The Very Base of the Arctic Food Chain Is Being Transformed

A July 2018 phytoplankton bloom in the Barents Sea, an increasingly common occurrence.
A July 2018 phytoplankton bloom in the Barents Sea, an increasingly common occurrence.
Image: NASA Earth Observatory

Thanks to climate change, the Arctic is becoming a deeply weird place from polar bears chowing down on whale carcasses to a microplastic invasion. A new study adds to the mountain of evidence that the region could be transformed within our lifetimes.

Advertisement

As sea ice recedes, the colorful spring phytoplankton blooms that dot the Arctic are becoming more vigorous and appearing at higher latitudes than ever before. The results, published this week in Geophysical Research Letters, showcase changes happening at the base of the food chain. How that propagates upward will have vast ramifications for the warmer, low-ice Arctic of the future.

Arctic sea ice hits its peak in February or March before receding toward a minimum in September. As the ice crawls back to the high Arctic and more sunlight reaches the open water, phytoplankton blooms appear on the surface for a few weeks each spring across the seas that ring the Arctic Ocean. Those bloom can account for half of all primary productivity—basically plant growth—in the Arctic, so even though the blooms are short-lived, they’re an essential ingredient for life.

Advertisement

But climate change has caused sea ice to drop precipitously, leaving more water exposed earlier and earlier in the year. That led researchers to ask whether plankton blooms were changing in response to receding ice. To find out, they analyzed 10 years of satellite data spanning 2003-2013. Because the blooms stand out sharply against the dark water and white ice, they were able use ocean color data.

The results show primary productivity across the Arctic rose an astonishing 31 percent over the 10 years of data. Notably, they show that phytoplankton blooms are occurring at higher latitudes in waters that were previously ice covered or inhospitable because of their low nutrient content.

“We were not expecting to see phytoplankton spring blooms in the central basin,” a region above 80 degrees north, Sophie Renaut, a PhD student at the University of Laval who led the research, told Earther.

The results also show that primary productivity is increasing, particularly in the Barents and Karas Seas that border the North Atlantic. That region has seen some of the greatest sea ice declines and warmer Atlantic water streaming into the area. Renaut said that while the results of the new study don’t necessarily add more evidence to the “Atlantification” process playing out, she said the intrusion of water waters is “strongly impacting the retreat of the ice cover in this region, and consequently the organisms living in these waters.”

Advertisement

The increase in spring phytoplankton productivity is both a symptom of rapid warming and disappearing ice and a potential cause of new changes, especially as the Arctic moves closer toward ice-free summers in the coming decades. Scientists don’t wholly know what that will mean for the delicate ecological balances that have evolved over millennia.

Renaut pointed to a potential mismatch between when and where phytoplankton blooms occur and when and where the tiny animals that graze on them, called zooplankton, are active. That’s just one potential impact that could ripple up the food chain.  

Advertisement

“It is difficult to say how other organisms are going to adapt to these changes,” she said.

Managing editor, Earther

Share This Story

Get our newsletter

DISCUSSION

dnapl
Dense non aqueous phase liquid

It’s a race for controlling factors here:

1) An increase in phytoplankton adds to Arctic ocean dissolved oxygen content. That should be good for the food chain.

2) Arctic Ocean temperature increases, thusly speeding up the transfer of dissolved oxygen to the atmosphere. That would be bad, if the transfer is too swift.

So I checked out Carbon Brief, a pretty good explainer website. They’ve reviewed some literature. This dovetails nicely with Brian’s review.

Guest post: How global warming is causing ocean oxygen levels to fall

Here’s a snippet from the above link:

Warming affects the ocean and its dissolved oxygen content in several ways. Among other things, it influences the solubility of oxygen in the water. The warmer the water, the less gas that can dissolve in it.

Until now, this process mainly affected the upper few hundred meters of the oceans, which have been in contact with the atmosphere most recently. This effect explains up to 20% of the total marine oxygen loss so far and about 50% of that in the upper 1,000 metres of the oceans.

In addition, warming alters patterns of global ocean circulation, which affects the mixing of oxygen-rich surface waters with deeper oxygen-poor water. It also changes how quickly organisms metabolise and respire, which affects consumption of marine oxygen.

You’d think the stereotypical “smart kid” going forward will no longer be some tech nerd writing social apps in Silicon Valley, but some earth science field jockey getting all earth science-y. We need super smart kids to go into earth sciences. All disciplines. Now.