MEPS 179:41-54 (1999)  -  doi:10.3354/meps179041

ABSTRACT: The copepod Pseudocalanus acuspes in the high arctic frequently occurs under fast ice in April and May, where it apparently feeds on ice algae. Excretion measurements for this species in summer from Barrow Strait, Northwest Territories, Canada, showed that urea frequently exceeded ammonia as the primary nitrogenous excretory product. Subsequent experiments in different seasons, also including observations on several other species of arctic zooplankton, notably the copepods Calanus hyperboreus, C. glacialis and Metridia longa, similarly demonstrated high levels of urea excretion. The Calanus spp. showed strong correlation between size (dry weight) and metabolic rates for oxygen consumption and for ammonia excretion, and, for C. glacialis, between size and urea excretion as well. No size-related metabolic relationships were found for P. acuspes, probably because of the small size range of the experimental specimens used. However, P. acuspes and both Calanus species demonstrated striking changes in weight-specific metabolism with season. For all species examined, weight-specific estimates of respiration and excretion frequently yielded O:N ratios less than 20, and occasionally less than 10, when urea and ammonia excretion were combined in the calculations.

KEY WORDS: Urea · Ammonia · Nitrate · Total dissolved nitrogen · Zooplankton · Excretion · Respiration · O:N ratio · Arctic · Fast ice