Sea ice loss is transforming the marine food web

A new study has revealed how melting sea ice is changing the Arctic marine food web. A team of experts led by scientists at the University of Maryland Center for Environmental Science found traces of plant material that originated in Arctic sea ice throughout the base of the marine food chain.

The biological compounds identified by the researchers are uniquely produced by microscopic plants in sea ice. The research is shedding new light on the potential of sea ice ecosystems as a source of food in the Arctic waters of Alaska.

“It is widely thought that the loss of sea ice habitat will have far-reaching implications for Arctic ecosystems,” said study lead author Chelsea Wegner Koch.

“As sea ice breakup occurs earlier and forms later each year, the open water period is expanding and the sources of food are shifting away from sea ice and towards greater proportions of open water production. This production in the absence of sea ice differs in the quality, quantity, and timing of delivery to the seafloor.”

The compounds examined in the study had sunk to the seafloor, where they provided food for organisms at the bottom of the marine food web. These organisms support larger animals like the bearded seal and the Pacific walrus. 

The investigation was focused on sediment samples collected during research cruises in the Bering and Chukchi seas. The team also analyzed samples from an under-ice moored sediment trap that is located off of Wainwright on Alaska’s North Slope.

The study revealed that ice-sourced food rapidly reaches the seafloor sediments, and the presence of significant ice cover provides long-term reserves of organic matter on the seafloor. 

“These reserves may buffer shifting food sources in the near-term for organisms that live within the surface sediments but are likely to become inaccessible in the future if current sea ice declines continue,” said Koch.

“Particularly as sea ice coverage decreases – and in recent years has become negligible in the north Bering Sea – we are entering a new era where we will have to use approaches such as this to evaluate how the ecosystem will obtain the basic building blocks needed to sustain the food web, including human communities that depend upon them for food security.”

The study is published in the journal PLOS ONE.

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By Chrissy Sexton, Earth.com Staff Writer