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Carbon-14 (C-14) has been a major contributor to the human radioactive exposure dose, as it is released into the environment from the nuclear industry in larger quantities compared to other radionuclides. This most abundant nuclide enters the biosphere as organically bound C-14 (OBC-14), posing a potential threat to public health. Yet, it remains unknown how this relatively low radiotoxic nuclide induces health risks via chemical effects, such as isotope effect. By establishing a trophic transfer model involving algae (Scenedesmus obliquus), daphnia (Daphnia magna) and zebrafish (Danio rerio), we demonstrate that rapid incorporation and transformation of inorganic C-14 by algae into OBC-14 facilitates the blending of C-14 into the biomolecules of zebrafish. We find that internalized C-14 is persistently retained in the brain of zebrafish, affecting DNA methylation and causing alterations in neuropathology. Global isotope tracing metabolomics with C-14 exposure further reveals the involvement of C-14 in various critical metabolic pathways, including one-carbon metabolism and nucleotide metabolism. We thus characterize the kinetic isotope effects for 12C/14C in the key reactions of these metabolic pathways through kinetic experiments and density functional theory computations, showing that the isotopic substitution of carbon in biochemicals regulates metabolism by disrupting reaction ratios via isotope effects. Our results suggest that inorganic C-14 discharged by the nuclear industry can be biotransformed into OBC-14 to impact metabolism via isotope effects, providing new insights into understanding the health risk of C-14, which is traditionally considered as a low radiotoxic nuclide. [ABSTRACT FROM AUTHOR]

To understand energy and material cycles on surface Earth, it is important yet challenging to estimate trophic transfer through ecosystems. To address this issue, the integrated trophic position (iTP), defined as a biomass-weighted average TP of a given food web, is useful because the iTP can be a proxy for the configuration of ecological pyramid. Here we conducted the compound-specific nitrogen isotope analysis of amino acids for macroinvertebrate communities collected from the Ado and Yasu Rivers in the Lake Biwa watershed, Japan, to estimate their iTP values. Unlike previous studies, no clear relationships between iTP and biodiversity (Shannon index H') were found. However, by comparing the irrigated period and the non-irrigated period within the Yasu River, the decrease in iTP values was fairly characterized by the increase in H'. A significant difference in the observed iTP values compared to those reported in the previous study suggests that the configuration of ecological pyramid in stream ecosystems is dynamic rather than static. We also found that the iTP values of stream macroinvertebrate communities (2.37 ± 0.24) (n = 43), marine mesozooplankton communities (2.33 ± 0.34) (n = 14), and animal communities with various taxonomic groups (2.42 ± 0.21) (n = 158) are all comparable with each other, suggesting that partial communities involving macroinvertebrates well represent the configuration of total ecological pyramid. This finding clearly delineates the promising performance of the iTP index for the trophic transfer of energy, which should be further explored in a variety of ecosystems. [ABSTRACT FROM AUTHOR]

Heavy metals (HMs) are ubiquitous in terrestrial and aquatic environments due to unplanned industrial waste discharge, the release of untreated wastewater, and improper mining activities. In particular, the concentrations of HMs are found to be higher in aquatic environments. As a result, the aquatic biota was heavily affected by HM contamination. This critical review aims to understand the sources and toxicity of HMs in commercial fish species, explore their ecological exchange, and examine the related human health challenges in Bangladesh. A modified PRISMA review technique is used in this paper to analyze the current status and research limitations of HM studies in Bangladesh fish species and their toxicity within aquatic food webs. Briefly, we searched several keywords to explore the research trend of HM concentrations and toxicity in fish species. Furthermore, potential toxicity and risk assessment of HMs through the aquatic food chain in Bangladesh were explored. On the other hand, a cross-tabulation approach was used to process the toxicity findings of HMs. Previous studies indicate that fish species can possess comparatively higher HMs than river water due to ecological exchange factors, including bioaccumulation and biotransformation. This review focuses on Bangladesh, highlighting areas for improvements and the need for further study to achieve a transparent understanding of HM deposition in fish species and the sustainable management of aquatic food chain toxicity. [ABSTRACT FROM AUTHOR]

Short-chain chlorinated paraffins (SCCPs) are a persistent organic pollutant, and limited information is available on their bioaccumulation and trophic transfer, which would be affected by carbon chain length, chlorine content, and hydrophobicity. In this study, relevant data on SCCPs in water, sediments, and organisms collected from Laizhou Bay were analyzed to investigate the specific distribution of SCCPs and their bioaccumulation and trophic transfer. In water and sediments, the average SCCP concentrations (ΣSCCPs) were 362.23 ± 81.03 ng/L and 609.68 ± 90.28 ng/g d.w., respectively. In 28 species of organisms, the ΣSCCPs varied from 70.05 to 47,244.13 ng/g l.w. (average = 648 ± 7360) and the predominant homologs were C13 (average = 34.91%) and Cl5–7 (average = 93.13%), differing from those in water (average = C11 32.75% and average = Cl5–7 88%) and sediments (average = C13 31.60% and average = Cl6–8 87.16%). The logarithm bioaccumulation factors (BAFs) of ΣSCCPs were 1.18–2.74 and were positively correlated with the log Kow. A significant negative linear relationship was observed between biota-sediment accumulation factors (BSAFs) and log Kow. It is suggested that the hydrophobicity may affect the bioaccumulation of SCCPs. SCCPs demonstrated a trophic magnification factor (TMF) ranging from 2.19 to 3.00 (average = 2.51) and exhibited a significant linear correlation with carbon chain length (p < 0.05) and log Kow values (p < 0.05), suggesting that SCCPs have biomagnification potential in Laizhou Bay that is affected by hydrophobicity and carbon chain length. [ABSTRACT FROM AUTHOR]

