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The Changing Role of Ice Algae in Greenland’s Melting Ice Sheets
May brings a familiar warmth as the sun rises higher in the sky, signaling the end of winter’s grip. As temperatures rise, melting snow gives way to vibrant flowers and plants seeking the light. This seasonal transformation has occurred for millennia.
However, the onset of spring is shifting earlier each year due to the impacts of climate change, allowing algae to potentially expand their territory on the ice. This algae, which contains a brown pigment, darkens the surface of the ice, reducing its reflectivity and hastening its melt.
Researchers in the polar regions have long recognized this phenomenon, but it was generally believed that the algae were limited in their ability to thrive on the barren ice due to a lack of nutrients. Recent findings challenge that assumption.
New research published in Nature Communications suggests that these algae are capable of surviving with minimal nutrient input and can store energy effectively. This adaptation may enable them to colonize greater expanses of ice than previously estimated.
Laura Halbach, a postdoctoral researcher at the Max Planck Institute for Marine Microbiology in Bremen and recent PhD graduate from Aarhus University, has been pivotal in this discovery. Her research focuses on unraveling the complexities within arctic ecosystems.
“My primary aim in visiting Greenland was to comprehend how algae blooms form. Utilizing new methodologies, I became the first researcher to measure the activity of individual algae cells from the Greenland Ice Sheet. This research revealed their remarkable ability to thrive on sparse nutrients while also storing energy,” Halbach explains.
The Life of Ice Algae
Ice algae are single-celled organisms that are elongate and brownish in appearance. They are resilient microbes found on icy surfaces globally, including the Greenland ice sheet, the Alps, and various glaciers across the Himalayas and Alaska.
Similar to plants, ice algae engage in photosynthesis, releasing oxygen and creating organic matter. They require sunlight, water, and carbon dioxide, along with trace amounts of phosphorus, nitrogen, and carbon for survival. During warmer months, they proliferate, covering the ice in dark patches.
Revealing a Diverse Ecosystem
Historically viewed as a lifeless expanse, the Greenland ice sheet is now understood to host a vibrant microbial environment. Since the first researchers ventured to Greenland in 2020, evidence has surfaced indicating that these ice formations support a diverse array of life.
Subsequent expeditions have unveiled the intricate ecosystems of microorganisms thriving on the ice, including bacteria, fungi, and various viruses. However, this diversity complicates focused research on ice algae, as studies of blackened ice samples frequently yield entire ecosystems, obscuring the specific contributions of individual organisms. Halbach sought to address this research challenge.
“When surface ice melts, you observe dark-pigmented algae alongside numerous other microorganisms—snow algae, other eukaryotic algae, bacteria, and fungi. Standard practice involves incubating the entire community and measuring nutrient uptake collectively, but this approach often leaves unclear the distinct roles of the various organisms,” she notes.
Investigating Individual Cells
To better understand the role of ice algae, Halbach implemented a strategy that involved feeding the entire ecosystem marked nutrients—traceable isotopic markers analyzed by mass spectrometry. This innovative technique enabled her to track nutrient uptake by individual cells.
“By labeling the nutrients we provided, we could determine which organisms consumed what. Together with an advanced machine known as SIMS, we attained precision measurements of nutrient absorption at the single-cell level,” Halbach says.
The data revealed that ice algae efficiently consumed the scant available nutrients and had the capability to store critical phosphorus, previously unknown to researchers. Phosphorus is essential for their metabolic processes, and research indicates that it may be sourced from local rocks, dispersing as mineral dust across the ice due to erosion.
Implications for Ecosystem Dynamics
Given their ability to store phosphorus, ice algae could inhabit areas of ice previously considered unsuitable for colonization due to nutrient scarcity. This flexibility may lead to an expanded darkening of ice, indicating a more widespread impact on ice melting than earlier predictions suggested.
“Each year, new areas of ice in Greenland are exposed as snow melts earlier. Historically, these regions were obscured by thick snow cover. With increased sunlight reaching formerly hidden ice surfaces, algae could rapidly begin colonizing these areas, potentially much sooner than previously believed,” Halbach explains.
Halbach’s findings are critical not only for understanding the ecological dynamics of ice algae but also for predicting the future consequences of their expansion on Greenland’s ice melt. Currently, microbial components are often omitted from climate models. Integrating these new insights into such models could enhance predictions regarding ice melt and its ramifications for global climate conditions.
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