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Research about Michigan, Wisconsin

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

At least 19 recordsLinked to original sources
USGS2026

Unraveling protracted modification of Archean and Paleoproterozoic crust in central Laurentia, Penokean orogen, with garnet and accessory mineral geochronology and microstructural analysis

Proterozoic metamorphism and deformation of the southern margin of the Superior craton in the Lake Superior region is attributed to the Penokean orogeny (1890−1830 Ma). This model includes a period of crustal inversion in which Archean basement blocks were exhumed through overlying Paleoproterozoic strata, producing the corridor of gneiss domes that parallels the trend of the Penokean orogen across the northern Midcontinent, USA. However, recent geologic mapping and 40 Ar/ 39 Ar geochronology challenge this interpretation, suggesting instead that the gneiss dome structures reflect younger episodes of tectonic activity along the southern margin of Laurentia. In absence of integrated pressure-temperature-time-deformation constraints for these rocks, interpretations are largely limited to their final cooling history, making it difficult to both identify the tectonic forces that shaped the architecture of the Penokean orogenic belt and assess the extent to which later Proterozoic tectonism modified the southern Superior craton. We address this problem with an approach joining thermodynamic modeling, garnet and accessory mineral geochronology, and microstructural analysis for several metamorphic rocks across the gneiss dome corridor. The U-Pb ages of titanite reveal that the Proterozoic geometries of exhumed basement gneiss domes are governed by preexisting Archean structures. Garnet Lu-Hf geochronology constrains the timing of prograde-to-peak metamorphism in the Penokean orogenic belt. Granulite facies metamorphism is related to the final stages of the Penokean orogeny at 1837 Ma and localized in a belt of high-grade rocks near a major Penokean suture. Garnet Lu-Hf ages of samples adjacent to gneiss domes reflect regional metamorphism following the accretionary phase of the Penokean orogeny, between 1825 Ma and 1782 Ma, which we suggest reflects continued crustal thickening related to convergence farther south during this time interval. Combination of garnet microstructures and Sm-Nd ages reflects later exhumation of gneiss domes and buried metasedimentary rocks by ca. 1750 Ma, consistent with previously published 40 Ar/ 39 Ar cooling ages across the region. Reset Lu-Hf and Sm-Nd garnet ages and U-Pb ages of syn-kinematic titanite reflect reactivation of primary Penokean structures during this period of basement uplift. These data document significant modification of the Penokean orogen and the Archean crust of the southern Superior province between 1800 Ma and 1700 Ma. Tectonic activity during this interval coincides with collisional events recognized in western Laurentia, suggesting that the period immediately following the Penokean orogeny may be a broadly important time for crustal growth and modification in proto-North America.

Michigan, Wisconsin↗
USGS2025

Muskellunge spawning habitat characteristics and availability in Green Bay, Lake Michigan

Objective Habitat degradation has been associated with the loss of many self-sustaining Muskellunge Esox masquinongy populations, including those in Green Bay, where stocking has provided an exceptional trophy fishery but restoration goals include establishing self-sustaining populations and there is little evidence of natural recruitment. Our objectives were to determine whether (1) Muskellunge spawning locations and occurrence of successful hatching were related to a suite of habitat characteristics, (2) proportions of Muskellunge spawning in or outside of tributaries to lower Green Bay were different, and (3) Muskellunge showed spawning site fidelity. Methods From 2017 to 2019, adult Muskellunge ( N = 60) were surgically implanted with radio and acoustic transmitters to identify spawning locations, where we measured a suite of habitat variables and attempted to collect eggs and larvae. Side-scan sonar was used to quantify the amount of habitat available to Muskellunge for egg deposition in the Fox and Menominee rivers, which are tributaries to Green Bay. Results Muskellunge eggs were collected at 58 locations, but only two larvae were collected from a single location. Bottom slope, depth, distance to shore, gravel substrate, organic matter, and dissolved oxygen best predicted the presence of Muskellunge eggs. We determined that little habitat associated with Muskellunge egg deposition was available in the Fox and Menominee rivers. However, approximately half of tagged Muskellunge appeared to spawn outside of tributaries. Muskellunge in Green Bay displayed moderate spawning site fidelity. Conclusions Our results suggest that successful hatching occurs at very low levels and the lack of suitable Muskellunge spawning habitat in Green Bay tributaries may be limiting natural reproduction. Changes in spatial allocation of stocked fish and enhancement of known spawning locations may increase egg deposition and subsequent natural reproduction.

