Shallow water meiobenthos of the bermuda platform

Abstract

The distribution and abundance of subtidal meiobenthos were studied monthly from June 1967 through May 1968 at five stations on the Bermuda platform: Two in Castle Harbor, two in Baileys Bay, and one in Harrington Sound. Total number of individuals ranged from 12.2–133.3x10⁴/m² and dry weight biomass from 33–259.3 mg/m². Free-living nematodes constituted 72.6% of the total numbers and 71.8% of the biomass and were the most abundant organisms at all but one station. Harpacticoid copepods were second in overall abundance and were the most abundant organism at one station. Polychaetes, ostracods, a kinorhynch and a priapulid were also common. Distinct seasonal patterns were observed. Total population values were highest in late spring, lowest in the winter. Nematodes often reached maximum values in the winter and appear to be correlated with minimum temperatures. Copepod abundance was related to reproductive cycles and changing sediment conditions. Copepods were abundant in the medium to coarse-grained sands, nematodes in the finer sediments. Meiofauna was greatly reduced in the lower layers of sediment; this reduction was attributed to decreased interstitial water and oxygen content. Field and laboratory results indicated specific grain size preferences of the Harpacticoida. Epigrowth feeding nematodes were dominant in sandy sediments, deposit feeders in the muds. Epigrowth dominance was probably related to carbon rich aggregated particles coating the sediments. Three distinct harpacticoid “parallel level bottom communities” were defined: (1) the Leptastacus macronyx (T. Scott)— Praeleptomesochra africana (Kunz) community in the submerged “beach sands,” (2) the Stenhelia (D.) bermudensis mihi—Typhlamphiascus lamellifer (Sars) —Cletodes dissimilis Willey community in the silty-sands and (3) the Phyllopodopsyllus hermani mihi community in the medium to coarse-grained sands. Diversity analyses of the harpacticoid communities indicated highly evolved, stable assemblages in those areas of low physical stress and less stable, variable assemblages in areas of high physical stress.