Geology topics

Research about Minnesota, Wisconsin

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

At least 19 recordsLinked to original sources

USGS2026

Occupancy rates of river otters (Lontra canadensis) in the St. Louis River Area of Concern

The St. Louis River Area of Concern (AOC), an estuarine system along the northeastern Minnesota-Wisconsin border, experienced significant ecological disturbances and degradation from unregulated industrial development during the 19 th and 20 th centuries. Recent restoration and remediation efforts in the AOC have led to substantial improvements in water quality, habitat, and fisheries populations. However, the status of wildlife populations following restoration efforts in the AOC remain largely unknown. We used remote cameras to estimate occupancy rates of river otters Lontra canadensis in the AOC and at two reference areas that had not been subjected to historical degradation. Because river otters occupy a high trophic level within these systems, we hypothesized that they would be an effective indicator species of overall habitat quality and recovery. Using data collected from June 2015 to February 2016, we developed single-season occupancy models for both summer and winter seasons. We found no differences in occupancy between the AOC and the reference sites, suggesting that river otter populations within the AOC were comparable to those in unaffected areas. Our results indicate that habitat restoration and remediation efforts in the St. Louis River estuary have been successful in promoting healthy wildlife populations.

Minnesota, Wisconsin↗

USGS2025

Water residence time and water depth influence on nutrient conditions, eutrophication endpoints and habitat quality in backwater lakes of a large floodplain river

Many eutrophication studies focus on the external supply of critical nutrients like nitrogen and phosphorus, but hydrology and geomorphology can enhance or dampen the effects of excessive nutrient supply. We studied six backwater lakes in the Upper Mississippi River that varied in water residence time and water depth. Eutrophication in these systems is responsible for negative impacts such as cyanobacterial blooms and toxicity, and floating plant and algal mats that disrupt recreational water uses. Increasing backwater residence time was associated with more nitrate removal and a greater likelihood of nitrogen limitation, as well as greater accumulations of duckweed. Backwaters with greater depth and lower nitrogen concentration had less likelihood of filamentous algal accumulations. The median water residence time of backwaters with low duckweed (11.7 days) and no filamentous algae (16.9 days) approached the 12-day target to maintain overwintering conditions in backwaters for fisheries survival, supporting that water residence times in this range would likely improve both winter and summer water quality. Mean depth in backwaters with low duckweed and no filamentous algae was ~1.3 m, while shallower backwaters were more likely to produce duckweed and filamentous algae mats. This indicates that deeper backwaters might reduce the likelihood of eutrophication impacts. Natural resource management at the local level may not always be able to answer global and regional threats, but habitat restoration of hydrology and geomorphology can possibly alleviate or reduce large-scale threats at the local level.

Minnesota, Wisconsin↗

USGS2025

Potential for hydroacoustic technology to describe physical habitat for imperilled native freshwater mussels

The lack of information on what constitutes suitable habitat for native freshwater mussels can limit restoration efforts. While many species reside in silt–sand–gravel substrates, species such as the Spectaclecase ( Cumberlandia monodonta ) and Salamander ( Simpsonaias ambigua ) mussels are thought to be associated with rock structures (e.g., wing dams and rock outcrops) in rivers. Our objective was to assess if hydroacoustic technology could be used to quantify physical habitat features for C. monodonta and S. ambigua . Multibeam echosounder, acoustic Doppler current profiler, sidescan sonar and underwater videography were used to quantify water depth, substrate hardness, bed roughness and bed slope of the riverbed, water velocity, shear velocity and the degree of rock clustering at six sites in the Saint Croix River, Minnesota. The sites varied in type of rock structures and relative abundances of both species. The strength of the associations among physical habitat features and mussel abundance was weak; R 2 values were typically < 0.5. However, species-specific differences in microhabitat were observed. For example, C. monodonta was typically observed at sites with higher velocity and shear velocity compared to S. ambigua . Mussel abundance was greatest at sites that contained crevices of sand surrounded by boulders and bedrock. Future refinements in hydroacoustic methods and post-processing computations could improve predictions. Information on habitat features from occupied and unoccupied sites could help resource managers characterize existing occupied habitats, identify potential reintroduction areas and implement restoration programmes.

