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At least 703 records · Page 39Linked to original sources
USGS2021

Climate-mediated changes to linked terrestrial and marine ecosystems across the northeast Pacific coastal temperate rainforest margin

Coastal margins are important areas of materials flux that link terrestrial and marine ecosystems. Consequently, climate-mediated changes to coastal terrestrial ecosystems and hydrologic regimes have high potential to influence nearshore ocean chemistry and food web dynamics. Research from tightly coupled, high-flux coastal ecosystems can advance understanding of terrestrial–marine links and climate sensitivities more generally. In the present article, we use the northeast Pacific coastal temperate rainforest as a model system to evaluate such links. We focus on key above- and belowground production and hydrological transport processes that control the land-to-ocean flow of materials and their influence on nearshore marine ecosystems. We evaluate how these connections may be altered by global climate change and we identify knowledge gaps in our understanding of the source, transport, and fate of terrestrial materials along this coastal margin. Finally, we propose five priority research themes in this region that are relevant for understanding coastal ecosystem links more broadly.

BioScience↗
USGS2021

Blue waters, green bottoms: Benthic filamentous algal blooms are an emerging threat to clear lakes worldwide

Nearshore (littoral) habitats of clear lakes with high water quality are increasingly experiencing unexplained proliferations of filamentous algae that grow on submerged surfaces. These filamentous algal blooms (FABs) are sometimes associated with nutrient pollution in groundwater, but complex changes in climate, nutrient transport, lake hydrodynamics, and food web structure may also facilitate this emerging threat to clear lakes. A coordinated effort among members of the public, managers, and scientists is needed to document the occurrence of FABs, to standardize methods for measuring their severity, to adapt existing data collection networks to include nearshore habitats, and to mitigate and reverse this profound structural change in lake ecosystems. Current models of lake eutrophication do not explain this littoral greening. However, a cohesive response to it is essential for protecting some of the world's most valued lakes and the flora, fauna, and ecosystem services they sustain.

BioScience↗
USGS2024

Imperiled Great Basin terminal lakes: Synthesizing ecological and hydrological science gaps and research needs for waterbird conservation

Terminal lakes are declining globally because of human water demands, drought, and climate change. Through literature synthesis and feedback from the resource and conservation community, we review the state of research for terminal lakes in the Great Basin of the United States, which support millions of waterbirds annually, to prioritize ecological and hydrologic information needs. From an ecological perspective, research priorities include measuring the underlying differences in waterbird resource selection and distribution, migratory connectivity, abiotic factors that interact with prey densities to affect prey availability, and waterbird fitness or demography. Integrated links between water availability, water quality, and food webs are lacking in the literature. Scarce water availability data hinder the current knowledge of water extraction and evapotranspiration rates. Research that can address these priorities would help advance our understanding of how the Great Basin terminal lakes function as an interrelated system and support conservation efforts to reverse the decline of these critical lakes.

California, Nevada, Oregon, Utah↗
USGS2013

Changing ecosystem dynamics in the Laurentian Great Lakes: Bottom-up and top-down regulation

Understanding the relative importance of top-down and bottom-up regulation of ecosystem structure is a fundamental ecological question, with implications for fisheries and water-quality management. For the Laurentian Great Lakes, where, since the early 1970s, nutrient inputs have been reduced, whereas top-predator biomass has increased, we describe trends across multiple trophic levels and explore their underlying drivers. Our analyses revealed increasing water clarity and declines in phytoplankton, native invertebrates, and prey fish since 1998 in at least three of the five lakes. Evidence for bottom-up regulation was strongest in Lake Huron, although each lake provided support in at least one pair of trophic levels. Evidence for top-down regulation was rare. Although nonindigenous dreissenid mussels probably have large impacts on nutrient cycling and phytoplankton, their effects on higher trophic levels remain uncertain. We highlight gaps for which monitoring and knowledge should improve the understanding of food-web dynamics and facilitate the implementation of ecosystem-based management.

