Benthos Research Articles

Polycyclic aromatic hydrocarbons in surface sediments of the western Bay of Bengal: Distribution, sources, and ecological risk assessment

This study investigated the distribution, sources, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in the surface sediments of the Western Bay of Bengal (WBoB). Coastal, shelf and slope sediments from the WBoB, collected from different research cruises, were analysed for 16 priority PAH pollutants. Total PAHs (TPAHs) were in the range of 1.87–918.79 ng/g and exhibited a significant association with organic matter and silt content with a predominance of high molecular weight (HMW) PAHs congeners. The preferential degradation of the labile low-molecular-weight (LMW) PAHs resulted in the sedimentary accumulation of HMW congeners. A comparison with reported values from other oceanic areas revealed a relatively low concentration of PAHs in WBoB. The isomeric ratios of PAHs could suggest a pyrogenic or petrogenic (crude oil) origin of PAHs. Principal component analysis indicated the dominance of HMW PAHs (petrogenic or combustion) over the LMW fraction. Based on sediment quality guidelines, four congeners [Pyrene (Py), Benzo[a]anthracene (BaA), Chrysene (Ch), and Dibenzo[a,h]anthracene (DbA)] exceeded the threshold effect levels, indicating an adverse impact of these PAHs on the benthic fauna occasionally. The corresponding risk quotients further indicated a moderate risk caused by Py, BaA, and Benzo[b]fluoranthene (BbF) to the biota. This study underscores the importance of proactive management and mitigation strategies to safeguard these vital oceanic ecosystems from the adverse effects of PAHs and other hazardous materials.

Spatiotemporal Changes and Recovery of Benthic Macroinvertebrate Communities after the Hebei Spirit Oil Spill in the Subtidal Area around the Taean Peninsula in South Korea

Marine oil pollution is a significant environmental issue that significantly threatens ocean ecosystems. It occurs frequently and has devastating consequences for marine life, coastal habitats, and human communities. We examined the recovery of benthic macroinvertebrate communities in shallow subtidal areas following the Hebei Spirit oil spill around the Taean Peninsula, South Korea, in 2007. Benthic macroinvertebrates were collected seasonally from 15 survey sites between 2008 and 2015. Immediately after the spill in 2008, species richness and density of benthic macroinvertebrates decreased by 66.7% and 37.0%, respectively, compared to before the oil spill in 2007. Cluster analysis based on benthic macroinvertebrate communities delineated the communities from 2008 to 2009 as a distinct cluster characterized by markedly low species richness. Communities from other periods exhibited spatiotemporal variability based on the sampling location and sediment characteristics. By 2011, species richness and density had recovered to levels similar to those in 2007, which was particularly pronounced regarding the resurgence of arthropods and mollusks. Notably, populations of amphipods that are particularly sensitive to oil, such as Urothoe sp. and Byblis spp., showed signs of recovery in 2011; however, recovery of the benthic community at the site nearest to the oil spill area, was not evident until July 2013, as indicated by the benthic opportunistic polychaete amphipod index. This underscores that prolonged time periods are required for communities to fully recuperate after oil spills.

Beyond the Surface: Mesophotic Reefs as Potential Refuges for Shallow Fish Assemblages.

The deep reef refugia hypothesis suggests that the effects of disturbance decrease as depth increases; thus, reefs in the mesophotic zone potentially serve as refuges for communities in shallower zones. This study challenged this hypothesis by evaluating fish diversity in shallow and mesophotic reefs in a marine protected area in the Gulf of California. During 2021-2022, we conducted 189 5-min video transects using remotely operated vehicles to document species richness and abundance. We evaluated six biological traits for each species (length, mobility, position, gregariousness, diet, and activity period) to estimate four functional indices (number of entities, richness, originality, and divergence), one phylogenetic index (Δ*), and Hill's numbers for taxonomic and functional indices. Benthic organisms were analyzed to explore relationships with ichthyofauna, while monthly water turbidity satellite data products were transformed into a light attenuation coefficient to identify the mesophotic zone (area between 10% and 0.1% of the incident light at the surface). At the study site, the mesophotic zone was identified to extend to 21 m under optimal conditions, which is shallower than what is typically observed in oligotrophic regions. Generalized linear models revealed significant variations in reef fish composition across spatial (site and zone) and temporal (season and year) dimensions. Additionally, generalized linear mixed models of functional richness and taxonomic Hill's numbers exhibited significantly higher values in the shallow zone. However, functional and phylogenetic indices showed similarities in fish assemblages. Despite differences in fish taxonomic diversity among zones that could be related to less environmental variation and resource availability in deep strata, mesophotic reef fish assemblages presented similar functions. Functions were maintained in mesophotic reefs, which suggests that the two zones are connected and that mesophotic reefs have the potential to act as partial refugia in the face of current and near-future climate change-related disturbances that could affect shallow zones.

