Effects of hydrostatic pressure on metabolic rates of six species of deep‐sea gelatinous zooplankton

This study addresses the effect of hydrostatic pressure on the metabolic rates of six species of deep‐living (∼500–1,500‐m typical depths) gelatinous zooplankton (three chaetognaths, two hydromedusans, and one polychaete). Metabolic rates were measured at 5°C and the hydrostatic pressure equivalent to that at either 0‐(0.101 MPa) or 1,000‐m depth (10.1 MPa). O 2 consumption rate vs. wet weight relationships at the two pressures were compared by ANCOVA for each species separately. Five of the species studied (the chaetognaths and medusans) showed no significant difference in slope or elevation in these relationships, indicating there was no significant effect of hydrostatic pressure on the metabolic rates of these species under the experimental conditions. The metabolic rate relationships of the sixth species, Poeobius meseres, were significantly different in slope, but the lines intersected within the weight range studied so the metabolic rates were not different overall. These data support the validity of measuring the metabolic rates of such species at surface pressures and indicate that metabolic rates of deeper living gelatinous species are relatively insensitive to hydrostatic pressure.