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USGS2019

Widespread loss of lake ice around the Northern Hemisphere in a warming world

Ice provides a range of ecosystem services—including fish harvest , cultural traditions , transportation , recreation and regulation of the hydrological cycle —to more than half of the world’s 117 million lakes. One of the earliest observed impacts of climatic warming has been the loss of freshwater ice , with corresponding climatic and ecological consequences . However, while trends in ice cover phenology have been widely documented , a comprehensive large-scale assessment of lake ice loss is absent. Here, using observations from 513 lakes around the Northern Hemisphere, we identify lakes vulnerable to ice-free winters. Our analyses reveal the importance of air temperature, lake depth, elevation and shoreline complexity in governing ice cover. We estimate that 14,800 lakes currently experience intermittent winter ice cover, increasing to 35,300 and 230,400 at 2 and 8 °C, respectively, and impacting up to 394 and 656 million people. Our study illustrates that an extensive loss of lake ice will occur within the next generation, stressing the importance of climate mitigation strategies to preserve ecosystem structure and function, as well as local winter cultural heritage.

Nature Climate Change↗

USGS2018

A laboratory-calibrated model of coho salmon growth with utility for ecological analyses

We conducted a meta-analysis of laboratory- and hatchery-based growth data to estimate broadly applicable parameters of mass- and temperature-dependent growth of juvenile coho salmon ( Oncorhynchus kisutch ). Following studies of other salmonid species, we incorporated the Ratkowsky growth model into an allometric model and fit this model to growth observations from eight studies spanning ten different populations. To account for changes in growth patterns with food availability, we reparameterized the Ratkowsky model to scale several of its parameters relative to ration. The resulting model was robust across a wide range of ration allocations and experimental conditions, accounting for 99% of the variation in final body mass. We fit this model to growth data from coho salmon inhabiting tributaries and constructed ponds in the Klamath Basin by estimating habitat-specific indices of food availability. The model produced evidence that constructed ponds provided higher food availability than natural tributaries. Because of their simplicity (only mass and temperature are required as inputs) and robustness, ration-varying Ratkowsky models have utility as an ecological tool for capturing growth in freshwater fish populations.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2001

Time series of suspended-solids concentration, salinity, temperature, and total mercury concentration in San Francisco Bay during water year 1998

Many physical processes affect how constituents within San Francisco Bay vary. Processes and their associated time scales include turbulence (seconds), semidiurnal and diurnal tides (hours), the spring-neap tidal cycle (days), freshwater flow (weeks), seasonal winds (months), ecological and climatic changes (years), and geologic changes (thousands of years). Continuous time series of data on basic state variables of the bay, such as suspended-solids concentration (SSC), salinity, and water temperature, provide insight on the effect and relative importance of physical processes on the bay. SSC time series and Regional Monitoring Program (RMP) water-quality data can be used to calculate time series of some traceelement concentrations (Schoellhamer, 1997a, 1997b). The purpose of this chapter is to describe qualitatively time series of SSC, salinity, water temperature, and mercury during water year 1998 (October 1997 through September 1998). Salinity, temperature, and sediment are important components of the San Francisco Bay estuarine system. Salinity and temperature affect the hydrodynamics (Monismith et al., 1996; Schoellhamer and Burau, 1998), geochemistry (Kuwabara et al., 1989), and ecology (Cloern, 1984; Nichols et al., 1986; Jassby et al., 1995) of the bay. Suspended sediments limit light availability in the bay, which, in turn, limits primary production (Cloern, 1987; Cole and Cloern, 1987), and thus food for higher trophic levels. Sediments deposit in ports and shipping channels, which must be dredged to maintain navigation (U.S. Environmental Protection Agency, 1992). Potentially toxic substances, such as metals and pesticides, adsorb to sediment particles (Kuwabara et al., 1989; Domagalski and Kuivila, 1993; Flegal et al., 1996; Schoellhamer, 1997a, 1997b). The transport and fate of suspended sediments are important factors in determining the transport and fate of constituents adsorbed on the sediments. For example, the concentration of suspended particulate chromium in the bay appears to be controlled primarily by sediment resuspension (Abu-Saba and Flegal, 1995). Concentrations of dissolved trace elements are greater in South Bay than elsewhere in San Francisco Bay, and bottom sediments are believed to be a significant source (Flegal et al., 1991). The sediments on the bay bottom provide habitat for benthic communities that can ingest these substances and introduce them into the food web (Luoma et al., 1985; Brown and Luoma, 1995, Luoma 1996). Bottom sediments also are a reservoir of nutrients that contribute to the maintenance of estuarine productivity (Hammond et al., 1985).

