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At least 109 records · Page 6Linked to original sources
USGS2025

Arsenic accumulation in Sonora Mud Turtles (Kinosternon sonoriense) in an unusual freshwater food web

Montezuma Well is an unusual fishless, spring-fed, desert wetland in central Arizona. Water in the wetland is naturally enriched with > 100 µg/l dissolved geogenic arsenic (As) and supports a simple aquatic food web dominated by a small number of endemic invertebrate species that achieve high abundances. Previous studies of As among various environmental compartments and organisms in Montezuma Well did not include omnivorous Sonora Mud turtles ( Kinosternon sonoriense ) despite their potential importance in the As cycle by virtue of their substantial biomass and role as top predators. We measured As concentrations in water, sediment, and organisms (macrophytes, amphipods, insects, leeches, and turtles) representing a range of trophic levels in order to document the importance of turtles at the apex of the Montezuma Well food web and in the As cycle. Concentrations of As in turtles varied according to tissue type. The greatest values (up to 26.77 mg/kg dry weight) were in the scutes of 1 of our oldest turtles (31.5 yrs). These elevated concentrations may be due to the affinity of As to react with sulfur in the keratin of scutes, and therefore might reflect duration of exposure in long-lived turtles. Although As concentrations generally tend to decrease when moving up to higher trophic levels in a food web, our results were different. Relatively elevated concentrations reported in sediments by us and a previous study declined in plant samples as expected. Amphipod concentrations increased but then decreased again in 3 of their invertebrate predators. Arsenic concentrations in endemic leeches were extremely elevated with a mean value of 72.2 mg/kg. The mean concentration of As in turtles was 7.08 mg/kg across tissue types and was greater than the plants or invertebrates they eat, with the notable exception of leeches, which have been proposed to be part of their diet.

Arizona↗
USGS2020

Shifting food web structure during dam removal—Disturbance and recovery during a major restoration action

We measured food availability and diet composition of juvenile salmonids over multiple years and seasons before and during the world’s largest dam removal on the Elwha River, Washington State. We conducted these measurements over three sediment-impacted sections (the estuary and two sections of the river downstream of each dam) and compared these to data collected from mainstem tributaries not directly affected by the massive amount of sediment released from the reservoirs. We found that sediment impacts from dam removal significantly reduced invertebrate prey availability, but juvenile salmon adjusted their foraging so that the amount of energy in diets was similar before and during dam removal. This general pattern was seen in both river and estuary habitats, although the mechanisms driving the change and the response differed between habitats. In the estuary, the dietary shifts were related to changes in invertebrate assemblages following a hydrological transition from brackish to freshwater caused by sediment deposition at the river’s mouth. The loss of brackish invertebrate species caused fish to increase piscivory and rely on new prey sources such as plankton. In the river, energy provided to fish by Ephemeroptera, Plecoptera, and Trichoptera taxa before dam removal was replaced first by terrestrial invertebrates, and then by sediment-tolerant taxa such as Chironomidae. The results of our study are consistent with many others that have shown sharp declines in invertebrate density during dam removal. Our study further shows how those changes can move through the food web and affect fish diet composition, selectivity, and energy availability. As we move further along the dam removal response trajectory, we hypothesize that food web complexity will continue to increase as annual sediment load now approaches natural background levels, anadromous fish have recolonized the majority of the watershed between and above the former dams, and revegetation and microhabitats continue to develop in the estuary.

Washington↗
USGS2018

Stable isotope comparison between mantle and foot tissues of two freshwater unionids: Implications for food web studies