Michigan, Wisconsin↗
USGS2025

Reproductive contribution of lake sturgeon transferred upstream of dams on a Great Lakes tributary

Dam construction contributes to declines in the distribution and abundance of many fishes. Increasing connectivity through adult transfer can be demographically and genetically beneficial, but assessing the effects resulting from transfer can be difficult if resident fish exist upstream. Genotypes of adult and larval lake sturgeon ( Acipenser fulvescens ) were used to quantify contributions to larval recruitment from adults transferred upstream of dams on the Menominee River, USA. We evaluated whether transfer timing, sex, and adult size were associated with the odds of reproduction. Elevator transfer operations in Fall 2019, Fall 2020, and Spring 2021 resulted in 152 male and 81 female lake sturgeon transferred upstream. In 2020 and 2021, 580 and 518 larvae were genotyped. We found that 86% (201/233) of adults reproduced and 62.3% (684/1098) of offspring had transferred parents. In total, we estimated that 392 resident adults contributed to offspring production. Mixed matings accounted for 53% of offspring genotyped, increasing levels of offspring genetic diversity relative to offspring produced from resident-only matings. Transferring adults may be a viable restoration alternative for other iteroparous fish in river systems where connectivity to spawning areas has been impeded.

Michigan, Wisconsin↗
USGS2024

Partly cloudy with a chance of mosquitoes: Developing a flexible approach to forecasting mosquito populations

Climate-induced shifts in mosquito phenology and population structure have important implications for the health of humans and wildlife. The timing and intensity of mosquito interactions with infected and susceptible hosts are a primary determinant of vector-borne disease dynamics. Like most ectotherms, rates of mosquito development and corresponding phenological patterns are expected to change under shifting climates. However, developing accurate forecast of mosquito phenology under climate change that can be used to inform management programs remains challenging despite an abundance of available data. As climate change will have variable effects on mosquito demography and phenology across species it is vital that we identify associated traits which may explain the observed variation. Here, we review a suite of modeling approaches that could be applied to generate forecasts of mosquito activity under climate change and evaluate the strengths and weaknesses of the different approaches. We describe four primary life-history and physiological traits that can be used to constrain models and demonstrate how this prior information can be harnessed to develop a more general understanding of how mosquito activity will shift under changing climates. Combining a trait-based approach with appropriate modeling techniques can allow for the development of actionable, flexible, and multi-scale forecasts of mosquito population dynamics and phenology for diverse stakeholders.

Michigan, Wisconsin↗
USGS2024

Great Lakes mallard population dynamics

Breeding mallard ( Anas platyrhynchos ) populations in the Great Lakes region (Michigan, Minnesota, Wisconsin, USA) declined by >40% between 2000–2022 based on abundance data collected during spring aerial surveys. Mallards are an important waterfowl species in this region, where an estimated 60–80% of the mallard harvest is composed of locally banded birds. Extensive population monitoring datasets are available for mallards, presenting an opportunity to address complex questions such as estimating productivity at large spatial and temporal scales, identifying the effects of harvest on mallard demography, quantifying mechanisms for harvest compensation, and integrating multiple datasets to quantify the demographic drivers of population change. Our objective was to simultaneously examine factors affecting demographic parameters and their relative contribution to Great Lakes mallard population dynamics. We used 32 years of banding, band recovery, and aerial survey data collected for mallards from Michigan and Wisconsin to develop an integrated population model (IPM). We used age ratios at banding to estimate productivity, band recoveries from hunter-harvested birds to estimate annual survival and cause-specific mortality (i.e., harvest or non-hunting), and modeled abundance using aerial survey and demographic parameter estimates from 1991–2022. The IPM results indicated the decline in Great Lakes mallard abundance was caused by increased non-hunting mortality and a decline in productivity. Productivity varied spatially but temporally declined with the loss of Conservation Reserve Program area. Moreover, our productivity assessment provided evidence of density dependence in reproduction. Non-hunting mortality was 3.5–6.7 times and 1.3–4.2 times greater than harvest mortality for adult and juvenile female mallards, respectively, indicating environmental factors during spring and summer, not harvest, most greatly influenced annual mortality for female mallards. Our IPM reduced uncertainty in the factors affecting Great Lakes mallard population dynamics and indicated management actions that address non-hunting mortality and productivity would be most effective in increasing Great Lakes mallard abundance.

