Tiny animals, including crustaceans, feed on phytoplankton. These form an important food supply for larger zooplankton species, which in turn feed birds, fish and some mammals.
With less sea ice, phytoplankton growing near the surface get more sunlight, potentially boosting their growth rates, but animals that use the sea ice for feeding, breeding or resting lose out.
At the base of the marine food chain are microscopic algae, called phytoplankton, harvesting energy from sunlight near the surface. Like plants, they need nutrients such as nitrogen, phosphorus and minerals. Nutrients and organic matter are made available either from the bottom sediment or are washed into the sea from the land by rivers. Both these important sources of nutrients are being affected by changes in the cryosphere.