Plankton.

Plankton comprises unicellular plants - phytoplankton - and generally small (millimetres or less) animals - zooplankton - that are adrift on the currents. Phytoplankton are responsible for about 45% of global annual primary production and are grazed by zooplankton, which in turn are suitably sized food items for predators including commercially important fish and great whales. Plankton are vital components of marine and freshwater water-column ecosystems. They also make major contributions to global biogeochemical cycling, and ameliorate atmospheric accumulation of carbon dioxide by 'pumping' carbon to the deep sea. The integrity of these roles is under threat from climate-related physiological impacts on individual organisms and on the wide-scale distribution of plankton communities.