Ecosystem Risk Research Articles

Soil moisture dominates the variation of gross primary productivity during hot drought in drylands

The frequency and severity of hot drought will increase in the future due to impact of climate change and human activities, threatening the sustainability of terrestrial ecosystems and human societies. Hot drought is a typical type of drought event, high vapor pressure deficit (VPD) and low soil moisture (SM) are its main characteristics of hot drought, with increasing water stress on vegetation and exacerbating hydrological drought and ecosystem risks. However, our understanding of the effects of high VPD and low SM on vegetation productivity is limited, because these two variables are strongly coupled and influenced by other climatic drivers. The southwestern United States experienced one of the most severe hot drought events on record in 2020. In this study, we used SM and gross primary productivity (GPP) datasets from Soil Moisture Active and Passive (SMAP), as well as VPD and other meteorological datasets from gridMET. We decoupled the effects of different meteorological factors on GPP at monthly and daily scales using partial correlation analysis, partial least squares regression, and binning methods. We found that SM anomalies contribute more to GPP anomalies than VPD anomalies at monthly and daily scales. Especially at the daily scale, as the decoupled SM anomalies increased, the GPP anomalies increased. However, there is no significant change in GPP anomalies as VPD increases. For all the vegetation types and arid zones, SM dominated the variation in GPP, followed by VPD or maximum temperature. At the flux tower scale, decoupled soil water content (SWC) also dominated changes in GPP, compared to VPD. In the next century, hot drought will occur frequently in dryland regions, where GPP is one of the highest uncertainties in terrestrial ecosystems. Our study has important implications for identifying the strong coupling of meteorological factors and their impact on vegetation under climate change.

Theoretical and methodological aspects of sea ecosystem risks management

In the context of worsening anthropogenic impact, climate change and natural disasters, the problem of managing the sea areas' ecosystem risks is becoming quite important. This research aims at exploring the modern theoretical and methodological aspects of the aforesaid scientific orientation and focuses on the analysis and evaluation of existing concepts and strategies.
 The article analyses main terms and principles and also presents a conceptual model for managing the sea ecosystem risks that plays a key role in reflecting the main theoretical components and their interrelationships. The model contributes to a better understanding of the structure and characteristics of this theory, emphasizing the complexity of interactions between socio-economic systems and marine ecosystems, as well as the risks arising from such interactions. The main elements of the model include natural and anthropogenic factors and consider their impact on the state of marine ecosystems and the risks associated therewith. The model also focuses on well-being, ecosystem stability and biodiversity, i.e. the parameters determining the status and functionality of marine ecosystems.
 The research presents a comparative analysis of various methodologies and strategies of ecosystem risks management. The analysis allowed identification of the most effective of them at certain stages of creating an optimum strategy for managing the ecosystem risks. Risk management strategies can be implemented using a variety of tools, such as marine spatial planning, creation of marine protected areas, basic ecosystem management, resource management, and a marine environmental quality management system developed in accordance with the requirements of the EU Marine Strategy Directive. These strategies integrate different approaches to managing the ecosystem risks and contribute to conservation of ecosystems ensuring the marine environment stability.
 The work made it possible to open up the prospects for further scientific research, namely development of hypotheses in order to increase theoretical knowledge and develop practical recommendations in the field of management of water areas' ecosystem risks.
 The conclusions of the research are aimed at creating a theoretical and methodological base that will contribute to analyzing and developing effective strategies for managing the water areas' ecosystem risks.

Effects of intensive agriculture and urbanization on water quality and pesticide risks in freshwater ecosystems of the Ecuadorian Amazon