California↗

USGS1998

Time series Of suspended-solids concentration, salinity, temperature, and total mercury concentration in San Francisco Bay during water year 1996

California↗

USGS2012

Quality of water in the White River and Lake Tapps, Pierce County, Washington, May-December 2010

The White River and Lake Tapps are part of a hydropower system completed in 1911–12. The system begins with a diversion dam on the White River that routes a portion of White River water into the southeastern end of Lake Tapps, which functioned as a storage reservoir for power generation. The stored water passed through the hydroelectric facilities at the northwestern end of the lake and returned to the White River through the powerhouse tailrace. Power generation ceased in January 2004, which altered the hydrology of the system by reducing volumes of water diverted out of the river, stored, and released through the powerhouse. This study conducted from May to December 2010 created a set of baseline data collected under a new flow regime for selected reaches of the White River, the White River Canal (Inflow), Lake Tapps Diversion (Tailrace) at the powerhouse, and Lake Tapps. Three sites, one on the White River at Headworks, one on the White River at R Street, and one on the Tailrace, were equipped for continuous recording of water-quality data, and three sites (Headworks, White River Canal Inflow, and Tailrace) were sampled for discrete water-quality data. Nine lake sites were measured for physical and water-quality properties and samples were collected for analyses of nutrients, suspended solids, and fecal-coliform bacteria concentrations. Samples from the lake also were analyzed for concentrations of chlorophyll a and organic chemicals. Discrete samples indicated that water from the White River, White River Canal Inflow, and Tailrace sites generally was turbid, warm, chemically dilute, and well-oxygenated. Exceptions occurred at the sites when flow to the White River Canal was suspended or when little or no flow was released from the lake into the Tailrace. The quality of physical properties and concentrations in water measured continuously at the three sites generally was good and met the freshwater criteria designated by Washington State Department of Ecology for recreational and aquatic-life uses, with several exceptions. The 7-day average of daily maximum temperatures (7–DADMax) was greater than the freshwater aquatic life criterion of 16 degrees Celsius (°C) for core summer salmonid habitat on 6 days at the Headworks site and 37 days at the R-Street site during the study. The 7-DADMax temperatures were greater than the 13°C criterion for spawning, rearing, and incubation on 6 days at the Headworks site and 20 days at the R-Street site. The freshwater aquatic life criterion for dissolved oxygen of 9.5 milligrams per liter (mg/L) for core summer salmonid habitat was not met at the Headworks and R-Street sites for periods during July and August 2010. Exceptions also occurred at the Headworks site for measurements of pH, which were greater than the aquatic life upper limit of 8.5 pH units during July 2010. Aquatic life pH criteria were not met at the Tailrace site during June, July, and August 2010, when pH was greater than 8.5 pH units, and during August 2010 when pH decreased to less than 6.5 pH units. Lake Tapps water near the surface was relatively clear, warm, and well oxygenated. The clearest water of the nine lake sites was at the Deep site with a median Secchi disk transparency measurement of 6.05 m (meters), which represents a two- to six-fold increase over historical measurements of transparency at this location. Median water temperatures were 18.2–18.9°C and maximums were