TRACKING THE SUCCESS OF REMEDIATION IN TEMPERATE LAKES USING BIOLOGICAL AND GEOCHEMICAL PROXIES

Effective management of freshwater resources is critical to biological conservation and sustainable economic development. This research aims to establish new biological and geochemical tools to measure the success of remediation measures to combat cultural eutrophication of freshwater lakes. In Wisconsin, we took surface sediment (“core-top”) samples from three impacted and three remediated lakes. These remediated lakes had undergone treatment with alum -KAl(SO₄)₂·12H₂O- in the 1970s to reduce nutrient loading. Our surface sediment samples were collected up to twenty meters from shore at five meter increments and in two replicate transects, yielding eight samples per lake. From these surface sediments, we analyzed agreement between the living and dead ostracode assemblages as well as potentially bioavailable heavy metals concentrations in the sediments. In the field, sediment samples were inculcated with Rose Bengal -C₂₀H₄Cl₄I₄O_5•2Na- to identify ostracodes living at the time of collection. Previous work has shown that low live/dead agreement of ostracodes in lacustrine environments, like mollusk in marine environments, is associated with human impacted environments, while high live/dead agreement is associated with environments relatively free of human influence. Here we test: 1) whether the remediated lakes show high live/dead agreement like the “pristine” lakes and 2) if heavy metals in the surface sediments show distinct signatures of human impact and remediation. All valves from adult ostracodes living-at-the-time-of collection and dead were identified to species. Live/dead agreement was tested in two ways: Jaccard-Chao, measuring agreement in species composition, and rho, measuring rank-abundance correlation. We found that live/dead agreement in remediated lakes is high, like unimpacted lakes, owing to the success of the remediation effort to reduce nutrient loading almost a half century ago. Determination of trace heavy metals in the sediment samples used microwave digestion (EPA 3051) and ICPMS for analysis. The results were compared to heavy metal concentrations from X-Ray Fluorescence of sediment cores from similar lakes, but inconsistencies revealed likely metal leaching from the sediments by the Rose Bengal solution during storage.