Relationships between the spectral characteristics of dissolved organic matter and river ecological health indicators: A case study in the Shichuan River basin on a typical semi-arid and semi-humid region of China

The spectral characteristics of dissolved organic matter (DOM) in rivers are considered as potential indicators of river health status. In this study, relationships between DOM spectral properties and river ecological health indicators in Shichuan River, such as total nitrogen (TN), total phosphorus (TP), chlorophyll-a (Chl-a) content, diversity of macrobenthic invertebrates, water quality index (WQI), and trophic level index (TLI), etc., were investigated. According to the WQI values, the water quality of the Ju River and Taoqupo Reservoir was generally better than that of other river sections, while the Qinghe and the mainstream sections performed the worst. The fluorescence index (FI) and WQI reflects that the mainstream of the Shichuan River bears a significant amount of sewage input. Besides, FI showed a significant positive correlation with nitrate nitrogen (NO3−-N), TN, TP, Chl-a, and TLI, while a significant negative correlation with WQI. The specific ultraviolet absorbance of 254 nm (SUVA254) had a positive correlation with TLI. Indeed, the UVC humic-like component (C1) showed a significant positive correlation with the macroinvertebrates diversity. The humification index (HIX) was significantly negatively correlated with sediment pollution index. Our results suggested that DOM fluorescence characteristics had the potential to be developed as a convenient method for assessing aquatic ecological health.

Assessment of recent lake sediment conditions in the conterminous U.S.

This study provides the largest sediment quality assessment of lakes in the conterminous United States (U.S.). A variety of lakes (n = 1005) were selected based on the randomized, probabilistic sampling design of the broader 2017 National Lakes Assessment study. Surficial sediment samples (0–5 cm) were collected at one representative site (generally the deepest point) for each lake (n = 969). The samples were analyzed for 16 metal(loid)s, 25 polycyclic aromatic hydrocarbons (PAHs), 53 polychlorinated biphenyl (PCB) congeners, 27 legacy pesticides and metabolites, total organic carbon, and grain size. Metal(loid)s and PAHs were widely distributed due to natural and potential anthropogenic sources, with regional variations observed for lakes in the nine ecoregions encompassing the U.S. Most sites did not have detectable PCB congeners or legacy pesticides. An integrative chemical index of mean probable effect concentration quotients, composed of seven metal(loid)s and ƩPAH13, was used to assess sediment quality for the estimated population of 224,916 lakes in the conterminous U.S. Nationally, 26.5% (CI of 20–33%) of lakes were in good condition (corresponding to predicted low incidences of toxicity to benthic organisms), 69.3% (CI of 63–76%) of lakes were in fair condition, and 1.8% (CI of 0.6–3%) of lakes were in poor condition (corresponding to predicted high incidences of sediment toxicity). Unweighted metal(loid) and ƩPAH13 concentrations were compared to lake, watershed, and land use data. Deeper lakes were significantly more contaminated (or naturally enriched) with As, Cd, Cu, Pb, Hg, Zn, and ƩPAH13 than shallow lakes. Lakes at lower elevation were also associated with more contamination (or natural enrichment) of As, Cr, Pb, Hg, Ni, Zn, and ƩPAH13 than higher elevation lakes. Greater contamination was associated with watersheds containing larger percentages of developed land. This study demonstrates an approach which can be used by others to assess sediment quality in their jurisdictions.

