Local bodies of water were the subject of intensive study by four Mount Holyoke students as part of the extensive research carried out by students and faculty members on campus this summer and presented on July 25 at the 11th Annual Mount Holyoke Summer Science Symposium.
Caitlin Dickinson '10 of Ann Arbor, Michigan, and Melissa Joyce '08 of Ashburnham, Massachusetts, looked at a technique to analyze the spread of an invasive pest, the hemlock woolly adelgid, through the eastern hemlock population so important to the ecosystem surrounding the massive Quabbin Reservoir east of Amherst.
Sarah Beth Cadieux '08 of Concord, New Hampshire, and Mignon Johnston '10 of Raleigh, North Carolina, took a hard look at the layers of sediment under Lake Wyola, a popular swimming hole in nearby Shutesbury.
On July 25, nearly 40 students made presentations of their summer work at Kendade Hall. These research efforts are sponsored by a number of organizations, including the National Science Foundation, the Howard Hughes Medical Institute (HHMI), and the National Institutes of Health.
Professor of biological sciences Craig Woodard, who helped head the summer research efforts as codirector of the HHMI Undergraduate Science Education Program, observed, "This year's Summer Science Symposium was a great event. I'm impressed by the high quality of the research our students are doing, and their presentations were excellent. Mount Holyoke is an exciting place to be in the summer."
As winters have grown warmer in recent years, the woolly adelgid, no longer deterred by extremely frosty weather, has spread north, devastating hemlock forests. The pest looks like a cottony substance under a hemlock's coniferous leaves. Ultimately, the infestation kills hemlocks, creating gaps in the forest canopy that allow more sunlight to reach feeder streams, increasing temperature and biological activity. Additionally, hemlocks release large pulses of nitrogen from their dead root systems that enter feeder streams and, ultimately, the reservoir, raising ambient nutrient levels, potentially causing significant harm.
Until now, analysis of infestation has been done using costly field methods--essentially investigating forests acre-by-acre and tree-by-tree. Dickinson and Joyce explored the use of multispectral images captured in 2004 and 2007 from airplanes, using Airborn Imaging Multispectral Sensor, or AIMS-1, technology, to attempt to map the spread of the infestation. This assessment was then checked against information gained from old-style, on-the-ground surveys.
The findings, according to Dickinson and Joyce, were that although the correlation is not perfect, the new method can be refined to become an effective tool to save forest managers much time in the future in plotting the spread of the pest.
"The project is important because the AIMS-1 remote sensing technology has the potential to supplement the costly ground work and help eliminate some of the long hours in the field," Joyce noted. Dickinson added, "This technology would also enable evaluation across a larger geographic extent--say, all of New England--an extent that would be nearly impossible if you were relying solely on ground methods."
The students worked with Thomas Millette, associate professor of geography; David Orwig of Harvard Forest; and Eugenio Marcano, geoprocessing lab manager at Mount Holyoke.
Digging the Lake
Cadieux and Johnston are in the midst of a detailed study of sedimentary layering beneath Lake Wyola, located some 22 miles north of South Hadley. They are working with professor of geology Al Werner.
According to Cadieux, "For this project, we are conducing a paleolimnological study on a sediment core retrieved from Lake Wyola in January of 2005. In other words, we are analyzing a 7.2-meter-long core of sub-lake sediment in order to reveal the history it preserves. Lakes are subject to a variety of extrinsic and intrinsic forcing variables that regulate the subsequent history of the lake, such as climate, watershed bedrock composition, vegetation, aquatic biota, and human activities. Lake sediments have been called an ecosystem's memory. Sediments are always accumulating and therefore act as a history book. Due to the low energy levels in lakes, their basins are 'natural traps' for sediment."
According to a synopsis of the study, "The lake setting suggests that Wyola originated as a kettle lake at the end of the Wisconsin glaciation (about 12,000 years ago). Sub-bottom acoustic profiling indicates well-layered sediments, resulting from changing environmental conditions over the past 14,000 years. Since the glacier's recession, the lake has undergone numerous natural and anthropogenic changes, including deglaciation; landscape stabilization; climate change; forest fires; hurricanes; and more recent anthropogenic influences, including the construction of a dam in the late 1800s."
Using paleolimnology, the study of water life and sediments from preexisting geological time periods, the two students are working to interpret the information contained in the core sample though conducting analyses that help define former environments, climates, and anthropogenic influences on the lake by examining sedimentary properties, organic carbon content, and magnetic properties.
In this particular case, the students' work may help the town of Shutesbury make an important decision.
"This project is of particular interest to the town of Shutesbury." Cadieux explained. "In the late 1800s/early 1900s, a dam was built on the Saw Mill River, which doubled the size of the lake. Last year, this dam was deemed to be unsafe. As the town questions whether or not to repair the lake or lower lake levels, this study will hopefully provide them with further insight on the history of the lake that might aid in their decision-making process."