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Research about Wisconsin

Source-linked reports with geographic coverage including Wisconsin.

At least 181 records · Page 10Linked to original sources
USGS2020

Electrofishing encounter probability, survival, and dispersal of stocked age-0 Muskellunge in Wisconsin lakes

Boat electrofishing is often used to sample age-0 Muskellunge Esox masquinongy for indexing recruitment or evaluating stocking success. However, electrofishing samples typically result in low CPUE, prompting concerns regarding whether catch rates reflect actual abundance or whether boat electrofishing is generally ineffective for capturing age-0 Muskellunge (i.e., if fish are not being encountered by the gear). To address these concerns, we used radiotelemetry to evaluate the probability of encountering stocked age-0 Muskellunge (230–350 mm TL) during standardized fall electrofishing surveys in three Wisconsin lakes. Our approach also allowed us to evaluate short-term survival and dispersal from stocking locations. Despite limited dispersal (<2.5 km) from the stocking locations and relatively high short-term survival (75–94%) of radio-tagged fish, few age-0 Muskellunge were located within the path of the electrofishing boat (7–30%). Furthermore, the probability of encounter by boat electrofishing varied by as much as 6.3 times among lakes. Differences in encounter probability among lakes appeared to be related to lake basin and habitat characteristics. Overlays of electrofishing sampling effort and fish locations revealed that traditional shoreline electrofishing may not be an effective way of estimating age-0 Muskellunge CPUE. Modifications to electrofishing protocols, including increased effort in offshore areas and consideration of basin characteristics and habitat, may be needed to increase encounter probabilities and the utility of boat electrofishing for sampling age-0 Muskellunge.

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USGS2020

Genotyping-by-sequencing illuminates high levels of divergence among sympatric forms of coregonines in the Laurentian Great Lakes

Effective resource management depends on our ability to partition diversity into biologically meaningful units. Recent evolutionary divergence, however, can often lead to ambiguity in morphological and genetic differentiation, complicating the delineation of valid conservation units. Such is the case with the "coregonine problem," where recent postglacial radiations of coregonines into lacustrine habitats resulted in the evolution of numerous species flocks, often with ambiguous taxonomy. The application of genomics methods is beginning to shed light on this problem and the evolutionary mechanisms underlying divergence in these ecologically and economically important fishes. Here, we used restriction site-associated DNA (RAD) sequencing to examine genetic diversity and differentiation among sympatric forms in the Coregonus artedi complex in the Apostle Islands of Lake Superior, the largest lake in the Laurentian Great Lakes. Using 29,068 SNPs, we were able to clearly distinguish among the three most common forms for the first time, as well as identify putative hybrids and potentially misidentified specimens. Population assignment rates for these forms using our RAD data were 93%-100% with the only mis-assignments arising from putative hybrids, an improvement from 62% to 77% using microsatellites. Estimates of pairwise differentiation ( F ST : 0.045-0.056) were large given the detection of hybrids, suggesting that reduced fitness of hybrid individuals may be a potential mechanism for the maintenance of differentiation. We also used a newly built C. artedi linkage map to look for islands of genetic divergence among forms and found widespread differentiation across the genome, a pattern indicative of long-term drift, suggesting that these forms have been reproductively isolated for a substantial amount of time. The results of this study provide valuable information that can be applied to develop well-informed management strategies and stress the importance of re-evaluating conservation units with genomic tools to ensure they accurately reflect species diversity.