Potentially toxic metals and metalloids (PTMs) may become a concern to plant and animal health when soil concentrations exceed toxicity limits. These limits are often exceeded in polluted environments (anthropogenic sources) and may transfer through the trophic system, from contaminated soil to plants, and thereafter to herbivores and predators. The aim of this mini review was to consider trophic transfer of PTMs in terrestrial ecosystems, focusing on arthropods as the endpoint. ScienceDirect® was used as search engine with a set of keywords. The most assessed PTMs were Cd, Pb, and Zn, and 63% of all PTMs considered in research were attributed to anthropogenic sources. Industrial or mining sites were most frequently studied, and agricultural sites the least. Brassica was the most studied plant genus as the main extractor of PTMs from the soil as they are easy growing food plants known to take up PTMs. Research mostly focused on primary consumers, with Coleoptera being the most investigated arthropod order, probably because of the diversity of the order and its common occurrence worldwide. Most research was conducted in Europe, while South America and Africa only contributed 6.8% and 2.6%, respectively. The majority of the investigated articles (61%) assessed trophic transfer. From those, only 24% directly measured PTM transfer with experimental trials and included only one trophic level, that is, primary consumers, while 7% of research directly measured PTM transfer across multiple trophic levels (primary and secondary consumers). [ABSTRACT FROM AUTHOR]

Seasonal differences in the availability of resources potentially result in the food web architecture also varying through time. Stable isotope analyses are a logistically simple but powerful tool for inferring trophic interactions and food web structure, but relatively few studies quantify seasonal variations in the food web structure or nutrient flux across multiple trophic levels. We determined the temporal dynamics in stable isotope compositions (carbon, nitrogen and sulphur) of a fish community from a highly seasonal, temperate estuary sampled monthly over a full annual cycle. Sulphur isotope values in fish tissues discriminated among consumers exploiting pelagic and benthic resources but showed no seasonal variation. This implied limited change in the relative consumption of pelagic and benthic resources by the fish community over the study period despite major seasonal changes in phytoplankton biomass. Conversely, carbon and nitrogen isotope values exhibited seasonality marked by the commencement of the spring phytoplankton bloom and peak chlorophyll concentration, with δ13C values following expected trends in phytoplankton growth physiology and variation in δ15N values coinciding with changes in major nitrogen sources to plankton between nitrate and ammonium. Isotope shifts in fish muscle were detected within 2 weeks of the peak spring phytoplankton bloom, suggesting a rapid trophic transfer of carbon and nitrogen along food chains within the estuarine food web during periods of high production. Therefore we caution against the assumption that temporal averaging effectively dampens isotopic variability in tissues of higher trophic‐level animals in highly dynamic ecosystems, such as temperate estuaries. This work highlights how stable isotope analyses can be combined with environmental data to gain a broader understanding of ecosystem functioning, while emphasising the need for temporally appropriate sampling in stable isotope‐based studies. [ABSTRACT FROM AUTHOR]

Abstract To understand energy and material cycles on surface Earth, it is important yet challenging to estimate trophic transfer through ecosystems. To address this issue, the integrated trophic position (iTP), defined as a biomass-weighted average TP of a given food web, is useful because the iTP can be a proxy for the configuration of ecological pyramid. Here we conducted the compound-specific nitrogen isotope analysis of amino acids for macroinvertebrate communities collected from the Ado and Yasu Rivers in the Lake Biwa watershed, Japan, to estimate their iTP values. Unlike previous studies, no clear relationships between iTP and biodiversity (Shannon index H’) were found. However, by comparing the irrigated period and the non-irrigated period within the Yasu River, the decrease in iTP values was fairly characterized by the increase in H’. A significant difference in the observed iTP values compared to those reported in the previous study suggests that the configuration of ecological pyramid in stream ecosystems is dynamic rather than static. We also found that the iTP values of stream macroinvertebrate communities (2.37 ± 0.24) (n = 43), marine mesozooplankton communities (2.33 ± 0.34) (n = 14), and animal communities with various taxonomic groups (2.42 ± 0.21) (n = 158) are all comparable with each other, suggesting that partial communities involving macroinvertebrates well represent the configuration of total ecological pyramid. This finding clearly delineates the promising performance of the iTP index for the trophic transfer of energy, which should be further explored in a variety of ecosystems.