The Ecuadorian Amazon has experienced a significant land use change due to the demographic increase and the expansion of the agricultural frontier. Such changes in land use have been associated to water pollution problems, including the emission of untreated urban wastewater and pesticides. Here we provide the first report on the influence of urbanization and intensive agriculture expansion on water quality parameters, pesticide contamination and the ecological status of Amazonian freshwater ecosystems of Ecuador. We monitored 19 water quality parameters, 27 pesticides, and the macroinvertebrate community in 40 sampling locations of the Napo River basin (northern Ecuador), including a nature conservation reserve and sites in areas influenced by African palm oil production, corn production and urbanization. The ecological risks of pesticides were assessed using a probabilistic approach based on species sensitivity distributions. The results of our study show that urban areas and areas dominated by African palm oil production have a significant influence on water quality parameters, affecting macroinvertebrate communities and biomonitoring indices. Pesticide residues were detected in all sampling sites, with carbendazim, azoxystrobin, diazinon, propiconazole and imidacloprid showing the largest prevalence (>80% of the samples). We found a significant effect of land use on water pesticide contamination, with residues of organophosphate insecticides correlating with African palm oil production and some fungicides with urban areas. The pesticide risk assessment indicated organophosphate insecticides (ethion, chlorpyrifos, azinphos-methyl, profenofos and prothiophos) and imidacloprid as the compounds posing the largest ecotoxicological hazard, with pesticide mixtures potentially affecting up to 26–29% of aquatic species. Ecological risks of organophosphate insecticides were more likely to occur in rivers surrounded by African palm oil plantations, while imidacloprid risks were identified in corn crop areas as well as in natural areas. Future investigations are needed to clarify the sources of imidacloprid contamination and to assess its effects for Amazonian freshwater ecosystems.

Reduction in size of the calcifying phytoplankton Calcidiscus leptoporus to environmental changes between the Holocene and modern Subantarctic Southern Ocean

The Subantarctic Zone of the Southern Ocean plays a disproportionally large role on the Earth system. Model projections predict rapid environmental change in the coming decades, including ocean acidification, warming, and changes in nutrient supply which pose a serious risk for marine ecosystems. Yet despite the importance of the Subantarctic Zone, annual and inter-annual time series are extremely rare, leading to important uncertainties about the current state of its ecosystems and hindering predictions of future response to climate change. Moreover, as the longest observational time series available are only a few decades long, it remains unknown whether marine pelagic ecosystems have already responded to ongoing environmental change during the industrial era. Here, we take advantage of multiple sampling efforts – monitoring of surface layer water properties together with sediment trap, seafloor sediment and sediment core sampling – to reconstruct the modern and pre-industrial state of the keystone calcifying phytoplanktonCalcidiscus leptoporus, central to the global marine carbonate cycle. Morphometric measurements reveal that modernC. leptoporuscoccoliths are 15% lighter and 25% smaller than those preserved in the underlying Holocene-aged sediments. The cumulative effect of multiple environmental factors appears responsible for the coccolith size variations since the Last Deglaciation, with warming and ocean acidification most likely playing a predominant role during the industrial era. Notably, extrapolation of our results suggests a future reduction in cell and coccolith size which will have a negative impact on the efficiency of the biological pump in the Southern Ocean through a reduction of carbonate ballasting. Lastly, our results tentatively suggest thatC. leptoporuscoccolith size could be used as a palaeo-proxy for growth rate. Future culture experiments will be needed to test this hypothesis.

Occurrence, sources, and ecological risks of polycyclic aromatic hydrocarbons (PAHs) in the Amazon river

The Amazon is the largest river by discharge volume and one of the most biodiverse biomes in the world. Lately, there has been a rapid increase of the urban population in the region, which has been translated into a growing emission of organic contaminants such as polycyclic aromatic hydrocarbons (PAHs) into surface water bodies. This study provides the most comprehensive evaluation of the PAH contamination levels in surface waters of the Amazon basin. We investigated the occurrence and potential sources of 16 priority PAHs and characterised their risks for freshwater ecosystems. For this, we took 40 water samples from different sites along the Brazilian part of the Amazon River, including three major tributaries, and smaller rivers crossing the main urban areas. The results of this study show that PAHs are widespread contaminants in rivers of the Brazilian Amazon. The sum of the total concentration of the 16 priority PAHs reached values of 134 ng L−1 in the Amazon River, and 163 ng L−1 near densely populated areas. On the other hand, the total PAH concentration was generally lower in the monitored tributaries. In most samples, the contamination pattern was dominated by high molecular weight PAHs, suggesting a major contribution of pyrogenic sources, although petrogenic contamination was also present in some locations near urban areas. We assessed ecological risks posed by PAH mixtures using a hazard index. The results indicated that PAH contamination is not likely to pose direct toxic effects for Amazonian freshwater organisms, however continued monitoring is recommended near densely populated areas.

