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 metabolism. For small C. subterranea (48.3 – 97.6 mg dw) the rate of CO2 release was estimated to be 1.69 to 3.63 μmol CO2·g dw−1·h−1 and for large specimens (330.9 – 543.0 mg dw) 0.28 to 1.52 μmol CO2·g dw−1·h−1 during the incubation period of 5 days (6°C). The rate of CO2 release increased by a factor of up to 2 during the first three days and increased more rapidly later in this incubation period. Direct calorimetry revealed a decrease in the rate of heat production from 0.39 to 0.25 J·g dw−1·h−1 (i.e. 64% of initial value) during long-term anoxia (110 h). Compared to normoxic values recalculated from literature data our results indicate a decrease in the heat production rate to 33% under prolonged anoxia. For a natural Callianassa population on station ‘Schlicksandgrund’ in the German Bight the rate of CO2 release was calculated to be 8.0 μmol·m−2·h−1 under anoxic conditions. ∑CO2 pore-water profiles on station ‘Schlicksandgrund’ were used to calculate a CO2 flux from the sediment to the near-bottom water of 110 μmol CO2·m−2·h−1 under normoxic and 338 μmol CO2·m−2·h−1 under hypoxic conditions. The anaerobic metabolic activity of the Callianassa population could account for about 7.3 (oxic conditions) to 2.4% (hypoxic conditions) of the above CO2 fluxes.