Plankton are tiny creatures that drift in the sunlit surface layer of the sea, and their choreography is conducted by sunlight and nutrients. Light only penetrates the top 30 meters of the ocean. While the deeper ocean is replete with nutrients, the increasingly stable surface later traps nutrients and organisms close to the sunlit later, where phytoplankton rapidly use up nutrients until they are at such low concentrations that growth is limited and the next cycle of growth only occurs when there is deep mixing. Physical forces drive these cycles, as phytoplankton rely on the optimal combination of both light and nutrients. This can be applied to seasonal patterns of growth as well as regional differences, for example, between polar and tropical areas. Phytoplankton are invisible to the naked eye and there are tens of thousands of them in a drop of sea water. These are important players in the food web; only about 10 percent of the energy and matter is transferred from one trophic level to the next. Climate change is warming the surface ocean; this increases the vertical stability of the water column. It takes more energy to mix surface and deeper waters – impacting marine productivity – and mid-latitudes may be less productive along with other changes. We don’t know what the complete effects of climate change will be on the largest ecosystem on our planet, the pelagic ocean.
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