Environmental exposure and ecotoxicological properties of a new-generation fluorosurfactant (cC6 O4 ): A comparison with selected legacy perfluoroalkyl acids.

Cyclic C6 O4 (cC6 O4 , CAS number 1190931-27-1) is a new-generation polyfluorinated alkyl substance (PFAS) used as a polymerization aid in the synthesis of fluoropolymers, which has been produced in Italy since 2011. A review of the properties of cC6 O4 , focused on environmental distribution and ecotoxicology, was conducted. The EQuilibrium Criterion model was applied, using default environmental scenarios, to estimate environmental distribution and fate. In a situation of static thermodynamic equilibrium in a closed system (Level I), cC6 O4 distributes mainly to water (97.6%) and in a minimal amount to soil (2.3%). In a more realistic scenario (Level III), with dynamic conditions in an open system, with advection in air and water and with equal emissions in air and water, the major amount of the compound is transported through water advection. Monitoring data, mainly referring to surface and groundwater, are available for water bodies close to the production sites (maximum measured concentration 52 μg/L) as well as for a wider area in the river Po watershed with concentrations generally lower than 1 μg/L. Few values are also available for concentration in biota. Effect data indicate low toxicity on all tested organisms with no observed effect concentration (NOEC) values always higher than the maximum concentrations tested (100 mg/L for acute tests). Bioaccumulation potential is also very low. A comparison with selected widely used PFAS with five to eight C atoms indicates that cC6 O4 is substantially less dangerous to aquatic organisms. For the time being, an ecological risk for the aquatic ecosystem may be excluded even in directly exposed ecosystems. However, for a complete assessment of the suitability of cC6 O4 as a substitute forother PFAS (namely, perfluorooctanoic acid), more comprehensive chronic experiments are necessary, to produce realistic NOEC, as well as higher tier experiments (e.g., mesocosms) capable of providingecologically relevant endpoints. Moreover, a more accurate evaluation of the environmental persistence would be necessary. Integr Environ Assess Manag 2023;19:1636-1648. © 2023 SETAC.

Exposure to polystyrene nanoparticles leads to changes in the zeta potential of bacterial cells

Polymer molecules, the main components of plastics, are an emerging pollutants in various environmental compartments (water, air, soil) that may induce several ecotoxicological effects on live organisms. Therefore, understanding how plastic particles interact with bacterial cell membranes is crucial in analysing their associated risks in ecosystems and human microbiota. However, relatively little is known about the interaction between nanoplastics and bacteria. The present work focuses on Staphylococcus aureus and Klebsiella pneumoniae, representing the Gram-positive and Gram-negative bacteria respectively, exposed to 100 nm diameter polystyrene nanoparticles (PS NPs). The nanoparticles attach to the cells’ membranes of both bacteria, changing their electrical charge, but without the effect of killing the cells. PS NPs caused a change in zeta potential values (both species of bacterial strains), dependent on particle concentration, pH, as well as on exposure time of bacteria to them. Through the application of AFM and FTIR techniques, the presence of PS NPs on bacterial surfaces was detected, suggesting the affinity of the particles to bacterial components, but without any changes in the morphology of the tested bacteria. The zeta potential can be more widely used in the study of interactions between nanostructures and cells.

