Ingested microscopic plastics translocate from the gut cavity of juveniles of the ascidian Ciona intestinalis

Effects of biological filtration by ascidians on microplastic composition in the water column

Plastic pollution, a widespread environmental challenge, significantly impacts marine ecosystems. The degradation of plastic under environmental conditions results in the generation of microplastic (MP; <5 mm) fragments, frequently ingested by marine life, including filter-feeders such as ascidians (Chordata, Ascidiacea). These organisms are integral to benthic-pelagic coupling, transporting MP from the water column through marine food web. Here, we explored the effect of filtration and digestion by the solitary ascidian Styela plicata on the composition of MP in the water column and on the sinking rates of faecal matter, focusing on differences between two distinct plastics, polystyrene (PS) and the biodegradable polylactic acid (PLA). The ascidians efficiently removed 2-5 μm particles within 2 h of filtration. Following digestion and secretion process, PS concentrations in water increased while PLA concentration remained stable. Some particles were egested into the water column repackaged inside faecal pellets, which significantly increased the pellets' drag force and sinking velocity. Raman spectral analysis of digested MP revealed distinct spectrum alterations due to coating by organic substances. These findings highlight the role of ascidians - and other filter-feeders- in modifying the structure of MP in their environment. Research into such modifications is crucial for understanding the MP cycle and its consequences in marine environments.

Optimizing CRISPR/Cas9 approaches in the polymorphic tunicate Ciona intestinalis

CRISPR/Cas9 became a powerful tool for genetic engineering and in vivo knockout also in the invertebrate chordate Ciona intestinalis. Ciona (ascidians, tunicates) is an important model organism because it shares developmental features with the vertebrates, considered the sister group of tunicates, and offers outstanding experimental advantages: a compact genome and an invariant developmental cell lineage that, combined with electroporation mediated transgenesis allows for precise and cell type specific targeting in vivo. A high polymorphism and the mosaic expression of electroporated constructs, however, often hamper the efficient CRISPR knockout, and an optimization in Ciona is desirable. Furthermore, seasonality and artificial maintenance settings can profit from in vitro approaches that would save on animals. Here we present improvements for the CRISPR/Cas9 protocol in silico, in vitro and in vivo. Firstly, in designing sgRNAs, prior sequencing of target genomic regions from experimental animals and alignment with reference genomes of C. robusta and C. intestinalis render a correction possible of subspecies polymorphisms. Ideally, the screening for efficient and non-polymorphic sgRNAs will generate a database compatible for worldwide Ciona populations. Secondly, we challenged in vitro assays for sgRNA validation towards reduced in vivo experimentation and report their suitability but also overefficiency concerning mismatch tolerance. Thirdly, when comparing Cas9 with Cas9:Geminin, thought to synchronize editing and homology-direct repair, we could indeed increase the in vivo efficiency and notably the access to an early expressed gene. Finally, for in vivo CRISPR, genotyping by next generation sequencing (NGS) ex vivo streamlined the definition of efficient single guides. Double CRISPR then generates large deletions and reliable phenotypic excision effects. Overall, while these improvements render CRISPR more efficient in Ciona, they are useful when newly establishing the technique and very transferable to CRISPR in other organisms.

Microplastics in oral healthcare products (OHPs) and their environmental health risks and mitigation measures

The environmental input of microplastics from personal care products has received significant attention; however, less focus has been paid to oral healthcare products. The present study assessed the occurrence of microplastics in commercially available oral healthcare products such as toothbrushes, toothpastes, toothpowder, mouthwash, dental floss, and mouth freshener spray that have a pan-India distribution. The extracted microplastics were quantified and characterised using a microscope and ATR-FTIR. All products showed microplastic contamination, where toothbrushes showed the maximum particles (30-120 particles/brush) and mouth freshener sprays (0.2-3.5 particles/ml) had the least abundance. Fragments, fibres, beads, and films were the various shapes of microplastics observed, where fragments (60%) were dominant. Various colours such as pink, green, blue, yellow, black, and colourless were observed, where colourless (40%) particles were dominant. Microplastics were categorized into three sizes: <0.1 mm (63%), 0.1-0.3 mm (35%), and >0.3 mm (2%). Four major types of polymers, such as polyethylene (52%), polyamide (30%), polyethylene terephthalate (15%), and polybutylene terephthalate (3%), were identified. Risk assessment studies such as Daily Microplastics Emission (DME), Annual Microplastics Exposure (AME), and Polymer Hazard Index (PHI) were carried out. The DME projection for India was the highest for mouthwash (74 billion particles/day) and the least for mouth freshener sprays (0.36 billion particles/day). The AME projection for an individual was the highest in toothbrushes (48,910 particles ind.-1 yr.-1) and the least in mouth freshener sprays (111 particles ind.-1 yr.-1). PHI shows that the identified polymers fall under the low-to high-risk categories. This study forecasts the community health risks linked to microplastics in oral healthcare products and suggests mitigation strategies. It has the potential to shape environmental policy development in response.