Ciguatoxins (CTXs), potent neurotoxins produced by dinoflagellates of the genera Gambierdiscus and Fukuyoa, accumulate in commonly consumed fish species, causing human ciguatera poisoning. Field collections of Pacific reef fish reveal that consumed CTXs undergo oxidative biotransformations, resulting in numerous, often toxified analogs. Following our study showing rapid CTX accumulation in flesh of an herbivorous fish, we used the same laboratory model to examine the tissue distribution and metabolization of Pacific CTXs following long-term dietary exposure. Naso brevirostris consumed cells of Gambierdiscus polynesiensis in a gel food matrix over 16 weeks at a constant dose rate of 0.36 ng CTX3C equiv g-1 fish d-1. CTX toxicity determination of fish tissues showed CTX activity in all tissues of exposed fish (eight tissues plus the carcass), with the highest concentrations in the spleen. Muscle tissue retained the largest proportion of CTXs, with 44% of the total tissue burden. Moreover, relative to our previous study, we found that larger fish with slower growth rates assimilated a higher proportion of ingested toxin in their flesh (13% vs. 2%). Analysis of muscle extracts revealed the presence of CTX3C and CTX3B as well as a biotransformed product showing the m/z transitions of 2,3-dihydroxyCTX3C. This is the first experimental evidence of oxidative transformation of an algal CTX in a model consumer and known vector of CTX into the fish food web. These findings that the flesh intended for human consumption carries the majority of the toxin load, and that growth rates can influence the relationship between exposure and accumulation, have significant implications in risk assessment and the development of regulatory measures aimed at ensuring seafood safety.

Microplastics have been found in the gastrointestinal (GI) fluid of bottlenose dolphins (Tursiops truncatus), inhabiting Sarasota Bay, FL, suggesting exposure by ingestion, possibly via contaminated fish. To better understand the potential for trophic transfer, muscle and GI tissues from 11 species of dolphin prey fish collected from Sarasota Bay were screened for microplastics (particles < 5 mm diameter). Suspected microplastics were found in 82% of muscle samples (n = 89), and 97% of GI samples (n = 86). Particle abundance and shapes varied by species (p < 0.05) and foraging habit (omnivore vs. carnivore, p < 0.05). Pinfish (Lagodon rhomboides) had the highest particle abundance for both tissue types (muscle: 0.38 particles/g; GI: 15.20 particles/g), which has implications for dolphins as they are a common prey item. Findings from this study support research demonstrating the ubiquity of estuarine plastic contamination and underscore the risks of ingestion exposure for wildlife and potentially seafood consumers. [ABSTRACT FROM AUTHOR]

Plastics are a major source of marine pollution. One form of plastic pollution is microfibers, which are synthetic fibers five micrometers or smaller that are shed by artificial clothing. The size of microfibers enables them to easily be ingested by a number of marine organisms, including oysters. Oysters are filter feeders and a major aquaculture asset, which presents a concern for the effects of microfiber ingestion on human health. Very few studies have been conducted quantifying microfibers using Pacific oysters (Crassostrea gigas) sourced from California. This study quantifies microfiber content in the Pacific oyster farmed for human consumption in Morro Bay, California. Microfibers were quantified after being isolated from oyster samples. An average of 9.12 microfibers were recovered per oyster sample. Although some of the smaller oysters contained more microfibers compared to larger oysters, this difference was not significant. There also was no significant difference between the quantities of black and blue microfibers. However, there was a significant increase in quantities of black microfibers compared to green or red microfibers. The results of this study indicate that a large amount of microfibers are present in commercial oysters, but more research needs to be conducted to determine how this will impact human health. [ABSTRACT FROM AUTHOR]

The global proliferation of synthetic microfiber waste has emerged as a pressing environmental concern due to its widespread distribution in both aquatic and terrestrial ecosystems. Primary sources of synthetic microfibers include laundering of synthetic textiles, manufacturing, and plastic breakdown, with transport via wastewater, runoff, atmospheric deposition, and animal ingestion. This review highlights the sources of microfiber formation and accumulation, ranging from freshwater lakes and rivers to deep-sea sediments. The presence of microfibers in agricultural soils, urban dust, and even remote locations indicates atmospheric transportation and diverse accumulation patterns. Additionally, this review discusses the transportation of microfibers through various pathways and elaborates on various treatment technologies for microfiber removal and reduction. The potential human health impacts and mitigation solutions are also highlighted. Overall, this review aims to provide comprehensive knowledge of the sources, transport mechanisms, and accumulation patterns of synthetic microfibers, emphasizing their multifaceted environmental impact and the need for further research to develop effective solutions. [ABSTRACT FROM AUTHOR]

The most up-to-date regulatory guidelines for establishing acute and chronic numeric limits for copper in freshwaters are based on a biotic ligand model for various species, but the model for Cu lacks data on dietary uptake. In addition, some common macroinvertebrate toxicity assay parameters are less representative of the ecosystem. We investigated the effects of diet and its type in the experimental setup and as an exposure pathway to an established amphipod (crustacean) Hyalella azteca (H. azteca) for Cu toxicity assays. We also investigated another overlooked aspect, the organic matter (OM) source. Our experiments compared the toxicity of pre-equilibrated and unequilibrated natural diets and a laboratory-favored diet in effluent and stormwater sources of organic matter adjusted to standard water characteristics. The experiments indicated a more toxic effect of the pre-equilibrated diet and natural dietary sources, and less toxic effects in the presence of effluent OM compared with stormwater OM, shifting LC50 or EC20 values by as much as 67% compared with the controls. The use of a pre-equilibrated natural diet in toxicity assays provides the advantage of producing toxicity data more representative of field conditions. Considering organic matter type, especially in dietary exposures, will better predict toxicity, accounting for copper complexation with OM from different sources and partitioning to the food supply. Adapting these ecologically relevant parameters in whole effluent toxicity testing or other assays will also provide safer regulatory oversite of discharges to surface waters. [ABSTRACT FROM AUTHOR]

