‘Red flag for the Arctic’: Nitrogen levels threaten marine food

The chemistry of nitrogen flowing from six of the Arctic’s largest rivers is changing, a significant shift that could alter the Arctic Ocean’s ecosystems, according to research published in Global Biogeochemical Cycles.

While the total nitrogen flowing to the sea is increasing, more of it is now locked in organic matter rather than in inorganic nitrogen, the form most readily used by marine life.

“This is a red flag for the Arctic,” said Bridger J. Ruyle of the NYU Tandon School of Engineering, who led the study. “Rapid changes in river nitrogen chemistry could completely transform how these marine ecosystems function.”

Researchers are linking the shift to permafrost thaw and changes in vegetation, both of which are being driven by a warming climate. The consequences could be far-reaching, from altering plankton growth, which forms the base of the marine food web, to affecting fisheries, carbon storage, and even global climate patterns.

Key Takeaways:

• Nitrogen flows are increasing, but changing form: While these six major Arctic rivers are exporting more nitrogen overall, a growing proportion is dissolved organic nitrogen (DON) rather than nitrate, depriving marine ecosystems of an essential nutrient
• Permafrost thaw is a major driver: Warming temperatures are thawing permafrost and altering vegetation cover, releasing organic-rich nitrogen into waterways instead of the more bioavailable nitrate.
• Shifts in river chemistry are widespread
  These changes were observed consistently across river systems from Eurasia to North America, suggesting a broad, pan-Arctic shift rather than localized anomalies.
• Carbon cycle implications: More organic nitrogen could interact with carbon cycling in the ocean, potentially altering the way the Arctic stores or releases greenhouse gases.
• Seasonal patterns are changing: The composition of nitrogen inputs is also shifting seasonally, with spring and summer flows showing different proportions of nitrate and DON, likely linked to changing snowmelt and runoff timing.
• Critical for Arctic food webs and communities: River transport of nitrogen supports up to 66% of primary production in Arctic coastal regions. Changes in nitrogen composition due to warming temperatures and thawing permafrost pose a major threat to the coastal foodweb that has sustained Indigenous communities for millennia

Why it matters: The observed changes in the Arctic nutrient supply could influence global ocean circulation and the ocean’s role in regulating Earth’s climate, making this a shift with far-reaching implications beyond the Arctic.

Mary McAuliffe, formerly a Jerusalem-based correspondent for an international news channel, is a freelance journalist, photographer and filmmaker, covering the most pressing issues facing society for television, digital, and radio.