Geology topics

Research about Great Lakes

Source-linked reports with geographic coverage including Great Lakes.

At least 19 recordsLinked to original sources

USGS2026

A framework for investigating fish population density responses to habitat fragmentation

Globally, fish populations that rely on rivers are being fragmented by in-stream barriers, but it is unclear how pervasive any negative population responses to fragmentation are. We developed a modeling framework for estimating density responses of fishes upstream and downstream of in-stream barriers and applied it to learn how low-head dams have influenced fish assemblages in 24 Great Lakes tributaries. Of the 29 species modeled, we found strong evidence for increased (n = 6 species) and decreased population densities (n = 6 species) in habitat upstream of low-head dams, while we only found strong evidence for population increases downstream of dams (n = 16 species). The time required for 50% of the dam-induced change to fish population density to occur, t 50 , was on the order of decades; mean t 50 was 41 years in habitat downstream of low-head dams and 21 years in upstream habitat. Estimates of t 50 suggest that negative effects occurred faster than positive effects. However, the power of this comparison remains limited because evidence for the logistic population growth model used to derive t 50 was strong for only 1 of 29 fish species. We propose that different mechanisms account for the responses observed, with positive responses driven by changes in assemblage structure and negative responses driven by decreased immigration. Our research demonstrates how frameworks considering metapopulation dynamics and the potential for time lags between barrier construction and fish population responses can advance understanding of how in-stream barriers structure the distribution and abundance of fish populations in rivers.

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USGS2026

Effects of turbulence-inducing baffles on passage performance of brook trout, white sucker, and sea lamprey: Implications for conservation and control

Invasive sea lamprey ( Petromyzon marinus ) control in the Great Lakes is ongoing. Installing passive selective passage structures could reduce costs, yet there is a need to evaluate such methods under realistic hydraulic conditions to inform designs. In this study, we evaluated the swimming performance of brook trout ( Salvelinus fontinalis ), white sucker ( Catostomus commersonii ), and sea lamprey under manipulated flows and baffle configurations in a 35 m flume lined with substrate preventing attachment. Using accelerated failure time models, we examined ascent distance (Dmax) under two slopes (1% and 3%) and velocities from 0.25–3.0 m s⁻¹. Responses varied by species: white sucker had the greatest Dmax, especially at 1% slope, whereas sea lamprey, despite lacking paired fins/rays, occasionally exceeded white sucker at 3% with small spoiler baffles and bare substrate. Contrary to common perception, brook trout, the only salmonid in this study, performed less well than the other two species. Across species, higher velocities impaired performance, with declines linked to energy dissipation (EDF). Findings show how hydraulic structures shape species-specific passage.

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USGS2026

A genomic tool to tackle cryptic diversity demonstrates the potential for off-target use of GT-seq panels

A comprehensive understanding of life history is vital to successful species conservation and management. When different life history stages are accompanied by considerable morphological or cryptic variation, such as the egg and larval phases exhibited by most fishes, genomic tools are essential for identifying species so that early-life ecology questions can be studied. Genotyping-in-thousands by sequencing (GT-seq) has recently emerged as a targeted and efficient approach for species identification. We leveraged existing genomic and transcriptomic data to develop a GT-seq panel capable of differentiating the members of the Coregonus artedi complex, a radiation of salmonids in the Laurentian Great Lakes whose members are indistinguishable with mitochondrial DNA barcoding loci and are the focus of bi-national conservation initiatives. Our panel of 494 loci was able to assign fishes in the C. artedi complex to species and lake. We examined cross-amplification in other coregonines with overlapping distributions and found that congeneric Lake Whitefish ( C. clupeaformis ) cross-amplified at 94% of loci and confamilial Round and Pygmy Whitefish ( Prosopium spp.) cross-amplified at 42% and 38% of loci, respectively. We adapted bioinformatic probes to account for Prosopium -specific variants including 22 new SNPs and developed a whitelist of 428 SNPs capable of distinguishing these whitefishes. Finally, we demonstrated performance by identifying 3066 coregonine larvae and juveniles collected in spring 2019–2021 from Lake Superior. These results hold promise for future insights into the species-specific ecology of early life coregonines and demonstrate the flexibility of GT-seq panels, which may cross-amplify hundreds of informative genome-wide loci in related taxa.

