Effects of temperature and pCO2 on the degradation of organic matter in the ocean

Abstract

Anthropogenic emissions have increased the concentration of carbon dioxide (CO2) during the last 200 years. Since radiative forcing by greenhouse gases plays an essential role in maintaining the Earth's temperature, increasing emissions resulted in an observed warming of the atmosphere and the ocean. Furthermore, the absorption of excess atmospheric CO2 by the ocean has increased the acidity of seawater at global scale. The experimental simulation of changes in seawater temperature and CO2 projected for the near future led to a substantial acceleration of organic matter degradation. Higher degradation rates were primarily induced by temperature and pH effects on bacterial extracellular enzymes that increased rates of polymer hydrolysis. Effects of changing ocean temperature and pH on bacterial activity and the consequences for the cycling of organic matter are highly relevant for marine organic carbon fluxes and the ocean-atmosphere CO2 exchange.