Linking denitrification and pesticide transformation potentials with community ecology and groundwater discharge in hyporheic sediments in a lowland stream

Contamination of rivers by nitrate and pesticides poses a risk for aquatic ecosystems in lowland catchments that are often intensively used for agriculture. Here, the hyporheic zone, the streambed underneath the stream, plays a vital role due to its efficient self-purification capacity. The present study aims to evaluate the denitrification and transformation potential of 14 pesticides and three transformation products in the hyporheic sediment from a lowland stream with a high N load and by comparing an agricultural straightened section to a natural meandering part of the stream influenced by different groundwater discharges. Batch experiments were set up to evaluate the denitrification and pesticide transformation potentials in hyporheic sediment from two depths (5–15 cm (a) and 15–25 cm (b)).Our results revealed that (i) differences between the agricultural and natural sections of the river did not influence pollutant attenuation, (ii) both the nitrate and pesticide attenuation processes were more rapid in the upper "a" layer compared to the "b" layer due to higher microbial abundance, (iii) high groundwater discharge reduced the denitrification potential while pesticide transformation was unaffected, (iv) denitrification correlated with denitrifier abundance (nirK) in the "b" layer, while this correlation was not seen in the "a" layer, and (v) a microbial community with low diversity can explain limited transformation for the majority of tested pesticides. Overall, our results suggest that high groundwater discharge zones with reduced residence time in the hyporheic zone can be an important source of pesticides and nitrate to surface water.

A dynamic framework for assessing and managing risks to ecosystems from fisheries: demonstration for conserving the krill-based food web in Antarctica

The ecosystem approach to fisheries has been discussed since the 1980s. It aims to reduce risks from fisheries to whole, or components of, ecosystems, not just to target species. Precautionary approaches further aim to keep the risk of damage to a low level. Here, we provide a dynamic framework for spreading the ecosystems risk of fisheries in space and time, a method that can be used from the outset of developing fisheries and continually updated as new knowledge becomes available. Importantly, this method integrates qualitative and quantitative approaches to assess risk and provides mechanisms to both spread the risk, including enabling closed areas to help offset risk, and adjust catch limits to keep regional risk to a baseline level. Also, the framework does not require uniform data standards across a region but can incorporate spatially and temporally heterogeneous data and knowledge. The approach can be coupled with the conservation of biodiversity in marine protected areas, addressing potential overlap of fisheries with areas of high conservation value. It accounts for spatial and temporal heterogeneity in ecosystems, including the different spatial and temporal scales at which organisms function. We develop the framework in the first section of the paper, including a simple illustration of its application. In the framework we include methods for using closed areas to offset risk or for conserving biodiversity of high conservation value. We also present methods that could be used to account for uncertainties in input data and knowledge. In the second section, we present a real-world illustration of the application of the framework to managing risks of food web effects of fishing for Antarctic krill in the Southern Ocean. Last, we comment on the wider application and development of the framework as information improves.

Assessment of heavy metal contamination and ecological risk in Morocco's marine and estuarine ecosystems through a combined analysis of surface sediment and bioindicator species: Donax trunculus and Scrobicularia plana

Morocco is one of the most affected regions by heavy metal pollution worldwide. In this study, two ecosystems in Agadir Bay, southern Morocco, were studied seasonally, using surface sediment and bivalve species. The concentrations of Cu, Pb and Cd were determined using the Shimadzu AAS 7000 flame atomic absorption spectrophotometer method. Our results marked average levels corresponding to an unpolluted sediment with a low contamination degree, low ecological risk associated with metal contamination, and levels that did not exceed the thresholds set by EC, USEPA, INERIS and INRH, except for Pb in tourist beach. The principal component analysis findings revealed a positive correlation in the bioaccumulation between the two compartments, with an influence of abiotic parameters. Thus, to better manage environmental pollution in these ecosystems, authorities must implement waste treatment strategies in the surrounding harbor and tourist complexes and prohibit the use of these toxic metals in the coastal areas.

