A Polar outlook: Potential interactions of micro- and nano-plastic with other anthropogenic stressors

New insights into the role of sediments in microplastic inputs from the Northern Dvina River (Russia) to the White and Barents Seas

The Northern Dvina River is one of the main sources of microplastic pollution entering to the White and Barents Seas. The coastal and bottom sediments of this river play an important role as a transfer link of microplastics. With Py-GC/MS and μFT-IR methods, it was found that the sediments contain up to 350 mg/kg or 650 particles/kg of microplastic (dry weight). The unique hydrologic conditions of the river branching area contribute to the formation of a microplastic pollution hotspot. The hotspot accumulates >30 % of microplastic pollution, mainly ABS plastic particles smaller than 0.3 mm with roughness and cracks, which increases the hazard class (from II to IV) of microplastic pollution. Obtained data and high annual variability of pollution indicates that this area acts as a place of accumulation, degradation and gradual release of microplastics into the White and Barents Seas, i.e. into the Arctic region.

The co-presence of polystyrene nanoplastics and ofloxacin demonstrates combined effects on the structure, assembly, and metabolic activities of marine microbial community

Nanoplastic is increasing in environments and can address toxic effects on various organisms. Particle size, concentration, and surface functionalization most influence nanoplastic toxicity. Besides, nanoplastic can adsorb other contaminants (e.g., antibiotics) to aggravate its adverse effects. The combined effects of nanoplastics and antibiotics on planktonic/benthic microbial communities, however, are still largely unknown. In this study, the combined effects of polystyrene nanoplastic and ofloxacin on the structure, assembly, and metabolic activities of marine microbial communities were investigated based on amplicon sequencing data. The results mainly demonstrate that: (1) nanoplastic and ofloxacin have greater impacts on prokaryotic communities than eukaryotic ones; (2) niche breadths of planktonic prokaryotes and benthic eukaryotes were shrank with both high nanoplastic and ofloxacin concentrations; (3) increased ofloxacin mainly reduces nodes/edges of co-occurrence networks, while nanoplastic centralizes network modularity; (4) increased nanoplastic under high ofloxacin concentration induces more differential prokaryotic pathways in planktonic communities, while benthic communities are less influenced. The present work indicates that co-presence of nanoplastics and ofloxacin has synergistic combined effects on community structure shifts, niche breadth shrinking, network simplifying, and differential prokaryotic pathways inducing in marine microbial communities, suggesting nanoplastics and its combined impacts with other pollutions should be paid with more concerns.

Plasticiser leaching from polyvinyl chloride microplastics and the implications for environmental risk assessment

Microplastics in aquatic environments is a growing concern, particularly due to the leaching of chemical additives such as plasticisers. To develop comprehensive environmental risk assessments (ERAs) of high-concern polymers and plasticisers, an understanding of their leachability is required. This work investigated diethylhexyl phthalate (DEHP) and bisphenol A (BPA) leaching from polyvinyl chloride (PVC) microplastics (average diameter = 191 μm) under simulated marine conditions. Leaching behaviours were quantified using gel permeation chromatography (GPC) and thermal gravimetric analysis (TGA), and the polymer's physiochemical properties analysed using differential scanning calorimetry (DSC), Fourier Transform-Infrared Spectroscopy (FT-IR) and optical microscopy. Experimental data were fitted to a diffusion and boundary layer model, which found that BPA leaching was temperature-dependent (diffusion-limited), whereas DEHP leaching was controlled by surface rinsing. Model predictions also highlighted the importance of microplastic size on leaching dynamics. These data contribute towards greater accuracy in ERAs of microplastics, with implications for water quality and waste management, including decommissioning of plastic infrastructure.