Minnesota, Wisconsin↗

USGS2025

Beach nourishment response and recent morphological evolution of Minnesota Point, Lake Superior

Beach nourishments are a popular nature-based alternative to armoring for shoreline erosion mitigation, but nourishments have been criticized due to their environmental impacts and uncertain sustainability. Monitoring is often nonexistent or insufficient to constrain nourishment longevity and inform the renourishment interval required to maintain shoreline protection. This study uses a combination of topobathymetric surveys, high-resolution satellite-derived shorelines, and coastal engineering analyses to investigate the recent evolution of Minnesota Point and the fate of three beach nourishments constructed adjacent to littoral barriers. We use semi-empirical formulations for sediment compatibility, wave runup, and longshore sediment transport to inform the observed nourishment behavior. Minnesota Point experienced widespread foredune retreat averaging 7±2.8 m from 2009–2019 and 130,000 (70,000–140,000) m 3 of sediment was eroded during this interval. The 2019 nourishment at the Superior Entry was rapidly eroded by strong storms, losing >80% of the added beach width by the following spring. The 2020 and 2021 nourishments at the Duluth Entry retained >80% of the nourishment material at the time of the last topobathymetric survey in the fall of 2022, and satellite-derived shorelines indicate that the beach remained 10 m wider than pre-nourishment conditions at the end of 2023. Modeled longshore transport rates over the period 2009–2022 averaged 11,400 m 3 yr −1 northwestward at the Superior Entry, nearly 3x greater than the 4000 m 3 yr −1 southeastward transport modeled at the Duluth Entry. These observations show that differences in shoreline orientation, littoral sediment supply, and grain size compatibility can lead to contrasting beach nourishment longevities, and this study provides additional measurements of Minnesota Point’s long-term morphological change which can help inform coastal resiliency efforts.

Minnesota, Wisconsin↗

USGS2025

Exploring management and environment effects on edge-of-field phosphorus losses with linear mixed models

Evaluating how weather, farm management, and soil conditions impact phosphorus (P) loss from agricultural sites is essential for improving our waterways in agricultural watersheds. In this study, rainfall characteristics, manure application timing, tillage, surface condition, and soil test phosphorus (STP) were analyzed to determine their effects on total phosphorus (TP) and dissolved phosphorus (DP) loss using 125 site-years of runoff data collected by the University of Wisconsin Discovery Farms and Discovery Farms Minnesota. Three linear mixed models (LMMs) were then used to evaluate the influence of those factors on TP and DP losses: (1) a model that included all runoff events, (2) manured sites only, and (3) precipitation events only. Results show that the timing of manure application relative to the timing of a runoff event only had a marginal association with P loads and concentrations, although the majority of the runoff events were collected after 10 days of manure application. Tillage was as influential factor, with greater DP loads and concentrations associated with no-till, especially during frozen conditions. Fields in this study had high STP values, but the model results only showed positive associations between DP load and DP flow-weighted mean concentration (FWMC) loss at the 0- to 15-cm depth. The precipitation event LMM (which included precipitation characteristics) was the model that resulted in the largest R 2 value. While the predictive capacity of the LMMs was low, they did illuminate the relative importance of management and environmental variables on P loss, and can be used to guide future research on P loss in this region.

Minnesota, Wisconsin↗

USGS2025

Partial diel vertical migration and niche partitioning in Mysis revealed by stable isotopes

