The hyperbenthic plankton community: composition, distribution, and abundance in a coral reef lagoon

Seasonal and diel variations in community structure and abundance of the lagoon hyperbenthic community were examined at Davies Reef, Great Barrier Reef. The lagoon floor community differed from that in the overlying water, it was faunistically more uniform, and it was assembled into statistically distinct seasonal and diel groupings. The lagoon floor community was characterized by reef-associated mysids, gammarids, calanoids, ostracods, harpacticoids, cyclopoids, nematodes, caprellids, and cumaceans. The community was most distinctive in October. The water column community had greater diel than seasonal variability. The nocturnal water column community was characterized by decapod larvae, zoea, larvaceans, fish larvae, gastropod larvae, and nauplii, but was dominated numerically by calanoid copepods (>60%). Catches on the lagoon floor ranged from 750 to 3330 ind. m–3, with peak abundance in October, while water column catches were lower (25 to 2500 ind. m–3), with peak nocturnal abundance in February. Most species in the hyperbenthic community do not migrate into the water column at night, but instead remain concentrated near the lagoon floor. Only the mysid Anisomysis laticauda, the copepod Acartia australis, and the ostracod Cypridina sp. A were consistently captured on the lagoon floor by day and in surface waters at night. The lagoon hyperbenthic community probably contributes to coral reef ecosystems through the remineralization of organic detritus. Given the high abundance of relatively large individuals, the contribution of the resident, lagoon floor community to coral reef ecosystems must be substantial.