Study of Arctic algae 'puts a microscope up to climate change'
As the summer sea ice in the Arctic waters off the coast of Alaska shrinks with each passing year, scientists are trying to predict changes in microscopic marine algae called phytoplankton in the ocean water. Their research offers one more piece in the puzzle to help us prepare for, and adapt to, significant changes on the Earth brought on by climate change.
Researchers investigated how various species of phytoplankton, the basis of the food web, are responding to changing conditions in the Chukchi Sea, where the seasonality of sea ice shapes how life operates under water. In response to recent warming, sea ice is thinner and retreating earlier each summer. Recent predictions suggest that the Arctic will be sea-ice-free in the summer as early as 2040.
“I wanted to see how the environmental variables in the water column related to the different types of phytoplankton we saw. If we can understand the mechanisms that drive phytoplankton community structure, maybe we can forecast what could happen in the future—if the phytoplankton communities will change under future conditions of less sea ice during the summer,” said Aimee Neeley, a graduate student at the University of Maryland Center for Environmental Science who has been working in the Arctic and Antarctic for more than a decade.
The researchers discovered that the warming climate and declining sea ice may be contributing to changes in phytoplankton, favoring smaller species that offer less carbon and may be less nutritious for sea life.
Half of all photosynthesis on the planet happens in the world’s oceans, and this includes the microscopic algae living in the Arctic Ocean. Phytoplankton plays a significant role in the photosynthesis that generates oxygen and other byproducts for life on Earth. Phytoplankton and other marine plants utilize atmospheric carbon dioxide during photosynthesis; the byproducts of that process become nutrient-rich organic matter for animals farther up the food chain. Phytoplankton also provide food for a wide range of sea creatures, from whales to snails.
“Whatever happens to phytoplankton will cascade down to everything else. Particularly in this delicate ecosystem, everything is tightly linked so if you change one thing, you could change everything,” said Neeley.
Neeley gathered the data with Karen Frey, an associate professor in Clark University's Graduate School of Geography, during the summer of 2011 aboard the U.S. Coast Guard Cutter Healy in the northern Chukchi and western Beaufort seas. Their research mission—and another in 2010 —was part of a multi-year, NASA-funded project called ICESCAPE (Impacts of Climate change on the Eco-Systems and Chemistry of the Arctic Pacific Environment).
The data were collected by Sam Laney at Woods Hole Oceanographic Institution using a Mclane Labs Imaging Flow Cytobot, a microscope-flow cytometer hybrid with a camera attached. It drew in a water sample, magnified the particles in the water, and took high resolution, live-stream images of phytoplankton that were used to model how different species respond to sea ice extent, sea surface temperature, nutrients, salinity, and light.
Neeley says understanding how tiny creatures like phytoplankton react in varying conditions in the Arctic is important understanding life in the ocean in the past, present and into the future.
“The ocean depends on their survival and what type are in the water,” said Neeley, “It’s important we understand not only for the food web but for the carbon cycle—taking up carbon dioxide from the atmosphere and producing oxygen—for the planet.”
The paper, “Unraveling Phytoplankton Community Dynamics in the Northern Chukchi Sea Under Sea-Ice-Covered and Sea-Ice-Free Conditions,” by Aimee Neeley and Lora Harris of the University of Maryland Center for Environmental Science and Karen Frey of Clark University’s Graduate School of Geography was published in Geophysical Research Letters in August, 2018.