Despite the extremely cold conditions that lead to the formation of the ice, a huge diversity of life depends on the ice to exist. Microbes, including algae that live in dense mats on the underside of the ice, make up the bulk of the biomass within the ice, and act as the base of the sea ice food web. Parasitic fungi can infect ice algae and may limit their growth. Bacteria within the ice serve to degrade dead organisms and recycle their nutrients for use by the ice algae. Zooplankton, including crustaceans like copepods, eat the ice algae and are then eaten by larger animals. Polar bears, seals, walruses, whales, birds, and other animals make use of the ice for feeding, breeding, and protection. Ice algae can also be important contributors to the benthic food web because they tend to sink rapidly to the bottom in the summer when the ice melts and they are released into the water column.