Geology topics

Research about Wisconsin and Michigan

Source-linked reports with geographic coverage including Wisconsin and Michigan.

4 recordsLinked to original sources

USGS2015

Habitat, not resource availability, limits consumer production in lake ecosystems

Food web productivity in lakes can be limited by dissolved organic carbon (DOC), which reduces fish production by limiting the abundance of their zoobenthic prey. We demonstrate that in a set of 10 small, north temperate lakes spanning a wide DOC gradient, these negative effects of high DOC concentrations on zoobenthos production are driven primarily by availability of warm, well-oxygenated habitat, rather than by light limitation of benthic primary production as previously proposed. There was no significant effect of benthic primary production on zoobenthos production after controlling for oxygen, even though stable isotope analysis indicated that zoobenthos do use this resource. Mean whole-lake zoobenthos production was lower in high-DOC lakes with reduced availability of oxygenated habitat, as was fish biomass. These insights improve understanding of lake food webs and inform management in the face of spatial variability and ongoing temporal change in lake DOC concentrations.

Wisconsin and Michigan↗

USGS2015

Evaluating the importance of abiotic and biotic drivers on Bythotrephes biomass in Lakes Superior and Michigan

The ability of planktivorous fishes to exert top-down control on Bythotrephes potentially has far-reaching impacts on aquatic food-webs, given previously described effects of Bythotrephes on zooplankton communities. We estimated consumption of Bythotrephes by planktivorous and benthivorous fishes, using bioenergetics and daily ration models at nearshore (18 m), intermediate (46 m), and offshore (110 m) depths along one western Lake Superior transect (April, and September-November) and two northern Lake Michigan transects (April, July, September). In Lake Superior, consumption (primarily by cisco Coregonus artedi) exceeded Bythotrephes production at all offshore sites in September-November (up to 396% of production consumed) and at the intermediate site in November (842%) with no evidence of consumption nearshore. By comparing Bythotrephes biomass following months of excessive consumption, we conservatively concluded that top-down control was evident only at the offshore site during September-October. In Lake Michigan, consumption by fishes (primarily alewife Alosa pseudoharengus) exceeded production at nearshore sites (up to 178%), but not in deeper sites (< 15%). Evidence for top-down control in the nearshore was not supported, however, as Bythotrephes never subsequently declined. Using generalized additive models, temperature, and not fish consumption, not zooplankton prey density, best explained variability in Bythotrephes biomass. The non-linear pattern revealed Bythotrephes to increase with temperature up to 16 °C, and then decline between 16 and 23 °C. We discuss how temperature likely has direct negative impacts on Bythotrephes when temperatures near 23 °C, but speculate that predation also contributes to declining biomass when temperatures exceed 16 °C.

Wisconsin and Michigan↗

USGS2015

Diet shifts by planktivorous and benthivorous fishes in northern Lake Michigan in response to ecosystem changes

In Lake Michigan, diets of planktivorous and benthivorous fishes have varied over the past decades, in part owing to food web changes. To update diet information and compare them to a similar effort in 1994–1995, we analyzed the diets of seven benthivorous and planktivorous fish species collected along two northern Lake Michigan transects that spanned nearshore (18 m), intermediate (46 m), and offshore (91, 110, 128 m) bottom depths during spring, summer, and autumn of 2010. Calanoid copepods (e.g., Limnocalanus macrurus, Leptodiaptomus sicilis, and Senecella calanoides) comprised a majority of the diets in at least one season for all sizes of alewife (Alosa pseudoharengus), bloater (Coregonus hoyi), and rainbow smelt (Osmerus mordax). Similarly, Mysis diluviana was the highest proportion in at least one season for large sizes of alewife, bloater, and rainbow smelt, as well as slimy sculpin (Cottus cognatus) and deepwater sculpin (Myoxocephalus thompsonii). The diets of the remaining two species, ninespine stickleback (Pungitius pungitius) and round goby (Neogobius melanostomus), were dominated by herbivorous cladocerans or dreissenid mussels, respectively. Interspecific diet overlap was minimal at 18 and 46 m. In offshore waters, however, overlap was relatively high, driven by frequent consumption of Mysis. Relative to 1994–1995, 2010 diets revealed increased feeding on calanoid copepods and Mysis, with corresponding declining consumption of Diporeia spp. and herbivorous cladocerans. Relative diet weight was also higher in 1994–1995 than in 2010 for small and large bloater and both sculpin species. We hypothesize that the shifts in diets are reflective of community-level changes in invertebrate prey availability.

Wisconsin and Michigan↗

USGS2011

Effects of dams in river networks on fish assemblages in non-impoundment sections of rivers in Michigan and Wisconsin, USA

Regional assessment of cumulative impacts of dams on riverine fish assemblages provides resource managers essential information for dam operation, potential dam removal, river health assessment and overall ecosystem management. Such an assessment is challenging because characteristics of fish assemblages are not only affected by dams, but also influenced by natural variation and human-induced modification (in addition to dams) in thermal and flow regimes, physicochemical habitats and biological assemblages. This study evaluated the impacts of dams on river fish assemblages in the non-impoundment sections of rivers in the states of Michigan and Wisconsin using multiple fish assemblage indicators and multiple approaches to distinguish the influences of dams from those of other natural and human-induced factors. We found that environmental factors that influence fish assemblages in addition to dams should be incorporated when evaluating regional effects of dams on fish assemblages. Without considering such co-influential factors, the evaluation is inadequate and potentially misleading. The role of dams alone in determining fish assemblages at a regional spatial scale is relatively small (explained less than 20% of variance) compared with the other environmental factors, such as river size, flow and thermal regimes and land uses jointly. However, our results do demonstrate that downstream and upstream dams can substantially modify fish assemblages in the non-impoundment sections of rivers. After excluding river size and land-use influences, our results clearly demonstrate that dams have significant impacts on fish biotic-integrity and habitat-and-social-preference indicators. The influences of the upstream dams, downstream dams, distance to dams, and dam density differ among the fish indicators, which have different implications for maintaining river biotic integrity, protecting biodiversity and managing fisheries.

Wisconsin and Michigan↗