Left: NOAA Explorer
Right: NPS Photo

While krill average only about two inches in length, they represent an enormous link in the marine food chain. These small shrimp-like crustaceans provide an important food source for fishes, birds, whales, and hundreds of other marine animals. Krill are primary consumers of phytoplankton, microscopic, single celled plants that drift near the ocean’s surface and live off carbon dioxide and UV rays from the sun’s rays. Most krill species undergo daily vertical migrations to feed, also providing food for animals living close to the surface.

Krill abundance and distribution is closely tied to oceanic conditions. Recent trends of delayed and intensified nutrient upwelling events may have dramatic effects on localized krill populations, subsequently affecting entire ecosystems that depend on krill. For example, delayed upwelling has been cited as a major cause of the reduction in the number of Coho salmon in coastal streams including those at Point Reyes National Seashore.