Persistent, viable seedbank buffers serotinous bishop pine over a broad fire return interval

BackgroundIn ecosystems where fire has been excluded, pyrosilviculture can restore some processes historically maintained by fire while mitigating risk where fire is inevitable. Pyrosilviculture in crown fire-adapted forests is, however, limited by insight into the temporal window of fire return matching canopy seedbank development. Here, we characterized demographic responses to fire and non-native pine pitch canker infection in a chronosequence of serotinous bishop pine stands burned at high-severity to quantify (1) temporal patterns of seedbank development given seed viability and density, cone production, and tree density, and (2) pine pitch canker incidence across tree ages and sizes to assess how infection might impact stand and seedbank development. We use our findings to elucidate pyrosilvicuture as a means of restoring fire given practical challenges of reintroducing high-severity fire in crown-fire adapted forests embedded within wildland urban interfaces (WUI).ResultsBishop pine produces an abundant, viable seedbank within eight years that persists across developmental stages and age classes. Seed abundance and viability are exceptionally high at even the earliest age (median > 600,000 seeds ha− 1 and 97% viability at 6 years) and remain high, with the oldest stands (36 years) maintaining median densities of > 500,000 seeds ha− 1 and viability of 95%. We additionally learned that pine pitch canker infection is most severe during the sapling stage (8–10 years post-fire), likely altering stand development trajectories as well as potentially limiting recruitment, and thus the aerial seedbank, into the canopy.ConclusionsIn bishop pine and equally-fecund serotinous species, pyrosilviculture appears a viable management tool across a broad fire return window given the early development and persistence of a robust, viable seedbank, allowing managers flexibility in restoring fire to promote forest persistence while simultaneously mitigating wildfire risk. Moreover, pyrosilviculture in pine pitch canker infected stands may also provide disease mitigation. Although the long-term effects of pine pitch canker infection remain unknown, bishop pines’ viable, persistent seedbank suggests that managers can ignite prescribed fire across a broad return interval — as short as eight years and as long as several decades — to promote bishop pine persistence, mitigate disease infection rates, and reduce wildfire risk in WUI-adjacent ecosystems.

Characteristics of ecological risks in ecosystems and their manifestation possibility assessment

Environment pollution with ecotoxicants of natural and anthropogenic origin creates risks of negative impact on the state of the environment, the biota of ecosystems, including humans. The study defnes the main sources of ecotoxic pollutants and analyzes the risks that may arise. Based on the ambiguity of the "risk" term defnition, the interpretation of the term is discussed. The approach to defning risk as the probability of certain adverse events or processes taking into account possible consequences is noted. The relationship between environmental risks and the reliability of ecosystems is indicated. Environmental risk assessment is a complex process that involves identifying the likelihood of reversible or irreversible changes in the structure and functions of ecosystems in response to anthropogenic or natural impacts. The quantitative measure of risk as a threat of danger is the product of the probability of an adverse outcome of the event and the expected loss as a result of the event. Considerable attention is paid to the assessment of possible ecological risks for agroecosystems, which are associated with environmental degradation, the impact on human health, and the possible ingress of toxic substances into food products and pet fodder. Ecological risks in agroecosystems arise, in particular, as a result of the use of plant protection products (pesticides), excessive use of agrochemicals. However, the process of risk management in agroecosystems involves the selection and use of risk reduction methods, in particular, the use of measures to regulate the impact of ecotoxicants by limiting, banning the most toxic and preventing pollution. The study of environmental risk is necessary to understand the impact of harmful factors on environmental components. It is emphasized that risk management in agriculture should be aimed at preserving the agroecosystem optimal state and protecting human health. Key words: environmental risk, environment, ecotoxicants, rating, danger, agroecosystem, pesticides.

Assessment of dynamic drought-induced ecosystem risk: Integrating time-varying hazard frequency, exposure and vulnerability

