Effects of benthic macrofauna and temperature on degradation of macroalgal detritus: the fate or organic carbon

The combined effects of bioturbation by the polychaete Nereis diversicolor and temperature (4”, 8”, 16°C) on diagenesis of short-term (48 h) 14C-labeled Chondrus crispus (new) detritus added to organic-poor sandy sediment were examined over 20 d. The overall rate of weight-specific CO, production was 5 times higher for C. crispus detritus than for indigenous (old) sediment detritus. N. diversicolor inc eased sediment 0, uptake and total CO2 production by 30-70%: most of this increase was due to worm respiration. Net release of 14C0, was not affected by the worms; microbial 14C0, production was reduced 30%, indicating competitive interaction between worms and bacteria. The activities ofN. diversicolor removed 20-50 % more of the particulate 14C label in bioturbated sediment than in defaunated. All of this excess loss was recovered in worm tissues. The increase in total CO, production, but not 14C0, production, in the presence of N. diversicolor indicated that bioturbation affected the net mineralization frelatively refractory (old) organic matter more than it affected the labile (new) pools. The temperature dependence of carbon diagenesis was not affected significantly by the worms. The microbial component of total benthic metabolism increased more with temperature (activation e ergy, E = 53-59 kJ mol-I) than worm respiration did (E