Annual pattern of calanoid copepod abundance, prosome length and minor role in pelagic carbon flux in the Solent, UK

Investigation of the calanoid copepods at a coastal station in the Solent, UK, over a 14 mo period revealed a numerical dominance by species of the ge nus Acartia (comprising A. bifilosa, A. clausi, A, discaudata and A. margal efi), and the species Temora longicornis and Centropages hamatus, with spor adic appearances of Paracalanus parvus and Pseudocalanus elongatus. There w as clear seasonality in the abundance of calanoids, with total numbers bein g highest from May onwards, and low after October. Stage-specific prosome l engths varied with season, and in most cases were negatively correlated wit h temperature. Individual weights and abundance of the copepods, together w ith measures of temperature, were used to predict weight-specific growth an d production rates using a published empirical relationship. Comparisons of annual copepod production with previous measures of annual primary product ion and production of bacteria and ciliates at this same site were made, an d a carbon flow diagram was constructed. Calanoid copepod annual production was 32.2 mgC m(-3) yr(-1) This represents only 0.5 % of the total annual p rimary production, and 0.6% of the annual primary production of algae >3 mu m. Ciliate annual production was almost 2 orders of magnitude higher. and constituted 33% of the total annual primary production. In other neritic st udies (with water column depths <200 m) annual production by copepods has v aried between 21 and 177 % of annual ciliate production, whereas at this So lent site the value was only 1.5%. It is suggested that the low biomass (an d production) achieved by calanoid copepods was the consequence of populati on loss through high local flushing rates, unfavourable feeding conditions resulting from high suspended particulate matter, and high levels of hydroc arbon contaminants in the area.