from 22.9–25.0°C. Median dissolved oxygen concentrations were greater than 8.42 mg/L and minimums generally were not lower than 7.4 mg/L. By early July 2010, weak thermal stratification developed at most lake sites into at least a warm surface layer overlying a small thermocline. A well-defined hypolimnion developed below the thermocline only at the Deep site. With the development of thermal stratification, hypolimnion water became anoxic at several sites (Deep, Tapps Island, Snag Island, and Lake Outlet). By late September 2010, an anoxic layer about 15 m thick had formed in the hypolimnion of the Deep site. Mixing during autumn overturn in late November re-oxygenated the water column of all the sites with about 10–12 mg/L of dissolved oxygen. On the basis of pH and specific conductance measurements, Lake Tapps water is pH neutral and chemically dilute. Median pH values for water in the epilimnion and the hypolimnion ranged from 6.84 to 7.64 pH units and maximums did not exceed 7.8 pH units at any site. Median specific conductance was typically less than 70 microsiemens per centimeter at 25°C for the epilimnion and the hypolimnion. Concentrations of nutrients and chlorophyll a in Lake Tapps were low. At most of the sites and in most of the samples from the epilimnion, total phosphorus concentrations were less than the Washington State Department of Ecology phosphorus criterion of 0.01 mg/L for maintaining oligotrophic conditions. Median concentrations of total nitrogen (unfiltered water) ranged from about 0.14 mg/L (Deep, Tapps Island, and Dike 2B sites) to about 0.18 mg/L (Allan Yorke and Lake Inlet sites). Chlorophyll a concentrations were low with median concentrations of 2.16 micrograms per liter (mg/L) or less. The majority of chlorophyll a concentrations were well below the Oregon Department of Environmental Quality action level of 10 mg/L. Using the Carlson Trophic-Status Index and average measures of transparency, chlorophyll a , and total phosphorus data from this study, Lake Tapps generally fits within the oligotrophic classification, but with a few exceptions. At Allan Yorke, Lake Inlet, and Southeast Arm sites, the chlorophyll a and total phosphorus indexes of nearly 40 approach the upper limit of oligotrophic conditions. In addition, average concentrations of total phosphorus at Lake Inlet and Southeast Arm are at Nürnberg's (1996) threshold concentration of 0.01 mg/L, which suggests a slight tendency towards mesotrophic conditions at these two sites during summer July–September. On the basis of epilimnetic nitrogen to phosphorus concentration ratios of greater than 17, Lake Tapps primary production is phosphorus limited at all but two study sites. At the Lake Inlet and Southeast Arm sites, ratios of 15 and 16, respectively, for the summer period suggest either nitrogen or phosphorus (or both) may limit algal growth. Water samples collected at the Allan Yorke, Snag Island, and Lake Outlet study sites were screened for the presence of more than 250 organic chemicals. A total of 14 compounds were detected in trace amounts (or determined to be present) at one or more of the 3 sites. The Allan Yorke site had 9 detections, the Snag Island site had 10 detections, and the Lake Outlet site had 5 detections of compounds mostly belonging to the group of wastewater indicator chemicals. Compounds detected (or with verified presence) at all three sites included the herbicide 2,4-D, the insecticide and mosquito repellant DEET, the herbicide fluridone used for Eurasian watermilfoil eradication, and the herbicide prometon. The largest concentrations of these compounds were in samples from the Allan Yorke site; the lowest concentrations were from the Lake Outlet site.

