Ecological Status of a Retired Mine Lake in a Protected Dune Ecosystem

Abstract

Ottawa Sands Lake (OSL) is a retired mine lake located in a protected dune ecosystem adjacent to Lake Michigan in west Michigan, USA. Development activities are planned for the lake and surrounding land, potentially threatening the lake’s ecological health. We conducted a baseline study of water quality and macroinvertebrates, combined with exclusion cage experiments to examine the role of predation. Our results revealed the lake’s littoral zone had very good water quality with low phosphorus (mean SRP: < 5 µg/L; mean TP: < 10 µg/L) and nitrogen (mean NO3 -: 38-190 µg/L; mean NH3: 8-19 µg/L, excluding deep hole) concentrations, high dissolved oxygen (>9.5 mg/L, excluding deep hole), and low chlorophyll a (< 12 µg/L, except for one sampling date) concentrations. The macroinvertebrate community was dominated by nine families, with the Chironomidae being most abundant. Three environmental factors were significantly related, albeit weakly, to macroinvertebrate community structure: specific conductivity, total dissolved solids, and ammonia. The exclusion cages did not result in a statistically significant difference in macroinvertebrate community structure, although high variance may have masked differences. Overall, OSL is a high-quality system but development plans, including the installation of a paved trail around the lake and the implementation of a non-motorized boating program, may result in changes. The baseline conditions outlined in this work will allow lake managers to assess the impact of development activity, and also add to the limited database regarding the limnology of retired mine lakes around the globe.