The Arctic Ocean has crossed a tipping point that is wreaking havoc on the region's food chain, with potentially dire consequences for commercial fishing and the ocean's capacity to soak up carbon, a new study reports.

Scientists found that vast areas of melting sea ice in the Arctic are leading to a significant reduction in nitrate, a key nutrient that forms the base of the marine food web and thus underpins important regional fisheries. As the ice disappears, more light hits the water's surface, promoting the growth of microscopic, plant-like organisms called phytoplankton. When phytoplankton die, their cells sink to the seafloor and are decomposed by nitrate- and oxygen-consuming bacteria.