Bioturbation effects and behavioral changes in buried bivalves after exposure to microplastics

Microplastic pollution has become an increasing concern. Vertical transport of microplastics is one of the major research questions concerning the distribution and fate of microplastics in the marine environment, and biologically mediated vertical transport is particularly significant. However, studies on the effects of different types of benthic organisms on the vertical distribution of microplastics in sediments are still scarce. The results of this study revealed that when exposed to environmentally relevant concentrations of fluorescent polystyrene microbeads (200 μm), Manila clams (Ruditapes philippinarum) exhibited prolonged acclimation period, yet subsequent burrowing behavior (burrowing rate and burrowing velocity) was unaffected. The condition index, clearance rate, and oxygen consumption rate of the clams similarly exhibited no stress response after 14 days of exposure. We determined that microplastics were rapidly transported to deeper layers (6-8cm below the surface) in the sediment under bioturbation. This study elucidates the mechanisms of microplastic transport, showing that clam behaviors such as burrowing, movement, and ingestion contribute to this process. The results suggest that a biologically based management strategy may be a more environmentally friendly means of mitigating microplastic pollution in seawater.

Silurian–Devonian boundary in Northern Xinjiang, NW China

During the Silurian–Devonian Boundary (SDB) interval, in contrast to the predominantly carbonate facies observed in Europe and North America, China was composed of several plates/terranes dominated by clastic and pyroclastic rocks. Continuous sections across the SDB have been only sporadically reported from the orogenic belts and southwestern margin of South China. In many regions or sections in China, the identification of the SDB is based solely on fossil assemblages or non-index fossils, which results in only a rough approximation of the position of the boundary. This study focuses on the Junggar area in the Central Asian Orogenic Belt, characterized by pyroclastic rocks and scarcity of fossils compared to regions with carbonate dominated successions. This paper summarizes previous research findings and discusses the SDB in northern Xinjiang, China, integrating new data on Devonian conodont Caudicriodus hesperius, the presence of benthic organisms represented by encrinurid trilobites and crinoids, and the occurrence of late Silurian graptolites, along with the first organic carbon isotope curve around the SDB for the Central Asian Orogenic Belt, and provided crucial evidence for the recognition of the SDB in the orogenic belt area of China, consindering the SDB in Northern Xinjiang is located within the Utubulag Formation in the western Junggar and the presence of the SDB in the Kaokesaiergai Formation of the eastern Junggar has also been confirmed. The age of the corresponding strata: Utubulag, Manger, Kaokesaiergai formations are revised, and a more detailed description of the classic sections of the SDB in northern Xinjiang is provided. The new fossil and geochemical data serve as basis for recognition of the Silurian–Devonian boundary in northern Xinjiang, and also contribute to a more comprehensive understanding of paleoenvironmental events at the Silurian–Devonian transition in the northern hemisphere and the orogenic belt areas.

Dynamic models for estimating radiation doses to hydrobionts in a freshwater ecosystem

A model of radionuclide transfer in freshwater bodies, along with dosimetric models for estimating doses to aquatic biota species (including phytoplankton, zooplankton, zoobenthos, and fish), is presented. The results of the reconstruction of radiation doses to aquatic organisms living in the closed (non-flowing, lentic) Lake Uruskul, located in the vicinity of the Kyshtym accident, are provided. The contributions of the main dose-forming radionuclides, as well as both internal and external exposures, to the doses received by aquatic organisms over the 50 years following the Kyshtym accident are discussed. It is shown that benthic organisms received the highest doses (2.6-8.3Gy per day), while zooplankton experienced somewhat lower doses (up to 3.3Gy per day). Fish received doses of up to 4mGy per day during the first 100 days. Phytoplankton, with doses reaching up to 0.5Gy per day, occupied an intermediate position in this sequence. These doses could lead to long-term radiation effects.

Fine sediments produce tipping points in the taxonomic and functional structure of benthic macroinvertebrates in neotropical streams

Fine sediments produce tipping points in the taxonomic and functional structure of benthic macroinvertebrates in neotropical streams

Decadal Variability in the Structure of Benthic Fauna of Subtropical Salt Marshes and Unvegetated Areas

Decadal Variability in the Structure of Benthic Fauna of Subtropical Salt Marshes and Unvegetated Areas

Seasonal prey taxa and size selection and drivers of age-0 walleye ontogenetic diet shifts

