THE CONTRIBUTION OF THE MUD SHRIMP CALLIANASSA-SUBTERRANEA (DECAPODA,THALLASSINIDEA) TO SEDIMENT METABOLISM DURING OXYGEN DEFICIENCY IN SOUTHERN NORTH-SEA SEDIMENTS

Long-term experiments with single isolated specimens of C. subterranea (Montagu) in closed systems under anoxic conditions were conducted to measure CO2 release and heat production as parameters for anaerobic m etabolism. For small C. subterranea (48.3 - 97.6 mg dw) the rate of CO 2 release was estimated to be 1.69 to 3.63 mu mol CO2 . g dw(-1). h(-1 ) and for large specimens (330.9 - 543.0 mg dw) 0.28 to 1.52 mu mol CO 2 . g dw(-1). h(-1) during the incubation period of 5 days (6 degrees C). The rate of CO2 release increased by a factor of up to 2 during th e first three days and increased more rapidly later in this incubation period. Direct calorimetry revealed a decrease in the rate of heat pr oduction from 0.39 to 0.25 J . g dw(-1). h(-1) (i.e. 64% of initial va lue) during long-term anoxia (110 h). Compared to normoxic values reca lculated from literature data our results indicate a decrease in the h eat production rate to 33% under prolonged anoxia. For a natural Calli anassa population on station 'Schlicksandgrund' in the German Bight th e rate of CO2 release was calculated to be 8.0 mu mol . m(-2) . h(-1) under anoxic conditions. Sigma CO2 pore-water profiles on station 'Sch licksandgrund' were used to calculate a CO2 flux from the sediment to the near-bottom water of 110 mu mol CO2 . m(-2). h(-1) under normoxic and 338 mu mol CO2 . m(-2). h(-1) under hypoxic conditions. The anaero bic metabolic activity of the Callianassa population could account for about 7.3 (oxic conditions) to 2.4% (hypoxic conditions) of the above CO2 fluxes.