Diel vertical migration (DVM) is critical for moving energy and nutrients between surface and deep waters. Mysis sp. (Crustacea: Mysidae) facilitates this process by serving as predator and prey in both benthic and pelagic habitats. Mysis can also exhibit partial DVM (pDVM), where some individuals do not migrate into the pelagia at night or to the benthos during the day. However, whether Mysis pDVM is a fixed (i.e., same individuals migrate) or random (i.e., random individuals migrate) behavior remains unclear. To evaluate that, we tested whether Mysis exhibit pDVM and niche partitioning in Lake Superior by collecting Mysis from benthic and pelagic habitats day and night across depths ranging from 50 to 250 m and estimating their isotopic niche size (δ 13 C, δ 15 N; Corrected Standard Ellipse Area − SEA c ) and overlap among three life stages. At the population level, Mysis exhibited fixed pDVM structured by life stage. Benthic Mysis (12.9 ± 3.2 mm, mean ± SD) were larger than pelagic Mysis during night (9.6 ± 3.6 mm) and day (8.5 ± 3.6 mm). Adult Mysis (> 15 mm) had larger SEA c (1.8 ± 0.4 ‰ 2 ) compared to juveniles (< 10 mm; 0.3 ± 0.1 ‰ 2 ) and sub-adults (10–15 mm; 0.7 ± 0.2 ‰ 2 ), and their isotopic niche did not overlap with smaller life stages. Adults exhibited random pDVM (i.e., high isotopic niche overlap), whereas juveniles exhibited fixed pDVM (i.e., low overlap). Our observations indicate complex behaviors across and within Mysis life stages, likely due to varying pressures including size-selective predation, light and temperature thresholds, and nutritional requirements. Consequently, the benthic behavior of adult Mysis needs to be considered in monitoring programs.

Minnesota, Wisconsin↗

USGS2025

Disentangling the historical impacts of warming and fishing on exploited freshwater fish populations

Worldwide, exploited fish populations are increasingly affected by the combined effects of warming and fishing. Disentangling the relative effects of these factors is challenging yet crucial for designing management strategies. We used a temperature-dependent population dynamics model to assess the impacts of lake warming and fishing on 521 freshwater fish populations in the Midwestern United States—a transitional zone between cold- and warmwater species. Overall, most warmwater species (65% of populations) exhibited increases in productivity from warming, while slightly more than half of the cool-/cold-water species (53% of populations) experienced reduced productivity. Populations closer to their carrying capacity showed greater resilience to warming. For the majority of populations (92%), fishing had a more pronounced effect on population dynamics than warming during the time period examined. Therefore, while warming is likely to increasingly threaten many fish populations, effective local fishery management remains a key lever to mitigate these impacts.

Minnesota, Wisconsin↗

USGS2024

New tools for a legacy problem: How isotope tracers inform area of concern actions in the St. Louis River in Lake Superior

Numerous mercury (Hg) sources can contribute to biological burdens within the Great Lakes, including atmospheric deposition (e.g., precipitation), non-point source land runoff (e.g., watershed), and legacy contamination. Due to these different environmental entry points, it is often difficult to ascertain if legacy Hg contamination contributes to contemporary fish consumption advisories within Areas of Concern (AOCs), as designated by the United States-Canada Great Lakes Water Quality Agreement. In this study, we aimed to assess the contributions of legacy Hg to sediments in nearshore wetland habitats and co-located prey items (dragonfly larvae and yellow perch) within the St. Louis River AOC using Hg stable isotopes. We observed that nearshore sediments had the same Hg source portfolio as previously examined main channel sites. Furthermore, this data confirmed that two major Hg sources were contributing to sediments within nearshore regions of the St. Louis River AOC: legacy and watershed Hg. The contribution of legacy Hg was estimated in biota and demonstrated that up to 64% of the Hg in fish tissue in the lower estuary (St. Louis Bay) was from legacy sources, but that this percentage declined substantially when examining upstream regions of the AOC. These data indicate the influence of legacy Hg to the food web varies spatially within the St. Louis River. We further found that watershed Hg sources are an important Hg contributor to the St. Louis River, which likely applies to other impacted and unimpacted tributaries across the Great Lakes region.

Minnesota, Wisconsin↗

USGS2024

Characterizing the movement patterns of host fish, Hiodon spp., for Spectaclecase (Cumberlandia monodonta) in the St. Croix National Scenic Riverway (SACN)

The goal of this project is to assist recovery of Spectaclecase through increased understanding of the movement of their host fish (Hiodon spp.) within the SACN and adjacent Mississippi River. Our specific objectives are to: (1) evaluate the most suitable methods for tracking movement of Hiodon spp. and (2) characterize the temporal and spatial movements of Hiodon spp. within the SACN and downstream into the Mississippi River.

