in the Hawaiian Islands and have concluded that wave heights determine coral abundance in the islands.
The researchers determined that coral cover was highest in areas with less wave action, including Kaneohe Bay on Oahu as well as reefs on Molokai, Lanai, Maui, the uninhabited island of Kahoolawe, and the Kohala coast of the Big Island, known as Hawaii. They integrated field surveys of corals provided by the US National Park Service and US National Oceanic and Atmospheric Administration with sunlight data and environmental data from a process known as wave exposure benthic geomorphology, or the study of shoreline landforms and how waves affect them. That data came from the University of Hawaii at Manoa Department of Ocean and Resources Engineering. While other factors play a role in shaping Hawaiian reefs, wave exposure and wave height played the most significant role.
“Average wave height and maximum wave height were the most influential variables explaining coral abundance in the Hawaiian Islands,” Erik Franklin, lead author of the study and Assistant Research Professor at the UHM Hawaii Institute of Marine Biology said in a press release put out by the university. “Our models also identified relationships between coral cover and island age, depth, sunlight, rugosity, slope, and aspect (direction a slope faces).”
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The researchers determined that the highest concentration of coral species were Porites lobata followed by Montipora patula, Pocillopora meandrina, Montipora capitata, Porites compressa, and Montipora flabellata. They also cite their approach as an advantage in that they are able to consider a wider range of areas than what is capable with just a field survey, enabling them to present more accurate data 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,” Franklin said. The other coral under consideration for listing is Montipora flabellata, which was not as abundant as the other species.
The researchers hope to further use this methodology to study more marine species in Hawaii, including reef fish. They also want to try and improve upon the predictive capacity of the models in hopes that they can better inform the marine resource management divisions in the islands.