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USGS2026

Decoding the oxidative digestion mechanism for polystyrene nanoplastic detection in the Great Lakes using a customizable Raman spectral processing algorithm

Despite the concerns surging around nanoplastics (NPs) regarding their prevalence and bioavailability in freshwater systems, robust detection of NPs in complex environmental matrices is hindered by the lack of standardized sample pretreatment and a mechanistic understanding of oxidative digestion. Here, we systematically investigate the interaction between hydrogen peroxide (H 2 O 2 ) and polystyrene (PS) NPs during digestion in deionized (DI) water and four environmental matrices from in and around the Great Lakes Basin. To facilitate high-throughput analysis, we develop Pre_peak, a customizable Raman spectral processing algorithm that achieves >99% accuracy for both NP identification and interference rejection, allowing reliable NP quantification via pixel counting and systematic decoding of the oxidative digestion mechanisms. In DI water, varying H 2 O 2 doses from 0 to 30% has negligible effects on the recovery and Raman signal intensity of PS NPs over 24 hours of digestion. However, morphological changes and aggregation of PS NPs are observed when the H 2 O 2 dose exceeds 20%. Prolonged digestion further leads to progressive NP loss. In natural waters, the optimal dosage and digestion duration depend on matrix characteristics, including dissolved organic matter (DOM) and ion composition. This study provides mechanistic insights into NP–oxidant interactions and underscores the need for matrix-tailored digestion protocols to advance standardized NP detection in freshwater environments.

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USGS2026

Acute toxicity and tissue concentrations of 6PPD-quinone in Arctic grayling (Thymallus arcticus, Thymallinae)

Studies of N -(1,3-dimethylbutyl)- N' -phenyl- p -phenylenediamine-quinone (6PPDQ) toxicity have identified sensitive and resistant species within the subfamily Salmoninae, but thus far fewer than 10 species, all in two genera ( Oncorhynchus and Salvelinus ), have shown sensitivity in experiments. The Arctic grayling ( Thymallus arcticus , Salmonidae, Thymallinae) was extirpated from its range in the Great Lakes region of the United States, but because of the importance of this species to the Native American tribes of Michigan, a reintroduction effort is underway. Because high 6PPDQ concentrations have been found in Great Lakes tributaries, it is important to understand if this species is at risk from 6PPDQ exposure. Using standard methods with flow-through exposures to provide stable 6PPDQ concentrations, we exposed Arctic grayling at 3 weeks after swim-up to a series of 6PPDQ concentrations for 96 hr, evaluating mortality and measuring tissue concentrations of 6PPDQ in surviving and dying fish. We observed that grayling were sensitive to 6PPDQ, with 24- and 96-hr median lethal concentrations of 5,136 and 3,137 ng/L, respectively. Tissue concentrations were much higher than those observed in other sensitive salmonines in previous studies. While this is only the third genus found to be sensitive to 6PPDQ leading to acute lethality and the first species outside of Salmoninae, the median lethal concentrations determined for the Arctic grayling exposed in this study are at 6PPDQ water concentrations unlikely to be encountered in situ.

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USGS2026

Design and function of the Autonomous Benthic Imaging and Surveying System (ABISS) for remote sensing of lake and seabed environments

Lake and seabed environments are home to fisheries and other biota that are important to ecosystems and economies, yet these environments and the species that use them are difficult to accurately assess and monitor. Traditional benthic survey techniques, like bottom trawling used by the U.S. Geological Survey, are limited by substrate constraints, poor spatial resolution and precision, and operational depth limits, hindering accurate assessment of benthic species and habitats. In response to these limitations, the U.S. Geological Survey developed the Autonomous Benthic Imaging and Surveying System, a camera system integrated into underwater vehicles, to capture high-resolution images of the lakebed. The system uses color and stereo cameras to collect imagery, which can be analyzed using computational methods to detect organisms and (or) characterize habitat features, such as geologic substrate types. The system has been integrated into autonomous underwater vehicles and into an underwater housing used by self-contained underwater breathing apparatus (SCUBA) divers. Although the engineering of the system was motivated by the need for data collection in the Great Lakes, it has potential to collect high quality data in any aqueous setting with sufficient water clarity and safe operating conditions. The Autonomous Benthic Imaging and Surveying System can operate across diverse depths and light conditions to map and quantify ecological patterns that were difficult or impossible to assess using traditional methods. The Autonomous Benthic Imaging and Surveying System offers the potential for accurate and precise monitoring and assessment of native benthic biota, invasive species, and habitat, potentially providing natural resource managers with improved information to support decision making about benthic resource management.

