“I remember, I remember everything”
- Zach Bryan, I Remember Everything
I’ve been working on building my family tree. I did both the Ancestry website and the DNA test to learn about the generations before me. All my relatives from the past three generations emigrated to the United States from Ireland or Germany in the mid-1800s. There’s also a sliver of Scandinavian ancestry in my DNA from 6-8+ generations ago. Maybe that’s from the Vikings that raided Ireland.
Some of my ancestors arrived when they were only in their teens. I can only imagine how bad it had to be during the potato famine in Ireland for them to leave and start a life in a whole new country as a teenager. Most of my Irish ancestors settled in southern Minnesota to farm. Most of my German ancestors settled in St. Paul, Minnesota.
I wonder if they had the same interests as me. That information is harder to come by in the earlier generations. I do know one of my Great Grandmothers was a published poet. Maybe that’s where my love of writing came from? My Grandpa was a doctor. Maybe that’s where my love of science came from? My Grandma was a singer and wrote songs. Maybe that’s where my love of music came from?
Like humans, lakes have a generational memory too. The lakes in Minnesota (and much of the northern hemisphere) formed after the glaciers retreated about 10,000 years ago. The glaciers pushed sand and gravel as they moved across the earth’s surface, and ice blocks broke off and melted into low areas to form lakes. Since lakes are depressions, everything around them runs downhill into them. In the early years, sediment and dirt eroded slowly and made its way into the lakes. As humans moved in, they started changing the landscape and clearing forests, making the sediment and dirt flow into the lake more quickly than they would naturally. Then due to human ingenuity, man-made chemicals were created and entered lakes too.
Scientists can reconstruct the timeline of what occurred in a lake’s history like we can reconstruct our family tree. A sediment core in a lake shows lines like a tree, and these lines can be dated based on certain year markers. One marker is radioactive material, which dates to the Cold War in the 1950s when the United States, United Kingdom, and Soviet Union were testing nuclear bombs. A thin layer of radioactive material has been found in lakes around the whole northern hemisphere. The Chernobyl accident in 1986 can also be detected in lakes in northern Europe.
Plastics and PFAS can be found more recently and can impact both human and lake health. To take care of our lakes it’s best to have a buffer of vegetation and trees surrounding the lakes to filter what flows into it. Recycling plastic and other materials can prevent them from ending up in our lakes and oceans.
Just like we learn about the health history of our family to determine our risk for diseases and conditions, a lake also experiences a health history. As we do our best to live healthy and minimize our risk of illness to be around for our children and grandchildren, let’s help our lakes stay healthy for our children and grandchildren to enjoy.
Moriya Rufer is a lake biologist with 20 years experience working with lakes in northern Minnesota.
The photo above is Moriya with her Grandma at Leech Lake in the early 1980s.
References:
Haltia, Eeva, Ari-Pekka Leppanen, Antti Kallio, Timo Saarinen. 2021. Sediment profile dating and reconstructing nuclear events from annually laminated lake sediments in northern Finland. Journal of Environmental Radioactivity. Volume 233, July 2021, 106611
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