Why biodiversity is important to oceanography: potential roles of genetic, species, and trophic diversity in pelagic ecosystem processes

The functioning of the global ecosystem is mediated in large part by pelagic marine organisms through their influence on biomass production, elemental cycling, and atmospheric composition. Growing theoretical and empirical evidence suggests that the stability and functioning of this complex system may depend, not only on aggregate biomass and production of pelagic producers and consumers, but also on the composition and richness of taxa within those compartments, Yet rigorous experimental tests of relationships between diversity and these aspects of pelagic ecosystem functioning are virtually unknown, Here, we argue for more attention to such research, and we marshal preliminary evidence that several mechanisms underlying diversity effects on ecosystem processes in marine benthic and terrestrial systems also may operate in pelagic systems. We review selected examples of how genetic, species, and functional group diversity may affect ocean ecosystem processes. We consider 3 types of examples that detail how (1) producer richness or composition can directly affect ecosystem processes, (2) consumer diversity can directly and indirectly affect these same processes, and (3) diversity at and below the species level can reduce variation of communities through time and enhance their resistance to perturbations. We suggest several promising avenues for assessing the role of biodiversity in pelagic ecosystems. Understanding and predicting responses of the global ocean ecosystem to accelerating climate and environmental change will be enhanced by more explicit and systematic attention to the functional diversity of microbial and macroscopic marine life