Short-chain chlorinated paraffins (SCCPs) are a persistent organic pollutant, and limited information is available on their bioaccumulation and trophic transfer, which would be affected by carbon chain length, chlorine content, and hydrophobicity. In this study, relevant data on SCCPs in water, sediments, and organisms collected from Laizhou Bay were analyzed to investigate the specific distribution of SCCPs and their bioaccumulation and trophic transfer. In water and sediments, the average SCCP concentrations (ΣSCCPs) were 362.23 ± 81.03 ng/L and 609.68 ± 90.28 ng/g d.w., respectively. In 28 species of organisms, the ΣSCCPs varied from 70.05 to 47,244.13 ng/g l.w. (average = 648 ± 7360) and the predominant homologs were C13 (average = 34.91%) and Cl5–7 (average = 93.13%), differing from those in water (average = C11 32.75% and average = Cl5–7 88%) and sediments (average = C13 31.60% and average = Cl6–8 87.16%). The logarithm bioaccumulation factors (BAFs) of ΣSCCPs were 1.18–2.74 and were positively correlated with the log Kow. A significant negative linear relationship was observed between biota-sediment accumulation factors (BSAFs) and log Kow. It is suggested that the hydrophobicity may affect the bioaccumulation of SCCPs. SCCPs demonstrated a trophic magnification factor (TMF) ranging from 2.19 to 3.00 (average = 2.51) and exhibited a significant linear correlation with carbon chain length (p < 0.05) and log Kow values (p < 0.05), suggesting that SCCPs have biomagnification potential in Laizhou Bay that is affected by hydrophobicity and carbon chain length.

Ocean warming and acidification may significantly alter the distribution and intensity of harmful algal blooms as well as their effects on marine food webs. Estimating such effects rely, in part, on understanding the physiological response of individual algal species to controlled laboratory simulations of climate change conditions. Here we report the physiological response of the harmful dinoflagellate Karlodinium veneficum to the combined effects of elevated temperature and CO2 (29°C/1000 ppm CO2). We first examined these effects by comparing ambient control (25°C/441 ppm CO2) and elevated conditions under short-term (~20 generations) growth. Next, we compared the short-term elevated condition to a longer-term (~200 generations) growth scenario under the same elevated temperature and CO2. Under the short-term elevated conditions, K. veneficum growth declined, cell toxicity increased, and saturated and mono-unsaturated fatty acid (FA) composition varied significantly from ambient conditions. Meanwhile, after ~ 200 generations of growth under elevated temperature and CO2, K. veneficum carbon assimilation, growth, and cell toxicity were significantly higher than the short-term elevated treatment. Further, while total saturated FA declined, essential fatty acids increased and likely represented an adaptive temporal response to long-term exposure to high temperature and CO2. Such shifts in FA profiles and cell toxicity may possibly alter K. veneficum nutritional quality as prey and its mixotrophic behavior, thereby affecting the energy and mass transfer through the marine food webs as well as bloom dynamics. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are a growing concern in marine ecosystems, with their presence reported in various aquatic environments. This editorial highlights the need for a better understanding of the ecological consequences of MPs, particularly their effects on eukaryotic microbes (EM). EM play a crucial role in carbon transfer and are affected by MPs through ingestion and interactions with other components of the microbial loop. The articles featured in this research topic explore the effects of MPs on copepod microbiota, the gut microbiome of ventiferous crabs, prey-predator interactions, and the overall functioning of marine ecosystems. These studies emphasize the far-reaching impacts of MPs on energy flow and the need for further research in this area. [Extracted from the article]

In this study, we collected 56 species of fishery organisms (including fish, crustaceans, cephalopods, gastropods, and bivalves) from four seasonal survey cruises at the Dachen fishery grounds. We measured the concentrations of seven heavy metals (Cd, Zn, Cu, Pb, Cr, As, and Hg) in these fisheries organisms. We determined their trophic levels using carbon and nitrogen stable isotope techniques. We analyzed the characteristics of heavy metal transfer in the food chain. The results showed significant differences in heavy metal concentrations among different species. Among all biological groups, bivalves and gastropods exhibited higher levels of heavy metal enrichment than other biological groups, while fish had the lowest levels of heavy metal enrichment. Heavy metals exhibited different patterns of nutritional transfer in the food chain. While Hg showed a biomagnification phenomenon in the food chain, it was not significant. Cd, Zn, Cu, Pb, Cr, and As exhibited a trend of biodilution with increasing nutritional levels, except for As, which showed no significant correlation with δ15N. [ABSTRACT FROM AUTHOR]

