Biogenic carbon cycling in the upper ocean: Effects of microbial respiration

Food-web processes are important controls of oceanic biogenic carbon flux a nd ocean-atmosphere carbon dioxide exchange. Two key controlling parameters are the growth efficiencies of the principal trophic components and the ra te of carbon remineralization. We report that bacterial growth efficiency i s an inverse function of temperature. This relationship permits bacterial r espiration in the euphotic zone to be computed from temperature and bacteri al production. Using the temperature-growth efficiency relationship, we sho w that bacterial respiration generally accounts for most community respirat ion. This implies that a Larger fraction of assimilated carbon is respired at Low than at high latitudes, so a greater proportion of production can be exported in polar than in tropical regions, Because bacterial production i s also a function of temperature, it should be possible to compute euphotic zone heterotrophic respiration at Large scales using remotely sensed infor mation.