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USGS2020

Advanced biofilm analysis in streams receiving organic deicer runoff

Prolific heterotrophic biofilm growth is a common occurrence in airport receiving streams containing deicers and anti-icers, which are composed of low-molecular weight organic compounds. This study investigated biofilm spatiotemporal patterns and responses to concurrent and antecedent (i.e., preceding biofilm sampling) environmental conditions at stream sites upstream and downstream from Milwaukee Mitchell International Airport in Milwaukee, Wisconsin, during two deicing seasons (2009–2010; 2010–2011). Biofilm abundance and community composition were investigated along spatial and temporal gradients using field surveys and microarray analyses, respectively. Given the recognized role of Sphaerotilus in organically enriched environments, additional analyses were pursued to specifically characterize its abundance: a consensus sthA sequence was determined via comparison of whole metagenome sequences with a previously identified sthA sequence, the primers developed for this gene were used to characterize relative Sphaerotilus abundance using quantitative real-time PCR, and a Sphaerotilus strain was isolated to validate the determined sthA sequence. Results indicated that biofilm abundance was stimulated by elevated antecedent chemical oxygen demand concentrations, a surrogate for deicer concentrations, with minimal biofilm volumes observed when antecedent chemical oxygen demand concentrations remained below 48 mg/L. Biofilms were composed of diverse communities (including sheathed bacterium Thiothrix) whose composition appeared to shift in relation to antecedent temperature and chemical oxygen demand. The relative abundance of sthA correlated most strongly with heterotrophic biofilm volume (positive) and dissolved oxygen (negative), indicating that Sphaerotilus was likely a consistent biofilm member and thrived under low oxygen conditions. Additional investigations identified the isolate as a new strain of Sphaerotilus montanus (strain KMKE) able to use deicer components as carbon sources and found that stream dissolved oxygen concentrations related inversely to biofilm volume as well as to antecedent temperature and chemical oxygen demand. The airport setting provides insight into potential consequences of widescale adoption of organic deicers for roadway deicing.

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USGS2020

Phosphorus, nitrogen and dissolved organic carbon fluxes from sediments in freshwater rivermouths entering Green Bay (Lake Michigan; USA)

Transitional areas between ecosystem types are often active biogeochemically due to resource limitation changes. Lotic-to-lentic transitions in freshwaters appear active biogeochemically, but few studies have directly measured nutrient processing rates to assess whether processing within the rivermouth is important for load estimates or the local communities. We measured oxic fluxes of inorganic nitrogen and phosphorus and dissolved organic carbon (DOC) from sediments in two rivermouths of Green Bay (Lake Michigan, USA). Soluble reactive phosphorus (SRP) flux was positive in most cases (overall mean 1.74 mg SRP m − 2 day − 1 ), as was ammonium (NH 4 ) flux (40.6 mg NH 4 m − 2 day − 1 ). Partial least square regression (PLSR) indicated a latent variable associated with both sediment [loosely bound phosphorus (P), iron bound P, organic content] and water column properties [temperature, DOC:dissolved inorganic nitrogen (DIN) and DOC:SRP ratios (negatively)] that was moderately associated with variation in SRP flux. PLSR analysis also indicated several sediment characteristics were moderately related to NH 4 flux, especially organic content, density (negative), and porosity. Flux of nitrates/nitrites (NO X ) and DOC were positively associated with the water column concentrations of NO X and DOC and qualitative estimates of the labile, non-humic types of DOC. In early summer, water column NO X and DOC concentrations were high and labile DOC may have fueled denitrification, resulting in net flux into sediments of both NO X and DOC. By late summer, water column NO X and DOC were very low and both these constituents were fluxing out of sediments into the water column. Based on our estimates for the entire period from April through September, rivermouth sediments were a net source of SRP and DIN, with a DIN:SRP ratio of ~ 44 and a NH 4 :NO X > 1. We estimated that the sediments in the Fox rivermouth probably contributed a small proportion of the total Fox River load during the growing season 2016 (< 5%), but at times may have contributed as much as 14% of the daily load. Despite the small size of the Fox rivermouth (< 0.5% of the watershed area), these results indicate that at times sediments can contribute substantially to the overall delivery of nitrogen and phosphorus to the nearshore zone.

