Tuesday, March 9, 2021 - 12:00pm
Professor Emeritus, University of Hawaii at Manoa
Different resiliencies in coral communities over ecological and geological time scales in American Samoa
In 1917, Alfred Mayor, sponsored by the Carnegie Institution, surveyed a 270-m transect on a reef flat on American Samoa. Additional surveys were conducted on the transect in 1973, 1980,1995,1998,1999, 2000, 2004, 2007, 2017, and 2019. The coral community on the reef crest was resilient over the century, occasionally being seriously damaged, but always recovering. In contrast, the originally most dense coral community on the reef flat has been steadily deteriorating throughout the century. The contrast between the resilience of the corals on the reef crest and on the reef flat was a result of differences in the solidity of the substrata, as determined by the roles and distributions of crustose coralline algal species.
Mayor drilled a geological core from the transect on the surface to the solid basalt base of the reef 48 m below. The coral communities on Mayor’s transect were dominated by scleractinians through much of the Holocene, while cores on another transect only 2 km away, taken by Lewis Cary in 1917, showed the reef was consistently occupied by alcyonaceans in the genus Sinularia, which built the massive reef with spiculite to the basalt base 38 m below. The consistency of scleractinians on Mayor’s transect and Sinularia on the transect 2 km away during most of the Holocene was likely because the shape of the bay allowed more water motion on Mayor’s scleractinian transect and more protected waters on Cary’s alcyonacean transect. After 10,000 years of reef-building by octocorals, coastal construction terminated spiculite-reef building in American Samoa.
Charles Birkeland earned his PhD in 1970 at the University of Washington, Seattle, under the guidance of Robert T. Paine. Charles compared the dynamics of corals in the Atlantic and Pacific in Panamá during a post-doc at the Smithsonian Tropical Research Institute 1970-1975. As a professor at the University of Guam Marine Laboratory 1975-2000, he studied coral reefs in Micronesia and American Samoa. He was the third President of the International Society of Reef Studies 1986 - 1989. From 2000 to the 2010, for USGS, he was Leader of the Hawaii Fishery Research Unit at the University of Hawaii. He retired in 2010, but he is still active in research, writing, and guest lectures for classes at the University of Hawaii. He has written or edited three books and dozens of peer-reviewed papers and dozens of tech reports on the ecology and management of coral reefs.
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