We recently returned from our winter 2014 expedition to the Lake Baikal region. This time there was no sampling of Lake Baikal itself, but rather, we spent a week collecting sediment cores from a few of the small lakes of the Selenga Delta and surrounding region.
The Selenga River is the major source of freshwater into Lake Baikal, contributing more than half of its annual inflow. The Selenga River enters Lake Baikal through a delta system in the southern basin of the Lake. As part of our larger Lake Baikal project, we seek to understand how lakes in the Selenga Delta have responded to various forms of pollution within the Selenga River Watershed during the recent past, and how the impacts of such pressures are transferred to Lake Baikal itself.
Landsat 5 image of the Selenga River Delta acquired on August 23, 2010. This image clearly shows the tributaries of the delta, meandering channels on the alluvial plain and sediment-laden waters on the delta front. Landsat GeoCover image by the United States Geological Survey.
We sampled these small lakes during the period of ice cover. To access the sediments at the bottom of the lakes we drilled a hole in the ice, which was about 80 cm think in all lakes, with a large enough diameter to fit our corer through. Sampling through the ice allows us to have a steady platform to core from, and access to remote lakes can often be easier at this time of year.
Sasha drilling a sampling hole in one of our Selenga lakes
However, coring shallow lakes in the winter can also bring about potential issues. When most of the lake depth is frozen, leaving only 20 or so cm of water between the ice and sediment, it can be tricky to drill a hole just deep enough to penetrate through the entire ice cover and reach water without disturbing the sediment below. We learned this the hard way and ended up having to drill 9 holes to collect three cores at our first site. Fortunately we were using a gas-powered auger and not a manual auger.
Freshly drilled holes through the ice at Selenga lake 4
As if such a challenge weren’t enough, we also ran into issues with the corer itself. Sampling in early March in southern Siberia can be bitterly cold and windy. Personally, we were all prepared for the cold weather. However we didn’t consider what the cold weather would do to our corer. In hindsight, we should have realized that sticking a metal device into cold water and then bringing it out into below freezing air temperatures would result in a frozen corer, which it did, leading to an improper seal between the corer and core tube. Solution? Well, on the flip-side we were lucky it was March and so cold, because this meant the ice cover on our lakes was thick enough that we could drive our vehicle right to our sampling points. A few minutes of drying the corer in the car with the heater on full blast and we were ready to collect our next sediment core!
Thanks to the cold Siberian weather, the ice on our lake was thick enough to drive our vehicle out to our sampling points
So, as most field expeditions go, our first day was full of unexpected bumps, but nothing too huge that a little improvisation and persistence couldn’t resolve. Sampling in these conditions was old hat by days 2 and 3, making our sediment core collection at our second Selenga site and Black Lake go much smoother. By the time our week in the Selenga Delta was up we had collected several sediment cores from three lakes, to be analyzed for pollution and various biological indicators and allowing for the reconstruction of food-web dynamics in the Delta lakes.
Selenga lake 3 in the distance
Analysis has already begun on our newly collected sediment cores, and I’ll be updating you on our progress as results unfold!
Jen with one of our Black Lake cores
Cheers for now.