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A joint research team from the Biodiversity Research Center, Academia Sinica, Taiwan, and the Kuroshio Biological Institute, Japan has revealed that a high-latitude coral community in the Tatsukushi, Shikokou, Japan is composed of over 60% living coral and has 73 hard coral species representing 7 different functional groups. Finding high coral cover, species diversity, and functional groups at high latitude is remarkable because winter temperatures can fall below the generally accepted limit for coral reef development. These results suggest that “marginal” coral communities at high latitude, such as the Tatsukushi, could serve as “refugia” for corals to migrate to in response to rising seawater temperatures caused by climate change. The article was published in PlosONE on January 14, 2013.
In contrast with historical data on coral species diversity, the team found relatively recent colonization/development of the coral Acroporahyacinthus in this region, and a potential increase in coral diversity over the last century. The low coverage of macroalgae (2% of the benthic [under sea] cover) did not correlate with the low abundance of herbivorous fish, but may be reasonably explained by the high density of sea urchins.
“Corals and coral reefs distributed over the Equator, Tropical of Cancer, and Tropical of Capricorn have an upper thermal limit of around 28°C to 30°C, and therefore enjoy a very narrow range of seawater temperature,” explained Dr. Allen Chen, the principle investigator of this international collaborative project. Thus, with seawater temperature rising on average between 0.5°C to 1.5°C per year, corals face threats from thermal stress, which will result in mass bleaching and, as a consequence, degradation of coral reefs. Under the business-as-usual (BAU) scenario presented by the Intergovernmental Panel on Climate Change in 2007, the coral reef ecosystem might face functional collapse in tropical and subtropical regions if the current trend of rising sea water temperature does not decline.
“Rather than facing local extinction in the tropical and subtropical regions, corals might respond to climate change by acclimatizing themselves by maximizing their current physiological constraints; adapting by developing fast evolving new genotypes which could let corals survive at higher temperatures; or migrating to high latitude regions where seawater temperature is suitable for them to survive”, added Dr. Chen. This study shows that the structure and composition of this high-latitude coral community is already relatively remarkable and suggests that high-latitude regions may play an important role as “refugia” for corals to migrate to when faced with the impact of climate change.
Dr. Chen also pointed out that in addition to increasing seawater temperatures, on-going management actions and maintenance of a healthy population of keystone species (e.g., sea urchin) might also explain the observed state of this community. These are some strategies that we should try to enhance coral and coral reef conservation in Taiwan, he added.
The full article entitled “Coverage, Diversity, and Functionality of a High-Latitude Coral Community (Tatsukushi, Shikoku Island, Japan)” is available at the PLoS One website at: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0054330.
The complete list of authors is: Vianney Denis, Takuma Mezaki, Kouki Tanaka, Chao-Yang Kuo, Stephane De Palmas, ShashankKeshavmurthy, and Chaolun Allen Chen.
The Biological Institute on Kuroshio (BIK) is a research institute supported by the Kuroshio Biological Research Foundation, Japan. The foundation eatablished in 2000 to aim at contributing towards the creation of society, where human and wildlife can live together by supporting research of interrelationship of life and environment under the influence of the Kuroshio Current. The study is funded by the Academia Sinica Thematic Grant (2011-2013).
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