They are responsible for about half of all photosynthesis on Earth — and plankton could be drastically affected by climate change.
Mridul Thomas and his team at Michigan State University in East Lansing considered 194 phytoplankton strains. Using the existing literature, the authors estimated the maximum growth rate, optimum temperature for growth and the temperature range over which growth can occur, for each of the strains. Many strains seem to be tightly adapted to the average temperature at their location. Tropical strains, in particular, tend to have optimal growth temperatures at or just below the mean temperature in their environment. The authors' models indicate that an average temperature rise of just 2 °C in the tropics by 2100 could reduce the diversity of phytoplankton in the region by a third — unless, that is, the plankton can evolve greater heat tolerance.
Science http://dx.doi.org/10.1126/science.1224836 (2012)