Unionid mussels are a key taxon for stable isotope studies of aquatic food webs, often serving as the primary integrator of the pelagic baseline. Past isotope studies with mussels have commonly used either foot tissue or mantle tissue, but no study has yet to quantify the relation of both carbon and nitrogen isotopes between these two tissue sources. This makes it difficult to justify cross-study comparisons when different tissue compartments and different species were used as the basis of food web models. Therefore, we collected foot and mantle tissues from two common mussel species, Amblema plicata and Fusconaia flava , from lotic and lentic sites in the Upper Mississippi and St. Croix rivers (Minnesota/Wisconsin). Paired tissue samples from each individual were analyzed for stable isotopes of nitrogen and carbon. There were strong relations between tissue types for both isotopes between species ( r 2 > 0.93). Paired t -tests indicated that there were statistically significant differences between the tissue sources in some instances, but the difference (0.04–0.21‰) was less than the analytical precision of the mass spectrometer (circa 0.2–0.3‰). We conclude that the isotopic values from these two tissue sources are biologically comparable and recommend that researchers use the tissue source and extraction technique that minimizes stress to the mussels. We also tested for significant differences between species within a site for either isotope or tissue type and found no statistically significant difference between species with the exception of carbon in foot tissue at two sites. The highly correlated isotopic response supports the interchangeable use of both tissue compartments and both species. These findings support comparisons between studies whether the results were based on either of these tissues or the two species studied. Comparability will also simplify sampling designs, save time, and save money for processing samples without diminishing the usefulness of the data.

Minnesota, Wisconsin↗
USGS2026

Mercury biomagnification across food webs with varying non-native fish presence: Implications for native fish conservation in the upper Colorado River Basin

Environmental contaminants and non-native species introductions negatively affect aquatic ecosystem conservation. Mercury (Hg) accumulates within food webs where it can biomagnify to toxic concentrations, which can be affected by altered trophic relationships from non-native species. This study examined Hg concentrations (n samples = 655) and stable carbon and nitrogen isotope ( n = 746) compositions in native ( n = 313) and non-native ( n = 342) species among four river subbasins (Gunnison, Lower Green, Colorado-Dolores, and White-Yampa), in the Upper Colorado River Basin (UCRB) during 2016 and 2017 to inform the potential combined effects of Hg exposure and non-native species interactions on native fishes of conservation concern. We assessed Hg biomagnification at the fish assemblage level, compared concentrations to risk thresholds for fish and human health, and evaluated niche overlap among trophic levels across subbasins. The generalist-invertivores feeding guild had the lowest Hg concentrations (0.001–0.191 μg g −1 wet weight), and no individuals exceeded the U.S. Environmental Protection Agency aquatic life criterion (0.225 μg g −1 ). Piscivores had the highest concentrations (0.008–1.840 μg g −1 ), and 74% of individuals exceeded the criterion. Biomagnification across trophic levels was observed throughout the UCRB, yet varied by subbasin, with higher magnification factors in the Lower Green and White-Yampa subbasins which also had the highest proportion of non-native species. Stable isotope compositions revealed niche overlap among native and non-native species. Additionally, trophic position varied within species among the subbasins. The proliferation of non-native species has likely reshaped food webs and may have intensified the potential threat Hg poses to native fish recovery and conservation. This study documented increased Hg concentrations relative to past assessments, suggesting that continued monitoring could assist in evaluating trends in Hg accumulation. Particularly studies that focus on sources entering the food web, vectors for accumulation, and competitive interactions among native and non-native species.

Colorado, Utah, Wyoming↗
USGS2023

Landscape diversity promotes stable food-web architectures in large rivers

Uncovering relationships between landscape diversity and species interactions is crucial for predicting how ongoing land-use change and homogenization will impact the stability and persistence of communities. However, such connections have rarely been quantified in nature. We coupled high-resolution river sonar imaging with annualized energetic food webs to quantify relationships among habitat diversity, energy flux, and trophic interaction strengths in large-river food-web modules that support the endangered Pallid Sturgeon. Our results demonstrate a clear relationship between habitat diversity and species interaction strengths, with more diverse foraging landscapes containing higher production of prey and a greater proportion of weak and potentially stabilizing interactions. Additionally, rare patches of large and relatively stable river sediments intensified these effects and further reduced interaction strengths by increasing prey diversity. Our findings highlight the importance of landscape characteristics in promoting stabilizing food-web architectures and provide direct relevance for future management of imperilled species in a simplified and rapidly changing world.