Chlorinated paraffins (CPs) are widely used persistent organic pollutants (POPs). Based on the carbon chain length, CPs can be classified as short-chain (C10-13) CPs (SCCPs), medium-chain (C14-17) CPs (MCCPs), and long-chain (C≥18) CPs (LCCPs). Since SCCPs have been listed as POPs of particular concern by the Stockholm Convention, the production of MCCPs and LCCPs is increased sharply. Therefore, the number of studies focusing on MCCPs and LCCPs has increased recently. Herein, we comprehensively reviewed recent studies on the biological occurrence, bioaccumulation, transmission, and transformation of CPs. CPs are pervasively distributed across biotas and exhibit diverse accumulation properties in different tissues. MCCPs and LCCPs are more abundant than SCCPs in some organisms. The absorption, translocation, and elimination behaviors of CPs directly influence their accumulation in organisms. The maternal transfer is an elimination pathway for CPs and could explain the discrepancy in CPs accumulation in opposite sexes of some organisms. With the establishment of novel screening methods, several transformation products of CPs have been identified in plants, microorganisms, and humans. By comparing the biotransformation pathways of CPs in different organisms, common and unique pathways have been identified in various species, although further studies on the transformation of CPs in humans and other animals are required. This review describes some noteworthy and prospective studies focused on the biological behavior of CPs. The review also derives novel conclusions based on recent studies in this field to provide a comprehensive understanding of the environmental fate of CPs. [ABSTRACT FROM AUTHOR]

In temperate lakes, eutrophication and warm temperatures can promote cyanobacteria blooms that reduce water quality and impair food-chain support. Although parasitic chytrids of phytoplankton might compete with zooplankton, they also indirectly support zooplankton populations through the “mycoloop”, which helps move energy and essential dietary molecules from inedible phytoplankton to zooplankton. Here, we consider how the mycoloop might fit into the biodiversity–ecosystem functioning (BEF) framework. BEF considers how more diverse communities can benefit ecosystem functions like zooplankton production. Chytrids are themselves part of pelagic food webs and they directly contribute to zooplankton diets through spore production and by increasing host edibility. The additional way that chytrids might support BEF is if they engage in “kill-the-winner” dynamics. In contrast to grazers, which result in “eat-the-edible” dynamics, kill-the-winner dynamics can occur for host-specific infectious diseases that control the abundance of dominant (in this case inedible) hosts and thus limit the competitive exclusion of poorer (in this case edible) competitors. Thus, if phytoplankton diversity provides functions, and chytrids support algal diversity, chytrids could indirectly favour edible phytoplankton. All three mechanisms are linked to diversity and therefore provide some “insurance” for zooplankton production against the impacts of eutrophication and warming. In our perspective piece, we explore evidence for the chytrid insurance hypothesis, identify exceptions and knowledge gaps, and outline future research directions. [ABSTRACT FROM AUTHOR]

The increase of micro- and nano-plastics (MNPs) in aquatic environments has become a significant concern due to their potential toxicological effects on ecosystems, food web dynamics, and human health. These plastic particles emerge from a range of sources, such as the breakdown of larger plastic waste, consumer products, and industrial outputs. This review provides a detailed report of the transmission and dangers of MNPs in aquatic ecosystems, environmental behavior, and interactions within aquatic food webs, emphasizing their toxic impact on marine life. It explores the relationship between particle size and toxicity, their distribution in different tissues, and the process of trophic transfer through the food web. MNPs, once consumed, can be found in various organs, including the digestive system, gills, and liver. Their consumption by lower trophic level organisms facilitates their progression up the food chain, potentially leading to bioaccumulation and biomagnification, thereby posing substantial risks to the health, reproduction, and behavior of aquatic species. This work also explores how MNPs, through their persistence and bioaccumulation, pose risks to aquatic biodiversity and disrupt trophic relationships. The review also addresses the implications of MNPs for human health, particularly through the consumption of contaminated seafood, highlighting the direct and indirect pathways through which humans are exposed to these pollutants. Furthermore, the review highlights the recommendations for future research directions, emphasizing the integration of ecological, toxicological, and human health studies to inform risk assessments and develop mitigation strategies to address the global challenge of plastic pollution in aquatic environments.

Ants (Formicidae) are ubiquitous in terrestrial ecosystems, including agricultural areas and forests. They are important for soil movement, decomposition, nutrient cycling, pollination, predation, scavenging and seed dispersal. Furthermore, they serve as a crucial food source for various wildlife. However, ants are no part of current ecotoxicity testing. Here, we systematically analyze whether and how ants can be exposed to active substances from plant protection products (PPPs) or genetically modified plants (GMPs). Like other arthropods, ants can be exposed via direct contact with PPPs after application, inhalation, uptake of contaminated drinking water or diet. For plant incorporated protectants (PIPs) expressed by GMPs, dietary exposure is the only relevant exposure route. Ants exhibit a diverse dietary spectrum, including plant material, honey dew collection, fungal cultivation, scavenging, and predation. Notably, foraging for dead or weakened arthropods, e.g., treated pest organisms, represents a significant exposure route because such food may be readily available in large amounts after spraying a field. Arthropods, alive or deceased, serve as the dominant protein source for numerous ant species, essential for larval development and the egg production of the queen(s). Consequently, exposure routes, via contaminated food items, can jeopardize entire ant colonies if it reaches the queen. However, effects arising from contaminated prey are not routinely assessed, neither for non-social nor for social insects such as the honey bee, which collects only nectar and pollen and is intensively tested in the assessment of PPPs. We conclude that ecotoxicity testing in ants would fill a gap and support the assessment of biodiversity effects. To achieve this, we recommend further research to explore the exposure of the different castes and developmental stages of ants in greater detail and to develop protocols allowing for ecological risk assessments of PPPs and PIPs via dietary uptake. This comprehensive approach will contribute significantly to our understanding of the potential consequences of PPP and GMP exposure to non-target ants.