Prey abundance and size vary seasonally, creating a dynamic connection between predator and prey. The natural complexity related to consuming multiple prey types as fish undergo ontogenetic diet shifts combined with the frequent sampling and substantial laboratory time investment required to investigate seasonal predator-prey dynamics limits understanding of seasonal prey availability and age-0 prey taxa and size selection. Our study used frequent prey sampling spanning a four-year period to understand which prey taxa and sizes are seasonally available to age-0 walleye Sander vitreus, which were sampled from May to November across all four years of this study to document food habits and prey sizes. Consumed prey were then compared to available prey within the reservoir to evaluate prey taxa and size selection. Age-0 walleye seasonal food habits were consistently simplistic as age-0 walleye in this study largely consumed a single zooplankton taxa (calanoida) and then shifted directly to piscivory where they again focused consumption on a single taxa, and age group (age-0 gizzard shad Dorosoma cepedianum) while passing over available benthic macroinvertebrates. The ontogenetic shift to larval gizzard shad coincided with peak larval shad availability. Interestingly, age-0 walleye were size selective for both prey types, selecting the largest calanoida available when zooplanktivorous but consuming some of the smallest age-0 gizzard shad despite increasing gape size that would have allowed for consumption of larger shad.

A Review of Plume Research in the Collection Process of Deep-Sea Polymetallic Nodules

A Review of Plume Research in the Collection Process of Deep-Sea Polymetallic Nodules

Microplastic burial potential and ecological risks in mangrove forests of the Amazon River delta

Coastal mangrove ecosystems have been shown to be important microplastic (MP) sinks. Yet, information regarding their MP sequestration capacity is scant. Here, we characterized the spatial and vertical distribution of MPs in mangrove ecosystems of the Amazon River delta and quantified, for the first time, their MP burial and potential economic value related to their surface water filtering capacity. Furthermore, we assessed the ecotoxicological risks considering differing effect mechanisms for benthic organisms (i.e., food dilution and translocation-mediated effects). Soil core samples (up to 3 m) were taken from seven locations in the northern part of the Amazon River delta and analyzed for MP contamination. MPs in the 100–5000 μm range were measured and the polymer type was characterized using Fourier Transform Infrared Spectroscopy. The collected soil samples were dated based on a radionuclide analysis, and a burial analysis was done based on the sediment mass accumulation rates and the mass concentration of MPs. The outcomes of this study show that MPs are ubiquitous contaminants in mangroves of the Amazon River delta (present in 30 out of the 35 analyzed samples). The largest MP concentration was found in the upper soil layer (0–15 cm), 138 MPs/kg dw, which has been deposited and reworked during the time of the soil core collection. However, moderate exposure levels were also found in older samples (71–138 MPs/kg dw), and in samples taken before the plastic era (≈ 1870–1930), suggesting a downward MP migration. We estimated a mean burial rate of 0.32 ± 0.17 kg of MPs km2/year, which corresponds to 0.55 ± 0.28 tons per year in the Amazon River delta. Based on the estimated burial rate, we valued the removal of MPs from surface waters by these mangroves at 0.3–1.1 million USD per year. Our study shows that the exposure levels of MPs in mangroves of the Amazon River delta are relatively low when compared to other mangrove ecosystems and ecotoxicological risks for benthic organisms are not expected given the current exposure levels.

Assessing the potential impacts of floating Offshore Wind Farms on policy-relevant species: A case study in the Gulf of Roses, NW Mediterranean

Our study investigates for the first time how floating Offshore Wind Farms (OWFs) technologies could impact policy-relevant Mediterranean species, focusing on planned OWFs in the Cape Creus/Gulf of Roses (Spain, NW Mediterranean). Using the Generalized Impact Assessment framework, we identified pressure on diverse taxonomic groups. Our species selection prioritized species under European policy (Birds and Habitats Directives) and international/local conventions protecting flora and fauna, as they are vital biodiversity indicators. Our analysis identified 135 policy-relevant species susceptible to OWF-induced stressors, notably marine mammals, seabirds, elasmobranchs, and benthic macroinvertebrates at the highest risk. Among the different stressors, noise and vibration, along with habitat loss, pose the greatest potential impacts. While decarbonizing energy production is crucial for addressing climate change, preserving ocean biodiversity is equally vital. Our study pioneers the assessment of emerging OWFs potential impacts on Mediterranean species, offering valuable insights for decision-makers during OWF planning.