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USGS2020

Utilization of multiple microbial tools to evaluate efficacy of restoration strategies to improve recreational water quality at a Lake Michigan Beach (Racine, WI)

Hydro-meteorological conditions facilitate transport of fecal indicator bacteria (FIB) to the nearshore environment, affecting recreational water quality. North Beach (Racine, Wisconsin, United States), is an exemplar public beach site along Lake Michigan, where precipitation-mediated surface runoff, wave encroachment, stormwater and tributary outflow were demonstrated to contribute to beach advisories. Multiple restoration actions, including installation of a stormwater retention wetland, were successfully deployed to improve recreational water quality. Implementation of molecular methods (e.g. human microbial source tracking markers and Escherichia coli ( E. coli ) qPCR) assisted in identifying potential pollution sources and improving public health response time. However, periodic water quality failures still occur. As local beach managers reassess restoration measures in response to climatic changes, use of expanded microbial methods (including bacterial community profiling) may contribute to a better understanding of these dynamic environments. In this 2-year study (2015 and 2019), nearshore/offshore Lake Michigan, stormwater, and tributary samples were collected to determine if, 1) the constructed wetland (~50 m from the shoreline) continued to provide stormwater separation/retention and 2) mixing between onshore sources, Root River and Lake Michigan, was increasing due to rising precipitation/lake levels. Monthly rainfall totals were 1.5× higher in 2019 than 2015, coinciding with a 0.63 m lake-level rise. The prevalence of more intense, onshore winds also increased, facilitating interaction between potential reservoirs of FIB with nearshore water through wind driven waves and lake intrusion, e.g. beach sands and the adjacent Root River. While a strong relationship existed between wet weather wetland and North Beach nearshore E. coli concentrations (all sites), bacterial communities were strikingly different. Conversely, bacterial community overlap existed between the Root River mouth and nearshore/offshore sites. These results suggest the constructed wetland can accommodate the climate-related changes observed in this study. Future restoration activities could be directed towards upstream tributary sources in order to minimize microbial contaminants entering Lake Michigan.

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USGS2020

Groundwater model simulations of stakeholder-identified scenarios in a high-conflict irrigated area

This study investigated collaborative groundwater‐flow modeling and scenario analysis in the Little Plover River basin, Wisconsin, USA where an unconfined aquifer supplies groundwater for agricultural irrigation, industrial processing, municipal water supply, and stream baseflow. We recruited stakeholders with diverse interests to identify, prioritize, and evaluate scenarios defined as management changes to the landscape. Using a groundwater flow model, we simulated the top 10 stakeholder‐ranked scenarios under historically informed dry, average, and wet weather conditions and evaluated the ability of scenarios to meet government‐defined stream flow performance measures. Results show that multiple changes to the landscape are necessary to maintain optimum stream flow, particularly during dry years. Yet, when landscape changes from three scenarios—transferring water from the local waste water treatment plant to basin headwaters, moving municipal wells further from the river and downstream, and converting 240 acre (97 ha) of irrigated land to unirrigated land—were simulated in combination, the probability of meeting or exceeding optimum flows rose to 75, 65, and 34% at upper, mid, and lower stream gages, respectively, in dry climate conditions. Discussions with stakeholders reveal that the collaborative model and scenario analysis process resulted in social learning that built upon the existing complex and dynamic institutional landscape. The approach provided a forum for solution‐based discussions, and the model served as an important mediation tool for the development and evaluation of community‐defined scenarios in a high conflict environment. Today, stakeholders continue to work collaboratively to overcome challenges and implement voluntary solutions in the basin.

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USGS2020

Hatchling emergence ecology of Ouachita map turtles (Graptemys ouachitensis) on the lower Wisconsin River, Wisconsin, USA

Despite its biological importance in shaping both individual fitness and population structure, much remains to be learned about the hatchling emergence ecology of most freshwater turtles. Here, we provide some of the first details on these early life stages for the Ouachita map turtle ( Graptemys ouachitensis ) obtained during 2015–2017 along the lower Wisconsin River, Iowa County, Wisconsin, and integrate our results into related research within the genus Graptemys . Dedicated trail cameras over in situ turtle nests provided otherwise difficult to obtain observational data relevant to natural hatchling emergence without disturbing nests or hatchlings. In contrast to some earlier reports for Graptemys , hatchling emergence was mostly diurnal and synchronous, primarily in the morning soon after soil temperatures began to rise from overnight low values. Data suggest a temperature change model of cueing hatchling emergence, which may represent a local or regional adaptation to reduce nocturnal predation risks, mostly from raccoons ( Procyon lotor ), or may simply reflect default diurnal hatchling activity patterns when not affected by thermal constraints. Aside from predation, hatchlings on this small study site are affected by vegetative shading, leading to relatively long times to first emergence periods (mean, 82.3 d), low mean nest temperatures (25.9°C), and a likely male-biased sex ratio. These findings highlight the value of hatchling emergence studies in revealing important influences on population viability and in guiding appropriate habitat management in conservation efforts.

