FLUX OF PARTICULATE MATTER THROUGH COPEPODS IN THE NORTHEAST WATER POLYNYA

Particulate organic carbon (POC) and nitrogen (PON) production by larg e calanoid copepods was investigated on the northeast Greenland shelf during August 1992 and May to August 1993. Both Calanus hyperboreus an d C. glacialis females, when suspended in seawater collected from the chlorophyll maximum, produced about 40 pellets per day, which containe d a carbon and nitrogen content equivalent to 8% and 6% of body carbon , respectively, and 2% of body nitrogen. In experiments, the carbon:ni trogen (C:N) ratio by weight of suspended particulates, C. hyperboreus , and fecal pellets was 6.7, 7.7 and 28.5, respectively. The unusually high C:N ratio for pellets, in part, may be attributed to elevated ra tios of > 20 mu m size fractions of particulate organic matter, the si ze fraction more common in the diet of these large copepods and the fr action dominated by diatoms according to microscopic and pigment data. The implied elevated C:N ratios of large phytoplankton cells were pro bably due to nitrogen deficiency, as shown by other studies in this re gion. In addition, female C. hyperboreus appeared to be more efficient in assimilating nitrogen than carbon, which also would have contribut ed to high C:N ratios in egested pellets. Unfractionated POC concentra tions explained 54% of the variability in carbon egestion and 70% of t he variability in nitrogen egestion in copepods, whereas copepod body content accounted for little of the variation on the short time scales of the experiments. Carbon egestion by C. hyperboreus was positively correlated with POC concentrations at the depth of the chlorophyll max imum, while nitrogen egestion was negatively correlated with PON conce ntrations in the euphotic zone. Estimates of potential community egest ion rates for the upper water column indicate that copepods represent a major pathway of organic carbon transformation in this Arctic shelf system. On average, copepods may have ingested 45% of the primary prod uction and egested fecal matter equivalent to 20% of the carbon and 12 % of the nitrogen particulate flux sedimenting from the surface layer. However, several lines of evidence suggest that pellets were reminera lized in the water column and, hence, may have contributed little orga nic carbon and nitrogen to the benthos.