Krill eat phytoplankton and tiny single-celled plants and algae. Most species of krill are omnivorous filter feeders, although there are some carnivorous species that eat the larvae of fish and zooplankton. Most krill use their frontal appendages to form fine combs, which allow them to filter food from the water.
Krill are crustaceans similar to shrimp, and they are an essential link in the global food chain. Without krill, countless aquatic creatures all over the world would become extinct. Hundreds of species of fish, penguins, seals, birds and whales depend on krill as their primary food source. For example, in 1998, declining krill populations are believed to have caused salmon not to breed for a season in the Bering Sea. Often ecosystem disturbances can have far-reaching consequences as the food chain is broken.
As of 2014, it's believed that global warming is causing a decline in Antarctic krill populations. As temperatures rise and the ice melts, ice-algae becomes more scarce, which is an important food source for krill. Studies have shown that the amount of krill in the Antarctic has decreased by as much as 80 percent since the 1970s. Continued declination of krill could cause a severe loss of animal life in the Antarctic. Although krill use sunlight and carbon dioxide for energy, additional sustenance is required.