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USGS2020

Dispersal of hatchling Ouachita map turtles (Graptemys ouachitensis) from natural nests on the lower Wisconsin River, Wisconsin, USA

Despite its importance to individual fitness and population dynamics, the dispersal behaviors of most neonate freshwater turtles after nest emergence are poorly known. We studied the initial dispersal tendencies of neonate Ouachita map turtles ( Graptemys ouachitensis ) exiting natural nests during 2015–2017 along the Wisconsin River, Wisconsin. Overall, dispersal was nonrandom, and hatchlings largely oriented toward the nearest substantial vegetative cover, a woodland north of the nesting area. However, variation sometimes occurred in routes taken among hatchlings within a clutch. Directional changes within an individual's dispersal track, including route reversals, were also observed. As our work appears to be the first to use standalone trail cameras as a primary data-gathering tool for a hatchling dispersal study, it highlights the potential benefits and limitations of this technique for similar research.

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USGS2020

Investigating maternity roost selection by northern long-eared bats at three sites in Wisconsin

One of the North American bat species most impacted by white-nose syndrome (WNS) is the northern long-eared bat Myotis septentrionalis , which as a result has been listed under the Endangered Species Act. WNS was first detected in Wisconsin in 2014. Unfortunately, little is known regarding the ecology of M. septentrionalis in this state pre-WNS to guide management supporting post-WNS recovery efforts. The objectives of our research were to (1) assess characteristics of trees that are associated with roost tree selection and (2) investigate how characteristics of maternity colony networks compare to colonies in the eastern USA. We mist-netted at 3 sites in Wisconsin in 2015 and 2016, and affixed radio transmitters to 39 female M. septentrionalis . We tracked bats to 53 confirmed day roosts. We found that roost trees were larger, more decayed, and more likely to be in dominant canopy closure areas than random trees. Oaks Quercus spp. were used most frequently and in proportion to their availability in the landscape at 2 field sites, whereas invasive black locust Robinia pseudoacacia was used more than expected based on availability at another site. Overall, minimum convex polygon sizes for maternity roosts were variable (5.2 to 8.9 ha) but similar to values reported for other regions. However, network centrality was low, indicating equitable use of day roosts and more frequent roost switching compared to other regions. Our findings provide information that increasing availability of potential day roosts in the landscape during the reproductive period may improve recruitment, which may in turn mitigate some of the detrimental population effects from WNS.

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USGS2019

Brook trout (Salvelinus fontinalis) movement and survival after removal of two dams on the West Branch of the Wolf River, Wisconsin

Dam removals allow fish to access habitats that may provide ecological benefits and risks, but the extent of fish movements through former dam sites has not been thoroughly evaluated for many species. We installed stationary PIT antennas in 2016 and 2017 to evaluate movements and survival of brook trout Salvelinus fontinalis in the West Branch of the Wolf River (WBWR) in central Wisconsin following removal of two dams and channel modifications designed to promote fish movement. These changes provided access to lacustrine habitats that might provide suitable winter habitat or act as ecological sinks. We used multistate models to estimate transition probabilities between river sections, to determine whether brook trout: (a) moved between multiple river sections and (b) entered lacustrine habitats as seasonal refuges, but eventually returned to lotic habitat. We also used a Cormack-Jolly-Seber model to evaluate whether apparent survival of brook trout in the WBWR was comparable to other populations. Few fish moved among river sections or used lacustrine habitat (<5% of tagged fish); most brook trout remained in sections where they were initially tagged, potentially due to quality habitat located throughout the river. Like other studies, brook trout in the WBWR appear to experience high mortality based on low number of detections, few physical recaptures and an estimated eight-month apparent survival rate of 0.27. In scenarios where fish can already access suitable habitat, removal of dams may not result in substantial increases in fish movement and colonisation of newly accessible habitat may not occur immediately.

