Warming waters are dramatically changing microbial life in Antarctica

For the first time, researchers have conducted a year-round evaluation of bacteria and microbial eukaryotes – small marine organisms like phytoplankton – at two Antarctic bases.

By sampling through all the seasons and using the same methods repeatedly, the research provides a thorough picture of how microbial communities respond to climate change.

Between July 2013 and April 2014, researchers took seawater samples from the British Antarctic Survey’s long-term ecological monitoring site at Rothera and from the Palmer research station, which is 400 kilometers to the north.

The scientists employed DNA sequence analysis to identify the bacteria, protists, and phytoplankton in the water.

Special statistical models were used to forecast microbial interactions – basically charting the “who eats whom” of the microscopic world.

Microorganisms shape marine ecosystems

The Antarctic Peninsula is warming at a rate faster than the global average, leading to unprecedented heatwaves and declining sea ice. However, regional variations exist.

In the waters around Palmer, sea ice has decreased significantly as temperatures have risen more rapidly when compared to Rothera. This divergence influences microbial community composition in unique ways.

“At the warmer Palmer site, bacteria influenced microbial community structure by interacting with other microorganisms, while at Rothera, it was the microbial eukaryotes that played a stronger role in shaping community dynamics,” explained Engelmann.

This trend towards increased bacterial prevalence in warming oceans might upset biological productivity.

Phytoplankton are producers in marine food chains, so a reduction in phytoplankton translates to fewer nutrients available for higher organisms such as krill, fish, seabirds, and marine mammals.

“These findings have significant implications for understanding and predicting microbial ecosystem responses to climate change, and are therefore relevant for a broad group of researchers and even for humanity as a whole,” Engelmann stated.

Microorganisms, through tiny, far outnumber all marine animals in terms of biomass.

Climate-driven changes in microbial food webs within the Southern Ocean could have far-reaching consequences that impact global marine ecosystems and nutrient cycles.

The role of microbial data in climate models

Looking ahead, researchers hope to integrate microbial data into climate and ocean models.

“The microbial food web is complex; bacteria and microbial eukaryotes have different functions and there are a lot of interactions among and between these groups, but also with larger organisms, including animals,” Engelmann commented.

“At this point, it is difficult to predict the impact of climate change on microbial productivity. Our research provides crucial baseline data for understanding the complexity of microbial communities in coastal Antarctic ecosystems, but we need more data and a better understanding of marine microbial communities before we can include them in climate and ocean models,” added Engelmann.

Researchers acknowledge the need for more data to achieve this goal and stress that including data on microbial productivity would make predictive models more accurate in future.

Expanding the research timeline

The 2013-2014 study marks the first comprehensive seasonal analysis of both bacterial and microbial eukaryote communities in Antarctic waters.

Future measurements will provide a clearer picture of long-term microbial trends.

“Now, we’ve drawn conclusions based on climate differences at two locations. We have samples ready from 2018-2019 and also from 2022. The more of these measurements we collect over time, the more we’ll learn about Antarctic marine microbial communities, their interactions, and susceptibility to climate change,” Engelmann explained.

Despite the valuable insights gained from these studies, conducting research in Antarctica presents significant logistical challenges.

Sampling requires extensive coordination, specialized equipment, and considerable resources. Furthermore, international collaboration is key to conducting successful research.

“International cooperation, such as with the British Antarctic Survey and the colleagues in the U.S. who worked at Palmer station and their home universities, is therefore crucial,” stressed Engelmann.

With continued efforts, these studies will help unravel the intricate role of microorganisms in the Antarctic ecosystem and their response to an ever-changing climate.

Microbial shifts and global ocean health

The microbial alterations that have been observed in Antarctic waters are just a part of a larger pattern being seen across marine ecosystems globally.

With rising ocean temperatures, changes in microbial communities impact nutrient cycles, carbon sequestration, and food webs, and there are likely implications for marine biodiversity and ecosystem stability.

Phytoplankton, in particular, are responsible for sustaining marine life and governing atmospheric carbon. So shifts in microbial interactions may reorganize the effectiveness of carbon sequestration in the ocean, influencing climate regulation on Earth.

Disruptions to the microbial food web could also have indirect impacts on more complex organisms and possibly reconfigure the structure of polar ecosystems.

Monitoring these microbial dynamics over a period of time will enable researchers to improve climate models and estimate how ocean ecosystems will adjust to ongoing environmental changes.

When the newly available data for the past years is analyzed, it will help scientists to better understand the long-term patterns that will guide the future of Antarctic marine ecosystems.

The full study was published in the journal Environmental Microbiome.

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