Ecology Letters↗
USGS2022

Methylmercury stable isotopes: New insights on assessing aquatic food web bioaccumulation in legacy impacted regions

Through stable isotope measurements of total mercury (HgT), identification of crucial processes and transformations affecting different sources of mercury (Hg) has become possible. However, attempting to use HgT stable isotopes to track bioaccumulation of Hg sources among different food web compartments can be challenging, if not impossible, when tissues have varying methylmercury (MeHg) contents. We measured HgT and MeHg stable isotope ratios within the lower Fox River to examine how these values differed across the food web and if isotope values in biota were influenced by legacy contamination. We showed that seston, invertebrates, and fish had a large range of δ 202 HgT (−0.74 to 0.15 ‰, n = 11) due to varying MeHg contents in tissues but a commonly conserved MeHg isotope value (δ 202 MeHg ave = 0.01 ± 0.12 ‰, 1 standard deviation, n = 11). We also examined some mathematical approaches to estimate the MeHg isotope values, which were mostly comparable to measured MeHg isotope values in the Fox River, with some exceptions. In this study, we observed that the MeHg isotope values can elucidate links between different food web compartments and provide insight on aquatic Hg cycling that can be masked by the sole use of HgT isotopes in contaminated sites.

Wisconsin↗
USGS2021

Movement of synthetic organic compounds in the food web after the introduction of invasive quagga mussels (Dreissena bugensis) in Lake Mead, Nevada and Arizona, USA

Introductions of dreissenid mussels in North America have been a significant concern over the last few decades. This study assessed the distribution of synthetic organic compounds (SOCs) in the food web of Lake Mead, Nevada/Arizona, USA and how this distribution was influenced by the introduction of invasive quagga mussels. A clear spatial gradient of SOC concentrations in water was observed between lake basins downstream of populated areas and more rural areas. Within the food web, trophic magnification factors (TMF) indicated statistically significant biomagnification for nine, and biodilution for two, of 22 SOCs examined. The highest value recorded was for PCB 118 (TMF, 5.14), and biomagnification of methyl triclosan (TMF, 3.85) was also apparent. Biodilution was observed for Tonalide® (0.06) and Galaxolide® (0.38). Total SOC concentration in quagga mussels was higher than in three pelagic fishes. Also, 19 of 20 SOC examined in Largemouth Bass ( Micropterus salmoides ) had substantially lower concentrations in 2013, when quagga mussels had become well established, than in 2007/08, soon after quagga mussels were introduced. Estimates of SOC concentrations in the water column and quagga mussels suggest that a considerable portion (~10.5%) of the SOC mass in the lake has shifted from the pelagic to the benthic environments due to quagga mussel growth. These observations suggest that benthic species, such as the endangered Razorback Sucker, may be experiencing increased risk of SOC exposure. In addition, stable isotope analysis (carbon and nitrogen) indicated a decrease in the nutritional value of zooplankton to consumers (e.g., Razorback Sucker larvae) since quagga mussels became established. These changes could affect Razorback Sucker larval survival and recruitment. Results from this study strongly suggest that the introduction of quagga mussels has greatly altered the dynamics of SOCs and other processes in the food web of Lake Mead.

Arizona, Nevada↗
USGS2018

Trophic compression of lake food webs under hydrologic disturbance

The need to protect biostructure is increasingly recognized, yet empirical studies of how human exploits affect ecological networks are rare. Studying the effects of variation in human disturbance intensity from decades past can help us understand and anticipate ecosystem change under alleviated or amplified disturbance over decades to come. Here, we use stable isotopes and an innovative analytical approach to compare the food webs of two akin lake ecosystems subject to disparate water use regimes, a pervasive, yet unappreciated stressor. We show that intensive water use (persistent, early season, rapid lake‐level drawdown) can compress trophic diversity by 46%, necessitating reorganization of biostructural elements configuring lake food webs. Compression occurred over the δ 13 C axis indicating erosion of basal trophic diversity, but food chain length remained intact over the period and intensity of disturbance examined. This study demonstrates the potential for water use, like other disturbances (warming, eutrophication, and invasive species), to mute opportunity for benthic‐pelagic coupling and benefits to lake food webs and the inherent capacity of lake ecosystems to adapt to stress. Trophically compressed lakes may be less able to adapt to intensified water use.

