Heather Burgess brings ashore a sample core of mud obtained from Lake Champlain.
Photo: Margaret Michiewitcz
On any given summer day, the 500 plus-mile-long shoreline of Lake Champlain teems with people and pets enjoying one of Vermont’s greatest natural resources. Yet more and more, disturbing news about the health of Lake Champlain comes to light.
So, at 28 I am back in college, pursuing a Master’s degree in Geology at the University of Vermont. I don’t study volcanoes or rocks or earthquakes; I study… lake mud. Dr. Andrea Lini, my advisor, is more environmental scientist than geologist, working with other environmental scientists around the state, observing changes in the lake over time through changes in lake mud.
Lake Champlain is always a hot topic: mercury levels, blue-green algae blooms (see Part Two for Kate Crawford’s research on this), phosphorus loading – all the result of human activities. In the larger history of the lake, humans have only inhabited this region for a short time. It has been a freshwater lake for roughly the last 10,000 years, since the Champlain Sea drained and the water was replaced by rain and run-off. In the last 200 years, the population of people around the lake has grown from less than a few thousand to nearly 600,000. What was the lake like before large populations settled the region? How has the lake changed since farms began to crop up along its shores? These are the questions I ask every day. The geologist in me wants to know what happened in the past; the rest of me asks, “How can we keep this amazing place in its pristine and natural condition for our children and grandchildren to enjoy?”
The goal of my degree is to answer the first question: what was the lake like 500, 100 or 50 years ago? If we can answer this question, we may be able to use this information to answer the second question, what we can do to keep the lake healthy. Everything that occurs within the lake and the surrounding landscape eventually makes its way into the bottom of the lake, to be recorded in the stuff that squishes between your toes.
Out on the lake, we take short cores of the soft, upper layers of the mud. This involves a boat, a hollow “core” tube and a contraption designed to lower the tube, seal the sediments within and retrieve the muck. What we get is a column of mud, with the oldest at the bottom and the most recent on top. The cores are divided up into one-centimeter-thick layers for analysis. At the bottom of the core, one centimeter may be 20 years’ worth of sediment, while at the top, only one or two years. This is the result of both compaction, as older sediments are buried by incoming material, and increased runoff caused by deforestation. Two hundred years ago, the shoreline was covered by forest; today it is largely open land. When vegetation is removed, soil and other components of the land are more easily transported into the lake.
Nutrients such as nitrogen and phosphorus feed everything that lives. We add nutrients to our lawns, gardens and crops as a fertilizer; they are present in soil, living things and even the air. Just as they feed a lawn or garden, these nutrients feed the algae living in the water. This causes “blooms” or “scums” like those observed in St. Albans and Missisquoi Bay. The amount of algae growing in the water is referred to as productivity. Blue-green algae naturally live in the waters of Lake Champlain; however, as we add more nutrients to the water, the algae increase.
As the algae die, they sink to the bottom and are collected in the sediments as organic matter, measured in the form of carbon. Measuring changes in the amount of carbon in the sediments through time enables us to determine the level of productivity within the lake. Since the sediments are dated, we are able to compare these changes to events that have occurred around the lake at the same time. Through comparison of the sediment record to the historical record, we can formulate a hypothesis of what activities affect algae growth in the water.
For example, we have found increased organic matter in parts of the lake, starting around the mid-1700s. The historical records tell us that these regions experienced deforestation and small-scale farming around this time. However, in the mid 20th century, the rates of organic matter accumulation increase much faster. These increases coincide with the advent of chemical fertilizers on large farms, sewage treatment, and large-scale development along the lake.
Other archives in the sediment include pollen, microscopic animal remains and changes in the size of the sediment particles. These can record changes and events within the region, and even on a global scale, such as climate change or acid deposition.
So why do we want to know how these activities affect the lake? Each summer, areas of the lake are closed to swimming due to toxic algae blooms. During the summers of 1999 and 2000, toxic algae blooms were responsible for the death of two dogs, after they had ingested lake water. As the owner of two water-loving dogs, this incident caused myself, as well as others, to sit up and take notice. The Vermont Depart-ment of Health, in conjunction with University of Vermont’s Rubenstein Ecosystem Science Laboratory and the Vermont Depart-ment of Environmental Control (DEC), have set up blue-green algae monitoring programs, as well as a status map on-line (http://healthvermont.gov/ enviro/bg_algae/bgalgae.aspx), to inform the public of safe and unsafe areas of the lake. In order to keep the lake healthy and repair damages done, we need to understand what the lake was like before human interference, and which of our activities affect it the most.
I started as a creative writing major in college, moved on to wilderness recreation leadership (aka, backpacking for credit!), and ended up receiving a Bachelor’s in environmental science. I never stopped writing, but now I am much more interested in writing about the environment. Not necessarily the tedious works found in scientific journals, but entertaining and enlightening pieces that can be enjoyed by anyone interested in the natural world. With the looming environmental crisis we are facing, it is vital for scientists to share their knowledge with the public. Lake Champlain is an important part of life for many people in Vermont, New York and Quebec. We all see deleterious changes occurring in parts of the lake, but only a few scientists truly know what is happening and why. For me, sharing what I have learned about the lake is the most important part of my work.
The Lake Champlain Basin Program, the Vermont DEC and UVM are all taking the initiative to care for our lake. They offer helpful and informative websites, detailing what you can do to minimize our impact on the lake. For more information, check these sites: http://healthvermont.gov/enviro/index.aspx, http://www.lcbp.org, and http://www.anr.state.vt.us/.
Heather Burgess lives in Winooski with her fiance, a roommate and two dogs. She spends her free time writing, sewing and gardening and hopes to finish her Master’s Degree this summer. You can send questions and comments to hburgess@uvm.edu.
