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LANDSCAPE INFLUENCES ON LAKE CHEMISTRY AND OSTRACOD COMMUNITY STRUCTURE OF SMALL DIMICTIC LAKES IN SOUTHERN WISCONSIN DIMICTIC LAKES
Citation:
ALLEN, P. LANDSCAPE INFLUENCES ON LAKE CHEMISTRY AND OSTRACOD COMMUNITY STRUCTURE OF SMALL DIMICTIC LAKES IN SOUTHERN WISCONSIN DIMICTIC LAKES. Presented at ERD Athens Laboratory Seminar Series, Athens, GA, September 20, 2007.
Description:
The natural land cover patterns that characterize the southern part of Wisconsin are legacies of a
glaciated past. Land cover pattern and geomorphology control the hydrologic connections between water
resources and the land by which ecosystems, including lakes are organized. Landscapes are the
combined result of natural forces and human action. Anthropogenic disturbance changes land patterns
and modifies natural landscape functions (e.g. the flow of nutrients); it induces chemical changes in lakes
that directly and indirectly affect aquatic community structure and function and the ecological services
that lakes provide.
I collected water and sediment from 12 small dimictic lakes during the spring and late summer of
2002 and 2003. I analyzed samples for trace elements, productivity surrogates, and atrazine. Further, I
assessed land cover patterns at local (catchment, riparian) and regional (watershed) spatial scales and used
correlation analyses, regression analyses, and nonmetric multidimensional scaling (NMS) ordination
techniques to (1) evaluate sources of atrazine in the study lakes, (2) explore the relationships between
water chemistry and landscape attributes different scales, and (3) test for associations between ostracods
(benthic microcrustaceans) and water chemistry (including trace elements and productivity surrogates)
together with land use to identify the important productivity measures and potential indicator species of
lake and landscape condition and macrophyte occurrence.
Atrazine was found in ecologically relevant concentrations in water (0.70 µg/L) and sediment
(130 µg/L), which warrants further investigation. Landscape attributes associated with undesirable water
quality attributes (e.g. nutrient enrichment, increased sedimentation) were correlated with agriculture,
whereas desirable water quality (e.g. decreased dissolved solids, nutrients and sediment), was correlated
with forests and wetlands. Total dissolved solids, lake depth, and chlorophyll a differentially explain most
of the variability in both species richness and abundance of ostracods. Species richness and the number
of ostracod feeding guilds were highest in lakes of intermediate depth due to an increase in habitat
complexity. Additionally, invasive macrophyte species associated with human impacts (e.g. riparian
agriculture) reduce optimal ostracod habitat and may limit their distributions. Thus, southeastern
Wisconsin lakes integrate the effects of geomorphology and land use on water chemistry and
hydrobiology.