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USGS2026

Reconstructing Great Lakes air temperature and ice dynamics data back to 1897

Ice cover on the Great Lakes plays an important role in regional climate, supports tourism and recreation, and provides ecological habitat. As the climate warms, ice cover in the Great Lakes is expected to decline, which in turn will create more lake effect precipitation, reduce ice cover for recreation, and alter habitat for aquatic species. While it is important to understand the historical ice patterns to better understand past distributions of aquatic species and improve the accuracy of forecasts for future ice cover on the lakes, Great Lakes ice cover data prior to 1973 is scarce, due to the limited routine satellite observations. We used weather station data around the Great Lakes to compile daily air temperature, calculate cumulative freezing degree-days and net melting degree-days from 1897–2023, and develop raster layers estimating ice duration and variability spatially during the historical period from 1897–1960.

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USGS2026

Unexpected appetites: Metabarcoding reveals grass carp (Ctenopharyngodon idella) foraging behaviors in the Great Lakes

Grass carp ( Ctenopharyngodon idella ) are herbivorous fish introduced to North America in the 1960s, and they are now established throughout the Mississippi River basin and Laurentian Great Lakes. Despite increasingly intensified management efforts, limited information exists on their foraging ecology. We used DNA metabarcoding to characterize the gut contents of grass carp captured from 2019 to 2022 to evaluate spatial, temporal, and environmental patterns in diet composition across Lake Erie and Lake Michigan. Contrary to long-standing assumptions that grass carp primarily consume submerged aquatic vegetation (SAV), results from Lake Erie’s western and central basins revealed a diet dominated by terrestrial and terrestrial-wetland plant genera, including maples ( Acer ), willows ( Salix ), cottonwoods ( Populus ), and nightshades ( Solanum ). In contrast, fish harvested from Lake Erie’s eastern basin and Lake Michigan tributaries consumed more SAV, particularly pondweeds like Potamogeton and Stuckenia . Diet composition varied by basin, river, and year, but not by ploidy (diploid vs. triploid). Distance-based redundancy analyses identified environmental variables as drivers of diet variability. These findings reframe previous risk assessments which were based on diets from small artificial environments, suggesting greater dietary plasticity and revealing previously overlooked terrestrial-aquatic food web connections. Results presented here could inform management actions and sampling locations. Understanding grass carp foraging behavior in invaded systems can provide a critical tool for refining removal strategies, preventing further expansion, and improving future ecological risk assessments.

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USGS2026

Decreased water transparency of nearshore Laurentian Great Lakes habitats is driven by increased dissolved organic carbon.

Little is understood of lake browning (due to increased dissolved organic carbon; DOC) in large lakes such as the Laurentian Great Lakes. Lake browning can alter whole lake ecosystems, including decreasing exposure to damaging ultraviolet radiation (UV-B) which is strongly and selectively attenuated by DOC more so than photosynthetically active radiation (PAR). We compared the changes in UV-B and PAR transparency to DOC data collected during the ice-free seasons from 62 nearshore sites in four of the five Great Lakes from 2002 to 2022 using linear mixed effects regression models based on backwards selected Bayesian information criteria. Regionally, DOC significantly increased from 2002 to 2022 by 0.5% per year on average. DOC strongly and inversely explained the variability of UV-B and PAR transparencies, as did seasons and offshore influence on these habitats. We provide regional evidence of lake browning within the nearshore habitats of the Great Lakes as a strong contrast to the well-documented increased offshore water transparency associated with the spread of invasive dreissenid mussels.

