Abstract

Temperature-dependencies of metabolic rates including photosynthesis and respiration could mean that large-scale ecosystem processes operated differently in past warm climate states, and may do so again under anthropogenic global warming. It is well known that sinking of organic matter in the ocean transfers carbon from the surface layer to the deep ocean reservoir causing a replacement flux of CO2 from the atmosphere (the biological pump). The efficiency of this process may be temperature-dependent because metabolic rates in heterotrophic bacteria and other respiring organisms are much more sensitive to temperature than are rates of primary production. Faster respiration rates in the warmer Eocene ocean may have resulted in more rapid remineralization of sinking organic matter higher in the water column, and hence a less efficient biological pump, with implications for carbon and nutrient cycling, rates of organic matter burial, and potential feedbacks on global temperature via the CO2 greenhouse effect.