CARBON-DIOXIDE PRODUCTION AND METABOLIC PARAMETERS IN THE OPHIURID OPHIOTHRIX FRAGILIS

As part of the evaluation of fluxes between the water column and a ric h benthic community of the Dover Strait (Eastern English Channel), lab oratory measurements of oxygen consumption were carried out on a commo n ophiurid, Ophiothrix fragilis (Abildgaard), from February 1993 to Fe bruary 1995. The mean O-2-consumption rate was evaluated at 0.31 mg O- 2 g(-1) h(-1); (ash-free dry weight). Simultaneous measurements of O-2 consumption and CO2 production using the pH-alkalinity method reveale d an average respiratory quotient of 0.69 proved suitable for converti ng oxygen demand to carbon flux. A seasonal trend in respiration data was demonstrated by sinusoidal curves fitted to O-2-uptake and CO2-rel ease data as a function of time. The influence on respiration rate of two seasonal parameters (temperature and food availability) is discuss ed; linear regression indicated a highly significant relationship betw een O-2 consumption (or CO2 production) and temperature; both O-2-cons umption and CO2-production rates decreased with starvation. The averag e O:N ratio was estimated at 8.46, close to the theoretical value when proteins constitute the catabolic substrate. The annual carbon respir ed by the O. fragilis community examined and the estimated annual prim ary production by phytoplankton indicate that the respiration of the O . fragilis community could supply 35% of phytoplankton carbon requirem ents.