Einfluss erhöhter CO:sub:2:/sub:-Partialdrücke auf die Physiologie mariner Wirbelloser und Fische

Currently rising concentrations of CO:sub:2:/sub: in atmosphere and surface ocean will cause a shift in marine carbonate chemistry, i.e. lowered seawater pH and increasing CO:sub:2:/sub: concentration. Thus, the development of a basic understanding of CO:sub:2:/sub: effects on the physiology of marine organisms is of utmost importance. Our present knowledge mainly originates from studies of organisms that occupy habitats characterized by regular CO:sub:2:/sub: oscillations. Under conditions of naturally elevated CO:sub:2:/sub: like in intertidal sediments, the invertebrate Sipunculus nudus for instance displays a dramatic reduction in aerobic energy turnover. The question arises if the highly energy consuming process of protein synthesis, amongst others, is compromised by a hypercapnia induced limitation of the cellular energy budget. Studies on isolated muscle tissue of S. nudus clearly showed that the 40-45% decrease in tissue oxygen consumption under severe acidosis was accompanied by a concomitant decline in N-excretion and a 60% reduction of protein biosynthesis rates. A similar decrease of up to 34% in cellular oxygen consumption associated with an almost complete shut down of hepatic protein synthesis was observed in comparative studies with hepatocytes from anarctic fish.Considering the non-transient character of future increases in ocean CO:sub:2:/sub: concentration, long term sensitivity of S. nudus was determined to figure out if the energy saving strategy of metabolic depression allows the animals to survive in an evironment with permanently elevated CO:sub:2:/sub: concentrations. S. nudus displayed a significantly increased mortality even under moderate but chronic hypercapnia indicating that though a reduction of the aerobic energy turnover enables organisms to deal with longer lasting periods of hypercapnia it does not lead to permanent CO:sub:2:/sub: tolerance.