Peering through the ice to uncover the secrets of Arctic lakes

The idea that these ecosystems could be so complex, yet so hidden beneath the surface, really intrigued me

From fishponds to lakes 

Václava Hazuková, or Vendy as she is known to colleagues and friends, had just returned from an excursion trip to Abisko when I met her at the KBC building. The cold does not seem to bother her, as she lets the crisp February air fill her office through the open window. “I haven’t seen the sun for many weeks, so I just had to let it in,” she says.

Václava Hazuková, KBC-Kempe postdoc with a fascination for water. 

ImageMattias Pettersson

That Vendy would come to be fascinated by bodies of water is perhaps not such a big surprise. Growing up in Czechia, fishponds dating back to medieval times were an ever-present part of her surroundings.
 
"These ponds are a big part of Czech culture and history”, she says, explaining that they were originally built to ensure a reliable food source. Today, Czechia still remains one of the world’s largest producers of carp and the ponds serve as ecological sanctuaries for birds, fish, and microbial life. 

"But you don’t want to swim there," she laughs, recalling how she spent her Bachelor’s studies collecting samples of phytoplankton from the murky waters.  

Although not the most glamorous of waters, for Vendy, they sparked something deeper – a curiosity about hydrological ecosystems. "The idea that these ecosystems could be so complex, yet so hidden beneath the surface, really intrigued me", she explains.

Even in the harshest of environments, life can still adapt and survive

A buried archive 

Vendy’s journey took her to Ohio, where she earned her master’s degree studying diatoms – microscopic algae found in Lake Erie, one of the Great Lakes. The Cuyahoga River, leading into the lake, was so toxic that its water caught on fire several times. "But it showed an example of how even in the harshest of environments, life can still adapt and survive." 

In her time in Ohio, she came in contact with the field of paleolimnology – the study of lakes from a historical perspective. "I realised early on that I like both archival work and microscopy. In my thesis, I got to do both," explaining that microalgae provide a snapshot of history when they die. 

“Microalgae are protected by silica shells. When they die, they sink to the lake floor and become part of the sediment layers. There they stay for thousands of years until I come along and collect the samples," she says. 
 
By studying species composition of diatoms in water samples and fossilised microalgae in sediment cores, she could infer the water quality and climate in Lake Erie from centuries and even millennia ago.

From blue to brown  

Her drive to understand aquatic ecosystems, whether thriving or struggling, led her to PhD studies in Ecology and Environmental Science at the University of Maine. There, she started studying Arctic lakes in Greenland, focusing on lake metabolism and how these lakes are affected by seasonal and climate changes.

“The Greenlandic lakes were translucent turquoise the first time I went on an excursion there”, she says. But now, many of them have abruptly turned brown, caused by an increase of precipitation and heat during autumn.

“Extreme precipitation in this historically very dry region has flushed a lot of terrestrial material into the lakes. It's worrying, and we don’t yet fully know what this means for the future of these lakes.” 

Václava Hazuková, have collected sediment core samples from an Arctic lake in Greenland. Although she prefers working from the stability of a thick ice cover, sometimes the small boats has to do.

Image Privat

Although concerned about these changes, she thrives in the remote environments in Greenland and Abisko. “There’s something peaceful about these serene, secluded places. It’s hard to describe, but I’m addicted to spending time there and I always long to return", she says, sharing that she will collect more data on Greenland this summer. 

“Although I prefer to collect samples when the lakes are ice-covered – it is much more stable working on the ice, than from a small, wobbly boat”, she laughs. 

Complex hydrological ecosystems require an interdisciplinary approach 

Today, she is researching carbon cycling in Arctic lakes – ecosystems undergoing rapid changes due to the warming climate. “We know that lakes are important for storing carbon on a global scale, but at the same time, there is still a lot that we do not know about the contribution of Arctic lakes to carbon cycling”, she says.  

Carbon in lakes, partly produced by algae, has three potential fates: “It will either leave the lakes somewhere downstream, get metabolised and transformed to carbon dioxide, or be buried in lake sediments. My project focuses on the last option, where I’m trying to answer whether these lakes will store more or less carbon in the future.” 

Václava Hazuková, cellting water samples from an Arctic lake in Greenland.

ImageMariusz Potocki

I began this project embracing the biogeochemistry aspect, but it’s all connected

Lakes are only one part of a larger hydrological ecosystem, and understanding the role of each component is central to Vendy’s research. Her hope is to provide clues and constraints on which parameters are most important in the Arctic lakes carbon cycling. “Is it the temperature, chemistry, location in the landscape, the amount of time the lakes are ice covered? What are the important factors here?” she says. 

Her drive to study these complex systems stems from her joy of solving puzzles. "I began this project embracing the biogeochemistry aspect, but it’s all connected, and I want to provide as many pieces to this puzzle as possible." 

Václava Hazuková, KBC-Kempe postdoc

Image Mattias Pettersson

Her postdoc project, supported by the Kempe Foundation, brings together researchers from three different fields connected at the Chemical Biological Centre, KBC: Jan Karlsson, ecology, Jean-François Boily, chemistry, and Martin Rosvall, physics. “To understand whether the bonding of minerals and organic matter could help preserve carbon in lake sediments is the chemistry part of the project, whereas physics comes in when we want to study the larger scales using network modelling,” she explains.

Having lived in Umeå since late summer 2024, she describes it as finding a home, appreciating both the city’s walkability and its rich cultural and music scene. In her spare time, she and her husband enjoy exploring the nearby nature and everything that Umeå has to offer.

For Vendy, every body of water holds a story waiting to be uncovered. As Arctic lakes change at an alarming rate, her research provides a crucial window into their past, and present – helping us better understand their future. 

Václava Hazuková, collecting samples from an Arctic lake in Greenland. 

ImageMariusz Potocki