A new ocean model developed by Stephanie Dutkiewicz at MIT predicts that global temperature changes will result in half of existing phytoplankton species either being replaced or disappearing entirely. This prediction is troubling because phytoplankton are at the bottom of the food chain and their disappearance could have a dire effect across the ocean food chain. The model, which includes 100 different phytoplankton species, shows how rising temperatures will warm water closer to the surface of the water - something that is beneficial for many phytoplankton - but will at the same time cause a separation between this warmer top layer of water and lower, colder layers. Because most of the nutrients that phytoplankton rely on originate in deeper waters, this separation between warm and cold water may mean that phytoplankton will not be able to obtain the nutrients required for their survival.