Minnesota, Wisconsin↗

USGS2023

An amplicon genotyping panel suitable for species identification and population genetics in sauger (Sander canadensis) and walleye (Sander vitreus)

Sauger ( Sander canadensis ) and walleye ( Sander vitreus ) are closely related North American fish species that are often managed by fishery agencies throughout their ranges. However, genotyping resources for sauger are presently limited to a small set of microsatellite loci. We evaluated whether primers in an existing walleye genotyping-in-thousands panel could amplify single nucleotide polymorphism loci (SNPs) in sauger. We identified 71 primer pairs that amplify 118 SNPs in both species. Allele frequency differences were large enough to confidently distinguish the species and identify hybrids. Additionally, we identified 41 loci with observed heterozygosity > 0.1 in sauger; these markers may be useful for simple population genetic analyses and parentage analysis when few contributors are present and for differentiating highly structured populations.

Minnesota, Wisconsin↗

USGS2023

Mercury isotope values in shoreline spiders reveal transfer of aquatic mercury sources to terrestrial food webs

The transfer of aquatic contaminants, including mercury (Hg), to terrestrial food webs is an often-overlooked exposure pathway to terrestrial animals. While research has implemented the use of shoreline spiders to assess aquatic to terrestrial Hg transfer, it is unclear whether Hg sources, estimated from isotope ratios, can be successfully resolved to inform site assessments and remedy effectiveness. To examine aquatic to terrestrial Hg transfer, we collected shoreline spiders ( Tetragnatha spp.) and aquatic insect larvae (suborder Anisoptera) across a mosaic of aquatic and shoreline habitats in the St. Louis River and Bad River, tributaries to Lake Superior. The fraction of industrial Hg in sediments was reflected in the δ 202 Hg values of aquatic dragonfly larvae and predatory fish, connecting benthic Hg sources to the aquatic food web. Shoreline spiders mirrored these aquatic Hg source signatures with highly positive correlations in δ 202 Hg between tetragnathids and dragonfly larvae ( r 2 = 0.90). Further assessment of different spider taxa (i.e., araneids and pisaurids) revealed that differences in prey consumption and foraging strategies resulted in isotope differences, highlighting the importance of spider taxa selection for Hg monitoring efforts.

Minnesota, Wisconsin↗

USGS2023

River geomorphology affects biogeochemical responses to hydrologic events in a large river ecosystem

Shifts in the frequency and intensity of high discharge events due to climate change may have important consequences for the hydrology and biogeochemistry of rivers. However, our understanding of event-scale biogeochemical dynamics in large rivers lags that of small streams. To fill this gap, we used high-frequency sensor data collected during four consecutive summers from a main channel and backwater site of the Upper Mississippi River. We identified high discharge events and calculated event concentration-discharge responses for both physical-chemical (nitrate, turbidity, and fluorescent dissolved organic matter) and biological (chlorophyll-a and cyanobacteria) constituents using metrics of hysteresis and slope. We found a range of responses across events, particularly for nitrate. Although fluorescent dissolved organic matter (FDOM) and turbidity exhibited more consistent responses across events, contrasting hysteresis metrics indicated that FDOM was flushed to the river from more distant sources than turbidity. Biological responses (chlorophyll a and cyanobacteria) differed more between sites than physical and chemical constituents. Lastly, we found that the event characteristics best explaining concentration responses differed between sites, with event magnitude more frequently related to responses in the main channel, and antecedent wetness conditions associated with response variation in the backwater. Our results indicate that event responses in large rivers are distinct across the diverse habitats and biogeochemical components of a large floodplain river, which has implications for local and downstream ecosystems as the climate shifts.