Illinois, Indiana, Michigan, Minnesota, new York, ↗
USGS2025

Methylmercury in subarctic amphibians: Environmental gradients, bioaccumulation, and estimated flux

Rapid warming in polar regions is causing large changes to ecosystems, including altering environmentally available mercury (Hg). Although subarctic freshwater systems have simple vertebrate communities, Hg in amphibians remains unexplored. We measured total Hg (THg) in wetland sediments and methylmercury (MeHg) in multiple life-stages (eggs to adults) of wood frogs ( Rana sylvatica ) and larval boreal chorus frogs ( Pseudacris maculata ) from up to 25 wetlands near Churchill, Manitoba (Canada), during the summers of 2018–2019. We used egg mass counts for wood frogs from 24 wetlands (2015–2019) and per-ovum MeHg concentrations to estimate site-level MeHg flux by metamorphs from wetlands to the terrestrial environment. Total Hg in wetland sediment was unrelated to MeHg concentrations of amphibian larvae, but sediment THg increased with from coastal tundra vegetation to inland boreal forests. Methylmercury concentrations of wood frog eggs (geometric mean = 35.9; range: 6.7–77.9 ng/g dry wt) exceeded previous reports for amphibians, including from sites contaminated by industrial sources of Hg. Methylmercury concentrations of adult wood frogs (298.9 ng/g dry wt) were also higher than that for frogs included in a recent assessment of MeHg in amphibians across the contiguous United States. Within wetlands, MeHg concentrations of wood frog larvae were strongly correlated with MeHg concentrations in eggs earlier in the summer, and concentrations increased with each life stage. We estimate there would have been 1,971.8–3,286.4 ng MeHg exported from wetlands by wood frog metamorphs, which is 3.4–5.6 times more MeHg than inputted by eggs. Collectively, these data provide an initial assessment of Hg concentrations, body burdens, and dynamics in subarctic food webs that are expected to experience large changes from climate warming.

Manitoba↗
USGS2025

Application of transcriptomics concentration-response modeling for prioritization of contaminants detected in tributaries of the North American Great Lakes

As part of the Great Lakes Restoration Initiative, chemical monitoring and surveillance efforts have detected approximately 330 chemicals in surface water of Great Lakes tributaries. There were 140 chemicals for which no empirical toxicity data were available. The aim of this study was to generate transcriptomic points of departure (tPODs) for 10 of these compounds and demonstrate how they could be applied in a screening-level prioritization. Organisms representing three trophic levels of the aquatic food web ( Pimephales promelas , Daphnia magna , and Raphidocelis subcapitata ) were exposed for 24 hr to a half-log dilution series of nominal exposure concentrations typically ranging from 66.7–0.021 µM of each chemical. In addition to observations of apical effects (e.g., survival and morphology), whole body transcriptomic responses (tPODs) to each chemical were evaluated with targeted analysis using TempO-seq for P. promelas and D. magna and nontargeted RNA-seq for R. subcapitata . The tPODs ranged from 0.18–10.8 µM for P. promelas and 0.32–29 µM for D. magna , with the most potent of the chemicals tested being fipronil carboxamide for both species. For R. subcapitata , the tPODs ranged from 0.04–1.77 µM, with gabapentin as the most potent chemical tested. Empirically derived tPODs from these data-poor chemicals were compared with concentrations detected in the Great Lakes basin. Environmental concentrations were less than the tPODs except for R. subcapitata and 3,4-dichlorophenyl isocyanate. Similarly, tPODs from previously tested data-rich chemicals were compared with environmental concentrations, in which case tPODs from several chemicals overlapped environmental concentrations. This work demonstrates the potential utility of emerging ecological high-throughput transcriptomics assays to support screening and prioritization of data-poor environmental contaminants.

