by Ludmila Brighenti
A lake is like a gigantic living creature that inhales and exhales carbon and exchanges energy with its surrounding environment. I became interested in this process and wanted to understand and predict whole-lake carbon exchange systems in Brazilian lakes. I worked on this topic for my Ph.D. (which I completed recently!), and deployed a high-frequency monitoring buoy to obtain data. This led to a new collaboration between researchers in Brazil and Denmark: Carbon Cycling on Lakes (COCLAKE), looking at the similarities and differences of temporal and tropical lake carbon cycling systems. All of this started from a simple conversation at a GLEON meeting. With the GLEON 16 meeting fast approaching, I wanted to share my story for those who are attending.
The GLEON 13 meeting at Lake Sunapee, New Hampshire, in 2011, was the starting point for this fruitful partnership between the Brazilian research team at Limnea (Post-Graduation Program in Ecology, Federal University of Minas Gerais) and Peter Staehr, a senior researcher at the Department of Biosciences, Aarhus University, Denmark.
It was my first GLEON meeting and Peter happened to be my Network Partnership Program (NPP) partner, a unique GLEON program to mentor new members during the meeting. I had just deployed our first high-frequency automated buoy as part of my PhD thesis on lake metabolism in tropical lakes. We discovered that we had lots of research interests in common, and Peter was happy to share his experience with buoy deployment and knowledge on carbon cycling in lakes. Furthermore, he had a few extra dissolved oxygen (DO) sensors that I could borrow. It was the beginning of our collaboration to study metabolism in lakes using high frequency DO data.
After the G13 meeting, the discussion about lake metabolisms continued, and Peter became my PhD co-supervisor. In 2013, he visited Brazil to run a PhD course on lake metabolism. “This was a great opportunity to get to know the Limnea team and their fascinating study area: Lakes Carioca and Dom Helvécio, State Park of Rio Doce, Minas Gerais state. I really learned a lot during those two weeks – not just samba!” said Peter.
At this occasion, we conceived the COCLAKE project, which was later sent to and approved by the Brazilian Science Without Borders program. “Our knowledge on carbon cycling in lakes is likely biased by the majority of studies being made in temperate systems,” said Peter. “This comparative study of tropical and temperate settings will help improve our current knowledge of the environmental controls of carbon cycling in lakes, with a focus on temporal and spatial variability in production, respiration and net CO2 fluxes.”
Carbon cycling in lakes concerns the flow of energy, oxygen and greenhouse gasses in the lake ecosystem. Lakes can roughly be viewed as super organisms which breathe oxygen as a result of production and degradation of organic matter and are strongly affected by daily changes in light and temperature and inputs of matter from the surroundings, according to Peter.
In lakes, much of the organic matter (carbon) comes from the surrounding landscape, which therefore can have a huge impact on energy available for organisms living in the lake and the outgassing of greenhouse gases. “Studies of the cycling of carbon in lakes are therefore fundamental to improve our understanding of life in lakes and for quantification of the importance of lakes for the flow of energy and greenhouse gases in the landscape,” said Peter.
In July 2014, a pilot study was conducted to test a mesocosm experiment on the effects of dissolved organic carbon (DOC), nutrients, and light on lake metabolism. The pilot study was very promising, and we look forward to running a full scale experiment in Lake Carioca, in January 2015, and later in Lake Bure (Denmark), in July 2015.