A broad-taxa approach as an important concept in ecotoxicological studies and pollution monitoring

Aquatic invertebrates play a pivotal role in (eco)toxicological assessments because they offer ethical, cost-effective and repeatable testing options. Additionally, their significance in the food chain and their ability to represent diverse aquatic ecosystems make them valuable subjects for (eco)toxicological studies. To ensure consistency and comparability across studies, international (eco)toxicology guidelines have been used to establish standardised methods and protocols for data collection, analysis and interpretation. However, the current standardised protocols primarily focus on a limited number of aquatic invertebrate species, mainly from Arthropoda, Mollusca and Annelida. These protocols are suitable for basic toxicity screening, effectively assessing the immediate and severe effects of toxic substances on organisms. For more comprehensive and ecologically relevant assessments, particularly those addressing long-term effects and ecosystem-wide impacts, we recommended the use of a broader diversity of species, since the present choice of taxa exacerbates the limited scope of basic ecotoxicological studies. This review provides a comprehensive overview of (eco)toxicological studies, focusing on major aquatic invertebrate taxa and how they are used to assess the impact of chemicals in diverse aquatic environments. The present work supports the use of a broad-taxa approach in basic environmental assessments, as it better represents the natural populations inhabiting various ecosystems. Advances in omics and other biochemical and computational techniques make the broad-taxa approach more feasible, enabling mechanistic studies on non-model organisms. By combining these approaches with in vitro techniques together with the broad-taxa approach, researchers can gain insights into less-explored impacts of pollution, such as changes in population diversity, the development of tolerance and transgenerational inheritance of pollution responses, the impact on organism phenotypic plasticity, biological invasion outcomes, social behaviour changes, metabolome changes, regeneration phenomena, disease susceptibility and tissue pathologies. This review also emphasises the need for harmonised data-reporting standards and minimum annotation checklists to ensure that research results are findable, accessible, interoperable and reusable (FAIR), maximising the use and reusability of data. The ultimate goal is to encourage integrated and holistic problem-focused collaboration between diverse scientific disciplines, international standardisation organisations and decision-making bodies, with a focus on transdisciplinary knowledge co-production for the One-Health approach.

Microplastics in marine mammal blubber, melon, & other tissues: Evidence of translocation

Marine mammals consume large quantities of microplastic particles, likely via trophic transfer (i.e., through prey who have consumed plastic) and direct consumption from seawater or sediment. Microplastics have been found in the stomachs, gastro-intestinal tracts, and feces of cetaceans and pinnipeds. Translocation of ingested microplastics has been documented in other organs of several aquatic species, but has not been examined in marine mammals. Marine mammals have highly specialized lipid-rich tissues which may increase susceptibility to lipophilic microplastics. Here we demonstrate the occurrence of microplastics, ranging in size, mass concentration, and particle count concentration from 24.4 μm - 1387 μm, 0.59 μg/g - 25.20 μg/g, and 0.04 - 0.39 particles/g, respectively, in four tissues (acoustic fat pad, blubber, lung, & melon) from twelve marine mammal species inclusive of mysticetes, odontocetes, and phocids. Twenty-two individuals were examined for microplastics using a combination of Raman spectroscopy and pyrolysis gas chromatography with mass spectrometry. Overall, 68% of individuals had at least one microplastic particle in at least one of the four tissue types, with the most common polymer and shape observed being polyethylene and fibers, respectively. These findings suggest some proportion of ingested microplastics translocate throughout marine mammal bodies posing an exposure risk to both marine mammals and people. For people, exposure could be directly through consumption for those who rely on marine mammals as food and indirectly to peoples globally who consume the same prey resources as marine mammals. Some individuals examined represent samples obtained over two decades ago, suggesting that this process, and thus exposure risk, has occurred for some time.

Microplastic burden in invasive signal crayfish (Pacifastacus leniusculus) increases along a stream urbanization gradient

Microplastics are a globally pervasive pollutant with the potential to directly impact species and accumulate in ecosystems. However, there remains a relative paucity of research addressing their accumulation in freshwater ecosystems and a near absence of work in crayfish, despite their high ecological and economic importance. This study investigated the presence of microplastics in the invasive signal crayfish Pacifastacus leniusculus along a stream urbanization gradient. The results demonstrate a ubiquitous presence of microplastics in crayfish digestive tracts at all sites and provide the first evidence of microplastic accumulation in tail tissue. Evidence of a positive linear trend was demonstrated between microplastic concentration in crayfish and upstream urban area size in generalized linear models. Evidence for a positive effect of the upstream urban area and a negative effect of crayfish length on microplastic concentrations in crayfish was demonstrated in multiple generalized linear regression models. Our results extend the current understanding of microplastics presence in freshwater ecosystems and demonstrate their presence in crayfish in the wild for the first time.