Environmental Toxicology and Chemistry↗
USGS2025

Fate and effects to the benthic community of a copper treatment to eradicate invasive mussels in a large western river, USA

Copper-based chemical treatments are commonly used to eradicate invasive mussels in small ponds and lakes, but their use in large rivers has been limited. In 2023, in response to a detection of invasive quagga mussels, a 10-km reach of the Snake River (Idaho, USA), was treated with an unprecedented 19,300 kg of chelated copper molluscicide to a target concentration of 1,000 µg/L for 10 days. We assessed the transport and fate of the copper and its exposure and effects on the nontarget benthic community downstream. Water samples were collected at seven locations throughout the treatment period, and sediment, periphyton, and benthic macroinvertebrates were collected pre- and posttreatment. Nearly half of the original mass of copper was removed from the water column via sedimentation, sorption to algae, or biological uptake within the 10-km treatment reach and the first 15 km downstream. Even so, dissolved copper concentrations exceeded the acute toxicity threshold at least as far as 28 km downstream for more than 2 weeks. Sediment copper increased by up to 8.3-fold, exceeding the consensus-based sediment quality threshold effect concentration at several sites. Effects on benthic macroinvertebrates varied by taxa. From 0–28 km downstream, invertebrate abundances decreased 52%–94%, with gastropods among the most affected. Of the unique taxa present at these sites pretreatment, 52%–64% were not found posttreatment but were replaced by other taxa, indicating a reorganization of the base of the food web. Additionally, from 0–15 km downstream, the percentage of individuals from tolerant taxa increased two to15-fold. Findings from this study can help watershed managers plan future invasive mussel responses while protecting culturally, economically, and ecologically important nontarget species in large rivers.

Idaho↗
USGS2025

Effects of dietary selenium on the amphipod Hyalella azteca and the midge Chironomus dilutus

Chronic selenium (Se) water quality criteria are based primarily on dietary organoselenium exposure and subsequent reproductive effects in fish. Available chronic Se toxicity data suggests that invertebrates are less sensitive than fish, but chronic invertebrate studies are limited. We evaluated yeast-based diets for chronic toxicity studies with Hyalella azteca and Chironomus dilutus. Growth and survival were similar among C. dilutus fed a yeast-only diet, a mixture of yeast and fish flake food, and a mixture of yeast and diatoms. Survival and growth of H. azteca were best in the yeast + diatom diet, so this diet was used for subsequent tests. In rangefinder tests, H. azteca 28-day survival, growth, and biomass, and C. dilutus 11-day survival were all significantly reduced at a dietary Se concentration of 49 µg/g dry weight, whereas C. dilutus growth and biomass were only affected at 200 µg/g dry weight Se. H. azteca had similar sensitivity to dietary Se in a 28–42-day chronic test—survival, growth, and biomass were significantly reduced at 44.5 µg/g dry weight Se. Dietary selenium reduced H. azteca reproduction by 75%–100% relative to Controls, but differences were not significant. Tissue Se EC10s were lower for H. azteca (9.0–23 µg/g dry weight) than for C. dilutus (11–56 µg/g dry weight). However, model evaluations suggest that the C. dilutus 11-day survival and H. azteca 42-day EC10s were less reliable than other endpoints. When tissue EC10s were converted to equivalent Se concentrations in fish tissue with a food web model, H. azteca (18 µg/g dry weight) and C . dilutus (68 µg/g dry weight) ranked 6th and 12th of 13 freshwater genera, respectively. Overall, these results suggest that the current U.S. Environmental Protection Agency tissue-based Se water quality criteria would be protective for fish and invertebrates and could be used for management of fishless waters.

Environmental Toxicology and Chemistry↗
USGS2025

Predictors of mercury and pesticide fluxes by emerging adult aquatic insects from prairie pothole wetlands