Minnesota, Wisconsin↗

USGS2023

Dissolved carbon export by large river systems is influenced by source area heterogeneity

Rivers and streams export inorganic and organic carbon derived from contributing landscapes and so downstream carbon fluxes are important quantitative indicators of change in ecosystem function and for the full accounting of terrestrial carbon budgets. Carbon concentration-discharge ( C-Q ) relationships in rivers provide important information about carbon source and behavior in watersheds and are useful for estimating carbon export. However, C-Q relationships are complex in large river systems because of spatial and temporal heterogeneity in carbon dynamics across the watershed and river networks. We quantified dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) fluxes in the Upper Mississippi River basin and investigated their relationships with land cover and hydrology. The magnitude of dissolved carbon yields ranged widely among stations, 0.6–5.7 g DOC m −2 yr −1 and 2.9–11.8 g DIC m −2 yr −1 . Spatial patterns in carbon fluxes were strongly related to land cover, with agricultural sites having high DIC/low DOC exports and forested and wetland areas having the opposite. DIC was always negatively related to discharge ( Q ), while the DOC- Q relationship varied with land cover. Differential behavior of carbon across the basin resulted in Q having a weak relationship with DOC and DIC at the basin outlet. Hence, there is a need to improve understanding of headwater terrestrial-to-aquatic carbon connections in order to improve basin-to-continental-scale carbon export estimates. Our results demonstrate that quantitative understanding of carbon export by large rivers can be improved by incorporating stream network information, such as the timing, location, and source of constituent flux, rather than relying solely upon relationships between constituent behavior and seasonality or discharge at the basin outlet.

Minnesota, Wisconsin↗

USGS2023

Evaluate propagation efforts and determine dispersal patterns for Quadrula fragosa from tagged, artificially infested host fish (Ictalurus punctatus) in the St. Croix National Scenic Riverway (SACN)

The St. Croix National Scenic Riverway (SACN) has been the site of propagation and restoration efforts for two federally endangered unionid mussels: Higgins’ Eye, Lampsilis higginsii and Winged Mapleleaf (WML), Quadrula fragosa. Since about 2000, government agencies have collaboratively developed techniques to successfully propagate Higgins’ Eye and reintroduce the captive-reared subadult mussels into rehabilitated habitats in the upper Mississippi River Basin and several tributaries, including the SACN. However, propagation efforts for the WML have had limited success from 2003 to present. The population of WML in the SACN has high value because it is physically isolated and genetically distinct from four southern populations, and it is the only known self-sustaining population within the upper Mississippi River. Unionids have a complex reproductive cycle that includes a parasitic larval stage (glochidia) that requires species-specific fish hosts. WML are one of the few species that are fall, short-term (~6 weeks) brooders—brooding begins at end of August. In the SACN, Channel Catfish ( Ictalurus punctatus ) are the only known host for WML and glochidia are assumed to overwinter on their host fish and detach the following spring. Research has shown that holding hatchery reared channel catfish that are infested with WML glochidia in cages, either in situ or in a hatchery, over winter has been a challenge due to high fish mortality; rearing juveniles after transformation has also resulted in high mortality rates and juvenile loss (Wege et al. 2007). The importance of the overwintering parasitic period and the overall health of the host fish for successful transformation of juvenile WML is unknown, but these key criteria could play an important role in successful propagation efforts. This research has three objectives: (1) compile historic data from >14 years of Q. fragosa propagation efforts into a searchable database to identify potential knowledge gaps that could be limiting its success, (2) explore in situ and ex situ propagation techniques to optimize production of Q. fragosa juveniles, and (3) characterize the movement pattern of Channel Catfish that are artificially inoculated with the SACN strain of Q. fragosa to identify potential juvenile release survey locations in future years.

Minnesota, Wisconsin↗

USGS2023

Hydroacoustic mapping for native freshwater mussel and host fish habitats using Quadrula fragosa and Ictalurus punctatus as a case study

No abstract available.