Ecosphere↗
USGS2021

Dynamics of the seasonal migration of Round Goby (Neogobius melanostomus, Pallas 1814) and implications for the Lake Ontario food web

Seasonal migrations of fish populations can have large effects on lake nutrient budgets and food web dynamics, but the addition of a migrating non‐native species may alter these dynamics. The Round Goby ( Neogobius melanostomus ) arrived in Lake Ontario (USA/Canada) about 20 years ago with a documented history of annual offshore–inshore migrations in its native range. Here we combined nearshore, fixed‐plot video with offshore trawl data to document the annual migration of this population over multiple years. This behaviour was correlated with seasonal, nearshore temperature changes. The population size structure and mean fish length of returning fish were smaller than those of out‐migrating fish. The out‐migrating population contained an estimated 37.7 metric tonnes of phosphorous; and we estimated roughly 20 metric tonnes were translocated to and remained in offshore waters over the winter months, representing an important nutrient subsidy to a variety of offshore piscivorous fish. Lake Sturgeon ( Acipenser fulvescens ) have incorporated Round Goby extensively into their diet and consume a size range of fish matching the size range of missing Round Goby that fail to return to the nearshore. We conclude Round Goby are an important prey within the food web of Lake Ontario and translocate roughly 6.5% of the monthly total phosphorous load entering from surface waters. Further investigations of the nutrient content, population size structure and fate of migrating Round Goby in Lake Ontario are warranted to clarify the extent of this prey and nutrient subsidy in ongoing assessments of lake condition.

Lake Ontario↗
USGS2004

The effects of mixotrophy on the stability and dynamics of a simple planktonic food web

Recognition of the microbial loop as an important part of aquatic ecosystems disrupted the notion of simple linear food chains. However, current research suggests that even the microbial loop paradigm is a gross simplification of microbial interactions due to the presence of mixotrophs—organisms that both photosynthesize and graze. We present a simple food web model with four trophic species, three of them arranged in a food chain (nutrients–autotrophs–herbivores) and the fourth as a mixotroph with links to both the nutrients and the autotrophs. This model is used to study the general implications of inclusion of the mixotrophic link in microbial food webs and the specific predictions for a parameterization that describes open ocean mixed layer plankton dynamics. The analysis indicates that the system parameters reside in a region of the parameter space where the dynamics converge to a stable equilibrium rather than displaying periodic or chaotic solutions. However, convergence requires weeks to months, suggesting that the system would never reach equilibrium in the ocean due to alteration of the physical forcing regime. Most importantly, the mixotrophic grazing link seems to stabilize the system in this region of the parameter space, particularly when nutrient recycling feedback loops are included.

Theoretical Population Biology↗
USGS2015

Evidence for the assimilation of ancient glacier organic carbon in a proglacial stream food web

We used natural abundance δ 13 C, δ 15 N, and Δ 14 C to compare trophic linkages between potential carbon sources (leaf litter, epilithic biofilm, and particulate organic matter) and consumers (aquatic macroinvertebrates and fish) in a nonglacial stream and two reaches of the heavily glaciated Herbert River. We tested the hypothesis that proglacial stream food webs are sustained by organic carbon released from glacial ecosystems. Carbon sources and consumers in the nonglacial stream had carbon isotope values that ranged from -30‰ to -25‰ for δ 13 C and from -14‰ to 53‰ for Δ 14 C reflecting a food web sustained mainly on contemporary primary production. In contrast, biofilm in the two glacial stream sites was highly Δ 14 C-depleted (-215‰ to 175‰) relative to the nonglacial stream consistent with the assimilation of ancient glacier organic carbon. IsoSource modeling showed that in upper Herbert River, macroinvertebrates (Δ 14 C = -171‰ to 22‰) and juvenile salmonids (Δ 14 C = −102‰ to 17‰) reflected a feeding history of both biofilm (~ 56%) and leaf litter (~ 40%). We estimate that in upper Herbert River on average 36% of the carbon incorporated into consumer biomass is derived from the glacier ecosystem. Thus, 14 C-depleted glacial organic carbon was likely transferred to higher trophic levels through a feeding history of bacterial uptake of dissolved organic carbon and subsequent consumption of 14 C-depleted biofilm by invertebrates and ultimately fish. Our findings show that the metazoan food web is sustained in part by glacial organic carbon such that future changes in glacial runoff could influence the stability and trophic structure of proglacial aquatic ecosystems.

