MEIOBENTHOS OF THE HATTERAS ABYSSAL-PLAIN AND PUERTO-RICO TRENCH - ABUNDANCE, BIOMASS AND ASSOCIATIONS WITH BACTERIA AND PARTICULATE FLUXES
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An abyssal station on the Hatteras Abyssal Plain (5411 m) and two hadal stations in the Puerto Rico Trench (7460 and 8189 m) were sampled to obtain quantitative information on the abundance and biomass of metazoan meiofauna and, for comparative purposes, bacteria and measurements of particulate flux rates. Average meiofauna abundance (no./10 cm2 1 S.E. integrated over a sediment depth of 15 cm) was lowest at the 7460 m site (44 10) and highest at the 8189 m (96 15) and Hatteras sites (114 26), the latter two not being statistically significant from each other. Biomasses (g dry wt/10 cm2 1 S.E., also integrated over a 15 cm depth) at the Hatteras and 7460 and 8189 m Trench sites were 38.4 10.3, 3.8 1.6 and 14.3 5.1, respectively; all differences were statistically significant. High biomass at the Hatteras site was due to large, burrowing harpacticoid copepods that were found to depths of 10-15 cm below the sediment surface, and which were most abundant below the surface (0-2 cm) layer of sediment. Nematodes, the numerically dominant taxon, were most abundant in the upper 6 cm of sediment at all sites, as were copepods at the two Trench sites. Average abundances of bacteria (no. of cells 109 per 10 cm2 of sediment to a depth of 15 cm), determined by epifluorescence microscopy, were 11.0, 10.5 and 5.6 at the Hatteras, 7460 and 8189 m Trench sites, respectively. Flux rates of organic carbon and total nitrogen (mg m-2 day-1) were about four times higher at the Hatteras site (e.g. 25.8 and 3.8) than at the 7460 m site in the Trench (6.3 and 0.8). An analysis of the meiofaunal and bacterial abundances obtained at the three sites revealed no significant associations between the two organismal groups, though abundances of both groups did decrease significantly and predictably with sediment depth at each station. Associations between particulate flux rates and meiofauna biomass were highly significant, suggesting that flux rates measured in near-bottom traps may be useful indicators of general resources available to the meiobenthos. 1989.