Michigan, Wisconsin↗
USGS2024

Classification of lakebed geologic substrate in autonomously collected benthic imagery using machine learning

Mapping benthic habitats with bathymetric, acoustic, and spectral data requires georeferenced ground-truth information about habitat types and characteristics. New technologies like autonomous underwater vehicles (AUVs) collect tens of thousands of images per mission making image-based ground truthing particularly attractive. Two types of machine learning (ML) models, random forest (RF) and deep neural network (DNN), were tested to determine whether ML models could serve as an accurate substitute for manual classification of AUV images for substrate type interpretation. RF models were trained to predict substrate class as a function of texture, edge, and intensity metrics (i.e., features) calculated for each image. Models were tested using a manually classified image dataset with 9-, 6-, and 2-class schemes based on the Coastal and Marine Ecological Classification Standard (CMECS). Results suggest that both RF and DNN models achieve comparable accuracies, with the 9-class models being least accurate (~73–78%) and the 2-class models being the most accurate (~95–96%). However, the DNN models were more efficient to train and apply because they did not require feature estimation before training or classification. Integrating ML models into benthic habitat mapping process can improve our ability to efficiently and accurately ground-truth large areas of benthic habitat using AUV or similar images.

Michigan, Wisconsin↗
USGS2023

Low Kirtland’s Warbler fledgling survival in Wisconsin plantations relative to Michigan plantations

The Kirtland’s Warbler ( Setophaga kirtlandii ) is a formerly endangered habitat specialist that breeds mainly in young jack pine ( Pinus banksiana ) forests in northern Lower Michigan, USA. The species is conservation-reliant and depends on habitat management. Management actions have primarily focused on creating jack pine plantations, but the species also breeds in red pine ( Pinus resinosa ) plantations in central Wisconsin, USA. However, the plantations were not intended as breeding habitat and have suboptimal pine densities. While nesting success is similar between low-density red pine plantations and optimal jack pine habitat, it is not clear if low-density red pine plantations support high fledging survival. If high-quality nesting and post-fledging habitat are not synonymous, fledgling survival and breeding population recruitment may be low. We characterized survival, habitat use, and movement patterns of dependent Kirtland’s Warbler fledglings in Wisconsin red pine plantations and compared fledgling survival between Wisconsin and Michigan. Mayfield cumulative survival estimates at 30 days post-fledging were 0.20 for Wisconsin fledglings and 0.43–0.78 for Michigan fledglings. Logistic exposure cumulative survival estimates for Wisconsin fledglings were 0.23–0.34 at 30 days post-fledging. Fledglings in Wisconsin used areas where vegetation cover and density of red and jack pine were high relative to available areas but not at greater proportions than what was available. Our findings demonstrate that red pine plantations with low pine densities were not equally suitable as nesting and post-fledging habitat, as fledgling survival rates were low. We hypothesize that reduced habitat structure, and not particular pine species, likely contributed to reduced fledgling survival in Wisconsin. Thus, we recommend including red pine as a component in managed Kirtland’s Warbler habitat only if tree densities approach optimal levels.

