Acidification mechanisms in a small, clear-water, low pH seepage lake, Upper Peninsula of Michigan
Lewin JC. 1991. Acidification mechanisms in a small, clear-water, low pH seepage lake, Upper Peninsula of Michigan. Michigan Technological University
Legion Lake in Pictured Rocks National Lakeshore, MI is an acidic (pH = 4.8), poorly buffered closed-basin lake (no streams flowing in or out). Several factors indicate that the lake has not been acidified recently. Water chemistry data was collected from the lake, from soil moisture in the lake's watershed, from precipitation under various tree canopy types in the watershed, and from direct precipitation over a period of five years. A lake sediment core was extracted to establish rates of organic deposition and the presence of heavy metals, and core samples were set aside for pollen analysis, lead-210 dating, and a diatom (algae)-inferred pH profile. Invertebrates and fish were sampled and identified. Data indicates that except for large storms when there is some run-off, the lake receives most of its moisture directly from precipitation. Comparison of the chemistry of watershed moisture and lake water indicates that there is little groundwater exchange with the lake water due to an impermeable layer of lake sediment. Organic acids produced in the sphagnum bogs surrounding Legion Lake are a possible long-term contributor to its acidity. Sulfur and lead were found in high concentrations in the cored sediments from the late 1800s to the present. Maps illustrating the watershed area are included.
- Type
- Academic
- Authors
- Lewin, Jeffrey
- Date of Issue
- 1991-04-29
- Publisher
- Michigan Technological University
- Units
- PIRO
- Keywords
- Acidity, Bogs, Fish, Heavy Metals, Invertebrates (Invertebrata), Lakes & Ponds, Legion Lake, Limnology, Map, Sediment, Thesis, Water Chemistry