Limnology and Oceanography↗
USGS2003

Potential for increased mercury accumulation in the estuary food web

Present concentrations of mercury in large portions of San Francisco Bay (Bay), the Sacramento-San Joaquin Delta (Delta), and the Sacramento and San Joaquin rivers are high enough to warrant concern for the health of humans and wildlife. Large scale tidal wetland restoration is currently under consideration as a means of increasing populations of fish species of concern. Tidal wetland restoration activities may lead to increased concentrations of mercury in the estuarine food web and exacerbate the existing mercury problem. This paper evaluates our present ability to predict the local and regional effects of restoration actions on mercury accumulation in aquatic food webs. A sport fish consumption advisory is in place for the Bay, and an advisory is under consideration for the Delta and lower Sacramento and San Joaquin rivers. Mercury concentrations in eggs of several water bird species from the Bay have exceeded the lowest observed effect level. A variety of mercury sources, largely related to historic mercury and gold mining, is present in the watershed and has created a spatially heterogeneous distribution of mercury in the Bay-Delta Estuary. Mercury exists in the environment in a variety of forms and has a complex biogeochemical cycle. The most hazardous form, methylmercury, is produced at a relatively high rate in wetlands and newly flooded aquatic habitats. It is likely that distinct spatial variation on multiple spatial scales exists in net methylmercury production in Bay-Delta tidal wetlands, including variation within each tidal wetland, among tidal wetlands in the same region, and among tidal wetlands in different regions. Understanding this spatial variation and its underlying causes will allow environmental managers to minimize the negative effects of mercury bioaccumulation as a result of restoration activities. Actions needed to reduce the uncertainty associated with this issue include a long term, multifaceted research effort, long term monitoring on local and regional scales, and careful evaluation of individual restoration projects with regard to potential increase of food web mercury.

California↗
USGS2018

Critical review: Grand challenges in assessing the adverse effects of contaminants of emerging concern on aquatic food webs

Much progress has been made in the past few decades in understanding the sources, transport, fate, and biological effects of contaminants of emerging concern (CECs) in aquatic ecosystems. Despite these advancements, significant obstacles still prevent comprehensive assessments of the environmental risks associated with the presence of CECs. Many of these obstacles center around the extrapolation of effects of single chemicals observed in the laboratory or effects found in individual organisms or species in the field to impacts of multiple stressors on aquatic food webs. In the present review, we identify 5 challenges that must be addressed to promote studies of CECs from singular exposure events to multispecies aquatic food web interactions. There needs to be: 1) more detailed information on the complexity of mixtures of CECs in the aquatic environment, 2) a greater understanding of the sublethal effects of CECs on a wide range of aquatic organisms, 3) an ascertaining of the biological consequences of variable duration CEC exposures within and across generations in aquatic species, 4) a linkage of multiple stressors with CEC exposure in aquatic systems, and 5) a documenting of the trophic consequences of CEC exposure across aquatic food webs. We examine the current literature to show how these challenges can be addressed to fill knowledge gaps.

Environmental Toxicology and Chemistry↗
USGS2014

Sustainability of the Lake Superior fish community: Interactions in a food web context