Washington↗

USGS2015

Progress and challenges in coupled hydrodynamic-ecological estuarine modeling

Numerical modeling has emerged over the last several decades as a widely accepted tool for investigations in environmental sciences. In estuarine research, hydrodynamic and ecological models have moved along parallel tracks with regard to complexity, refinement, computational power, and incorporation of uncertainty. Coupled hydrodynamic-ecological models have been used to assess ecosystem processes and interactions, simulate future scenarios, and evaluate remedial actions in response to eutrophication, habitat loss, and freshwater diversion. The need to couple hydrodynamic and ecological models to address research and management questions is clear because dynamic feedbacks between biotic and physical processes are critical interactions within ecosystems. In this review, we present historical and modern perspectives on estuarine hydrodynamic and ecological modeling, consider model limitations, and address aspects of model linkage, skill assessment, and complexity. We discuss the balance between spatial and temporal resolution and present examples using different spatiotemporal scales. Finally, we recommend future lines of inquiry, approaches to balance complexity and uncertainty, and model transparency and utility. It is idealistic to think we can pursue a “theory of everything” for estuarine models, but recent advances suggest that models for both scientific investigations and management applications will continue to improve in terms of realism, precision, and accuracy.

Estuaries and Coasts↗

USGS2008

Arctic climate change and its impacts on the ecology of the North Atlantic

Arctic climate change from the Paleocene epoch to the present is reconstructed with the objective of assessing its recent and future impacts on the ecology of the North Atlantic. A recurring theme in Earth's paleoclimate record is the importance of the Arctic atmosphere, ocean, and cryosphere in regulating global climate on a variety of spatial and temporal scales. A second recurring theme in this record is the importance of freshwater export from the Arctic in regulating global- to basin-scale ocean circulation patterns and climate. Since the 1970s, historically unprecedented changes have been observed in the Arctic as climate warming has increased precipitation, river discharge, and glacial as well as sea-ice melting. In addition, modal shifts in the atmosphere have altered Arctic Ocean circulation patterns and the export of freshwater into the North Atlantic. The combination of these processes has resulted in variable patterns of freshwater export from the Arctic Ocean and the emergence of salinity anomalies that have periodically freshened waters in the North Atlantic. Since the early 1990s, changes in Arctic Ocean circulation patterns and freshwater export have been associated with two types of ecological responses in the North Atlantic. The first of these responses has been an ongoing series of biogeographic range expansions by boreal plankton, including renewal of the trans-Arctic exchanges of Pacific species with the Atlantic. The second response was a dramatic regime shift in the shelf ecosystems of the Northwest Atlantic that occurred during the early 1990s. This regime shift resulted from freshening and stratification of the shelf waters, which in turn could be linked to changes in the abundances and seasonal cycles of phytoplankton, zooplankton, and higher trophic-level consumer populations. It is predicted that the recently observed ecological responses to Arctic climate change in the North Atlantic will continue into the near future if current trends in sea ice, freshwater export, and surface ocean salinity continue. It is more difficult to predict ecological responses to abrupt climate change in the more distant future as tipping points in the Earth's climate system are exceeded.

Ecology↗

USGS2011

Using body mass dynamics to examine long-term habitat shifts of arctic-molting geese: Evidence for ecological change

From 1976 onward, molting brant geese ( Branta bernicla ) within the Teshekpuk Lake Special Area, Alaska, shifted from inland, freshwater lakes toward coastal wetlands. Two hypotheses explained this redistribution: (1) ecological change: redistribution of molting brant reflects improvements in coastal foraging habitats, which have undergone a succession toward salt-tolerant plants due to increased coastal erosion and saltwater intrusion as induced by climate change or (2) interspecific competition: greater white-fronted geese ( Anser albifrons ) populations increased 12-fold at inland lakes, limiting food availability and forcing brant into coastal habitats. Both hypotheses presume that brant redistributions were driven by food availability; thus, body mass dynamics may provide insight into the relevance of these hypotheses. We compared body mass dynamics of molting brant across decades (1978, 1987–1992, 2005–2007) and, during 2005–2007, across habitats (coastal vs. inland). Brant lost body mass during molt in all three decades. At inland habitats, rates of mass loss progressively decreased by decade despite the increased number of greater white-fronted geese. These results do not support an interspecific competition hypothesis, instead suggesting that ecological change enhanced foraging habitats for brant. During 2005–2007, rates of mass loss did not vary by habitat. Thus, while habitats have improved from earlier decades, our results cannot distinguish between ecological changes at inland versus coastal habitats. However, we speculate that coastal forage quality has improved beyond that of inland habitats and that the body mass benefits of these higher quality foods are offset by the disproportionate number of brant now molting coastally.

Alaska↗

USGS2011

Defining conservation priorities for freshwater fishes according to taxonomic, functional, and phylogenetic diversity

To date, the predominant use of systematic conservation planning has been to evaluate and conserve areas of high terrestrial biodiversity. Although studies in freshwater ecosystems have received recent attention, research has rarely considered the potential trade-offs between protecting different dimensions of biodiversity and the ecological processes that maintain diversity. We provide the first systematic prioritization for freshwaters (focusing on the highly threatened and globally distinct fish fauna of the Lower Colorado River Basin, USA) simultaneously considering scenarios of: taxonomic, functional, and phylogenetic diversity; contemporary threats to biodiversity (including interactions with nonnative species); and future climate change and human population growth. There was 75% congruence between areas of highest conservation priority for different aspects of biodiversity, suggesting that conservation efforts can concurrently achieve strong complementarity among all types of diversity. However, sizable fractions of the landscape were incongruent across conservation priorities for different diversity scenarios, underscoring the importance of considering multiple dimensions of biodiversity and highlighting catchments that contribute disproportionately to taxonomic, functional, and phylogenetic diversity in the region. Regions of projected human population growth were not concordant with conservation priorities; however, higher human population abundance will likely have indirect effects on native biodiversity by increasing demand for water. This will come in direct conflict with projected reductions in precipitation and warmer temperatures, which have substantial overlap with regions of high contemporary diversity. Native and endemic fishes in arid ecosystems are critically endangered by both current and future threats, but our results highlight the use of systematic conservation planning for the optimal allocation of limited resources that incorporates multiple and complementary conservation values describing taxonomic, functional, and phylogenetic diversity.