Aquatic and terrestrial food webs are linked by movements of aquatic insects during their development from larvae to adults. Contaminants can affect these linkages by reducing insect survival and increasing tissue contaminant concentrations through adult metamorphosis, thus changing contaminant flux from water to land. Most anthropogenically influenced freshwater ecosystems are exposed to multiple contaminants. To better understand the combined effects of contaminants on aquatic–terrestrial linkages, we investigated how adult aquatic insect emergence and tissue contaminant concentrations affect insect-mediated contaminant flux of mercury and pesticides from wetlands. In a field survey of 15 wetlands in the Prairie Pothole Region, an important agricultural region of North America, we found that insect-mediated mercury flux was 3.5 times more strongly predicted by emergence biomass than tissue mercury concentration. Thus, factors that were previously found to influence aquatic insect emergence biomass in this system—including insecticide tissue concentrations in adult insects, open water surface area, and agricultural land use—were the most likely to drive insect-mediated mercury flux. Pesticide flux, however, was 3.3 times more strongly predicted by the tissue pesticide concentration than by emergence. Thus, factors that influence pesticide exposure and, to a smaller extent, emergence biomass were the most likely to drive pesticide flux. Our results show how factors driving contaminant fluxes by adult aquatic insects differ by contaminant class, and they suggest one mechanism by which toxic effects of one contaminant (pesticides) could influence the flux of another (mercury). Predicting contaminant fluxes in areas where different mixtures of contaminants are present can aid in identifying risk to insectivores.

Prairie Pothole Region↗
USGS2018

Acetylenotrophy: A hidden but ubiquitous microbial metabolism?

Acetylene (IUPAC name: ethyne) is a colorless, gaseous hydrocarbon, composed of two triple bonded carbon atoms attached to hydrogens (C 2 H 2 ). When microbiologists and biogeochemists think of acetylene, they immediately think of its use as an inhibitory compound of certain microbial processes and a tracer for nitrogen fixation. However, what is less widely known is that anaerobic and aerobic microorganisms can degrade acetylene, using it as a sole carbon and energy source and providing the basis of a microbial food web. Here, we review what is known about acetylene degrading organisms and introduce the term 'acetylenotrophs' to refer to the microorganisms that carry out this metabolic pathway. In addition, we review the known environmental sources of acetylene and postulate the presence of an hidden acetylene cycle. The abundance of bacteria capable of using acetylene and other alkynes as an energy and carbon source suggests that there are energy cycles present in the environment that are driven by acetylene and alkyne production and consumption that are isolated from atmospheric exchange. Acetylenotrophs may have developed to leverage the relatively high concentrations of acetylene in the pre-Cambrian atmosphere, evolving later to survive in specialized niches where acetylene and other alkynes were produced.

FEMS Microbiology Ecology↗
USGS2025

On the importance and practical conservation of nongame fishes.

Fisheries management has historically focused conservation efforts on game or sport species. However, most species are nongame—those not traditionally captured for sport or harvest in countries where recreational fisheries predominate. Greater conservation of nongame species could help ensure that population declines do not go unnoticed. Unfortunately, fisheries managers already manage complex ecosystems with limited resources, and they frequently are directed to focus on game fishes. However, game fish populations can also be tightly coupled to nongame fishes, so nongame management can sometimes also benefit game species. We reviewed functional roles of freshwater nongame fishes and suggest categories that may be especially important for conservation. Of note, nongame fishes are more imperiled than game fishes and fill largely distinct functional roles. These roles include food-web impacts, ecosystem engineering, and mussel hosting. Management priorities could include nongame piscivores and species with high biomass, especially herbivores, nest builders, and imperiled mussel hosts. We provide practical options for including nongame fishes in current management, many of which require little additional funding. These include recognizing when sport fish funding and conservation can also benefit nongame species, whole-community sampling at some monitoring locations, collecting catch data for select species observed during game fish surveys, embracing environmental DNA sampling, and making presence–absence record keeping the default option.

Fisheries↗
USGS2025

Sustaining Namāēw (Lake Sturgeon): Partner-led climate adaptation for Indigenous fisheries in the Laurentian Great Lakes

Namāēw (Menominee; Lake Sturgeon Acipenser fulvescens ) have long supported Indigenous culture and food sovereignty but have declined by over 80% in the Laurentian Great Lakes, exacerbating their sensitivity to climate change. Following interest from Indigenous leaders, we initiated a partnership-driven effort to (1) assess climate effects and (2) develop potential adaptation options for Namāēw using a participatory, transdisciplinary approach that combines multiple ways of knowing. Through a literature review and nine semistructured conversations with officials from Indigenous Nations and organizations in the Great Lakes, we identified central themes including access, culture, and fish persistence. Other concerns included habitat, food web shifts, and water quality. Prominent adaptation themes involved population assessments, stocking, regulations, habitat restoration, interagency coordination, and cultural advocacy. These findings underscore the importance of partnership-driven research to support Indigenous fisheries through knowledge coproduction and equitable adaptation. Our approach provides a model to inform stewardship planning for fisheries that are facing global change.