Michigan, Wisconsin↗
USGS2022

Biofouling of a unionid mussel by dreissenid mussels in nearshore zones of the Great Lakes

In North America, native unionid mussels are imperiled due to factors such as habitat degradation, pollution, and invasive species. One of the most substantial threats is that posed by dreissenid mussels, which are invasive mussels that attach to hard substrates including unionid shells and can restrict movement and feeding of unionids. This dreissenid mussel biofouling of unionids varies spatially in large ecosystems, such as the Great Lakes, with some areas having low enough biofouling to form effective refugia where unionid mussels might persist. Here, we measured biofouling on mussels suspended in cages over the growing season (generally first week in June to last week of August) over 3 years in nearshore areas in Lake Erie (2014–2016), Lake Michigan (Grand Traverse Bay, 2015 and Green Bay, 2016), and Lake Huron (2015). Biofouling varied substantially by years within Lake Erie, with increasingly higher biofouling rates each year. Although dreissenid mussels are present throughout these lakes, we observed very low biofouling in Grand Traverse Bay (Lake Michigan) and Saginaw Bay (Lake Huron), with no dreissenid mussels in 8 of 9 sites across these two bays. Sampling in the rivermouth of the Fox River (Wisconsin) and the Maumee River (Ohio) both showed very high biofouling in areas adjacent to the outlet of these tributaries into Green Bay and Maumee Bay (Lake Erie), respectively. These watersheds are dominated by agriculture, and we would expect high growth of primary producers (i.e., mussel food) and primary consumers (unionids and zebra mussels) in these areas compared to the other sampled bays or the open waters of the Great Lakes.

Michigan, Wisconsin↗
USGS2022

High-density genomic data reveal fine-scale population structure and pronounced islands of adaptive divergence in lake whitefish (Coregonus clupeaformis) from Lake Michigan

Understanding patterns of genetic structure and adaptive variation in natural populations is crucial for informing conservation and management. Past genetic research using 11 microsatellite loci identified six genetic stocks of lake whitefish ( Coregonus clupeaformis ) within Lake Michigan, USA. However, ambiguity in genetic stock assignments suggested those neutral microsatellite markers did not provide adequate power for delineating lake whitefish stocks in this system, prompting calls for a genomics approach to investigate stock structure. Here, we generated a dense genomic dataset to characterize population structure and investigate patterns of neutral and adaptive genetic diversity among lake whitefish populations in Lake Michigan. Using Rapture sequencing, we genotyped 829 individuals collected from 17 baseline populations at 197,588 SNP markers after quality filtering. Although the overall pattern of genetic structure was similar to the previous microsatellite study, our genomic data provided several novel insights. Our results indicated a large genetic break between the northwestern and eastern sides of Lake Michigan, and we found a much greater level of population structure on the eastern side compared to the northwestern side. Collectively, we observed five genomic islands of adaptive divergence on five different chromosomes. Each island displayed a different pattern of population structure, suggesting that combinations of genotypes at these adaptive regions are facilitating local adaptation to spatially heterogenous selection pressures. Additionally, we identified a large linkage disequilibrium block of ~8.5 Mb on chromosome 20 that is suggestive of a putative inversion but with a low frequency of the minor haplotype. Our study provides a comprehensive assessment of population structure and adaptive variation that can help inform the management of Lake Michigan's lake whitefish fishery and highlights the utility of incorporating adaptive loci into fisheries management.

Michigan, Wisconsin↗
USGS2022

Lake Sturgeon movement after trap and transfer around two dams on the Menominee River, Wisconsin-Michigan