The present review critically examines the advancements in the past 5 years regarding research on the bioavailability and toxicity of the nanoplastics (NPLs) to freshwater plankton. We discuss the recent progress in the understanding of adsorption, absorption, trophic transfer, and biological effects in phyto- and zooplankton induced by NPLs exposure. The influence of plankton on NPLs’ bioavailability via the excretion of biomolecules and formation of eco-corona is also examined. Despite important research developments, there are still considerable knowledge gaps with respect to NPLs’ bioavailability and trophic transfer by plankton as well as a potential adverse effect in natural aquatic systems. As plankton play a critical role in primary production, nutrient cycling, and food web structure, understanding the interactions between NPLs and plankton is essential in assessing the potential implications of NPLs pollution for aquatic ecosystem biodiversity and services.

The most up-to-date regulatory guidelines for establishing acute and chronic numeric limits for copper in freshwaters are based on a biotic ligand model for various species, but the model for Cu lacks data on dietary uptake. In addition, some common macroinvertebrate toxicity assay parameters are less representative of the ecosystem. We investigated the effects of diet and its type in the experimental setup and as an exposure pathway to an established amphipod (crustacean) Hyalella azteca (H. azteca) for Cu toxicity assays. We also investigated another overlooked aspect, the organic matter (OM) source. Our experiments compared the toxicity of pre-equilibrated and unequilibrated natural diets and a laboratory-favored diet in effluent and stormwater sources of organic matter adjusted to standard water characteristics. The experiments indicated a more toxic effect of the pre-equilibrated diet and natural dietary sources, and less toxic effects in the presence of effluent OM compared with stormwater OM, shifting LC50 or EC20 values by as much as 67% compared with the controls. The use of a pre-equilibrated natural diet in toxicity assays provides the advantage of producing toxicity data more representative of field conditions. Considering organic matter type, especially in dietary exposures, will better predict toxicity, accounting for copper complexation with OM from different sources and partitioning to the food supply. Adapting these ecologically relevant parameters in whole effluent toxicity testing or other assays will also provide safer regulatory oversite of discharges to surface waters.

Blooms of the red, filamentous cyanobacterium Planktothrix rubescens occur frequently in pre-alpine lakes in Europe, often with concomitant toxic microcystin (MC) production. Trophic transfer of MCs has been observed in bivalves, fish, and zooplankton species, while uptake of MCs into Diptera species could facilitate distribution of MCs into terrestrial food webs and habitats. In this study, we characterized a Planktothrix bloom in summer 2019 in Lake Mindelsee and tracked possible trophic transfer and/or bioaccumulation of MCs via analysis of phytoplankton, zooplankton (Daphnia) and emergent aquatic insects (Chaoborus, Chironomidae and Trichoptera). Using 16 S rRNA gene amplicon sequencing, we found that five sequence variants of Planktothrix spp. were responsible for bloom formation in September and October of 2019, and these MC-producing variants, provisionally identified as P. isothrix and/or P. serta, occurred exclusively in Lake Mindelsee (Germany), while other variants were also detected in nearby Lake Constance. The remaining cyanobacterial community was dominated by Cyanobiaceae species with high species overlap with Lake Constance, suggesting a well-established exchange of cyanobacteria species between the adjacent lakes. With targeted LC–HRMS/MS we identified two MC-congeners, MC-LR and [Asp3]MC-RR with maximum concentrations of 45 ng [Asp3]MC-RR/L in lake water in September. Both MC congeners displayed different predominance patterns, suggesting that two different MC-producing species occurred in a time-dependent manner, whereby [Asp3]MC-RR was clearly associated with the Planktothrix spp. bloom. We demonstrate an exclusive transfer of MC-LR, but not [Asp3]MC-RR, from phytoplankton into zooplankton reaching a 10-fold bioconcentration, yet complete absence of these MC congeners or their conjugates in aquatic insects. The latter demonstrated a limited trophic transfer of MCs from zooplankton to zooplanktivorous insect larvae (e.g., Chaoborus), or direct transfer into other aquatic insects (e.g. Chironomidae and Trichoptera), whether due to avoidance or limited uptake and/or rapid excretion of MCs by higher trophic emergent aquatic insects.

