Landscape-lake interactions, including anthropogenic effects in modern human-dominated landscapes, are essential elements of our understanding of aquatic community ecology. This study links land use (six categories) to the aquatic environment (30 water chemistry, lake morphology, and vegetation variables) and to zooplankton community richness (32 common taxa) and composition in 73 small and shallow lakes of southeastern Wisconsin, USA. The sites differed most according to two environmental variables (principal components analysis [PCA] ordination): the presence/absence of riparian vegetation and the water source (whether ground or atmospheric). Shallow lakes in different land use categories (reference, urban, and agricultural) differed significantly in terms of the two major environmental variables, especially presence of riparian and aquatic vegetation.Reference sites were characterized by the most vegetation and the highest zooplankton richness. Agricultural sites with wide riparian vegetative buffer strips (Ͼ30 m) had significantly more zooplankton taxa than agricultural lakes with narrow buffer strips. A nonmetric multidimensional scaling (NMS) ordination of zooplankton community composition suggested a single community among land use categories, with some variation related to vegetation and the water source. The first NMS axis was correlated with PCA1 axis (vegetation) and with zooplankton taxon richness, and the second axis was correlated with PCA2 (water source). The third axis was not strongly correlated with any of the measured environmental factors, suggesting that an unmeasured factor related to disturbance was also important in determining taxon composition. Our analysis supports the hypothesis that zooplankton community structure (taxon richness and composition) is indirectly associated with land use, via the effect of land use on vegetation and the hydrological continuum.

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Waterfowl and limnological data were monitored on Waterfowl Production Area (WPA) wetlands in northwestern Wisconsin over a 6-yr period to determine the impact of macroinvertebrates and macrophytes on waterfowl utilization. Interrelationships between limnological conditions and Waterfowl Breeding Pair Densities (BPDs reported as pairs/ha water surface) were analyzed using correlation and general linear model analysis techniques.Annual changes in waterfowl BPDs differed between wetlands according to differences in the structure of macrophyte communities and basin morphometry. The strength of associations differed between the two dominant waterfowl species. In a wetland dominated by dense stands of submersed vegetation, annual fluctuations in blue-winged teal (Anas discors) BPDs corresponded directly with changes in macrophyte biomass, but not with changes in macroinvertebrate density. In a nearby less densely vegetated wetland of similar water chemistry and trophic status, fluctuations in teal BPDs corresponded directly with changes in macroinvertebrate density, but not with changes in macrophyte biomass. These associations occurred despite a significant positive correlation between macroinvertebrates and macrophyte biomass in the latter habitat. Annual fluctuations in mallard (Anas platyrhynchos) BPDs were not correlated significantly with either macrophyte biomass or macroinvertebrate density in either wetland.

/ A map of summer total phosphorus in lakes was compiled recently for a three-state area of the upper Midwest for purposes of identifying regional patterns of total phosphorus in lakes and attainable lake trophic state. Spatial patterns in total phosphorus from approximately 3000 lakes were studied in conjunction with maps of geographic characteristics that tend to affect phosphorus balance in lakes to identify regions of similarity in phosphorus concentrations in lakes or similarity in the mosaic of values as compared to adjacent areas. While degrees of relative homogeneity are apparent at many scales, the map was designed at a scale that would yield regions with sufficient homogeneity to be useful for lake management throughout the area. In this study, data from 210 lakes in a 1560-mi 2 area in northwestern Wisconsin, sampled by the Wisconsin Department of Natural Resources in the spring of 1988 (subsequent to the compilation of the phosphorus map), were examined to: (1) substantiate the existence of the regions depicted on the map in northwest Wisconsin, (2) determine the nature and relative precision of the regional boundaries, (3) determine the relative importance of natural and anthropogenic watershed characteristics, lake types, lake area, and lake depth in explaining within-region differences in lake phosphorus, and (4) demonstrate how the regions might be used by local lake managers.Lakes are a highly valued environmental resource in much of the United States. Like many other types of resources, such as streams and forests,-the types, numbers, and quality of lakes vary considerably from one part of the country to another as do the characteristics that cause within-region variability in quality. Generally small, clear alpine glacial lakes are typical in the western mountainous states; numerous, mostly solution or sink-hole lakes formed in karst topography are tound in Florida; thousands of continental glacial lakes of various sizes and qualities are scattered throughout much of the upper Midwest and Northeast; and impoundments can be found in all of these

Over a five year period we compared summer temperature and dissolved oxygen (DO) at 10 sites within dense beds of Mvriovhvllum svicatum L. to an unvegetated reference site in a moderately eutrophic Wisconsin lake. Average surface temperatures in the Eurasian watermilfoil beds were significantly elevated in two of the five years, while bottom temperatures were significantly depressed each year. Dissolved o gen concentrations in surface layers of the bed were elevated by at ? least 1 mg L during roughly 30-40% of site-date visits, while DOs in the bottom layers were depressed on the average more than 50% of monitoring visits. Both depressed DOs and low DOs ( < 3.0 mg L -') in bottom layers were positively correlated with average annual air temperatures but were not directly related to variations in milfoil biomass. Dissolved oxygen and temperature appeared to be most severely impacted at shallow, densely vegetated sites close to shore.