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USGS2019

Wind sheltering impacts on land-atmosphere fluxes over fens

Wetlands and their ability to mitigate climate change motivates restorative and protective action; however, scientific understanding of land-atmosphere interactions is restricted by our limited continuous observations of gaseous fluxes. Many wetlands are small in spatial scale and embedded in forested landscapes. Yet, little is known about how the relative sheltering of forests affects net carbon (C) and energy balance. Here, we analyze coterminous USGS and Ameriflux eddy covariance flux tower observations over three years in two shrub fens in Northern Wisconsin, one more sheltered (US-ALQ) than the other (US-Los). Unsurprisingly, the open site showed higher overall wind speeds. This should have implications for atmospheric fluxes in wetlands as wind-forced processes are essential in promoting gas exchange over water. While both sites had similar half-hourly net ecosystem exchange of CO2 (NEE) during daytime, there were significant differences in nighttime NEE, as well as in net radiation partitioning in early spring and late summer. Sensible heat (H) fluxes were smaller at the sheltered fen except for the months of July-September. In contrast, latent heat (LE) fluxes were higher in every month except July. Additionally, sheltered fen ecosystem respiration had a weaker linear correlation with air temperature (R: 0.08 versus 0.57 for the open fen). Our work suggests that canopy sheltering does not cause significant differences in half-hourly NEE during the day, but rather the largest differences such as lower CO2 emissions occur at nighttime due to higher variance at very low wind speeds. Sheltering also influenced direction of air flow, mean wind speeds in day versus night, energy balance, and sensible and latent heat fluxes. We discuss implications of these findings for wetland restoration.

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USGS2019

Vertical distribution of microplastics in the water column and surficial sediment from the Milwaukee River basin to Lake Michigan

Microplastic contamination was studied along a freshwater continuum from inland streams to the Milwaukee River estuary to Lake Michigan, and vertically from the water surface, water subsurface and sediment. Microplastics were detected in all 96 water samples and nine sediment samples collected. Results indicated a gradient of polymer presence with depth: low-density particles decreased from water surface to subsurface to sediment, and high-density particles had the opposite result. Polymer identification results indicated water surface and subsurface samples were dominated by low-density polypropylene particles and sediment samples were dominated by more dense polyethylene terephthalate particles. Of the five particle-type categories (fragments, films, foams, pellets/beads and fibers/lines), fibers/lines were the most common particle type and were present in every water and sediment sample collected. Fibers represented 45% of all particles in water samples and were distributed vertically throughout the water column regardless of density. Sediment samples were dominated by black foams (66%, identified as styrene-butadiene rubber, SBR) and to a lesser extent fibers/lines (29%) with approximately 89% of all the sediment particles coming from polymers with densities greater than 1.1 g cm-3. Results demonstrated polymer density influenced partitioning between water surface and subsurface and the underlying surficial sediment and the common practice of sampling only the water surface can result in substantial bias, especially in estuarine, harbor and lake locations where water surface concentrations tend to overestimate mean water column concentrations.

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USGS2019

Seasonal epilimnetic temperature patterns and trends in a suite of lakes from Wisconsin (USA), Germany and Finland