Microplastics in gastrointestinal tracts of gentoo penguin (Pygoscelis papua) chicks on King George Island, Antarctica

Microplastics (< 5 mm) have been found in marine ecosystems worldwide, even in Antarctic ecosystems. In this study, the stomach and upper intestines of 14 dead gentoo penguin (Pygoscelis papua) chicks were collected and screened for microplastics on King George Island, a gateway to Antarctic research and tourism. A total of 378 microplastics were identified by Fourier-transform infrared spectroscopy, with 27.0 ± 25.3 microplastics per individual. The detected number of microplastics did not increase with the mass of penguin chicks, suggesting no permanent accumulation of microplastics. However, the concentration of microplastics was much higher (9.1 ± 10.8 microplastics per individual within the size range 100-5000 μm) than the previously reported concentration in the penguin feces, and a greater number of smaller microplastics were found. Marine debris surveys near the breeding colony found various plastic (79.3%) to be the most frequent type of beached debris, suggesting that local sources of marine plastic waste could have contributed to microplastic contamination of penguin chicks being fed by parents that forage in nearby seas. This finding confirms the presence of microplastics in an Antarctic ecosystem and suggests the need for stronger waste management in Antarctica and a standardized scheme of microplastic monitoring in this once-pristine ecosystem.

Improvement of biodegradation of PET microplastics with whole-cell biocatalyst by interface activation reinforcement

Polyethylene terephthalate (PET) is an important basic polymer, which was used widely in variety of fields. Due to its high crystallinity, compact structure and strong surface hydrophobicity, PET has prominent resistance to biodegradation. In recent years, microplastics, especially polyethylene terephthalate (PET) microplastics, was considered as serious threaten to ecosystems. In this study, alkali-resistant bacteria were used as whole-cell catalysts to try to improve the biodegradation of PET microplastics by increasing the bio-interfacial activity of the polymer substrate. Surfactants were applicated to enhance interfacial activation of enzyme and PET interactions. And an integrated strategy was constructed based on alkali resistant bacteria to catalysis the hydrolysis of PET. The results showed that Tween 20 had the most obvious promoting effect among the four interfacial biocatalysts on biological-chemical combined hydrolysis of PET microplastics with whole-cell biocatalysts in alkaline environment. Obvious etching and fracture were observed on the PET fibre surface after biodegradation in presence of surfactant. The weight loss rate of PET substrate can reach 11.04% after 5 days of biodegradation. Thus, this research provides a promising method for efficient degradation of PET microplastics.

Scoping intergenerational effects of nanoplastic on the lipid reserves of Antarctic krill embryos

Antarctic krill (Euphausia superba) plays a central role in the Antarctic marine food web and biogeochemical cycles and has been identified as a species that is potentially vulnerable to plastic pollution. While plastic pollution has been acknowledged as a potential threat to Southern Ocean marine ecosystems, the effect of nanoplastics (<1000 nm) is poorly understood. Deleterious impacts of nanoplastic are predicted to be higher than that of larger plastics, due to their small size which enables their permeation of cell membranes and potentially provokes toxicity. Here, we investigated the intergenerational impact of exposing Antarctic krill to nanoplastics. We focused on whether embryonic energy resources were affected when gravid female krill were exposed to nanoplastic by determining lipid and fatty acid compositions of embryos produced in incubation. Embryos were collected from females who had spawned under three different exposure treatments (control, nanoplastic, nanoplastic + algae). Embryos collected from each maternal treatment were incubated for a further 6 days under three nanoplastic exposure treatments (control, low concentration nanoplastic, and high concentration nanoplastic). Nanoplastic additions to seawater did not impact lipid metabolism (total lipid or fatty acid composition) across the maternal or direct embryo treatments, and no interactive effects were observed. The provision of a food source during maternal exposure to nanoplastic had a positive effect on key fatty acids identified as important during embryogenesis, including higher total polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) when compared to the control and nanoplastic treatments. Whilst the short exposure time was ample for lipids from maternally digested algae to be incorporated into embryos, we discuss why the nanoplastic-fatty acid relationship may be more complex. Our study is the first to scope intergeneration effects of nanoplastic on Antarctic krill lipid and fatty acid reserves. From this, we suggest directions for future research including long term exposures, multi-stressor scenarios and exploring other critical energy reserves such as proteins.