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USGS2025

Evaluation of the acute toxicity of the piscicide TFM to Burbot

Non-target animal sensitivity remains a concern when treating Laurentian Great Lakes streams with 4-nitro-3-(trifluoromethyl)phenol (TFM), the main pesticide used to control Sea Lamprey Petromyzon marinus as part of the bi-national Great Lakes Fishery Commission's Sea Lamprey Control Program. Populations of Burbot Lota lota , a historically and culturally important fish, inhabit some of the streams that are treated with TFM. While many species of fish inhabiting the Great Lakes streams have been assessed for sensitivity to TFM, we are not aware of previous research to assess the risk to Burbot. We assessed the sensitivity of Burbot to TFM using replicate 12-hour flow-through diluter toxicity tests. We found Burbot to have a median lethal concentration (LC 50 ) of 9.74 mg/L, while the minimum lethal concentration (LC 99.9 ) for Sea Lamprey was predicted to be 2.5 mg/L in similar waters. The resulting toxicity ratio (LC 50 of non-target organism/LC 99.9 of Sea Lamprey) of Burbot was 3.90, well above the toxicity ratios for known sensitive species. Our results suggest Burbot are not expected to be adversely affected during a typical TFM stream treatment.

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USGS2025

Development of PCR blocking primers enabling DNA metabarcoding analysis of dietary composition in hematophagous sea lamprey

Conventional dietary assessments are challenging in hematophagous species, particularly in sea lamprey ( Petromyzon marinus ). However, recent technological developments and molecular approaches have provided an attractive alternative through the use of DNA metabarcoding. While DNA metabarcoding has been used for dietary analyses in numerous species, including lampreys, applications of universal primers that detect a diverse set of prey items can be limited by the amplification of predator DNA. In this study, we designed and tested eight blocking primers designed to suppress the amplification of sea lamprey DNA with vertebrate-universal primers targeting the mitochondrial 12S rRNA gene. This approach allowed for the use of a single marker to amplify a taxonomically diverse suite of host species, in contrast to previous studies that used multiple taxon-specific primer pairs (e.g., Salmonidae, Cyprinidae, and Catostomidae). Candidate blocking primers evaluated in this study differed in base pair length, end sequence modification, and purification method. Samples with different sea lamprey-to-host DNA ratios were subjected to multiple detection methods including gel electrophoresis, quantitative PCR, and DNA metabarcoding to assess the ability of each blocking primer to selectively suppress amplification of the sea lamprey 12S gene region. All blocking primers tested performed well and demonstrated high effectiveness, suppressing sea lamprey reads by > 99.9% in mock communities and improving host DNA sequence recovery across various sample types, including wild-caught lamprey. Results show that the blocking primers evaluated can facilitate molecular diet analysis in sea lamprey, allowing the amplification of a taxonomically diverse range of host fish species with universal primers.

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USGS2025

Ecological factors decouple Great Lakes fish mercury concentrations trends decadal declines in mercury emissions

Atmospheric mercury (Hg) deposition has been declining in North America but remains the dominant delivery mechanism to the Great Lakes. The Lakes are highly efficient at bioaccumulating methylmercury, making the fish excellent sentinels for tracking shifts in atmospheric Hg deposition. Invasive mussels have altered biogeochemical processes, prey populations and fish dietary strategies asynchronously and to varied extents across the lower four lakes, impacting fish Hg exposure. To test if fish are adapting to new biogeochemical conditions, we analyzed a 40 year fish archive for carbon and nitrogen isotope ratios and amino acid-specific nitrogen isotope ratios. To assess Hg sources, we measured Hg isotope ratios. We reconstructed and compared energetic pathways that impact fish Hg concentrations to Hg-source trends. We found fish-Hg concentrations are declining but not monotonically due to ecological disturbances. Fish-Hg isotope values, unimpacted by ecological disturbance, confirm that sources of bioaccumulated Hg shift contemporaneously with changes in atmospheric Hg concentrations. Across Lakes, the degree of responsiveness to changes in atmospheric Hg concentrations mirrors the proportion of atmospheric-delivered Hg we previously modeled. Changes in both fish concentrations and fish isotope values outpace paleolimnetic reconstructions suggesting declines in atmospheric Hg concentrations impact fish Hg more than sediment.

