Microbial ecology: from local to global scales

Over the past 30 yr, microbial ecology has taken major leaps in bringing microscopic organisms into the context of aquatic ecosystems and shown that they regulate carbon and nutrient processes on a global scale. More recently, molecular biology has enabled prokaryotic organisms to be identified at the species level and contributed information on functional groups of specific significance to the ecosystem. Although microbial ecology has covered all common aquatic systems it has spatially been focused on a narrow range of habitats, leaving, for example, polar ice with modest activity and the deep, dark oceans practically untouched. In addition, temporal scales have been skewed towards daylight studies and only recent studies have focused on day/night process controls, recognizing that the diel rhythm is connected to fast-growing prokaryotic organisms. The key to going forward with predictions on the fate of microbial food webs in the ecosystem is to recognize physical structures and their persistence in the water body and identify the biological hotspots in terms of spatial and temporal significance. The present ecological models do not handle short-term, spatially restricted hotspot events adequately. Evidently, we need to combine our research efforts into targeted approaches, coupling modeling activity with physical and chemical oceanography as well as fisheries biology and 'sell our goods', even though our primary interest is microbial processes. Understanding the micro-environment of a single cell and its interaction with the environment should, by extrapolation, enable us to predict global processes. In the nitrogen cycle, this understanding has evolved rapidly, but in the carbon cycle, the role of microbes is still far from fully understood, especially in terms of loss processes. This should rapidly be addressed, instead of undertaking further major questionable experiments such as fertilizing the seas at very large scales.