Contribution of plastic and microplastic to global climate change and their conjoining impacts on the environment - A review

Plastics are fossil fuel-derived products. The emissions of greenhouse gases (GHG) during different processes involved in the lifecycle of plastic-related products are a significant threat to the environment as it contributes to global temperature rise. By 2050, a high volume of plastic production will be responsible for up to 13 % of our planet's total carbon budget. The global emissions of GHG and their persistence in the environment have depleted Earth's residual carbon resources and have generated an alarming feedback loop. Each year at least 8 million tonnes of discarded plastics are entering our oceans, creating concerns regarding plastic toxicity on marine biota as they end up in the food chain and ultimately affect human health. The unsuccessful management of plastic waste and its presence on the riverbanks, coastlines, and landscapes leads to the emission of a higher percentage of GHG in the atmosphere. The persistence of microplastics is also a significant threat to the fragile and extreme ecosystem containing diverse life forms with low genetic variation, making them vulnerable to climatic change. In this review, we have categorically discussed the contribution of plastic and plastic waste to global climate change covering the current plastic production and future trends, the types of plastics and plastic materials used globally, plastic lifecycle and GHG emission, and how microplastics become a major threat to ocean carbon sequestration and marine health. The conjoining impact of plastic pollution and climate change on the environment and human health has also been discussed in detail. In the end, we have also discussed some strategies to reduce the climate impact of plastics.

Organic or junk food? Microplastic contamination in Antarctic krill and salps

Microplastics (MP) have been reported in Southern Ocean (SO), where they are likely to encounter Antarctic zooplankton and enter pelagic food webs. Here we assess the presence of MP within Antarctic krill (Euphausia superba) and salps (Salpa thompsoni) and quantify their abundance and type by micro-Fourier transform infrared microscopy. MP were found in both species, with fibres being more abundant than fragments (krill: 56.25% and salps: 22.32% of the total MP). Polymer identification indicated MP originated from both local and distant sources. Our findings prove how in situ MP ingestion from these organisms is a real and ongoing process in the SO. MP amount was higher in krill (2.13 ± 0.26 MP ind^-1) than salps (1.38 ± 0.42 MP ind^-1), while MP size extracted from krill (130 ± 30 µm) was significantly lower than MP size from salps (330 ± 50 µm). We suggest that differences between abundance and size of MP ingested by these two species may be related to their food strategies, their ability to fragment MP as well as different human pressures within the collection areas of the study region. First comparative field-based evidence of MP in both krill and salps, two emblematic zooplankton species of the SO marine ecosystems, underlines that Antarctic marine ecosystems may be particularly sensitive to plastic pollution.

Understanding plasticiser leaching from polystyrene microplastics

Plastic pollution in our oceans is of growing concern particularly due to the presence of toxic additives, such as plasticisers. Therefore, this work aims to develop a comprehensive understanding of the leaching properties of plasticisers from microplastics. This work investigates the leaching of phthalate acid ester (dioctyl terephthalate (DEHT) and diethylhexyl phthalate (DEHP)) and diphenol (bisphenol A (BPA) and bisphenol S (BPS)) plasticisers from polystyrene (PS) microplastics (mean diameter = 136 μm to 1.4 mm) under controlled aqueous conditions (temperature, agitation, pH and salinity). The leaching behaviours of plasticised polymers were quantified using gel permeation chromatography, high performance liquid chromatography and thermal gravimetric analysis, and the particle's plasticisation characterised using differential scanning calorimetry. Leaching rates of phthalate acid ester and diphenol plasticisers were modelled using a diffusion and boundary layer model, whereby these behaviours varied depending on their plasticisation efficiency of PS, the size of the microplastic particle and the surrounding abiotic conditions. Leaching behaviours of DEHT and DEHP were strongly influenced by the microplastic-surface water boundary layer properties, thus wave action (i.e., water agitation) increased the leaching rate of these plasticiser up to 66 % over 21-days, whereas BPA and BPS plasticisers displayed temperature- and size-dependent leaching and were limited by molecular diffusion throughout the bulk polymer (i.e., the microplastic). This information will improve predictions of plasticiser concentration (both that remain in the plastic and released into the surrounding water) at specific time points during the lifetime of a plastic, ultimately ensuring greater accuracy in the assessment of toxicity responses and environmental water quality.

