Intra-annual Variability in Hawaiian Shallow-water, Soft-bottom Macrobenthic Communities Adjacent to a Eutrophic Estuary

Temporal variability in shallow-water (10 m), soft-bottom macrobenthic communities was examined over a period of 25 months (November 1992–November 1994) off-shore of the Ala Wai canal, a tropical eutrophic estuary on the south shore of O'ahu, Hawaii. Despite significant temporal variations in the density of major taxonomic groups at the four stations examined, there was no evidence of a regular seasonal signal in the density fluctuations. Although all stations showed a steady decline in mean density during the unusually dry period in the spring of 1993, there was no evidence that observed macrofaunal density fluctuations (maximum and minimum) were associated with periods of increased runoff. Intensive macrobenthic sampling after a large runoff event showed no evidence that the event influenced the density or community composition of the benthos over a two month period. Total macrofaunal density ranged from 491 to 4743 ind. 0·1 m−2with total macrofaunal biomass ranging from 4·7 to 109 mg AFDW 0·1 m−2(AFDW—ash free dry weight), values consistent with those of other tropical and subtropical studies. A significant between-year difference in the density of total macrofauna was observed, perhaps associated with the 1991–1994 El Nino Southern Oscillation (ENSO) event and the corresponding decreased rainfall in Hawaii.