This blog post was co-authored by Dr. Julia Boike and her team (AWI) and Zhila Rashidi (Eosense)
Polygonal ponds in Siberian permafrost and their effect on CO2 emissions
The Lena River Delta in northern Yakutia, northeast Siberia, Russia, is one of the largest catchment areas (2,430,000 km2) in the Arctic. The bed of Lena Delta and it’s permafrost affected soil can be described as a widely distributed polygonal-patterned ground.
Polygonal structures, which are common components of arctic Siberian wetlands, are small ponds, 10-15 meters in diameter, separated by ridges. Within the Lena Delta, there are about 60,000 of these ponds. Therefore, the amount of biological activity at these sites and their carbon feedbacks can not be simply ignored. Investigating environmental dynamics (e.g., greenhouse gas emissions, temperature change) in these remote areas is thus the key to gain more insights on causes and effects of the climatic variations observed over the last decades.
The findings, thus far!
According to past studies, during September at the end of the vegetation period, CO2 emissions from lakes and ponds have been shown to increase the net CO2 flux by at least one order of magnitude. Consequently, over a complete growing season, vegetated tundra surfaces can be expected to be CO2 sinks, whereas lakes and ponds are continuous sources of atmospheric CO2 (Kling et al., 1991). On the other hand, penetration of solar radiation down to the sediment results in positive contribution of the phytobenthic community to the total autotrophic productivity. This allows the habitation of large crustacean communities in polygonal ponds during the open water period (Abramova et al., 2017). Further production of zooplankton in these ponds is based on carbon sources other than phytoplankton, which is believed to increase the total biological productivity of the small ponds to be much higher than the tundra lakes. This permits ponds to become a large carbon sink through sedimentation period, while at the same time they are net contributors of carbon to the atmosphere through greenhouse gas emissions. However, the source of the carbon that fuels both the intensive metabolisms in the ponds and the CO2 that they release is yet not well understood.
Where does the carbon go?
The question now is whether all the carbon is used up toward planktonic activity or is there much of it left within the sediment? To find the answer, a Russian-German research team led by Dr. Julia Boike (Alfred Wegener Institute for Polar and Marine Research (AWI)), Dr. Katja Abramova and Dr. Lars Kutzbach (Universitat Hamburg) have proposed two hypotheses. The first hypothesis is that any available carbon in ponds is rapidly consumed, especially in ponds that have no direct connection to an active drainage system and therefore do not receive any additional carbon other than that generated within the ponds by photosynthetic fixation of CO2. The other possibility points at high photo-degradation of the dissolved organic carbon (DOC) within the water columns of ponds, since they are only shallow and solar radiation is effective over 24 hours of the day during the summer months.
In situ measurements with Eosense
Samoylov Island has been used as a base for joint Russian-German research and fieldwork since 1998. The joint Russian-German “LENA” research expeditions, coordinated by the AWI, the Arctic and Antarctic Research Institute in St. Petersburg, and the Melnikov Permafrost Institute in Yakutsk. Russian-German permafrost research and long-term observations have been continuing for more than fifteen years and access to the data is available through the European Fluxes Database Cluster and the Global Terrestrial Network for Permafrost (GTN-P). This station also runs continuous climate and soil measurements at this site since 1998 and multi year eddy covariance and hydrological stations since 2002. Along with a team of experts with various scientific backgrounds, this station aims to perform first time in situ quantification of CO2 emissions at this imperative location.
eosGP – a Reliable and Self-sufficient Technique
The CO2 concentration measurements from June to September are performed using the eosGP CO2 Gas Probe. During the testing period, eosGP units are placed in 2 polygonic ponds located close to the scientific station in Samoylov Island in the Lena River Delta. The ponds used in this project were selected according to their approximate equality in surface area and volume with depths ranging from 0.3 to 1 meter via food webs.
There are many aspects of the eosGP design that make it a good choice for this project, including:
- The compact and waterproof design of eosGP offers accurate, in situ monitoring of DIC within the polygonal ponds in various depths of soil or water (immersible up to 3m)
- The eosGP has lower power requirements in comparison to available options in the market, an important consideration at high-latitude sites especially in winter.
- Simple operational protocol and compatibility with most dataloggers allows for quick training and integration with existing infrastructure
- Single and dual range calibrations offer control over both low and high calibration ranges to maximize accuracy and minimize data loss.
For more information on technical specification of eosGP please download our brochure.
And stay tuned for our upcoming scientific presentations and case study, which will present preliminary data collected at the Samoylov Island site.