Introduction: Artificial upwelling has been discussed as a nature-based solution to fertilize currently unproductive areas of the ocean to enhance food web productivity and atmospheric CO2 sequestration. The efficacy of this approach may be closely tied to the nutrient stoichiometry of the upwelled water, as Si- rich upwelling should benefit the growth of diatoms, who are key players for primary production, carbon export and food web efficiency. Methods: With a mesocosm experiment in subtropical waters, we assessed the physiological and functional responses of an oligotrophic phytoplankton community to artificial upwelling under varying Si:N ratios (0.07-1.33). Results: Deep water fertilization led to strongly enhanced primary productivity rates and net autotrophy across Si scenarios. At the community level, Si-rich upwelling50 temporarily increased primary production and consistently enhanced diatom growth, producing up to 10-fold higher abundances compared to Si-deficient upwelling. At the organism level, contrasting effects were observed. On the one hand, silicification and size of diatom cells remained unaffected by Si:N, which is surprising given the direct dependency of these traits on Si. On the other hand, diatom Chlorophyll a density and carbon density were strongly reduced and particulate matter C:N was elevated under Si- rich upwelling. Discussion: This suggests a reduced nutritional value for higher trophic levels under high Si:N ratios. Despite these strong qualitative changes under high Si, diatom cells appeared healthy and showed high photosynthetic efficiency. Our findings reveal great physiological plasticity and adaptability in phytoplankton under artificial upwelling, with Si-dependent trade-offs between primary producer quantity and quality. [ABSTRACT FROM AUTHOR]

Fire can lead to transitions between forest and grassland ecosystems and trigger positive feedbacks to climate warming by releasing CO2 into the atmosphere. Climate change is projected to increase the prevalence and severity of wildfires. However, fire effects on the fate and impact of terrestrial organic matter (i.e., terrestrial subsidies) in aquatic ecosystems are unclear. Here, we performed a gradient design experiment in freshwater pond mesocosms adding 15 different amounts of burned or unburned plant detritus and tracking the chronology of detritus effects at 10, 31, 59, and 89 days. We show terrestrial subsidies had time‐ and mass‐dependent, non‐linear impacts on ecosystem function that influenced dissolved organic carbon (DOC), ecosystem metabolism (net primary production and respiration), greenhouse gas concentrations (carbon dioxide [CO2], methane [CH4]), and trophic transfer. These impacts were shifted by fire treatment. Burning increased the elemental concentration of detritus (increasing %N, %P, %K), with cascading effects on ecosystem function. Mesocosms receiving burned detritus had lower [DOC] and [CO2] and higher dissolved oxygen (DO) through Day 59. Fire magnified the effects of plant detritus on aquatic ecosystem metabolism by stimulating photosynthesis and respiration at intermediate detritus‐loading through Day 89. The effect of loading on DO was similar for burned and unburned treatments (Day 10); however, burned‐detritus in the highest loading treatments led to sustained hypoxia (through Day 31), and long‐term destabilization of ecosystem metabolism through Day 89. In addition, fire affected trophic transfer by increasing autochthonous nitrogen source utilization and reducing the incorporation of 15N‐labeled detritus into plankton biomass, thereby reducing the flux of terrestrial subsidies to higher trophic levels. Our results indicate fire chemically transforms plant detritus and alters the role of aquatic ecosystems in processing and storing carbon. Wildfire may therefore induce shifts in ecosystem functions that cross the boundary between aquatic and terrestrial habitats. [ABSTRACT FROM AUTHOR]

Ciguatoxins (CTXs), potent neurotoxins produced by dinoflagellates of the genera Gambierdiscus and Fukuyoa, accumulate in commonly consumed fish species, causing human ciguatera poisoning. Field collections of Pacific reef fish reveal that consumed CTXs undergo oxidative biotransformations, resulting in numerous, often toxified analogs. Following our study showing rapid CTX accumulation in flesh of an herbivorous fish, we used the same laboratory model to examine the tissue distribution and metabolization of Pacific CTXs following long-term dietary exposure. Naso brevirostris consumed cells of Gambierdiscus polynesiensis in a gel food matrix over 16 weeks at a constant dose rate of 0.36 ng CTX3C equiv g−1 fish d−1. CTX toxicity determination of fish tissues showed CTX activity in all tissues of exposed fish (eight tissues plus the carcass), with the highest concentrations in the spleen. Muscle tissue retained the largest proportion of CTXs, with 44% of the total tissue burden. Moreover, relative to our previous study, we found that larger fish with slower growth rates assimilated a higher proportion of ingested toxin in their flesh (13% vs. 2%). Analysis of muscle extracts revealed the presence of CTX3C and CTX3B as well as a biotransformed product showing the m/z transitions of 2,3-dihydroxyCTX3C. This is the first experimental evidence of oxidative transformation of an algal CTX in a model consumer and known vector of CTX into the fish food web. These findings that the flesh intended for human consumption carries the majority of the toxin load, and that growth rates can influence the relationship between exposure and accumulation, have significant implications in risk assessment and the development of regulatory measures aimed at ensuring seafood safety. [ABSTRACT FROM AUTHOR]