Plastic pollution of four understudied marine ecosystems: a review of mangroves, seagrass meadows, the Arctic Ocean and the deep seafloor

Plastic pollution is now a worldwide phenomenon affecting all marine ecosystems, but some ecosystems and regions remain understudied. Here, we review the presence and impacts of macroplastics and microplastics for four such ecosystems: mangroves, seagrass meadows, the Arctic Ocean and the deep seafloor. Plastic production has grown steadily, and thus the impact on species and ecosystems has increased, too. The accumulated evidence also indicates that plastic pollution is an additional and increasing stressor to these already ecosystems and many of the species living in them. However, laboratory or field studies, which provide strong correlational or experimental evidence of ecological harm due to plastic pollution remain scarce or absent for these ecosystems. Based on these findings, we give some research recommendations for the future.

The relative effects of interspecific and intraspecific diversity on microplastic trapping in coastal biogenic habitats

Our understanding of how anthropogenic stressors such as climate change and plastic pollution interact with biodiversity is being widened to include diversity below the species level, i.e., intraspecific variation. The emerging appreciation of the key ecological importance of intraspecific diversity and its potential loss in the Anthropocene, further highlights the need to assess the relative importance of intraspecific versus interspecific diversity. One such issue is whether a species responds as a homogenous whole to plastic pollution. Using manipulative field transplant experiments and laboratory-controlled hydrodynamic simulations, we assessed the relative effects of intraspecific and interspecific diversity on microplastic trapping in coastal biogenic habitats dominated by two key bioengineers, the brown intertidal macroalgae Fucus vesiculosus and F. guiryi. At the individual level, northern morphotypes of F. guiryi trapped more microplastics than southern individuals, and F. vesiculosus trapped more microplastics than F. guiryi. Canopy density varied among species, however, leading to reversed patterns of microplastic accumulation, with F. guiryi canopies accumulating more microplastics than those of F. vesiculosus, while no differences were observed between the canopies of F. guiryi morphotypes. We emphasize the importance of assessing the effects of intraspecific variation which, along with other crucial factors such as canopy density, flow velocity and polymer composition, modulates the extent of microplastic accumulation in coastal biogenic habitats. Our findings indicate that a realistic estimation of plastic accumulation in biogenic habitats requires an understanding of within- and between-species traits at both the individual and population levels.

A whale of a plastic tale: A plea for interdisciplinary studies to tackle micro- and nanoplastic pollution in the marine realm

Plastic is one of the most ubiquitous sources of both contamination and pollution of the Anthropocene, and accumulates virtually everywhere on the planet. As such, plastic threatens the environment, the economy and human well-being globally. The related potential threats have been identified as a major global conservation issue and a key research priority. As a consequence, plastic pollution has become one of the most prolific fields of research in research areas including chemistry, physics, oceanography, biology, ecology, ecotoxicology, molecular biology, sociology, economy, conservation, management, and even politics. In this context, one may legitimately expect plastic pollution research to be highly interdisciplinary. However, using the emerging topic of microplastic and nanoplastic leachate (i.e., the desorption of molecules that are adsorbed onto the surface of a polymer and/or absorbed into the polymer matrix in the absence of plastic ingestion) in the ocean as a case study, we argue that this is still far from being the case. Instead, we highlight that plastic pollution research rather seems to remain structured in mostly isolated monodisciplinary studies. A plethora of analytical methods are now available to qualify and quantify plastic monomers, polymers and the related additives. We nevertheless show though a survey of the literature that most studies addressing the effects of leachates on marine organisms essentially still lack of a quantitative assessment of the chemical nature and content of both plastic items and their leachates. In the context of the ever-increasing research effort devoted to assess the biological and ecological effects of plastic waste, we subsequently argue that the lack of a true interdisciplinary approach is likely to hamper the development of this research field. We finally introduce a roadmap for future research which has to evolve through the development of a sound and systematic ability to chemically define what we biologically compare.