Terrestrial ecosystems, occupying 28.26% of Earth's surface, are extensively at risk from droughts, which is likely to propagate into human communities owing to loss of vital services. Ecosystem risk also tends to fluctuate within anthropogenically-forced nonstationary environments, raising considerable concerns about effectiveness of mitigation strategies. This study aims to assess dynamic ecosystem risk induced by droughts and identify risk hotspots. Bivariate nonstationary drought frequency was initially derived as a hazard component of risk. By coupling vegetation coverage and biomass quantity, a two-dimensional exposure indicator was developed. Trivariate likelihood of vegetation decline was calculated under arbitrary droughts to intuitively determine ecosystem vulnerability. Ultimately, time-variant drought frequency, exposure and vulnerability were multiplied to derive dynamic ecosystem risk, followed by hotspot and attribution analyses. Risk assessment implemented in the drought-prevalent Pearl River basin (PRB) of China during 1982–2017 showed that meteorological droughts in eastern and western margins, although less frequent, were prolonged and aggravated in contrast to prevalence of less persistent and severe droughts in the middle. In 86.12% of the PRB, ecosystem exposure maintains high levels (0.62). Relatively high vulnerability (>0.5) occurs in water-demanding agroecosystems, exhibiting a northwest-southeast-directed extension. A 0.1-degree risk atlas unveils that high and medium risks occupy 18.96% and 37.99% of the PRB, while risks are magnified in the north. The most pressing hotspots with high risk continuing to escalate reside in the East River and Hongliu River basins. Our results provide knowledge of composition, spatio-temporal variability and driving mechanism of drought-induced ecosystem risk, which will assist in risk-based mitigation prioritization.

Mercury and Sulfur Redox Cycling Affect Methylmercury Levels in Rice Paddy Soils across a Contamination Gradient.

Methylmercury (MeHg) contamination in rice via paddy soils is an emerging global environmental issue. An understanding of mercury (Hg) transformation processes in paddy soils is urgently needed in order to control Hg contamination of human food and related health impacts. Sulfur (S)-regulated Hg transformation is one important process that controls Hg cycling in agricultural fields. In this study, Hg transformation processes, such as methylation, demethylation, oxidation, and reduction, and their responses to S input (sulfate and thiosulfate) in paddy soils with a Hg contamination gradient were elucidated simultaneously using a multi-compound-specific isotope labeling technique (200HgII, Me198Hg, and 202Hg0). In addition to HgII methylation and MeHg demethylation, this study revealed that microbially mediated reduction of HgII, methylation of Hg0, and oxidative demethylation-reduction of MeHg occurred under dark conditions; these processes served to transform Hg between different species (Hg0, HgII, and MeHg) in flooded paddy soils. Rapid redox recycling of Hg species contributed to Hg speciation resetting, which promoted the transformation between Hg0 and MeHg by generating bioavailable HgII for fuel methylation. Sulfur input also likely affected the microbial community structure and functional profile of HgII methylators and, therefore, influenced HgII methylation. The findings of this study contribute to our understanding of Hg transformation processes in paddy soils and provide much-needed knowledge for assessing Hg risks in hydrological fluctuation-regulated ecosystems.

Systematically Identifying and Evaluating Strategies for Strengthening Community Resilience

Introduction:Vulnerable populations were the most impacted by the COVID-19 pandemic. This included those with underlying health conditions, self-employed, low-income, people with limited access to health care, and the elderly. To capture these lessons and identify resilience actions, the Health Emergency and Disaster Risk Management (Health EDRM) Framework was used to guide the application of the Public Health System Resilience Scorecard (Scorecard).Method:This study was conducted in Australia, Bangladesh, Japan, Slovenia, Turkey, and the United States. Participants included emergency professionals, doctors, nurses, environmental health specialists, researchers, and government officials. The Scorecard was used to rank the level of preparedness from 0-5 (5 the highest) for the public health system resilience indicators. Following the individual workshops, recommendations were collated and interpreted to develop consolidated priority actions.Results:The priority actions related to surge capacity, mental health, ecosystems, societal needs, and high-risk populations. To address surge capacity issues, determining whether existing disaster structures have the capacity to provide support for hospitals during patient surges. This could include services that enable telehealth and primary health care to support hospitals during a crisis. Mental health services at the local government level should be evaluated and awareness of ecosystem risks in urban and rural areas needs to increase. Strategies for achieving reciprocal trust are required to enable uptake of public health information, and the extent at which pre-existing chronic health issues are likely to exacerbate needs to be understood and addressed.Conclusion:This study revealed several areas for strengthening public health system resilience. Priority actions relate to addressing needs relating to surge capacity, mental health, ecosystems, societal needs, and high-risk populations. This serves as a framework for transforming public health systems to become more adaptive, flexible, and focused on enabling societies to function at the highest possible level when responding to a disaster or pandemics.