Particle uptake by filter-feeding macrofoulers from the Mar Grande of Taranto (Mediterranean Sea, Italy): potential as microplastic pollution bioremediators

Microplastics (MPs) are a serious threat to the marine environment affecting ecosystem functioning and biodiversity. There is a vast literature about the uptake of MPs at different trophic levels, mainly focused on ecotoxicological effects in commercially relevant species. Little is still known about possible strategies to face MP pollution. Bioremediation is recently gaining attention in this framework. The clearance rate and particle retention of Sabella spallanzanii, Mytilus galloprovincialis, Phallusia mammillata, Paraleucilla magna at three MP concentrations (C1: 1.4 · 10¹ p/L; C2: 1.4 · 10² p/L; C3: 1.4 · 10³ p/L) were investigated to test their potential as MP remover. Digestion protocol removed 98 % of tissues simplifying the MP quantification. P. magna clearance rate decreased with increasing concentration while P. mammillata showed no significant variations. S. spallanzanii and M. galloprovincialis instead exhibited the highest values of clearance rate. Yet, unlike mussels, S. spallanzanii can inhibit particle return to the surrounding water storing them in the tube, resulting to be the best candidate for bioremediation purposes.

Microplastics in environment: global concern, challenges, and controlling measures

Plastic pollution in various forms has emerged as the most severe environmental threat. Small plastic chunks, such as microplastics and nanoplastics derived from primary and secondary sources, are a major concern worldwide due to their adverse effects on the environment and public health. Several years have been spent developing robust spectroscopic techniques that should be considered top-notch; however, researchers are still trying to find efficient and straightforward methods for the analysis of microplastics but have yet to develop a viable solution. Because of the small size of these degraded plastics, they have been found in various species, from human brains to blood and digestive systems. Several pollution-controlling methods have been tested in recent years, and these methods are prominent and need to be developed. Bacterial degradation, sunlight-driven photocatalyst, fuels, and biodegradable plastics could be game-changers in future research on plastic pollution control. However, recent fledgling steps in controlling methods appear insufficient due to widespread contamination. As a result, proper regulation of environmental microplastics is a significant challenge, and the most equitable way to manage plastic pollution. Therefore, this paper discusses the current state of microplastics, some novel and well-known identification techniques, strategies for overcoming microplastic effects, and needed solutions to mitigate this planetary pollution. This review article, we believe, will fill a void in the field of plastic identification and pollution mitigation research.

Mixotrophic flagellate ingestion boosts microplastic accumulation in ascidians

Microplastics are contaminants of global environmental concern. They can be ingested by a variety of organisms when they enter the food web. Several studies have reported trophic transfer of microplastics from low trophic levels to higher ones. Bioaccumulation has been suggested to occur but few studies have demonstrated it for marine environments. In this article, in controlled laboratory conditions, we exposed filter-feeder ascidian juveniles to microplastics in the presence or in absence of mixotrophic cryptomonad flagellates. Cryptomonads can efficiently ingest microbeads, and their presence significantly increased the concentration of microplastics in the digestive tract of the ascidians. Our results demonstrate the occurrence of microplastic bioaccumulation in the lower levels of the marine trophic chain and suggest that unicellular organisms can be key actors in microplastic trophic transfer at the microscale level.

Ecological Review of the Ciona Species Complex

AbstractThe set of four closely related solitary ascidians Ciona spp. were once considered a single cosmopolitan species, Ciona intestinalis, but are now recognized as genetically and morphologically distinct species. The possibility of ecological differences between the species was not widely considered in studies preceding the schism of Ciona spp. Consequently, there may be an over-generalization of the ecology of Ciona spp., with potential implications for the broad range of studies targeting these species, encompassing the evolution, development, genomics, and invasion biology of Ciona spp. We completed a comprehensive review of the ecology of Ciona spp. to establish the similarities and differences between the widely distributed Ciona robusta and C. intestinalis (and what little is known of the two other species, Ciona sp. C and Ciona sp. D). When necessary, we used study locations and the species' geographic ranges to infer the species in each study in the review. As expected, ecological similarities are the norm between the two species, spanning both abiotic and biotic interactions. However, there are also important differences that have potential implications for other aspects of the biology of Ciona spp. For example, differences in temperature and salinity tolerances likely correspond with the disparities in the geographic distribution of the species. Asymmetries in topics studied in each species diminish our ability to fully compare several aspects of the ecology of Ciona spp. and are priority areas for future research. We anticipate that our clarification of common and unique aspects of each species' ecology will help to provide context for future research in many aspects of the biology of Ciona spp.

