Last year, Field Notesintroduced you to Jasmine Saros, a lake ecologist from the University of Maine investigating if tiny freshwater diatoms can offer clues on what impact climate change may have on Arctic freshwater lake ecosystems.
Her project, Deciphering the ecology of key diatom taxa to understand climate-induced changes in west Greenland lakes, is funded by the National Science Foundation.
In 2013, Saros and her team conducted extensive surveys to get a better idea of the plankton communities in different lakes and under different environmental conditions in Greenland.
Field Notes recently caught up with her to learn more about her team’s 2014 fieldwork in Kangerlussuaq where they conducted a whole-lake manipulation to mimic warmer conditions caused by different climate change scenarios.
“We did a large-scale experiment on an entire lake this year where we changed the temperature structure of a lake,” Saros explained. “There’s a warm surface layer in lakes and we wanted to change the thickness of that layer. The characteristics of the warm layer set up the habitat for the plankton. So once we change the warm layer, what does that do to the plankton community in the lake and how can that help us understand the longer term effects of climate change on lake ecosystems?”
Churning the Water
To start, Saros and her team established an experimental lake, as well as a nearby control lake that was very similar in size and depth.
“We selected two lakes that had species of plankton that we think are likely good indicators of climate change in the area, which is what we are testing for. These two lakes were also on the small end of the lakes we study, so they were much easier to manipulate,” Saros said.
Their next step was to anchor a large hydraulic lift system called a SolarBee in the experimental lake to circulate the water. Powered by the sun, the SolarBee works by pulling up cooler water from deeper parts of the lake and redistributing it at the surface. “By keeping the cold water circulating, the SolarBee actually deepens the warm surface layer,” Saros explained.
Once the SolarBee was in place and mixing the water column in the experimental lake, the scientists collected water samples from both lakes. They also deployed sensors like temperature and water quality probes in the lakes to collect data that was downloaded at the end of the eight-week experiment.
“We’re processing the samples now and we still have a lot of microscope work ahead of us where we’ll look at the communities to see if the temperature manipulations had any effect,” she said. “The good news is that the manipulations were successful!”
Conducting extensive sampling and conducting a series of experiments on not one, but two entire lakes was no small feat. Among the bigger challenges was installing and securing the large SolarBee. For this they needed a helicopter.
“There were a lot of logistics with the helicopter that lifted the SolarBee in to place. We had to make sure it was harnessed properly to get it into the lake. Then, once in the lake, we worked from inflatable boats to arrange the hoses and chains that are all part of the instrument,” Saros recalled.
The team also logged hours on the water connecting the sensors and probes that tracked what the SolarBee was doing, as well as those that monitored various lake conditions.
With the second year of field work now behind them, the group will spend the next academic year analyzing the plankton samples and crunching data to see what effects the lake manipulations had on the plankton communities.
“This work will help us gain a better understanding of how lake ecosystems may change in the future with warming. We’ll also know more about how lake systems function under different conditions as we head in to the future,” Saros said. –Alicia Clarke