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.

The new study, published May 28 in the journal Communications Earth & Environment, found that the bacteria are consuming more nitrate than the Arctic ecosystem can withstand.

This effect, known as "denitrification," is irreversible under current climate conditions because we have passed a threshold where so much sunlight reaches the ocean that it's supercharging phytoplankton's productivity, said Marta Santos-García, a doctoral student of Arctic marine biogeochemistry at the University of Edinburgh in Scotland and the first author of the study.

"Even if sea ice were to increase temporarily, the Arctic nutrient system responds over much longer timescales," Santos-García told Live Science in an email. "Short-term increases in sea ice would be unlikely to rapidly reverse the decline in nitrate inventories, which may take much longer to recover."