Fish behavior after passage or transfer around dams is a critical component in determining whether the goals of these efforts are achieved, but these behaviors are often poorly understood. An elevator was constructed in the lowermost hydroelectric dam on the Menominee River, Wisconsin–Michigan; it is the first elevator specifically designed to capture Lake Sturgeon Acipenser fulvescens for upstream transfer above two dams, providing access to high-quality spawning and early life habitat. Our objectives were to determine whether (1) Lake Sturgeon transferred upstream remained upstream for at least one spawning opportunity; (2) spawning opportunity, time to reach the next dam upstream, and residency in different segments of the river were related to sex, capture method (elevator versus electrofishing), and season of transfer; and (3) the probability of fish transitioning back downstream of the two dams varied among months. We evaluated posttransfer behaviors of 139 Lake Sturgeon that were captured in the elevator or by electrofishing, implanted with acoustic transmitters, transferred upstream (in spring or fall) from fall 2014 to spring 2017, and monitored until fall 2018 using 20–23 stationary acoustic receivers deployed throughout the river. Most Lake Sturgeon (91%) remained upstream for at least one spawning opportunity. The probability of remaining for one spawning opportunity was not related to sex, fish capture method, or season of transfer. Residency times within the two impoundments and time to reach the next dam upstream varied among individual fish. A multistate model indicated that monthly survival after upstream transfer was high and that Lake Sturgeon typically remained above both dams in late fall to early spring, with most downstream movements occurring in April and May. Our results indicate that Lake Sturgeon transferred upstream have the potential to contribute offspring that may help to bolster the Lake Sturgeon population in Lake Michigan, but additional research may help in determining whether these contributions occur.

Michigan, Wisconsin↗
USGS2021

Projected changes of regional lake hydrologic characteristics in response to 21st century climate change

Inland lakes are socially and ecologically important components of many regional landscapes. Exploring lake responses to plausible future climate scenarios can provide important information needed to inform stakeholders of likely effects of hydrologic changes on these waterbodies in coming decades. To assess potential climate effects on lake hydrology, we combined a previously published spatially explicit, processed-based hydrologic modeling framework implemented over the lake-rich landscape of the Northern Highlands Lake District within the United States with an ensemble of climate change scenarios for the 2050s (2041–2070) and 2080s (2071–2100). Model results quantify the effects of climate change on water budgets and lake stage elevations for 3692 lakes and highlight the importance of landscape and hydrologic setting for the response of specific lake types to climate change. All future climate projections resulted in loss of ice cover and snowpack as well as increased evaporation, but variability in climate projections (warmer conditions, wet winters combined with wet or dry summers) interacted with lake characteristics and landscape position to produce variable lake hydrologic changes. Water levels for drainage lakes (lakes with substantial surface water inflows and outflows) showed nearly no change, whereas minimum water levels for seepage lakes (minimal surface water fluxes) decreased by an average of up to 2.64 m by the end of the 21st century. Our physically based modeling approach is parsimonious and computationally efficient and can be applied to other lake-rich regions to investigate interregional variability in lake hydrologic response to future climate scenarios.

Michigan, Wisconsin↗
USGS2021

Using uncrewed aerial vehicles for identifying the extent of invasive Phragmites australis in treatment areas enrolled in an adaptive management program

Higher spatial and temporal resolutions of remote sensing data are likely to be useful for ecological monitoring efforts. There are many different treatment approaches for the introduced European genotype of Phragmites australis , and adaptive management principles are being integrated in at least some long-term monitoring efforts. In this paper, we investigated how natural color and a smaller set of near-infrared (NIR) images collected with low-cost uncrewed aerial vehicles (UAVs) could help quantify the aboveground effects of management efforts at 20 sites enrolled in the Phragmites Adaptive Management Framework (PAMF) spanning the coastal Laurentian Great Lakes region. We used object-based image analysis and field ground truth data to classify the Phragmites and other cover types present at each of the sites and calculate the percent cover of Phragmites , including whether it was alive or dead, in the UAV images. The mean overall accuracy for our analysis with natural color data was 91.7% using four standardized classes (Live Phragmites , Dead Phragmites , Other Vegetation, Other Non-vegetation). The Live Phragmites class had a mean user’s accuracy of 90.3% and a mean producer’s accuracy of 90.1%, and the Dead Phragmites class had a mean user’s accuracy of 76.5% and a mean producer’s accuracy of 85.2% (not all classes existed at all sites). These results show that UAV-based imaging and object-based classification can be a useful tool to measure the extent of dead and live Phragmites at a series of sites undergoing management. Overall, these results indicate that UAV sensing appears to be a useful tool for identifying the extent of Phragmites at management sites.

