A Fortunate Collaboration
Given our recent pattern of heavy snows, high winds, and bitter cold, we lucked out with February 28 as our chosen day to collect sediment core samples from the bottom of Kezar Lake in Lovell. Though day dawned with sub-zero temperature, the day warmed beautifully to the mid-20’s with cloudless skies, brilliant sunshine, and barely a breeze: absolutely perfect conditions for a day on the ice.
The effort was organized by the Kezar Lake Watershed Association’s Climate Change Observatory in collaboration with Plymouth State University in New Hampshire. Dr. Lisa Doner, a paleo-limnologist with Plymouth State’s Center for the Environment, and five of her students directed the project with the logistical and moral support of 26 volunteers from the Kezar Lake area.
What was the goal and purpose of the samples?
The goal of the sediment core sampling project is to determine the source and composition of the sediments in the Lake; how quickly sediment is accumulating; and how Kezar has been affected, over time, by environmental impacts, natural and otherwise. We collected “short core” samples which should produce about 200 years of sediment history (as opposed to “long cores” which go back thousands of years), hopefully shedding light on the impacts on Kezar of colonial sheep farming, major weather events, historic timber harvests, lakeside development and dredgings, conservation efforts, and Chernobyl, etc.
The results should be fascinating. And, moving forward, this knowledge can help inform decisions about how we manage the watershed in the face of increased intense storm events due to climate change, future lakeside development pressures, and proposed timber harvests, etc.
Method and Analysis
So how and where did we collect these sediment core samples? Gathering at Kezar Lake’s north end last Saturday at 10:00 AM, dozens of enthusiastic volunteers and sleds full of equipment were shuttled on six snowmobiles to the Lake’s deepest waters, about one mile to the south. Drilling a hole through the 18” thick ice, our depth finder read 153’. With the theory that most sediment will settle in the Lake’s deepest holes, this location was perfect.
Once the core sampling apparatus was assembled with its five-foot plexiglass tube, brass collar, steel braces, and plunge-ball capping mechanism, it was lowered by rope down through the ice. The line had been measured so we’d know when the sampler was approaching the bottom. At that point, the mechanism was released in a controlled faster drop, allowing gravity to drive the hollow tube deep into the soft muddy substrate 153 feet down.
After letting the tube settle for a few minutes, the mechanism was hauled up with 52 centimeters of black muck securely trapped in the tube, likely representing the Lake’s history to pre-colonial times. It was essential to keep the tube upright after retrieval, because any shifting of sediment would negate the intact snapshot of geological history. This is a primary reason to collect core samples in the winter: a lake’s frozen surface is much more stable than that of a rocking boat.
After carefully removing the plastic tube from the collection apparatus, it was tenderly transferred to a stand in a portable ice-shack for processing. Using a specially designed core slicer, one centimeter sections were sliced off and placed in precisely labeled containers, each representing a small period of time in history. The slicer was carefully cleaned with distilled water between each cut to avoid any contamination between layers.
Back at Plymouth State, multiple analyses will be performed on these sediment layers to determine organic content, dates, magnetic resonance, and mineral composition, etc. It will be fascinating to discover the sediment’s story.
While volunteers were processing the deep hole core, the bulk of the crew retreated back to Kezar’s north end for lunch. A Base Camp had been established at two “permanent” ice shacks and a festive picnic ensued with yummy hot soups, grilled sausages, hot dogs, and cookies. The field team was grateful for those who had prepared the meal and had kept the woodstoves burning. And, yes, we did remember to deliver nourishment to those still in the tent, processing the core.
After a quick but hearty feast, the snowmobiles were reloaded with volunteers and gear to collect a final sediment core sample near the mouth of Great Brook, the source of approximately one third of Kezar Lake’s water. Here the Lake was 33 feet deep, and the core sampling went fairly quickly. Upon the core’s retrieval, Dr Doner pointed out a layer of woody debris in the sediment. This may have been from the old marina’s dredging in the 1970’s or some other event. There is much to learn and the cores will help tell the stories…
The Kezar Lake Watershed Association is grateful for all of the community help and interest in this exciting project. The knowledge we gain will help us fulfill our mission to preserve, protect and maintain the ecological, scenic and recreational resources of Kezar Lake and its watershed for the benefit and enjoyment of residents, summer residents, and visitors, now and in future generations.
How Can I Help?
There are many projects that would benefit from your support and involvement. Help us sustain this wonderful environment for many generations to come. Give to KLWA so that we might reserve the watershed for children and grandchildren the same experiences that have been so meaningful to each of us. Volunteer and share your gifts with us.