Quantitative Detection of Microplastics in Water through Fluorescence Signal Analysis

Microplastics (MPs) have recently been acknowledged as a new major and ubiquitous environmental pollutant with still unclear, yet potentially high, risks for different ecosystems and human health. Nevertheless, quantitative identification protocols rely on long and subjective visual counting necessarily performed on microscopes by well-trained operators. In this study, an automatic, fast, portable, and inexpensive method for the quantitative detection of MPs in water is proposed. The system is based on the typical optical setup of a fluorescence confocal microscope specifically adapted to automatically count dye-stained MPs in flowing liquids using a low-power laser beam. The fluorescence pulses emitted by flowing MPs are revealed and processed by a specific software using a pattern recognition algorithm to discriminate and count real fluorescence pulses out of noise fluctuations. The system was calibrated with commercial orange fluorescent 10 µm and 1 µm polystyrene microspheres, and remarkable agreement with theoretical predictions was obtained regarding different parameters. Tests were also performed with laboratory-prepared MPs dispersed in different types of real water samples. In this case, the agreement with theory was slightly worse and differences found in the quantitative results require further investigation. However, the present study demonstrated the proof of concept of a method for quick automated MP counting in water.

Toxicity interaction of polystyrene nanoplastics with sulfamethoxazole on the microalgae Chlamydomonas reinhardtii: A closer look at effect of light availability

The coexistence of nanoplastics and antibiotics in the aquatic environment has raised a complicated risk for ecosystems and human health. How the environmental factors e.g., light, regulate the interaction between nanoplastics and antibiotics and the resulting combined toxicity is poorly understood. Here, we investigated the individual and combined toxicity of polystyrene nanoplastics (nPS, 100 mg L1) and sulfamethoxazole (SMX, 2.5 and 10 mg L−1) toward the microalgae Chlamydomonas reinhardtii under low (LL, 16 μmol m−2·s−1), normal (NL, 40 μmol m−2·s−1), and high light (HL, 150 μmol m−2·s−1) in terms of cellular responses. Results indicated that the joint toxicity of nPS and SMX commonly exhibited a strong antagonistic/mitigative effect under LL/NL at 24 h, and under NL at 72 h. nPS could adsorb more SMX under LL/NL at 24 h (1.90/1.33 mg g−1) and under NL at 72 h (1.01 mg g−1), thereby alleviating SMX toxicity to C. reinhardtii. However, the self-toxicity of nPS had a negative influence on the degree of antagonism between nPS and SMX. The experimental results coupled with computational chemistry further revealed that the adsorption capacity of SMX on nPS was stimulated by low pH under LL/NL at 24 h (∼7.5), while by less co-existing saline ions (0.83 ppt) and algae-derived dissolved organic matter (9.04 mg L−1) under NL at 72 h. nPS toxicity that was responsible for the toxic action modes was mainly attributed to the shading effect induced by hetero-aggregation and hindrance of light transmittance (>60%), as well as being regulated by additives leaching (0.49–1.07 mg L−1) and oxidative stress. Overall, these findings provided a critical basis for the risk assessment and management of multiple pollutants in the complex natural environment.

Dietary exposure to nTiO2 reduces byssus performance of mussels under ocean warming

Nano‑titanium dioxide (nTiO2) is a widely used nanomaterial posing potential ecological risk for marine ecosystems that might be enhanced by elevated temperatures such as expected during climate change. nTiO2 may affect benthic filter feeders like mussels through waterborne exposures and via food chain due to the adsorption on/in algae. Mussel byssus are proteinaceous fibers secreted by byssal glands of the mussels for attachment. Byssus production and mechanical properties are sensitive to environmental stressors but the combined effects of warming and nTiO2 on byssus performance of mussels are unclear hampering our understanding of the predation and dislodgement risk of mussels under the multiple stressor scenarios. We explored the effects of a short-term (14-day) single and combined exposures to warming (28 °C) and 100 μg L−1 nTiO2 (including food co-exposure) on the byssus performance of the thick shell mussel Mytilus coruscus. The mechanical strength (measured as the breaking force) of the byssal threads was impaired by warming and nTiO2 (including food co-exposure), but the number and length of the byssal threads were increased. The mRNA expression levels of mussel foot proteins (mfp-3, mfp-5) and pre-collagens (preCOL-D, preCOL-P, preCOL-NG) were up-regulated to varying degrees, with the strongest effects induced by warming. This indicates that the physiological and molecular mechanisms of byssus secretion are plastic. However, downregulation of the mRNA expression of preCOL-D and preCOL-P under the combined warming and nTiO2 exposures indicate the limits of these plasticity mechanisms and suggest that the attachment ability and survival of the mussels may be impaired if the pollution or temperature conditions further deteriorate.