Epilimnetic temperatures from the early 1980s through 2017 were analyzed for 12 Wisconsin, German and Finnish lakes. Seasonal temperature metrics exhibited large interannual variability with trends differing among regions. In the Wisconsin lakes, only late summer and fall temperatures increased significantly. In the northeastern Germany lakes, temperatures increased in all seasons, but only significantly for some metrics. The Finnish lakes, which spanned the country’s latitude range, exhibited large spring temperature increases influenced by earlier ice-out; summer temperatures also increased significantly, but fall changes were varied. To elucidate longer-term epilimnetic temperature patterns, earlier records from 4 lakes were analyzed. For Lake Mendota (southern Wisconsin), spring and late fall temperatures increased modestly but significantly since 1894; summer temperatures also increased modestly due to a higher frequency of recent summers with warm temperatures and not from new record high temperatures. Trout Lake (northern Wisconsin) exhibited warm temperatures in some summers during the 1930s-1940s similar to warm temperatures in some recent summers. Air-water temperature relationships coupled with long-term regional air temperature data also indicated summer epilimnetic temperatures in the study lakes were likely as warm in the 1930s-1940s as in recent years. Lake data confirmed cooler epilimnetic temperatures occurred in many summers during the 1950s-1980s coincident with intervening cooler air temperatures during this period. Because epilimnetic temperatures have not increased monotonically since 1900, our study supports continued temperature monitoring in lakes with extensive historical data to better understand and project future effects of climate change on lake ecosystems.

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USGS2019

Isolation by a hydroelectric dam induces minimal impacts on genetic diversity and population structure in six fish species

Reduced connectivity created by artificial barriers can influence the genetic integrity of isolated subpopulations by reducing local population sizes and altering patterns of gene flow. We investigated the genetic impacts of one such barrier, the Prairie du Sac dam, Wisconsin, USA, using microsatellite data from six fish species with varying life history traits sampled above and below the dam. Contrary to many past studies in other systems, we did not detect any significant differences in genetic diversity between populations found above and below the Prairie du Sac dam. Our results also revealed low genetic differentiation ( F ST = 0–0.008) between populations above and below the dam for all species. In fact, we found that more genetic variation was partitioned among sampling years than between above and below dam populations for all but one of the species. Results from coalescent simulations designed to model our study system indicated that the genetic impacts of the dam will likely be detectable approximately 40–60 generations after the dam was constructed, and that it is possible to largely mitigate these impacts with a fish passage strategy that facilitates a migration rate of ≥ 1% between above and below dam populations. In summary, our findings suggest the genetic impacts of dams can be relatively minimal on short time scales, and that fish passage strategies can significantly reduce genetic impacts if designed appropriately.

Wisconsin↗
USGS2019

A simple method for simulating groundwater interactions with fens to forecast development effects

Protection of fens–wetlands dependent on groundwater discharge–requires characterization of groundwater sources and stresses. Because instrumentation and numerical modeling of fens is labor intensive, easy-to-apply methods that model fen distribution and their vulnerability to development are desirable. Here we demonstrate that fen areas can be simulated using existing steady-state MODFLOW models when the unsaturated zone flow (UZF) package is included. In cells where the water table is near land surface, the UZF package calculates a head difference and scaled conductance at these “seepage drain” cells to generate average rates of vertical seepage to the land. This formulation, which represents an alternative to blanketing the MODFLOW domain with drains, requires very little input from the user because unsaturated flow-routing is inactive and results are primarily driven by easily obtained topographic information. Like the drain approach, it has the advantage that the distribution of seepage areas is not predetermined by the modeler, but rather emerges from simulated heads. Beyond the drain approach, it takes account of intracell land surface variation to explicitly quantify multiple surficial flows corresponding to infiltration, rejected recharge, recharge and land-surface seepage. Application of the method to a basin in southeastern Wisconsin demonstrates how it can be used as a decision-support tool to first, reproduce fen distribution and, second, forecast drawdown and reduced seepage at fens in response to shallow pumping.

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USGS2019

Benthos and plankton of western Lake Michigan Areas of Concern in comparison to non-Areas of Concern for selected rivers and harbors, 2012 and 2014