Ecological Applications↗

USGS2025

Range-wide ecology, conservation, and research needs for yellow lampmussel (Lampsilis cariosa)

The freshwater mussel yellow lampmussel ( Lampsilis cariosa ) is declining throughout its range along the Atlantic Slope of the eastern United States and Canada, and the species is a target for proactive conservation to avoid federal listing. This paper synthesizes information about the ecology (physiology and life history, host fishes, and habitat), species distribution, genetics, and threats to L. cariosa . Identified threats include climate change, habitat alteration, and invasive species, dependent on location. We outline 16 emergent research and conservation management needs based on literature review and discussion with stakeholders (state and federal mussel biologists, researchers, and tribal groups). These needs range from research on the basic physiology and behavior of the species, to creating standardized protocols for surveys and DNA sampling, to ultimately developing a range-wide species conservation and restoration plan. Addressing these information gaps and incorporating the findings into future management may facilitate the implementation and success of large-scale restoration and conservation initiatives such as habitat protection and reintroduction of L. cariosa to historical locations.

Hydrobiologia↗

USGS2015

Fire effects on aquatic ecosystems: An assessment of the current state of the science

Fire is a prevalent feature of many landscapes and has numerous and complex effects on geological, hydrological, ecological, and economic systems. In some regions, the frequency and intensity of wildfire have increased in recent years and are projected to escalate with predicted climatic and landuse changes. In addition, prescribed burns continue to be used in many parts of the world to clear vegetation for development projects, encourage desired vegetation, and reduce fuel loads. Given the prevalence of fire on the landscape, authors of papers in this special series examine the complexities of fire as a disturbance shaping freshwater ecosystems and highlight the state of the science. These papers cover key aspects of fire effects that range from vegetation loss and recovery in watersheds to effects on hydrology and water quality with consequences for communities (from algae to fish), food webs, and ecosystem processes (e.g., organic matter subsidies, nutrient cycling) across a range of scales. The results presented in this special series of articles expand our knowledge of fire effects in different biomes, water bodies, and geographic regions, encompassing aquatic population, community, and ecosystem responses. In this overview, we summarize each paper and emphasize its contributions to knowledge on fire ecology and freshwater ecosystems. This overview concludes with a list of 7 research foci that are needed to further our knowledge of fire effects on aquatic ecosystems, including research on: 1) additional biomes and geographic regions; 2) additional habitats, including wetlands and lacustrine ecosystems; 3) different fire severities, sizes, and spatial configurations; and 4) additional response variables (e.g., ecosystem processes) 5) over long (>5 y) time scales 6) with more rigorous study designs and data analyses, and 7) consideration of the effects of fire management practices and policies on aquatic ecosystems.

Freshwater Science↗

USGS2025

The role of ecology in allopatric speciation of darters in the Central Highlands, USA

Allopatric speciation is the predominant mode of speciation in riverine fishes. However, the relative importance of genetic drift versus natural selection in the allopatric speciation of these fishes remain uncertain. Here, we present a case study that demonstrates the role of ecology in the diversification of a group of imperiled freshwater fishes from the central United States. We integrate a phylogenomic dataset with analyses of streamwise distance, environmental variables, meristic and morphological traits, and diet to investigate the ecological context and outcomes of allopatric speciation within a species complex comprising the Slenderhead Darter Percina phoxocephala (Nelson), Ouachita Darter Percina brucethompsoni (Robison, Cashner, and Near), and Longnose Darter Percina nasuta (Bailey). We find that two of the species traditionally delimited based on disparity in snout length, P. phoxocephala and P. nasuta , are polyphyletic, revealing three instances of the parallel evolution of snout length disparity. We propose a revised taxonomy including the delimitation of six new species based on disparity in phenotypic traits and phylogenomic analyses. We find that morphological differences are not correlated with genetic divergence but are congruent with variations in diet and environmental niches, suggesting a role for ecological factors in allopatric speciation of riverine fishes.