Plastics in scene: A review of the effect of plastics in aquatic crustaceans

Plastic pollution in aquatic environments is present in all compartments from surface water to benthic sediment, becoming a topic of emerging concern due to the internalization, retention time, and its effects on aquatic biota. Crustacea with nearly 70,000 species, broad distribution and different roles in the trophic webs is a significant target of the increasing plastic pollution. At least 98 publications in the last 10 years report the impact of plastics in crustaceans, all suggesting that this taxon is at high risk for ecosystem disadvantage by plastic contamination loads. This review compiles the current knowledge on physiological effects (endpoints) by plastic contamination analyzed in crustaceans in the last 10 years, highlighting their use as model species for ecotoxicological tests, sentinels species and bioindicators. Plastic contamination analyzed in this review includes macroplastic, microplastic, and nanoplastic, in a wide variety of types. The studies were focused on 38 marine species with an economic interest in fisheries and aquaculture; 14 freshwater with a higher frequency in standard test species and 4 estuarial and 3 mangrove species with ecological interest. The publications reviewed were divided into studies describing plastic presence in crustaceans without reporting toxic effects and those with analysis of plastic toxicity. Publications describing the plastic presence in the organisms show that the ingestion in individual effects and food-web transfer in ecological effects were the most frequent endpoints. The publications that analyzed plastic toxicity through survival, nutrition-metabolism-assimilation, and reproduction in individual effects, and bioaccumulation in ecological effects were the most frequent endpoints. This review gathers the available information on the use of crustaceans as model species in environmental impact for toxicity screening and hazard assessment. Besides, identifying knowledge gaps will let us propose some future directions in research and the effects on target fisheries species which involves a possible effect on human health.

First documentation of plastic ingestion in the arctic glaucous gull (Larus hyperboreus)

Arctic wildlife is facing multiple stressors, including increasing plastic pollution. Seabirds are intrinsic to marine ecosystems, but most seabird populations are declining. We lack knowledge on plastic ingestion in many arctic seabird species, and there is an urgent need for more information to enable risk assessment and monitoring. Our study aimed to investigate the occurrence of plastics in glaucous gulls (Larus hyperboreus) breeding on Svalbard. The glaucous gull is a sentinel species for the health of the arctic marine ecosystem, but there have been no studies investigating plastic occurrence in this species since 1994. As a surface feeder and generalist living in an area with high human activity on Svalbard, we expected to find plastic in its stomach. We investigated for plastic >1 mm and documented plastic ingestion for the first time in glaucous gulls, with a frequency of occurrence of 14.3% (n = 21). The plastics were all identified as user plastics and consisted of polypropylene (PP) and polystyrene (PS). Our study provides new quantitative and qualitative data on plastic burden and polymer type reported in a standardized manner establishing a reference point for future research and monitoring of arctic gulls on national and international levels.