Laurentian Great Lakes↗
USGS2019

Micro-geographic population genetic structure within Arctic cod (Boreogadus saida) in Beaufort Sea of Alaska

Many marine organisms show significant levels of genetic heterogeneity on local spatial scales despite exhibiting limited genetic structure at large geographic scales which can be produced through a variety of mechanisms. The Arctic cod ( Boreogadus saida ) is a circumpolar species and is a vital species in Arctic food webs. To examine population genetic structure of Arctic cod at macro- and micro-geographic scales, we characterized variation at mitochondrial DNA (mtDNA) and microsatellite loci among Arctic cod located in the Chukchi and Beaufort seas in Alaska. We found two distinct mtDNA haplotype clusters, although there was no underlying geographic pattern ( F ST = −0.001). Congruent with this finding, microsatellite loci suggested a panmictic population ( F ST = 0.001) across northern Alaskan marine waters at a large spatial scale. However, we found slight but significant micro-geographic partitioning of genetic variation in the southern shelf of the Beaufort Sea that appeared to be associated with the western reaches of the Mackenzie River plume. This fine-scale spatial pattern was not associated with kin-associated groups, suggesting larvae cohorts are not remaining together throughout development. We hypothesize that this pattern reflects the intermixing of Pacific and Arctic origin lineages of Arctic cod.

Alaska↗
USGS2015

Effects of fire on small mammal communities in frequent-fire forests in California

Fire is a natural, dynamic process that is integral to maintaining ecosystem function. The reintroduction of fire (e.g., prescribed fire, managed wildfire) is a critical management tool for protecting many frequent-fire forests against stand-replacing fires while restoring an essential ecological process. Understanding the effects of fire on forests and wildlife communities is important in natural resource planning efforts. Small mammals are key components of forest food webs and essential to ecosystem function. To investigate the relationship of fire to small mammal assemblages, we live trapped small mammals in 10 burned and 10 unburned forests over 2 years in the central Sierra Nevada, California. Small mammal abundance was higher in unburned forests, largely reflecting the greater proportion of closed-canopy species such as Glaucomys sabrinus in unburned forests. The most abundant species across the entire study area was the highly adaptable generalist species, Peromyscus maniculatus . Species diversity was similar between burned and unburned forests, but burned forests were characterized by greater habitat heterogeneity and higher small mammal species evenness. The use and reintroduction of fire to maintain a matrix of burn severities, including large patches of unburned refugia, creates a heterogeneous and resilient landscape that allows for fire-sensitive species to proliferate and, as such, may help maintain key ecological functions and diverse small mammal assemblages.

California↗
USGS2025

Carbon and nitrogen isotopes of different native fish tissues from the Santa Ana River, California

Objective Stable isotopes are commonly used to understand the role of fishes in aquatic food webs. However, variability in species- and tissue-specific isotopic values can affect the inference that is drawn from a stable isotope study. We evaluated differences in stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) among three tissue types (white muscle, caudal fin rays, and eye lenses) for Santa Ana Sucker Pantosteus santaanae and Arroyo Chub Gila orcuttii to inform the design of a stable isotope study in the Santa Ana River, an urban river that is located in southern California. Methods We used multivariate analyses to test for differences in the stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) among the three tissue types that were collected from Santa Ana Sucker and Arroyo Chub. We also summarized the variability in isotopic values that was recorded over time in fish eye lenses and interpreted this variability in reference to the spatial patterns in isotopic values that have been previously reported throughout the Santa Ana River. Results We found that fin ray tissue and white muscle tissue were not significantly different for either isotope or fish species. Fish eye lenses were significantly higher in δ 13 C than muscle tissue, and eye lenses were significantly higher in δ 15 N than fin ray tissue for both fishes. We also found a greater range in δ 13 C and δ 15 N across eye lens layers for Santa Ana Sucker (δ 13 C = 2.01 ± 0.96‰, δ 15 N = 4.93 ± 4.18‰) than for Arroyo Chub (δ 13 C = 0.96 ± 0.65‰, δ 15 N = 4.63 ± 1.45‰). Conclusion Our results indicate that fin rays may be a viable nonlethal alternative to white muscle tissue for use in a stable isotope study of native fish of the Santa Ana River. Additionally, eye lenses could provide a chemical history of fishes within the river, but species-specific correction factors may be needed if stable isotope values for eye lenses are to be compared with more conventional tissue types (e.g., white muscle).