Arkansas, Kansas, Missouri, Oklahoma↗

USGS2021

eDNA metabarcoding outperforms traditional fisheries sampling and reveals fine-scale heterogeneity in a temperate freshwater lake

Understanding biodiversity in aquatic systems is critical to ecological research and conservation efforts, but accurately measuring species richness using traditional methods can be challenging. Environmental DNA (eDNA) metabarcoding, which uses high-throughput sequencing and universal primers to amplify DNA from multiple species present in an environmental sample, has shown great promise for augmenting results from traditional sampling to characterize fish communities in aquatic systems. Few studies, however, have compared exhaustive traditional sampling with eDNA metabarcoding of corresponding water samples at a small spatial scale. We intensively sampled Boardman Lake (1.4 km 2 ) in Michigan, USA, from May to June in 2019 using gill and fyke nets and paired each net set with lake water samples collected in triplicate. We analyzed water samples using eDNA metabarcoding with 12S and 16S fish-specific primers and compared estimates of fish diversity among methods. In total, we set 60 nets and analyzed 180 1 L lake water samples. We captured a total of 12 fish species in our traditional gear and detected 40 taxa in the eDNA water samples, which included all the species observed in nets. The 12S and 16S assays detected a comparable number of taxa, but taxonomic resolution varied between the two genes. In our traditional gear, there was a clear difference in the species selectivity between the two net types, and there were several species commonly detected in the eDNA samples that were not captured in nets. Finally, we detected spatial heterogeneity in fish community composition across relatively small scales in Boardman Lake with eDNA metabarcoding, but not with traditional sampling. Our results demonstrated that eDNA metabarcoding was substantially more efficient than traditional gear for estimating community composition, highlighting the utility of eDNA metabarcoding for assessing species diversity and informing management and conservation.

Michigan↗

USGS2018

A comparison of the chemical sensitivities between in vitro and in vivo propagated juvenile freshwater mussels: Implications for standard toxicity testing

Unionid mussels are ecologically important and are globally imperiled. Toxicants contribute to mussel declines, and toxicity tests using juvenile mussels—a sensitive life stage—are valuable in determining thresholds used to set water quality criteria. In vitro culture methods provide an efficient way to propagate juveniles for toxicity testing, but their relative chemical sensitivity compared with in vivo propagated juveniles is unknown. Current testing guidelines caution against using in vitro cultured juveniles until this sensitivity is described. Our objective was to evaluate the relative sensitivity of juvenile mussels produced from both in vitro and in vivo propagation methods to selected chemicals. We conducted 96-h acute toxicity tests according to ASTM International guidelines with 3 mussel species and 6 toxicants: chloride, nickel, ammonia, and 3 copper-based compounds. Statistically significant differences between in vitro and in vivo juvenile 96-h median effect concentrations were observed in 8 of 17 tests, and in vitro juveniles were more sensitive in 6 of the 8 significant differences. At 96 h, 4 of the 8 statistically different tests for a given chemical were within a factor of 2, which is the intralaboratory variation demonstrated in a recent evaluation of mussel toxicity tests. We found that although differences in chemical sensitivity exist between in vitro and in vivo propagated juvenile mussels, they are within normal toxicity test variation. Therefore, in vitro propagated juvenile mussels may be appropriate for use in ASTM International-based toxicity testing.

Environmental Toxicology and Chemistry↗

USGS2020

Trophodynamics of per- and polyfluoroalkyl substances in the food web of a large Atlantic slope river

Per- and polyfluoroalkyl substances (PFASs) have attracted scientific and regulatory attention due to their persistence, bioaccumulative potential, toxicity, and global distribution. We determined the accumulation and trophic transfer of 14 PFASs (5 short-chain and 9 long-chain) within the food web of the Yadkin-Pee Dee River of North Carolina and South Carolina, US. Food web components and pathways were determined by stable isotope analyses of producers, consumers, and organic matter. Analyses of water, sediment, organic matter, and aquatic biota revealed that PFASs were prevalent in all food web compartments. Biofilm, an aggregation of bacteria, fungi, algae, and protozoans and a basal resource for the aquatic food web, showed high PFAS accumulation (in 10 of 14 compounds), particularly for perfluorooctanoic acid, with the greatest mean concentration of 463.73 ng/g. The food web compartment with the most detections and greatest concentrations of PFASs was aquatic insects; all 14 PFASs were detected in individual aquatic insect samples (range of <limit of detection [<LOD] to 1670.10 ng/g of wet weight [WW]). These findings may suggest a trophic link between biofilm PFASs and aquatic insect PFASs. Individual fish tissue samples ranged from <LOD to 797.00 ng/g of WW, where perfluorooctanesulfonate (PFOS) was the dominant PFAS among all samples (64%). The ova of an imperiled fish, the robust redhorse ( Moxostoma robustum ), had concentrations of 10 PFASs (range of <LOD to 482.88 ng/g of WW) and the highest PFOS concentration (482.88 ng/g of WW), indicating a likely maternal transfer. The trophic magnification factors (TMFs) calculated in this study showed that various taxa accumulated PFAS compounds differently. PFBS, a short-chain PFAS compound that would presumably exhibit lesser TMFs, had nine values among our compartments and organisms >1.0 (range of 0.57 to 2.33); it is possible that an unmeasured PFBS precursor may be accumulating in biota and metabolizing to PFBS, leading to a higher than expected TMFs for this compound. Our findings demonstrate the prevalence of PFASs in a freshwater food web with potential implications for ecological and human health.