From farm sustainability to ecosystem sustainability: Exploring the limitations of farm-applied aquaculture eco-certification schemes

Aquaculture eco-certification schemes provide standards against which individual farms are assessed, and those farms that comply with eco-certification criteria receive certified status. These schemes aim to improve aquaculture sustainability, but the site-by-site approach of eco-certification can be a barrier to the inclusion of ecosystem perspectives in the evaluation of farm sustainability. However, the ecosystem approach to aquaculture demands a management approach that considers broader scale ecosystem impacts. This study explored how eco-certification schemes and processes account for potential ecosystem impacts of salmon farms. Interviews with eco-certification auditors, salmon producers, and eco-certification staff were conducted. The experience of participants and information from eco-certification scheme criteria and other eco-certification scheme documents were used to identify thematic challenges associated with the consideration of ecosystem impacts including: assessing far-field impacts, managing cumulative effects, and anticipating ecosystem risks. Results indicate that eco-certification schemes work within the limitations of farm-scale application of global eco-certification standards to address potential ecosystem impacts by: (1) including eco-certification scheme criteria that address ecosystem impacts, (2) relying on the experience, expertise, and judgement of eco-certification auditors, and (3) referencing and deferring to local regulations. Results indicate that eco-certification schemes can address ecosystem impacts to some degree, despite their site-by-site approach. The integration of additional tools while supporting the capacity of farms to apply those tools, as well as increasing transparency during compliance assessment could help eco-certification schemes shift from providing assurance of farm sustainability to providing assurance of ecosystem sustainability.

Heavy Metals in Sediments of Hulun Lake in Inner Mongolia: Spatial-Temporal Distributions, Contamination Assessment and Source Apportionment

The spatial and temporal distributions, contamination evaluation, and source apportionment of Cu, Zn, As, Pb, Cd, and Cr in the sediments of Hulun Lake were explored in this work. The pollution characteristics of six heavy metals were assessed by single factor pollution index (PI) and geo-accumulation index (Igeo). The sources of heavy metals in the surface sediments were analyzed by the positive definite matrix factorization (PMF) and Pearson correlation analysis. The sedimentary records of heavy metals in core sediments were reproduced by radioisotopes. The average concentrations of 6 heavy metals except Cd were lower than the corresponding background values. The spatial distributions of Cu, Zn, Cr, Cd and As were generally similar and showed higher abundances in the southwestern part of the lake. With the use and import of heavy metals, the concentration of heavy metals in core sediments increased with the fluctuation of years. The peak of heavy metal concentration was related to the high growth rate of gross domestic product in 2003-2008. The single factor pollution index and geo accumulation index results showed that the surface sediment was mainly polluted by Cd, followed by Zn and As. Natural parent material, agricultural activities and industrial activities were the main sources of heavy metal pollution in the sediments, accounting for 17.03%, 26.34%, and 56.63% of the total heavy metal accumulation, respectively. Pb was derived mainly from natural parent material. Cd and As were closely associated with agricultural activities. Cu and Zn were mainly attributed to industrial mining activities. Source apportionment of the ecological risks of heavy metals illustrated that industrial sources were the primary ecosystem risk sources (66.1%), followed by agricultural sources (23.75%) and natural sources (10.15%). The results will also provide reference data for future studies of heavy metals pollution in sediments from Hulun Lake and other lakes.