Michigan, Wisconsin↗
USGS2020

Occupancy and detectability of northern long-eared bats in the Lake States Region

The northern long‐eared bat ( Myotis septentrionalis ) is one of the bat species most affected by white‐nose syndrome. Population declines attributed to white‐nose syndrome contributed to the species’ listing as federally threatened under the 1973 Endangered Species Act. Although one of the most abundant Myotine bats in eastern North America prior to white‐nose syndrome, little is known about northern long‐eared bats in the upper Midwest, USA. We assessed the habitat associations of the northern long‐eared bats on a regional scale using occupancy models that accounted for uncertainty in nightly detection to provide needed information on the distribution as white‐nose syndrome has recently arrived in this area. We monitored bat activity using zero‐crossing frequency‐division bat detectors for 10–15 nights at 20 detector sites at each of 3 sampling areas in Michigan, USA, and 6 sampling areas in Wisconsin, USA, stratified by mesic and xeric habitat types. We constructed northern long‐eared bat nightly detection histories for our occupancy analysis using maximum likelihood estimates from 2 commercially‐available automated identification programs: Kaleidoscope and Echoclass. We sampled for a total of 2,174 detector‐nights. Both Kaleidoscope and Echoclass identified northern long‐eared bat passes on 110 detector‐nights, whereas on 1,968 detector‐nights neither program identified a northern long‐eared bat call. Only one program or the other identified northern long‐eared bat calls on 206 detector‐nights, indicating an overall agreement rate of 35% on nights when calls were detected. We analyzed these data using an occupancy analysis accounting for the potential for false positives to assess the relationship between northern long‐eared bat presence and habitat characteristics. Our analyses indicated that the probability of a false positive at a site was low (0.015; 95% CI 0.009–0.021), and detection probability, but not occupancy, declined from 2015 to 2016 for sites in Wisconsin sampled in both years. Occupancy was positively associated with distance into the forest interior (distance from nearest road).

Michigan, Wisconsin↗
USGS2020

Genetic structure of Smallmouth Bass in the Lake Michigan and Upper Mississippi River drainages relates to habitat, distance, and drainage boundaries: Smallmouth bass population genetic structure

Analysis of genetic connectivity helps to define stock boundaries and provides information on interpopulation dynamics, such as migration and spawning site fidelity. We used 16 microsatellite loci to describe the genetic population structure of 1,215 Smallmouth Bass Micropterus dolomieu from 32 sites throughout the upper Mississippi River and Lake Michigan watersheds. We found that Smallmouth Bass populations formed two genetically distinct units separated by the Mississippi River–Lake Michigan drainage boundary. Smallmouth Bass from the Lake Michigan drainage could be parsimoniously grouped into two or six genetically distinct units that largely corresponded with either river or lake habitats, while fish from the Mississippi River drainage grouped into two, six, or nine genetic units that were mostly associated with watershed boundaries. In the Lake Michigan and Mississippi River drainages, relative migration was limited between lake and river sites, suggesting that gene flow between neighboring sites with different habitat attributes can be low. Our research provides a higher‐resolution assessment of Smallmouth Bass genetic structure in a core portion of the species’ range and provides strong evidence that Smallmouth Bass populations are structured at small spatial scales that are potentially associated with habitat type. These results demonstrate the importance of evaluating genetic structure at small spatial scales and adopting management strategies that preserve genetic diversity of black bass populations at both the watershed level and the habitat level.

Michigan, Wisconsin↗
USGS2020

Defining the need for genetic stock assignment when describing stock demographics and dynamics: An example using Lake Whitefish in Lake Michigan