Lead (Pb) is ubiquitous in urban environments, and it is a risk factor for wildlife. But wildlife are particularly at risk for exposure near smelters in urban areas where higher than safe Pb levels in the soil have the potential to transfer to the food chain. Therefore, we investigated whether wildlife are at risk of Pb exposure and differences in Pb bioaccumulation in trophic levels at a Superfund site in an urban area of Colorado. We sampled soil, vegetation, arthropods, and birds at four sites: two contaminated sites (one at the Superfund site and one near the Superfund site) and two reference sites with low predicted Pb contamination. We found significantly higher Pb levels in the soil at the contaminated Slag pile at the Superfund site, compared to the other sites. At the Slag pile, Pb levels were the highest in vegetation and both arthropods and birds accumulated Pb. However, Pb did not increase between trophic levels in the terrestrial food web at the site. We concluded that smelter operations at the Superfund site resulted in significantly higher levels of Pb in the soil and sublethal accumulation in all taxa studied. This research can be used to mitigate the risks to vulnerable wildlife populations exposed to Pb at the Superfund site. Further examination of Pb toxicity in vulnerable taxa is critical to conserving wild populations and ecosystems near contamination zones. [ABSTRACT FROM AUTHOR]

The present review critically examines the advancements in the past 5 years regarding research on the bioavailability and toxicity of the nanoplastics (NPLs) to freshwater plankton. We discuss the recent progress in the understanding of adsorption, absorption, trophic transfer, and biological effects in phyto- and zooplankton induced by NPLs exposure. The influence of plankton on NPLs' bioavailability via the excretion of biomolecules and formation of eco-corona is also examined. Despite important research developments, there are still considerable knowledge gaps with respect to NPLs' bioavailability and trophic transfer by plankton as well as a potential adverse effect in natural aquatic systems. As plankton play a critical role in primary production, nutrient cycling, and food web structure, understanding the interactions between NPLs and plankton is essential in assessing the potential implications of NPLs pollution for aquatic ecosystem biodiversity and services. [ABSTRACT FROM AUTHOR]

IntroductionArtificial upwelling has been discussed as a nature-based solution to fertilize currently unproductive areas of the ocean to enhance food web productivity and atmospheric CO2 sequestration. The efficacy of this approach may be closely tied to the nutrient stoichiometry of the upwelled water, as Si-rich upwelling should benefit the growth of diatoms, who are key players for primary production, carbon export and food web efficiency.MethodsWith a mesocosm experiment in subtropical waters, we assessed the physiological and functional responses of an oligotrophic phytoplankton community to artificial upwelling under varying Si:N ratios (0.07-1.33).ResultsDeep water fertilization led to strongly enhanced primary productivity rates and net autotrophy across Si scenarios. At the community level, Si-rich upwelling50 temporarily increased primary production and consistently enhanced diatom growth, producing up to 10-fold higher abundances compared to Si-deficient upwelling. At the organism level, contrasting effects were observed. On the one hand, silicification and size of diatom cells remained unaffected by Si:N, which is surprising given the direct dependency of these traits on Si. On the other hand, diatom Chlorophyll a density and carbon density were strongly reduced and particulate matter C:N was elevated under Si-rich upwelling.DiscussionThis suggests a reduced nutritional value for higher trophic levels under high Si:N ratios. Despite these strong qualitative changes under high Si, diatom cells appeared healthy and showed high photosynthetic efficiency. Our findings reveal great physiological plasticity and adaptability in phytoplankton under artificial upwelling, with Si-dependent trade-offs between primary producer quantity and quality.

Emerging organophosphate flame retardants (E-OPFRs) are a new class of pollutants that have attracted increasing attention, but their bioaccumulation patterns and trophodynamic behaviors in aquatic food webs still need to be validated by comparison with legacy OPFRs (L-OPFRs). In this study, we simultaneously investigated the bioaccumulation, trophic transfer, and dietary exposure of 8 E-OPFRs and 10 L-OPFRs in a tropical estuarine food web from Hainan Island, China. Notably, the Σ10L-OPFRs concentration (16.1–1.18 × 105 lipid weight (lw)) was significantly greater than that of Σ8E-OPFRs (nondetectable (nd) - 2.82 × 103 ng/g lw) among the investigated organisms, and they both exhibited similar trends: fish

Plastic pollution has become a global environmental problem of major concern. However, the plastic contamination in the marine top predators, particularly in endangered species, is incompletely understood because of the limited amount of data on their presence in the digestive system and prey. This study investigated the stomach contents of an endangered but poorly known shark species, the longfin mako shark (Isurus paucus), found in the tropical western Pacific Ocean. We examined the plastics in this female specimen (1.22-m fork length) and her prey to assess the potential for trophic transfer of microplastics. Polypropylene bottle cap and lollipop packaging, longnose lancetfish (Alepisaurus ferox), and squid were found in the stomach of I. paucus, while no apparent internal injuries were noted. The microplastic fragments and granules, confirmed by laser direct infrared spectroscopy, were found in the digestive system of the intact squid ingested by I. paucus, suggesting that trophic transfer may occur between shark and prey. These results indicate that I. paucus is vulnerable to plastic ingestion and provide evidence of trophic transfer of microplastics in shark species. Our study emphasizes the need to evaluate the potential ecotoxicological consequences of increasing plastic pollution to endangered marine top predators. [ABSTRACT FROM AUTHOR]