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USGS2025

Per- and polyfluoroalkyl substances in surface water and sediment in Great Lakes tributaries and relations with watershed attributes

Per- and polyfluoroalkyl substances (PFAS) are chemicals of emerging concern that potentially pose risks to human and environmental health. In May–Oct 2018, sediment and passively collected surface water samples were collected from 62 tributary sites of the Laurentian Great Lakes with site catchments spanning various land cover types. Discrete samples of sediment collected manually and time-integrated surface water samples collected with polar organic chemical integrative samplers (POCIS) were analyzed for 23 and 34 PFAS, respectively. Concentrations of individual PFAS in sediment and surface water varied immensely among sites from below detection to 20,800 ng kg −1 and 247 ng L −1 , respectively. Of all target compounds, PFOS was the most frequently detected in sediment (56 of 62 sites) and had the highest median concentration (132 ng kg −1 ). PFOA, PFHxS, PFOS, PFHpA, and PFNA (full chemical names are listed in online supplementary material Table S2) were detected in all 60 surface water sites, with median estimated concentrations of 5.9, 5.2, 4.6, 3.7, and 1.3 ng L −1 , respectively. Compounds with 8–13 fluorinated carbons comprised a larger proportion of sediment PFAS than compounds with 4–7 fluorinated carbons, whereas compounds with 4–7 fluorinated carbons comprised a greater proportion of PFAS in surface waters. Watershed attributes, including urban land cover, airports per catchment area, and wastewater treatment plants flow percentage were significantly ( p < 0.05) and positively related with PFAS sum concentrations in sediment and (or) surface water. Collectively, these results, albeit with some uncertainty in the estimated concentrations, highlight the relation PFAS occurrence has with human activities and documents widespread low-level PFAS contamination across the Great Lakes basin.

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USGS2025

Sea Lamprey control reduction during the COVID-19 pandemic corresponds to rapid increase in Sea Lamprey abundance

The Sea Lamprey Petromyzon marinus control program in the Laurentian Great Lakes is one of the longest-running and most successful invasive species suppression programs in the world. Although several techniques are used to suppress Sea Lamprey, the control program relies heavily on regular application of lampricide to kill stream-dwelling larvae. The COVID-19 pandemic disrupted lampricide application from 2020 to 2022, which provided a unique opportunity to test how Sea Lamprey populations and wound counts on fishes would respond. We evaluated the consequences of decreased control effort at a basin-wide level using standard control program metrics and through a focused analysis of multispecies wounding in Lake Ontario, which experienced the greatest disruption in Sea Lamprey control. The reduction in control effort corresponded to increased basin-wide adult Sea Lamprey abundance but was only weakly associated with Lake Trout Salvelinus namaycush wounding. However, the novel multispecies wounding rate metric calculated for Lake Ontario increased and was consistent with observations by anglers and managers regarding a sharp increase in Sea Lamprey abundance following reduced effort. Ultimately, our research highlights that consistent treatment is critically important for preventing damage stemming from Sea Lamprey and that reductions in suppression could quickly lead to a resurgence in abundance.

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USGS2025

Retrospective stepwise prioritization of chemicals detected in Great Lakes tributaries (2008–2018)

Through the U.S. Great Lakes Restoration Initiative, a 10-year, multiagency chemical monitoring effort was undertaken across the Great Lakes. In this effort, 586 chemicals were monitored and 334 were detected in grab/composite water samples. To help inform potential future actions, a stepwise prioritization framework was used to identify compounds for which publicly accessible water quality guidelines or effects information suggested there was potential aquatic ecotoxicity. Because water quality guidelines were only available for some chemicals, this framework used apical toxicity data collated from publicly accessible databases (e.g., the ECOTOXicology Knowledgebase) and alternative data, including literature-derived non-apical effect concentrations, in vitro bioactivities from high-throughput screening, and modeled ecotoxicity. To account for the diverse levels of confidence in these data, chemicals were prioritized within specific action categories, which suggested potential management or experimental activities that may be considered based on the types of data available for each compound. Overall, 11 detected chemicals were identified as high priority in different action categories. This included four chemicals prioritized for environmental management or targeted risk assessment, three chemicals prioritized for effects-based monitoring, one chemical prioritized for apical effects assessment, and three chemicals targeted for non-apical effects evaluation. This framework also identified 164 low-priority chemicals, among which more than 50% were prioritized based on water quality guidelines or apical effect concentrations (thus could be considered low priority for future risk assessment or management activities). Results aim to help regulatory agencies, environmental managers, and other stakeholders focus available resources on carrying out monitoring, experimental, and risk assessments for the chemicals that display the greatest potential to adversely impact Great Lakes ecosystems.