In situ oil contamination in young mangroves: Biodegradation of petroleum hydrocarbons and effects on the microbial and benthic communities, an experimental study in French Guiana

An in-situ experiment was conducted in a young mangrove with no history of oil contamination (French Guiana). Control and oil-contaminated sediments were sampled one month after exposure and analyzed to a depth of 18 cm to assess natural oil depletion and changes in benthic communities. High biodegradation percentages (89–99 %) of n-alkanes and polycyclic aromatic hydrocarbons were measured. The microbiological results suggest that this degradation is strongly connected to several bacterial taxa. A 90 % decrease in the meso- (>250 mm) and macro-benthic organisms' (>1 mm) densities was observed. The oil has also significantly impacted the composition of the benthos, as well as the microorganisms responsible for mediating biogeochemical functions associated with nitrogen turnover. While chemical and microbiological analyses revealed a high bioremediation potential by the indigenous microbes, an oil spill would be a catastrophic event for the benthic fauna, which could, in turn, affect the microbial communities.

Mortality patterns and recovery challenges in Millepora alcicornis after mass bleaching event on Northeast Brazilian reefs

Coral reefs are suffering globally from the increased frequency and intensification of thermal anomalies, caused by anthropogenic climate change, leading to major mass bleaching events over the past three decades. Environmental factors, including temperature, geomorphology, interspecific competition, protection status and local settings, can modulate the severity of bleaching and the subsequent survival capacity of corals and hydrocorals after mass bleaching events. However, the complexity of environmental factors interacting over fine-scale spatial-temporal scales is still a major gap in understanding coral bleaching events of South Atlantic reefs. Here, we examined mortality and recovery patterns of the predominant hydrocoral species Millepora alcicornis after a mass bleaching event at the Northeastern coast of Brazil in 2019–2020. The ecological impact was evaluated by analyzing spatial factors, coral morphology, protection status and mortality rates in combination with the subsequent recovery potential influenced by overgrowth competition of dominant benthic organisms. The results indicate that hydrocorals located in proximity to the shore and shallow depths were more vulnerable with mortality rates of up to 90%, presumably related to higher light and temperature fluctuations. A total coral cover loss of approx. 50% was estimated for M. alcicornis within the study area and dead skeletons were overgrown by algal turfs and crustose coralline algae with the former being the predominant colonizer. In summary, our findings reveal fin-scale heterogeneous spatial vulnerability within the same coastal reef complex, indicating zones of high coral mortality. The described heterogeneous spatial vulnerability of the studied reef complex is an important factor to be considered in coral reef restauration and management plans to secure coral ecosystem services for the coming decades.

Community-level responses and environmental fate of metformin in freshwater mesocosms.

The type 2 diabetes drug metformin is among the most frequently prescribed, dispensed, and consumed pharmaceuticals worldwide; and its heavy use and poor breakdown means it is consequently detected in various wastewater treatment plant (WWTP) effluents and surface waters. The resulting environmental concentrations of metformin can have adverse impacts on aquatic ecosystems. An 8-week in-lake mesocosm experiment was conducted in a freshwater boreal lake at the IISD-Experimental Lakes Area (Ontario, Canada) to determine the environmental fate and effects of metformin. Mesocosms were assigned to nominal concentrations of 0, 5, or 50 μg L-1 metformin, in replicates of four. Biotic communities (i.e. microbial, phytoplankton, zooplankton, benthic macroinvertebrate) were assessed and complementary Lemna gibba and Daphnia magna bioassays were conducted in the laboratory. Metformin was extremely stable during the 8-week experiment, with mean measured concentrations of 0.00, 5.42, and 42.79 μg L-1 in mesocosm surface waters for the 0, 5, and 50 μg L-1 treatments, respectively. While trace amounts of metformin were detected in mesocosm sediments, the compound was primarily found in the water column. After over 1 year following metformin additions, the mean loss of metformin from surface water was 94.0 % and 91.0 % for the 5 and 50 μg L-1 treatment groups, respectively. No adverse effects of metformin treatment on the diversity, abundance, or biomass of microbial, phytoplankton, zooplankton, or benthic macroinvertebrate communities were found. Additionally, no survival or reproductive effects were observed in the 21-d Daphnia magna bioassays and no significant effects were observed in the 7-d Lemna gibba growth assays. No substantial metformin transformation to guanylurea was observed in mesocosm surface waters or sediments, likely due to a lack of bacterial degradation occurring within mesocosms relative to WWTPs.