The restoration and rehabilitation of the native fish communities is a long-term goal for the Laurentian Great Lakes. In Lake Superior, the ongoing restoration of the native lake trout populations is now regarded as one of the major success stories in fisheries management. However, populations of the deepwater morphotype (siscowet lake trout) have increased much more substantially than those of the nearshore morphotype (lean lake trout), and the ecosystem now contains an assemblage of exotic species such as sea lamprey, rainbow smelt, and Pacific salmon (chinook, coho, and steelhead). Those species play an important role in defining the constraints and opportunities for ecosystem management. We combined an equilibrium mass balance model (Ecopath) with a dynamic food web model (Ecosim) to evaluate the ecological consequences of future alternative management strategies and the interaction of two different sets of life history characteristics for fishes at the top of the food web. Relatively rapid turnover rates occur among the exotic forage fish, rainbow smelt, and its primary predators, exotic Pacific salmonids. Slower turnover rates occur among the native lake trout and burbot and their primary prey—lake herring, smelt, deepwater cisco, and sculpins. The abundance of forage fish is a key constraint for all salmonids in Lake Superior. Smelt and Mysis play a prominent role in sustaining the current trophic structure. Competition between the native lake trout and the exotic salmonids is asymmetric. Reductions in the salmon population yield only a modest benefit for the stocks of lake trout, whereas increased fishing of lake trout produces substantial potential increases in the yields of Pacific salmon to recreational fisheries. The deepwater or siscowet morphotype of lake trout has become very abundant. Although it plays a major role in the structure of the food web it offers little potential for the restoration of a valuable commercial or recreational fishery. Even if a combination of strong management actions is implemented, the populations of lean (nearshore) lake trout cannot be restored to pre-fishery and pre-lamprey levels. Thus, management strategy must accept the ecological constraints due in part to the presence of exotics and choose alternatives that sustain public interest in the resources while continuing the gradual progress toward restoration.

Ecosystems↗
USGS2014

Incorporation of inorganic mercury (Hg2+) in pelagic food webs of ultraoligotrophic and oligotrophic lakes: the role of different plankton size fractions and species assemblages

In lake food webs, pelagic basal organisms such as bacteria and phytoplankton incorporate mercury (Hg 2+ ) from the dissolved phase and pass the adsorbed and internalized Hg to higher trophic levels. This experimental investigation addresses the incorporation of dissolved Hg 2+ by four plankton fractions (picoplankton: 0.2–2.7 μm; pico + nanoplankton: 0.2–20 μm; microplankton: 20–50 μm; and mesoplankton: 50–200 μm) obtained from four Andean Patagonian lakes, using the radioisotope 197 Hg 2+ . Species composition and abundance were determined in each plankton fraction. In addition, morphometric parameters such as surface and biovolume were calculated using standard geometric models. The incorporation of Hg 2+ in each plankton fraction was analyzed through three concentration factors: BCF (bioconcentration factor) as a function of cell or individual abundance, SCF (surface concentration factor) and VCF (volume concentration factor) as functions of individual exposed surface and biovolume, respectively. Overall, this investigation showed that through adsorption and internalization, pico + nanoplankton play a central role leading the incorporation of Hg 2+ in pelagic food webs of Andean lakes. Larger planktonic organisms included in the micro- and mesoplankton fractions incorporate Hg 2+ by surface adsorption, although at a lesser extent. Mixotrophic bacterivorous organisms dominate the different plankton fractions of the lakes connecting trophic levels through microbial loops (e.g., bacteria–nanoflagellates–crustaceans; bacteria–ciliates–crustaceans; endosymbiotic algae–ciliates). These bacterivorous organisms, which incorporate Hg from the dissolved phase and through their prey, appear to explain the high incorporation of Hg 2+ observed in all the plankton fractions.

Patagonia↗
USGS2019

Negative frequency-dependent foraging behaviour in a generalist herbivore (Alces alces) and its stabilizing influence on food-web dynamics

