Analysis of biofouling communities on settling plates at the proposed ocean thermal energy conversion site of Guam

Rowley, Dana

Concrete blocks with plexiglass and PVC settling plates were submerged off Luminao Barrier Reef, Guam. Settling plates were exposed at 6, 12, 24, and 37 m for 37-, 77-, 100-, and 180-day durations. The plates were placed in replicate groups of four in horizontal, vertical, and shaded orientations. Exposed and protected surfaces were examined. Biomass accumulation increased as the duration of exposure changed from 37 to 180 days for each depth. There was an increased rate of biofouling from 100 to 180 days at 6 m that was not evident at the other depths. Biomass was greatest at shallower depths and decreased as depth increased. Horizontally-placed plates accumulated more biomass than did vertically-placed plates. Exposed horizontal and vertical plates accumulated more biomass than did shaded plates. Biomass accumulation rates on small plexiglass plates oriented horizontally at 6 m were compared between Guam, the Caribbean, and the Pacific coast of Panama. Guam and the Caribbean had similar rates of fouling accumulation for the first 100 days, but at 180 days the fouling was greater off Guam. The rates of fouling off the Pacific coast of Panama was seven times that off Guam after six months and was probably the result of upwelling of nutrients. Biomass accumulation on large, vertically oriented, PVC plates submerged off Guam was less than fouling accumulations on asbestos plates set off Hawaii. This difference was presumed to be the result of the variance in faunal representatives between the two areas and the increased nutrients from terrigenous run-off around a large island chain such as Hawaii as compared to Guam.