Minnesota, Wisconsin↗

USGS2022

Riparian spiders: Sentinels of polychlorinated dibenzo-p-dioxin and dibenzofuran-contaminated sediment

Polychlorinated dibenzo- p -dioxin and polychlorinated dibenzofuran (PCDD/F) are persistent, toxic, and bioaccumulative. Currently, PCDD/F monitoring programs primarily use fish and birds with potentially large home ranges to monitor temporal trends over broad spatial scales; sentinel organisms that provide targeted sediment contaminant information across small geographic areas have yet to be developed. Riparian orb-weaving spiders, which typically have small home ranges and consume primarily adult aquatic insects, are potential PCDD/F sentinels. Recent studies have demonstrated that spider tissue concentrations indicate the source and magnitude of dioxin-like chlorinated compounds in contaminated sediments, including polychlorinated biphenyls (PCBs). Our aim in the present study was to assess the utility of riparian spiders as sentinels for PCDD/F-contaminated sediments. We measured PCDD/F (total [Σ] and homologs) in surface sediments and spiders collected from three sites within the St. Louis River basin (Minnesota and Wisconsin, USA). We then compared (1) patterns in ΣPCDD/F concentrations between sediment and spiders, (2) the distribution of homologs within sediments and spiders when pooled across sites, and (3) the relationship between sediment and spider concentrations of PCDD/F homologs across 13 stations sampled across the three sites. The ΣPCDD/F concentrations in sediment (mean ± standard error 286 591 ± 97 614 pg/g) were significantly higher than those in riparian spiders (2463 ± 977 pg/g, p < 0.001), but the relative abundance of homologs in sediment and spiders were not significantly different. Spider homolog concentrations were significantly and positively correlated with sediment concentrations across a gradient of sediment PCDD/F contamination ( R 2 = 0.47, p < 0.001). Our results indicate that, as has been shown for other legacy organic chemicals like PCBs, riparian spiders are suitable sentinels of PCDD/F in contaminated sediment.

Minnesota, Wisconsin↗

USGS2022

The role of hydraulic and geomorphic complexity in predicting invasive carp spawning potential: St. Croix River, Minnesota and Wisconsin, United States

Since they were first introduced to the United States more than 50 years ago, invasive carp have rapidly colonized rivers of the Mississippi River Basin, with detrimental effects on native aquatic species. Their continued range expansion, and potential for subsequent invasion of the Great Lakes, has led to increased concern for the susceptibility of as-yet uncompromised lotic and lentic systems in the central United States. Because invasive carp eggs and larvae must drift in the river current for the first several days following spawning, numerical drift modeling has emerged as a useful technique for determining whether certain river systems and reaches have the potential to support suspension-to-hatching survival of invasive carp eggs, a critical first step in recruitment. Here we use one such numerical modeling approach, the Fluvial Egg Drift Simulator (FluEgg), to estimate bighead carp ( Hypophthalmichthys nobilis ) egg hatching success and larval retention in a 47.8-kilometer (km) reach of the multi-thread St. Croix River, Minnesota and Wisconsin, United States. We explore three approaches for obtaining the hydraulic data required by FluEgg, parameterizing the model with either (a) field hydraulic data collected within the main channel during a high-flow event, or hydraulic data output from a one-dimensional hydrodynamic model with both (b) steady, and (c) unsteady flows. We find that the three approaches, along with the range of water temperatures and discharge used in simulations, produce vastly different predictions of streamwise transport and in-river egg hatching probability (0% for field data, 0 to 96% for steady-state hydraulic modeling, and 1.8 to 65% for unsteady modeling). However, all FluEgg simulations, regardless of the source of hydraulic data, predicted that no larvae reach the gas bladder inflation stage within the study reach where nursery habitat is abundant. Overall, these results indicate that the lower St. Croix River is suitable for invasive carp spawning and egg suspension until hatching for a range of discharge and water temperatures. These results highlight the role of complex channel hydraulics and morphology, particularly multi-thread reaches, and their inclusion in ecohydraulic-suitability modeling to determine susceptibility of river systems for invasive carp reproduction. Our work also emphasizes the scientific value of multi-dimensional hydrodynamic models that can capture the spatial heterogeneity of flow fields in geomorphically complex rivers. This work may help to guide management efforts based on the targeted monitoring and control and improve invasive carp egg and larvae sampling efficiency.

Minnesota, Wisconsin↗

USGS2022

Evaluate propagation efforts and determine dispersal patterns for Quadrula fragosa from tagged, artificially infested host fish (Ictalurus punctatus) in the St. Croix National Scenic Riverway (SACN)

Minnesota, Wisconsin↗