North Carolina, South Carolina↗

USGS2026

Drift and dispersion of silver carp (Hypophthalmichthys molitrix) eggs and larvae for hypothetical spawning scenarios in the Upper Mississippi River

Invasive carp pose ecological and economic risks to North American freshwater systems. This study uses the Fluvial Egg Drift Simulator to model the drift of invasive silver carp ( Hypophthalmichthys molitrix) eggs and larvae after hypothetical spawning in Pools 1–10 of the Upper Mississippi River. Although adult invasive carps have been detected in this region, no reproduction has been confirmed as of this publication. A total of 450 spawning scenarios were simulated, representing 5 water temperatures, 9 flows, and 10 spawning locations in the tailwaters of lock and dam structures. The study examined egg and larval positions at two key developmental stages: hatching and gas bladder inflation, when larvae seek nursery habitat. Under a wide variety of flow conditions and water temperatures, eggs spawned upstream from Lake Pepin (Pool 4) are likely to settle in the lake before hatching, possibly increasing mortality rates. Eggs that survive passage through Lake Pepin reach gas bladder inflation within the study area, except in scenarios with lower temperatures and higher flows. Conversely, larvae spawned downstream from Lake Pepin generally drift out of the study area before reaching gas bladder inflation, except in cases of higher temperatures and lower flows. These findings inform ichthyoplankton sampling strategies and management actions aimed at reducing invasive carp populations in areas likely to support recruitment.

Iowa, Minnesota, Wisconsin↗

USGS2024

A novel tool to selectively deliver a control agent to filter-feeding silver and bighead carp

Invasive carp pose substantial economic and ecological damage when populations are widespread in freshwater systems within the United States. Resource managers in the United States have few chemical control tools to selectively remove nuisance fish. This study examined whether Antimycin–A (antimycin) wax encapsulated microparticles could cause selective lethality in invasive carps. The antimycin microparticles were selective toward bighead carp ( Hypophthalmichthys nobilis ) and silver carp ( Hypophthalmichthys molitrix ) across multiple experimental scales. Microparticles applied in experimental pond studies caused approximately 50 percent lethality in invasive carp. Effluent pond studies performed at Rathbun Fish Hatchery (Moravia, Iowa) caused silver carp lethality at a lower rate than previous pond or laboratory studies (approximately 1 percent); however, minimal effects on other fish species were observed. The antimycin microparticle formulation shows the ability to cause lethality in filter-feeding invasive carp relative to other fish species and demonstrated the plausibility for delivering a typically nonselective toxicant in a selective manner to specific species based on their physiological feeding traits.

Open-File Report↗

USGS2025

Freshwater and diadromous Fishes of Puerto Rico

Freshwater and Diadromous Fishes of Puerto Rico describes the diversity of fishes in Puerto Rico’s freshwater environments and provides information on the history of research, management and conservation, and culture of fish and fisheries in Puerto Rico. This book’s catalog of fishes guides the reader in the identification of more than 50 native and nonnative species of fish from 22 families that occur in Puerto Rico’s freshwater lagoons, rivers, streams, and reservoirs. Each species account includes a map of known occurrences, and a description of each species’ morphological characteristics, biology, and distribution. Freshwater and Diadromous Fishes of Puerto Rico is the result of decades of scientific research; however, it is intended to be accessible and useful to readers with a variety of backgrounds, including scientists, students, and outdoor enthusiasts such as recreational anglers and freshwater snorkelers. Conservation and management are underlying themes of Freshwater and Diadromous Fishes of Puerto Rico . Though the main goal of this book is to be a resource for the identification of Puerto Rico’s freshwater fishes, and on their biology and ecology, it is also intended to increase awareness of threats to these fishes and their value to people and ecosystems.

Puerto Rico↗