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USGS2024

Synthesizing professional opinion of Lake Whitefish and Cisco recruitment drivers across the Great Lakes

Disentangling the suite of ecological drivers that explain recruitment variability for Lake Whitefish Coregonus clupeaformis and Cisco C. artedi is of critical importance for their conservation, management, and stewardship in the Laurentian Great Lakes. However, recruitment is inherently variable and can be regulated by many interacting processes, the relative importance of which can vary spatially, temporally, and ontogenetically. Given this complexity, comparisons across lakes and species that identify overarching hypotheses could efficiently guide future research. Using facilitated deliberations among fishery professionals (n = 57) with expertise in Great Lakes Coregonus spp., we synthesized current knowledge regarding (1) which biophysical processes are most important for driving contemporary recruitment between species, among lakes, and across life stages and (2) mechanisms by which those drivers regulate recruitment at key life stages. Participants affirmed the hypothesis that many drivers interact in complex ways to regulate Lake Whitefish and Cisco recruitment. Large-scale climatic processes affecting early life-stage growth and survival were consistently considered important. Other drivers were only deemed influential in certain lakes, highlighting perceived context-dependent recruitment dynamics. Notably, recruitment in Lakes Superior, Michigan, and Huron was considered limited during larval and early juvenile life stages by low productivity, whereas spawning-habitat degradation and reduced metapopulation diversity were hypothesized to limit recruitment during embryonic and larval stages in Lakes Erie and Ontario. Several drivers were hypothesized to similarly impact Lake Whitefish and Cisco during early life stages, while drivers acting on post-larval life stages were typically distinct between species. The hypotheses synthesized herein can guide future research on Lake Whitefish and Cisco recruitment dynamics in the Great Lakes.

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USGS2023

Potential effects of climate change on Acipenser fulvescens (lake sturgeon)

Acipenser fulvescens (Rafinesque, 1817; lake sturgeon) are the only sturgeon species native to the Great Lakes region and are threatened across most of their range. They are historically vulnerable because of overfishing and habitat fragmentation with the potential for climate change acting as an increasing stressor in the future. Lake sturgeon span multiple habitats during their long lifespans, including high gradient streams, nearshore areas, and deep rivers and lakes. Climate change is projected to strongly affect the suitability of these habitats through increasing precipitation and temperatures and decreasing ice cover and snowmelt. Changes in flow timing and amount can affect movement to spawning and nursery sites, and increased water temperatures are likely to affect species activity patterns, survival, and prey availability. Ultimately, the Great Lakes region is expected to face wide ranging effects from climate change, which may have positive and negative effects on lake sturgeon depending on a variety of factors, including the life stages affected, habitat availability, and interactions with other stressors, but all shifts are likely to affect spawning. Importantly, several areas of further research would be beneficial to understanding the complex effects of climate change on lake sturgeon.

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USGS2023

Toward a total water level forecast of the Great Lakes

The combined effect of storm surge and large waves is the main driving mechanism that erodes beaches, inundates low-lying areas, leading to millions of dollars in property damage, loss of natural resources, and lives. The U.S. Geological Survey (USGS) aims to expand the real-time total water level (TWL) forecast provided in the Operational Total Water Level and Coastal Change Forecasts (TWL&CC) to the Great Lakes short- (0 – 36 hours) to medium-term (3 – 5 days) coastal-hazard forecasts to inform planners and emergency responders. This study assesses the skill of forecast water levels and wave characteristics required as input to the TWL forecasts. It finds that, while skill generally decreases as forecast period increases, these data are suitable as input to the TWL forecast system. As the TWL predictions depend on the water level and wave forecasts, validation against field observations allow evaluation of their suitability for the Great Lakes. These results have implications on the prediction of water levels and their potential impacts on coastal resiliency in North America.

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