A new study suggests that the rapid loss of Arctic sea ice is causing a significant decline in nitrate, a vital nutrient for plankton and the wider marine ecosystem. Scientists warn that this could affect fish, seabirds, and marine mammals while reducing the Arctic Ocean’s ability to absorb atmospheric carbon.
Melting sea ice exposes shallow Arctic waters to more sunlight, accelerating nitrate loss. With less nitrate available, plankton growth could decline, potentially limiting the amount of marine life the ecosystem can support.
University of Edinburgh scientists analyzed over 20 years of ocean data from the Fram Strait. Their findings showed that nitrate levels began falling steadily around 2009, coinciding with the rapid acceleration of sea-ice loss.
Benthic Denitrification Drives Nitrate Loss
Researchers linked the decline to benthic denitrification, which converts nitrate into nitrogen gas. These continental shelves make up nearly half of the Arctic Ocean.
Overall, the study points to a major shift in the Arctic’s nutrient balance caused by shrinking sea ice.
Researchers caution that declining nitrate levels could create conditions that favor smaller plankton species. Since these organisms generally support less productive food webs, less energy may be available for larger marine animals.
The effects could also reach beyond the Arctic. Plankton absorb carbon dioxide through photosynthesis, so reduced plankton growth could weaken the ocean’s ability to store carbon.
Scientists warn the Arctic Ocean may not return to its former state.
Potential Impacts Beyond the Arctic
The researchers emphasize that further studies are needed to determine how these changes might influence marine ecosystems beyond the Arctic, particularly in the North Atlantic and major commercial fishing areas.
The findings were published in Communications Earth & Environment and supported by NERC’s Changing Arctic Ocean project, with contributions from several international research institutions.
Arctic Ecosystem Shifts from Light to Nutrient Limits
Marta Santos-García said scientists expected melting sea ice to increase phytoplankton growth, but the study shows nitrate now limits growth, potentially affecting marine life and climate regulation.
Ganeshram said the Arctic ecosystem may have reached a tipping point around 2009, potentially affecting food chains and North Atlantic fisheries.
Read the original article on: sciencedaily
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