1. Resource selection is widely appreciated to be context‐dependent and shaped by both biological and abiotic factors. However, few studies have empirically assessed the extent to which selective foraging behaviour is dynamic and varies in response to environmental conditions for free‐ranging animal populations. 2. Here, we assessed the extent that forage selection fluctuated in response to different environmental conditions for a free‐ranging herbivore, moose (Alces alces), in Isle Royale National Park, over a 10‐year period. More precisely, we assessed how moose selection for coniferous versus deciduous forage in winter varied between geographic regions and in relation to (a) the relative frequency of forage types in the environment (e.g. frequency‐dependent foraging behaviour), (b) moose abundance, (c) predation rate (by grey wolves) and (d) snow depth. These factors are potentially important for their influence on the energetics of foraging. We also built a series of food‐chain models to assess the influence of dynamic foraging strategies on the stability of food webs. 3. Our analysis indicates that moose exhibited negative frequency dependence, by selectively exploiting rare resources. Frequency‐dependent foraging was further mediated by density‐dependent processes, which are likely to be predation, moose abundance or some combination of both. In particular, frequency dependence was weaker in years when predation risk was high (i.e. when the ratio of moose to wolves was relatively low). Selection for conifers was also slightly weaker during deep snow years. 4. The food‐chain analysis indicates that the type of frequency‐dependent foraging strategy exhibited by herbivores had important consequences for the stability of ecological communities. In particular, the dynamic foraging strategy that we observed in the empirical analysis (i.e. negative frequency dependence being mediated by density‐dependent processes) was associated with more stable food web dynamics compared to fixed foraging strategies. 5. The results of this study indicated that forage selection is a complex ecological process, varying in response to both biological (predation and moose density) and abiotic factors (snow depth) and over relatively small spatial scales (between regions). This study also provides a useful framework for assessing the influence of other aspects of foraging behaviour on the stability of food web dynamics.

Michigan↗
USGS2026

An ecosystem-scale model of PFAS dynamics in stream-to-riparian food webs

Per- and polyfluoroalkyl substances (PFAS) are widespread contaminants in aquatic ecosystems, where they bioaccumulate and trophically transfer through food webs. We derived an ecosystem-scale model assessing Σ 12 PFAS partitioning, bioaccumulation by larval aquatic insects, bioamplification by adult aquatic insects, and trophic transfer from aquatic insects to riparian spiders using data collected across five streams in a mildly impacted watershed. Partitioning involved the greatest PFAS enrichments (range in posterior median log 10 k d values = 1.5–2.1), with lesser concentration increases from particulates to larval aquatic insects and from larval to adult aquatic insects, and Σ 12 PFAS concentration decreases from adult aquatic insects to spiders. Among the 12 compounds, PFOS had the largest proportional contribution to Σ 12 PFAS concentrations for all sample types, with consistently increasing concentrations from surface water to adult aquatic insects. Σ 12 PFAS concentrations (5.4–51 ppb wet weight), body burdens (0.44–5.2 ng per individual), and bioamplification factors (0.15–4.9) differed considerably among five common aquatic insect taxa. This study presents a robust modeling framework for PFAS trophodynamics and offers insights into the biological controls that contribute to the context dependency of PFAS at the interfaces of aquatic and terrestrial food webs.

Connecticut, Massachusetts↗
USGS2017

Food-web dynamics and isotopic niches in deep-sea communities residing in a submarine canyon and on the adjacent open slopes

Examination of food webs and trophic niches provide insights into organisms' functional ecology, yet few studies have examined trophodynamics within submarine canyons, where the interaction of canyon morphology and oceanography influences habitat provision and food deposition. Using stable isotope analysis and Bayesian ellipses, we documented deep-sea food-web structure and trophic niches in Baltimore Canyon and the adjacent open slopes in the US Mid-Atlantic Region. Results revealed isotopically diverse feeding groups, comprising approximately 5 trophic levels. Regression analysis indicated that consumer isotope data are structured by habitat (canyon vs. slope), feeding group, and depth. Benthic feeders were enriched in 13 C and 15 N relative to suspension feeders, consistent with consuming older, more refractory organic matter. In contrast, canyon suspension feeders had the largest and more distinct isotopic niche, indicating they consume an isotopically discrete food source, possibly fresher organic material. The wider isotopic niche observed for canyon consumers indicated the presence of feeding specialists and generalists. High dispersion in δ 13 C values for canyon consumers suggests that the isotopic composition of particulate organic matter changes, which is linked to depositional dynamics, resulting in discrete zones of organic matter accumulation or resuspension. Heterogeneity in habitat and food availability likely enhances trophic diversity in canyons. Given their abundance in the world's oceans, our results from Baltimore Canyon suggest that submarine canyons may represent important havens for trophic diversity.

Baltimore Canyon↗