Metabolic rates of epipelagic marine zooplankton as a function of body mass and temperature

The metabolic rates (oxygen uptake, ammonia excretion, phosphate excretion) of epipelagic marine zooplankton have been expressed as a function of body mass (dry, carbon, nitrogen and phosphorus weights) and habitat temperature, using the multiple-regression method. Zooplankton data used for this analysis are from phylogenetically mixed groups (56 to 143 species, representing 7 to 8 phyla, body mass range: 6 orders of magnitude) from various latitudes (habitat temperature range:-1.4° to 30°C). The results revealed that 84 to 96% of variation in metabolic rates is due to body mass and habitat temperature. Among the various body-mass units, the best correlation was provided by carbon and nitrogen units for all three metabolic rates. Oxygen uptake, ammonia excretion and phosphate excretion are all similar in terms of body-mass effect, but differ in terms of temperature effect. With carbon or nitrogen body-mass units, calculated Q₁₀ values are 1.82 to 1.89 for oxygen uptake, 1.91 to 1.93 for ammonia excretion and 1.55 for phosphate excretion. The effects of body mass and habitat temperature on the metabolic quotients (O:N, N:P, O:P) are insignificant. The present results for oxygen-uptake rate vs body mass do not differ significantly from those reported for general poikilotherms by Hemmingsen and for crustaceans by Ivleva at a comparable temperature (20°C). The importance of a body-mass measure for meaningful comparison is suggested by the evaluation of the habitat-temperature effect between mixed taxonomic groups and selected ones. Considering the dominant effects of body mass and temperature on zooplankton metabolic rates, the latitudinal gradient of community metabolic rate for net zooplankton in the ocean is estimated, emphasizing the non-parallelism between community metabolic rates and the standing stock of net zooplankton.