Managing NPSA`s coral reefs in the face of global warming: Research project report for year 1

Smith, Lance; Birkeland, Charles

This report describes results from the first year of a three year research project on coral ecology in the National Park of American Samoa. Shallow pools in Ofu Lagoon in The National Park of American Samoa vary in thermal conditions with temperatures in some pools reaching 35 degrees C and fluctuating daily by >6 degrees C. Yet the pools support diverse coral communities, including many species thought to be sensitive to high temperatures such as Acropora, Pocillopora, and Millepora spp. A one year experiment was carried out to evaluate the survival and growth of corals transplanted from cooler to warmer pools and vice versa. Nubbins of Pocillopora damicornis and Porites cylindrica were obtained from three sites in Ofu Lagoon and one site in Ofu Harbor, dyed with Alizarin red S for measuring growth, and transplanted between the sites. The Ofu Lagoon sites varied in daily maximum temperatures and daily temperature ranges, and Ofu Harbor had more frequent warm temperatures and greater daily ranges than the Ofu Lagoon sites. Water temperatures were monitored hourly at the four sites during the one year period, and other water quality and physical characteristics were studied at the lagoon sites. Regardless of site or origin, both species had the greatest growth in Pool 300, the lagoon pool with the highest daily maximum temperatures and greatest daily temperature ranges of the three lagoon sites. Pool 300 is also the shallowest of the three lagoon sites, thus likely subject to the greatest irradiance. These results do not support the hypothesis that corals found in Ofu Lagoon pools were relatively high temperatures are better acclimatized or adapted to high temperatures than corals in the cooler portions of the lagoon. The hypothesis that corals found in Ofu Lagoon are better acclimatized or adapted to high temperatures than corals outside the lagoon in deeper water has not yet been tested. Extrinsic factors such as water motion, dissolved oxygen, or habita

Managing NPSA`s coral reefs in the face of global warming: Research project report for year 1

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