Refinement and Validation of the SPEcies at Risk Index for Metals (SPEARmetal Index) for Assessing Ecological Impacts of Metal Contamination in the Nakdong River, South Korea

The SPEcies At Risk index for metals (SPEARmetal index) was refined using updated physiological sensitivity data and validated to assess the ecological impact of metal contamination on benthic macroinvertebrate communities in the upper Nakdong River, near a Zn smelter in Korea. Biosurvey and chemical monitoring data were collected at 18 sites surrounding the smelter and nearby mines. Acute ecotoxicity tests on 20 indigenous species from the Korean peninsula were conducted and used to update taxon-specific metal sensitivity data. The refined SPEARmetal index, based on this updated sensitivity, was significantly lower than previous versions, with most values below the severe impact threshold (0.5) in the main stream. The correlation between hazard quotients in water and the SPEAR index improved, with the correlation coefficient increasing from 0.63 to 0.70. Despite consistently high benthic macroinvertebrate indices (BMIs) across the study area, generic ecological indices, such as total richness, EPT (Ephemeroptera, Plecoptera, and Trichoptera taxa richness), and Shannon’s diversity index, showed correlations with metal contamination levels. Principal component analysis identified the SPEARmetal index as the primary indicator associated with metal contamination in both water and sediment. These findings highlight the improved performance of the refined SPEARmetal index as a more sensitive and specific tool for assessing the ecological status of metal-impacted aquatic ecosystems compared to traditional indices.

Volunteer Accuracy in a Benthic Macroinvertebrate Participatory Science Project

Concerns about the accuracy of volunteer-derived aquatic macroinvertebrate identifications and the resulting influence on calculated water quality metrics can limit use of volunteer-generated data in freshwater-focused participatory science programs. To address these concerns, we assessed 357 benthic macroinvertebrate quality control (QC) samples collected by volunteers using leaf packs, kick nets, and visual assessments between 2011 and 2016 for the Environmental Quality Institute (EQI) in North Carolina, USA. We reviewed each sample for quality, and compared macroinvertebrate identifications and water quality metric scores determined by volunteers to identification and metrics determined by an entomologist. About 80% of the QC samples were identified to be of high quality, indicating proper preparation, preservation, and labeling of samples. The majority of samples that received low quality ratings were improperly or poorly preserved. We recommend use of 95% (rather than 70%) ethanol for macroinvertebrate preservation, and increased communication to volunteers during QC sampling periods to enhance their success in properly preserving samples. We observed significant (p < 0.005) linear relationships between volunteer and entomologist-derived water quality metrics including a biotic index, Taxa Richness, and percent intolerant Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa. However, visual assessments – those in which no sampling equipment was used to collect aquatic macroinvertebrates – reduced the goodness of fit between volunteer and entomologist-derived biotic index scores and artificially increased the goodness of fit between volunteer and entomologist derived Taxa Richness and percent EPT scores. We recommend calculating water quality metrics based only on leaf pack and kick net samples collected by volunteers.

Evidence from In Situ Bioassays and Suspect Analysis Revealed the Region-Specific Aquatic Risk across Socioeconomic Gradients in China.

Various contaminants are present in aquatic environment and pose potential threats to pelagic and benthic organisms, calling for effective risk assessment. Traditional risk assessments based on target analysis are useful when the principal contaminants responsible for ecological risk are known; however, these approaches become challenging when dealing with chemical mixtures. In addition, the compositions of chemical mixtures often differ in regions with different levels of socioeconomic development, requiring risk assessment methods that are applicable under different pollution scenarios. Herein, in situ bioassays were conducted with two native species, Chinese rare minnows (Gobiocypris rarus) and Asian clams (Corbicula fluminea), in economically developed watersheds in China (Pearl River Basin (PRB) and Taihu Lake Basin (THB)) and agriculture-dominated Poyang Lake Basin (PYB). Significant lethal and sublethal effects (e.g., neurotoxicity, reproductive toxicity, and metabolic and oxidative stress) were observed in fish and clams irrespective of economic gradients. Notably, ecological effects differed significantly between water and sediment phases within the same region. Target (98 contaminants) and suspect screening (942 contaminants) revealed regional-specific characteristics. Ecological risk assessments using a weight of evidence approach demonstrated that both water and sediment in the PRB were at moderate to high risk, as was the sediment in the less developed PYB. However, the characteristics of mixture pollution varied greatly among regions. Suspect screening identified many pollutants that are not regularly monitored but are present at high environmental concentrations and are linked to local industrial production. These distinct mixture risk characteristics across different basins suggest that mitigating aquatic pollution requires region-specific management measures.