Differential temperature effects on the efficiency of carbon pathways in Antarctic marine benthos

Abstract

Enzymatic activ~ties and metabolic rates, which play key roles in benthic carbon turnover. were character~zed w ~ t h respect to cold adaptation In aphotic Antarctic sediments. Temperature optima for CO2 dark fixation and mineralization of glucose coincided largely th the maximal growth temperatures of obligate psychrophilic bacteria (at 20°C and below). On the other hand, predominantly extracellular enzyme activities involved in the conversion of particulate organic matter (POM) into dissolved organic matter [DOIVI), such as scleroprotease and chitinase, had considerably higher temperature ophma (40 to 55°C) This lack of cold adaptation at the activity level was less strongly expressed in other hydrolases [sulfatase, alkaline phosphatase). Substrate affinihes or a c t ~ v a t ~ o n energles were often inapplicable or insignificant as a potential measure of temperature adaptation. Alternative strategies of cold adaptation may be relevant at the level of synthesis of POM-solubilizing enzymes.