A record of microplastic in the marine nearshore waters of South Georgia

The polar plastics research community have recommended the spatial coverage of microplastic investigations in Antarctica and the Southern Ocean be increased. Presented here is a baseline estimate of microplastics in the nearshore waters of South Georgia, the first in situ study of the north-east coast of the island. Our results show that the microplastic concentration in seawater at twelve stations in proximity to King Edward Point Research Station ranged from 1.75 ± 5.17 MP/L (mean ± SD), approximately one order of magnitude higher than similar studies of sea surface waters south of the Polar Front. Levels of microplastics in freshwater (sampled from Gull Lake) and precipitation (collected adjacent to the research station) were 2.67 ± 3.05 MP/L, and 4.67 ± 3.21 MP/L respectively. There was no significant difference in the microplastic concentration between seawater sites, and no significant bilateral relationship between concentration and distance from the research station outlets. We report an average concentration of 1.66 ± 3.00 MP/L in wastewater collected from the research station but overall, the counts of microplastics were too low to attach any statistical significance to the similarity in the microplastic assemblages of seawater and wastewater, or assemblages retrieved from penguin species in the region in other studies. Using a calculation described in contemporary literature we estimate the number of microfibres potentially being released from ships and stations annually in the region but acknowledge that further samples are needed to support the figures generated. More extensive research into microplastic distribution, characteristics, and transport in the region is recommended to fully compute the level of risk which this pollutant represents to the ecosystem health of this remote region.

The fundamental links between climate change and marine plastic pollution

Plastic pollution and climate change have commonly been treated as two separate issues and sometimes are even seen as competing. Here we present an alternative view that these two issues are fundamentally linked. Primarily, we explore how plastic contributes to greenhouse gas (GHG) emissions from the beginning to the end of its life cycle. Secondly, we show that more extreme weather and floods associated with climate change, will exacerbate the spread of plastic in the natural environment. Finally, both issues occur throughout the marine environment, and we show that ecosystems and species can be particularly vulnerable to both, such as coral reefs that face disease spread through plastic pollution and climate-driven increased global bleaching events. A Web of Science search showed climate change and plastic pollution studies in the ocean are often siloed, with only 0.4% of the articles examining both stressors simultaneously. We also identified a lack of regional and industry-specific life cycle analysis data for comparisons in relative GHG contributions by materials and products. Overall, we suggest that rather than debate over the relative importance of climate change or marine plastic pollution, a more productive course would be to determine the linking factors between the two and identify solutions to combat both crises.

Under pressure: Nanoplastics as a further stressor for sub-Antarctic pteropods already tackling ocean acidification

In the Southern Ocean (SO), plastic debris has already been found in waters and sediments. Nanoplastics (<1 μm) are expected to be as pervasive as their larger counterparts, but more harmful to biological systems, being able to enter cells and provoke toxicity. In the SO, (nano)plastic pollution occurs concomitantly with other environmental threats such as ocean acidification (OA), but the potential cumulative impact of these two challenges on SO marine ecosystems is still overlooked. Here the single and combined effects of nanoplastics and OA on the sub-Antarctic pteropod Limacina retroversa are investigated under laboratory conditions, using two surface charged polystyrene nanoparticles (PS NPs) as a proxy for nanoplastics. Sub-Antarctic pteropods are threatened by OA due to the sensitivity of their shells to changes in seawater carbonate chemistry. Short-term exposure (48 h) to PS NPs compromised the ability of pteropods to counteract OA stress, resulting in a negative effect on their survival. Our results highlights the importance of addressing plastic pollution in the context of climate change to identify realistic critical thresholds of SO pteropods.

Micro- and nanoplastic transfer in freezing saltwater: implications for their fate in polar waters

Plastic debris accumulates in the Arctic by way of oceanic and atmospheric circulation. High concentrations of microplastics (1 μm to 5 mm) have been measured, and nanoplastics (<1 μm) are expected to be abundant as well. However, little is known about the mobility of micro- and nanoplastics at the seawater/ice interface. This study investigates the fate of micro- and nanoplastics during sea-ice formation. A novel experimental approach simulates the growth of sea ice by progressively freezing a saline solution. After different durations of freezing, the concentrations of NaCl, natural organic matter, microplastics, and nanoplastics were measured in the ice and liquid. Micro- and nanoplastic distribution coefficients between saltwater and ice were determined, reflecting their behavior during congelation sea-ice growth. The results show that microplastics are retained in ice while nanoplastics are expulsed from it. Furthermore, natural organic matter plays a crucial role in stabilizing nanoplastics at this interface. These results raise new questions concerning the impact of micro- and nanoplastics in fragile polar environments and the analytical strategy to detect them.