SEASONAL VARIABILITY IN THE INDIVIDUAL CARBON CONTENT OF THE CALANOIDCOPEPOD ACARTIA-BIFILOSA FROM THE NORTHERN BALTIC SEA

The seasonal variation in the carbon content of the calanoid copepod A cartia bifilosa was studied in the northern Baltic Sea. Monthly length -weight relationships were followed from November 1990 to October 1991 by analysing the organic carbon content of individuals, using a high temperature combustion method. The monthly length (L) on carbon (C) re gressions of copepodites were best described by power functions (C = a L(b)), where 75% to 88% of the variation could be explained by length. Nauplii length explained less of their carbon content (63-71%). The c arbon content per length was highest in summer when the nutritional si tuation was good and temperature at its highest. However, the carbon-l ength regressions differed significantly between months, except in win ter, when two subsequent months had similar regressions. The results p ointed out the importance of seasonal variation as well as the risk of making errors if biomass estimates based on length on carbon regressi ons are used. Carbon analysis should, if possible, be done on every sa mple or should at least be tested as to whether the regressions are co nsistent with the study material before estimations are calculated.