Master of Science (MS)
Oceanography and Coastal Sciences
The northern Gulf of Mexico (GOM) is one of the most productive oil and gas exploration areas in the world, currently containing approximately 3,800 offshore platforms. These platforms serve as artificial reefs in shallow water, which until their introduction was nearly devoid of shallow hard substrata. The question is raised whether this newly available substrate could help expand coral populations in the GOM. In this study, I examined adult scleractinian corals on oil and gas platforms in the northern GOM, in the vicinity of the Flower Garden Banks (FGB; approximately 180 km SE of Galveston, Texas) and attempted to determine the degree of genetic affinity among the natural and platform populations there. Adult coral tissue samples were collected from seven platforms surveyed in the region of the FGB at a depth range of 0-30 m. The three most abundant scleractinian, hermatypic species were sampled: Madracis decactis, Diploria strigosa, and Montastraea cavernosa. Genetic variation was revealed by Amplified Fragment Length Polymorphisms (AFLPs), a DNA-fingerprinting technique based on the polymerase chain reaction (PCR). This tool successfully distinguished between closely related colonies derived from populations on different platforms and on the two Flower Garden Banks. AMOVA analyses indicated that the East and West FGB were homogeneous for Madracis decactis and Diploria strigosa; however, the Montastraea cavernosa populations at the two banks were significantly different. Randomized data sets of two Madracis decactis populations were run with AFLPOP using a minimum log-likelihood difference of zero and one. These analyses determined that a log-likelihood difference of one is a more conservative and more reliable option, and all subsequent analyses were run using this setting. AFLPOP analyses showed that Montastraea cavernosa at the two banks was highly self-contained, indicating a possible high degree of self-seeding with regard to this species. It appears that Madracis decactis, a brooding species, is highly effective at dispersing to neighboring habitats over distances of kms to tens of kms. By comparison, Diploria strigosa and Montastraea cavernosa, both broadcasting species, are not. They may be more effective at larger scale dispersal, but this remains to be demonstrated.
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Atchison, Amy D., "Offshore oil and gas platforms as stepping stones for expansion of coral communities: a molecular genetic analysis" (2005). LSU Master's Theses. 140.
Paul W. Sammarco