Genetic stock assignment is not routinely used when describing the dynamics and demographics of individual stocks supporting mixed-stock fisheries, and capture location and timing are often used as alternative assignment methods. However, variation in stock demographics and dynamics may not be accounted for if stock assignments based on capture location or timing do not accurately reflect genetic assignments. We used Lake Whitefish Coregonus clupeaformis in Lake Michigan as a model fishery to determine whether stock mixing could undermine efforts to describe stock status when using October capture location as a proxy for genetic stock assignment. Accuracy of stock assignments based on October capture location ranged from 54% to 100% among management zones. Metrics describing length and age distributions, weight at length, fecundity, and growth varied among genetic stocks. Stock-specific metrics were typically similar between stock assignment methods (capture location versus genetics) because only one or two genetic stocks were collected in most locations and the majority of those fish were from spatially proximal stocks with similar metrics. However, more extensive mixing of Lake Whitefish stocks has been documented; thus, using capture location for stock assignment could result in incorrect conclusions regarding stock status and harvest management depending on stock composition. Ambiguity in genetic stock assignments was a problem in two management zones, where between 23% and 42% of Lake Whitefish did not assign to a specific stock with a probability of at least 0.70. In the future, using genomic techniques rather than microsatellites may provide different conclusions regarding genetic stock structure; these differences could affect the accuracy of using capture location for stock assignment. Use of capture location as a proxy for genetic stock assignment may not be warranted for all mixed-stock fisheries but may be appropriate when stock mixing is limited or is restricted to stocks with consistently similar characteristics.

Michigan, Wisconsin↗
USGS2020

Distribution of niclosamide following granular Bayer applications in lentic environments

Temporal and spatial distribution of niclosamide in the water column and sediment were evaluated after the application of granular Bayluscide in six lentic sea lamprey ( Petromyzon marinus ) larval assessment plots. Water and sediment were collected 0.25, 1, 3, 5, and 7 hours after application and were analyzed for niclosamide, the active ingredient in granular Bayluscide. Water samples were collected from five heights in the water column (1 cm, 13 cm, 26 cm, 1/2 water column, and water surface) at five locations inside and four locations 10 m outside of each assessment plot. Sediment was collected from 18 locations within each plot. Niclosamide water concentrations inside and outside of the plots did not vary by depth but did vary between plots and by time. Niclosamide water concentrations also varied by sampler location outside of the plots. Following granular Bayluscide applications the mean niclosamide concentration in water for all levels, within the plots, decreased from 0.12 mgL -1 (SD = 0.12 mgL -1 ) at 15 minutes to 0.061 mgL -1 (SD = 0.040 mgL -1 ) at hour 1. The mean niclosamide concentration in the top 4 cm of sediment was 2.9 mgkg -1 (SD = 2.4 mgkg -1 ) 15 minutes after application and was 1.3 mgkg -1 (SD = 1.8 mgkg -1 ) at hour 7. Concentrations in all sediment samples ranged from < 0.001 to 30.730 mgkg -1 and varied between the six plots. Niclosamide concentrations measured in sediment samples were more than 1 order of magnitude greater than in the water and varied spatially by over 4 orders of magnitude.

Michigan, Wisconsin↗
USGS2019

Seasonal patterns in hydrochemical mixing in three Great Lakes rivermouth ecosystems

Rivermouth ecosystems in the Laurentian Great Lakes represent complex hydrologic mixing zones where lake and river water combine to form biologically productive areas that are functionally similar to marine estuaries. As urban, industrial, shipping, and recreational centers, rivermouths are the focus of human interactions with the Great Lakes and, likewise, may represent critical habitat for larval fish and other biota. The hydrology and related geomorphology in these deltaic systems form the basis for ecosystem processes and wetland habitat structure but are poorly understood. To this end, a multidisciplinary team of scientists examined hydrogeomorphic structure and lake-tributary mixing in rivermouths using water chemistry, stable isotopes, and current profiling over a five-month period. Results showed that the maximum depth of the rivermouth ecosystem influenced mixing, with temperature-related, density-dependent wedging and layering that isolated lake water below river water occurring in deeper systems. The inherent size of the rivermouth ecosystem, local geomorphology, and human modifications such as shoreline armoring and dredging influenced mixing by altering the propensity for density differences to occur. The improved scientific understanding and framework for characterizing hydrogeomorphic processes in Great Lakes rivermouths across a disturbance gradient is useful for conservation, management, restoration, and protection of critical habitats needed by native species.

Michigan, Wisconsin↗