Coral clam project

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On Pulau Gaya, Sabah, Malaysian Borneo, heads of coral (Platygyra spp.) were observed to play host to live, embedded bivalves. We thought that clams may seek shelter in corals and have a damaging effect on the hosts. The corals appeared to grow around the embedded clams thereby limiting the growth shape of the corals. If this damaging effect of the clams on the coral were to be true, then we expected the number of clams to influence or even accelerate coral bleaching. Specimens of coral belonging to the Platygryra genus were examined to test the hypothesis of a close association between bivalve presence and bleaching status. Seven 10-m transects were taken parallel to shore over a distance of 3-4 m, and all Platygyra heads within 1 m to the left or right of the transect line were codified as follows: distance along the transect; height, length, and width; bleaching status on a scale of 1 to 5 (1 signified no bleaching, 2 signified less than 25% of the coral was bleached, 3 about 50% of the coral was bleached, 4 about 75% of the coral was bleached and 5 that the entire coral was bleached); embedded bivalve number and whether the bleaching was most predominant from the bottom or from the top of the coral.

Our results indicate that there was no significant correlation between the number of clams living in a coral and the level of bleaching of the coral. We ran correlation tests between clam presence, coral condition, and all of our environmental parameters. Statistically significant results of our tests were that the greater the volume of the coral, the worse the condition of the coral, and that larger coral may be more prone to damage (perhaps due to by collision with boats). Another significant result (p = 0.0146) was the correlation between the transect number, which represented the distance from the beach, and the the condition of the coral; in other words, the further away from the beach, the more bleached the coral appears to be.

The most promising domains of future research include tracking individual coral heads to determine whether there are any sequential relationships between clam colonization and bleaching (either in situ or using captive specimens), examining the association between the presence of embedded bivalves and the degree of coral surface covered by filamentous brown algae, and investigating the effects of clam death or removal on coral morality.