Arctic Ocean food chain disrupted as key tipping point passed

Peer-Reviewed Publication

University of Edinburgh

News Release 28-May-2026

An irreversible shift in the chemical make-up of the Arctic Ocean driven by climate change is disrupting the region’s food chain, a study suggests.

Widespread loss of Arctic sea ice has led to a sharp fall in levels of a key nutrient, affecting populations of plankton, fish, seabirds and marine mammals, researchers say.

Their analysis reveals that exposure to sunlight of vast shallow regions of the ocean previously covered by ice fuels a process that breaks down the nutrient – nitrate – and removes it from seawater.

Nitrate is vital for the growth of plankton at the base of the Arctic food chain, and reduced levels of the nutrient limit the amount of life the ecosystem can support, the team says.

Dwindling levels of nitrate could also reduce the Arctic Ocean’s capacity to store carbon, as plankton play a key role in capturing it from the atmosphere through photosynthesis, they add.

While recent studies have reported changes in animal populations in Arctic waters, the causes were poorly understood as there have been few in-depth analyses of the ocean’s chemical make-up.

Now, researchers from the University of Edinburgh have gained new insights into the changing nutrient levels in the Arctic Ocean by analysing data spanning a 20-year period.

The team assessed more than two decades of sampling data from Fram Strait, the main gateway through which Arctic waters flow into the Atlantic.

Their analysis reveals a clear shift from 2009 onwards, with nitrate levels in waters leaving the Arctic falling steadily. The drop in nitrate levels coincided with a drastic reduction in Arctic sea ice that began around the same time, the team says.

The extensive loss of sea ice ramped up a process that converts nitrate to nitrogen gas – called benthic denitrification – in shallow continental shelves that underly nearly half of the Arctic Ocean, the team says.

The shift to nitrate-limited conditions suggests the Arctic Ocean may only be able to support smaller species of plankton in the future, meaning less food is available moving up the food chain.

Since the change in nutrient conditions is driven by ongoing sea ice loss, it is very unlikely the Arctic Ocean will ever revert to its previous state, researchers say.

Further research is needed to understand the possible wider effects that changes in Arctic waters could have on marine populations in other parts of the world’s oceans, including the North Atlantic.

The research, published in the journal Communications Earth & Environment, was supported by the Natural Environment Research Council (NERC)’s Changing Arctic Ocean project.

The work also involved researchers from the Norwegian Polar Institute, Scottish Association for Marine Science, Technical University of Denmark and Alfred-Wegener-Institut, Germany.

Marta Santos-García, a PhD student in the University of Edinburgh’s School of GeoSciences, who co-led the study, said: “For years, sea-ice loss in the Arctic Ocean was expected to increase phytoplankton growth because more sunlight could reach surface waters. Our findings suggest that this relationship has changed: the Arctic Ocean appears to have shifted from a system mainly limited by light to one increasingly limited by nitrate availability, with far-reaching consequences for marine ecosystems, food chains and the role of the Arctic in the Earth’s climate.”

Professor Raja Ganeshram, of the University of Edinburgh’s School of GeoSciences, who has led the study over the last two decades, said: “The changes we report suggest that the Arctic Ocean ecosystem passed a tipping point around 2009. How this change cascades through the food chain needs to closely monitored as this has profound implications for us, including on commercial fishing in the North Atlantic Ocean.”