California↗
USGS2020

Disease can shape marine ecosystems

This chapter reviews how marine ecosystems respond to parasites. Evidence from several marine ecosystems shows that parasites can wield control over ecosystem structure, function, and dynamics by regulating host density and phenotype. Like predators, parasites can generate or modify trophic cascades, regulate important foundational species and ecosystem engineers, and mediate species coexistence by affecting competitive outcomes. Sometimes the parasites have clear positive impacts within ecosystems, such as increasing species diversity or maintaining ecosystem stability. Other times, parasites may have destabilizing effects that signal an ecosystem out of balance. But it is now clear that some (but not all) parasites can have strong and, at times, predictable effects, and should thus be incorporated into food web and ecosystem models.

Book chapter↗
USGS2022

Minimal diel vertical migration and consistent zooplankton capturability in low productivity reservoirs, Oregon

Diel migrations of zooplanktons occur in marine and freshwater systems and can complicate inferences from studies. If populations perform vertical or horizontal diel migrations, daytime-only sampling can mischaracterize distributions and abundances. Zooplanktons also often display reduced capture avoidance at night and occupy areas easier to sample near the surface and away from littoral structure and the benthos. We examined zooplankton abundance, water column position and taxonomic composition during daytime and nighttime new moon periods using discrete depth sampling in oligo-mesotrophic reservoirs in Oregon, USA. These reservoirs have limited littoral structures, but support populations of zooplanktivorous fishes that we expected to drive diel vertical migrations. Contrary to our expectations, at night, most zooplankton taxa were within 2 m of their daytime distributional peak and did not display differences in abundance from day to night sampling. We consider factors that may help predict whether diel vertical migration occurs in a system. Where daytime sampling is sufficient to characterize zooplankton densities and distributions, costs and risks specific to nighttime sampling may be avoided. Improving our knowledge of zooplankton dynamics, particularly in ecosystems with limited diurnal variability, is an important part of understanding lake and reservoir food webs and can optimize the efforts of future studies.

Oregon↗
USGS2014

Diet of Mysis diluviana reveals seasonal patterns of omnivory and consumption of invasive species in offshore Lake Michigan

Recent changes in Lake Michigan’s lower trophic levels were hypothesized to have influenced the diet of omnivorous Mysis diluviana. In this study, the stomach contents of Mysis were examined from juvenile and adults collected monthly (April–October) from a 110-m bottom depth site to describe their seasonal diet in LakeMichigan during 2010. Diatoms were the most common prey item ingested, followed by calanoid copepods, and chrysophytes. Dreissenid veligers were documented in mysid diets for the first time in the Great Lakes, and Cercopagis pengoi were not only consumed but even preferred by adults in summer. Diet proportions by weight were dominated by calanoids, although diets showed a marked shift toward cladocerans in autumn. Juvenile and adult Mysis selected primarily for cladoceran prey but also selected for some calanoid copepod taxa. Comparing available Mysis diet data from 1985 to 2010 indicated generally fewer cladocerans and rotifers per gut and less consistent differences in copepods and Peridinium consumed. The seasonal composition of phyto- and zooplankton prey documented herein should be useful to those seeking to understand the trophic role of Mysis in offshore food webs, but caution should be expressed when generalizing similarities in Mysis diets across other lakes because Lake Michigan’s population seems relatively more herbivorous.

Lake Michigan↗