Since their designation in the 1980s, Areas of Concern (AOCs) around the Great Lakes have been the focus of multi-State and international cleanup efforts that were needed after decades of human activity resulted in severely contaminated sediment, water-quality degradation, loss of habitat for aquatic organisms, and impaired public use. Although individual Great Lake States had been working to cleanup and mitigate environmental concerns, there was insufficient funding and little coordination between Federal and State efforts to address the large and complex set of problems. The Great Lakes Ecosystem Protection Act was passed in 2010, providing for comprehensive multi-State planning and dedicating Federal funds to accelerate cleanup and improve conditions at the AOCs with a particular focus on 14 beneficial use impairments, such as degradation of benthos and degradation of phytoplankton and zooplankton populations. Of Wisconsin’s five AOCs, four lie adjacent to Lake Michigan: Lower Menominee River, Lower Green Bay and Fox River, Sheboygan River, and Milwaukee Estuary (which includes the Milwaukee River, Menomonee River, Kinnickinnic River, and Milwaukee Harbor). The Wisconsin Department of Natural Resources has focused much of the cleanup on removal of contaminated sediment from these AOCs because many beneficial use impairments were a result of contaminated sediment. However, recent and quantitative assessments of the status of benthos and plankton at the AOCs were lacking. Therefore, to inform management decisions regarding the status of benthos and plankton at AOCs, the U.S. Geological Survey, in cooperation with the Wisconsin Department of Natural Resources (WDNR) and the U.S. Environmental Protection Agency, Great Lakes National Program Office, assessed the condition of benthos (benthic invertebrates) and plankton (zooplankton and phytoplankton) at sites in the 4 AOCs and at 6 less-degraded comparison sites (hereafter referred to as “non-AOCs”). The U.S. Geological Survey collected benthos, plankton, sediment, and water three times per year in 2012 and 2014 between May and August at the AOC and non-AOC comparison sites. Except for Lower Green Bay and Milwaukee Harbor, each AOC site or subsite was paired with sites in two non-AOCs with similar environmental conditions. Community-based metrics were compared using univariate and multivariate statistics between each AOC and the mean of all non-AOCs and between each AOC and the mean of two non-AOC comparison sites. Although it was assumed that, because of their designation as AOCs, the relationships would indicate degraded conditions compared to the non-AOC sites, several metrics for the AOCs did not significantly differ between the AOCs and non-AOCs in 2014. Of all four AOCs examined for benthos, only the Lower Menominee River AOC differed from its two non-AOC comparison sites; the density and richness of taxa in insect orders Ephemeroptera-Plecoptera-Trichoptera (mayflies, stoneflies, and caddisflies) in combined benthos (dredge and artificial substrate samples) were lower at the AOC. For plankton, the assemblages for zooplankton at the Fox River near Allouez (a subsite in the Lower Green Bay AOC) and the Milwaukee River differed from their two non-AOC comparison sites; density of zooplankton was lower at both AOCs. Metrics for combined benthos and combined phytoplankton (soft algae and diatoms) at the Sheboygan River AOC did not differ from the two non-AOC comparison sites; however, the diversity of zooplankton in 2014 was lower at the Sheboygan River AOC than at the two non-AOC comparison sites. The combination of univariate and multivariate statistics provided a way to evaluate the status of the aquatic assemblage at each AOC and whether or not the assemblage differed from less-degraded non-AOC comparison sites. Results for this study provide multiple lines of evidence for evaluating the status of aquatic communities at AOC sites in Wisconsin along the western Lake Michigan shoreline in 2012 and 2014.

Wisconsin↗
USGS2019

Complex response of sediment phosphorus to land use and management within a river network

Rivers affected by anthropogenic nutrient inputs can retain some of the phosphorus (P) load through sediment retention and burial. Determining the influence of land use and management on sediment P concentrations and P retention in fluvial ecosystems is challenging because of different stressors operating at multiple spatial and temporal scales. In this study, we sought to determine how land use and management influenced sediment P concentrations and P retention within a river network draining a watershed modified by mixed land use activities; the Fox River, Wisconsin, USA. Results show current land use had no detectable effect on sediment P concentrations, and only a small potential effect on P retention capacity. However, sites draining predominantly forested areas were associated with riverbed sediments less saturated in P, whereas sites draining mainly agricultural areas were more likely to release sediment-bound P. Current management actions, including the implementation of best management practices, had a small positive effect on P retention capacity but had no observed effect on sediment P concentrations. Our results suggest that fine riverbed sediment throughout the Fox River network is saturated with P and has the capability to release P when water column P concentrations are low. These P-saturated riverbed sediments represent a potential legacy effect of past land use disturbances on P dynamics in the Fox River network.

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