Functional Characterization of Hexacorallia Phagocytic Cells

Phagocytosis is the cellular defense mechanism used to eliminate antigens derived from dysregulated or damaged cells, and microbial pathogens. Phagocytosis is therefore a pillar of innate immunity, whereby foreign particles are engulfed and degraded in lysolitic vesicles. In hexacorallians, phagocytic mechanisms are poorly understood, though putative anthozoan phagocytic cells (amoebocytes) have been identified histologically. We identify and characterize phagocytes from the coral Pocillopora damicornis and the sea anemone Nematostella vectensis. Using fluorescence-activated cell sorting and microscopy, we show that distinct populations of phagocytic cells engulf bacteria, fungal antigens, and beads. In addition to pathogenic antigens, we show that phagocytic cells engulf self, damaged cells. We show that target antigens localize to low pH phagolysosomes, and that degradation is occurring within them. Inhibiting actin filament rearrangement interferes with efficient particle phagocytosis but does not affect small molecule pinocytosis. We also demonstrate that cellular markers for lysolitic vesicles and reactive oxygen species (ROS) correlate with hexacorallian phagocytes. These results establish a foundation for improving our understanding of hexacorallian immune cell biology.

Ecotoxicological and physiological risks of microplastics on fish and their possible mitigation measures

Microplastics (MPs) are widely distributed and extensively found within marine ecosystems, and approximately 8 million tons of plastics are being dumped into the sea annually. Once reached the marine environment, plastics tend to get fragmented into smaller particles through photo-degradation, mechanical and biological processes. These MPs have raised concerns globally due to their potential toxic impacts on a wide variety of aquatic fauna and humans. Ingested microplastics can cause severe health implications in fishes, including reduced feeding intensity, improper gill functioning, immuno-suppression, and compromised reproducibility. Several studies were also conducted to scrutinize MPs trophic transfer through the food chain from primary producers to top predators and their bioaccumulation. This paper briefly summarizes all the possible sources, routes, bioavailability, trophic transfer, and consequences of microplastics in fishes. The review article also intended to highlight various mitigation strategies like implementing Four R's concept (refuse, reduce, reuse, and recycle), integrated strategies, ban on single-use plastics, use bioplastics, and create behavioural changes with public awareness.

Recommended best practices for collecting, analyzing, and reporting microplastics in environmental media: Lessons learned from comprehensive monitoring of San Francisco Bay

Microplastics are ubiquitous and persistent contaminants in the ocean and a pervasive and preventable threat to the health of marine ecosystems. Microplastics come in a wide variety of shapes, sizes, and plastic types, each with unique physical and chemical properties and toxicological impacts. Understanding the magnitude of the microplastic problem and determining the highest priorities for mitigation require accurate measures of microplastic occurrence in the environment and identification of likely sources. The field of microplastic pollution is in its infancy, and there are not yet widely accepted standards for sample collection, laboratory analyses, quality assurance/quality control (QA/QC), or reporting of microplastics in environmental samples. Based on a comprehensive assessment of microplastics in San Francisco Bay water, sediment, fish, bivalves, stormwater, and wastewater effluent, we developed recommended best practices for collecting, analyzing, and reporting microplastics in environmental media. We recommend factors to consider in microplastic study design, particularly in regard to site selection and sampling methods. We also highlight the need for standard QA/QC practices such as collection of field and laboratory blanks, use of methods beyond microscopy to identify particle composition, and standardized reporting practices, including suggested vocabulary for particle classification.

Effect of microplastics in water and aquatic systems

Surging dismissal of plastics into water resources results in the splintered debris generating microscopic particles called microplastics. The reduced size of microplastic makes it easier for intake by aquatic organisms resulting in amassing of noxious wastes, thereby disturbing their physiological functions. Microplastics are abundantly available and exhibit high propensity for interrelating with the ecosystem thereby disrupting the biogenic flora and fauna. About 71% of the earth surface is occupied by oceans, which holds 97% of the earth's water. The remaining 3% is present as water in ponds, streams, glaciers, ice caps, and as water vapor in the atmosphere. Microplastics can accumulate harmful pollutants from the surroundings thereby acting as transport vectors; and simultaneously can leach out chemicals (additives). Plastics in marine undergo splintering and shriveling to form micro/nanoparticles owing to the mechanical and photochemical processes accelerated by waves and sunlight, respectively. Microplastics differ in color and density, considering the type of polymers, and are generally classified according to their origins, i.e., primary and secondary. About 54.5% of microplastics floating in the ocean are polyethylene, and 16.5% are polypropylene, and the rest includes polyvinyl chloride, polystyrene, polyester, and polyamides. Polyethylene and polypropylene due to its lower density in comparison with marine water floats and affect the oceanic surfaces while materials having higher density sink affecting seafloor. The effects of plastic debris in the water and aquatic systems from various literature and on how COVID-19 has become a reason for microplastic pollution are reviewed in this paper.

Embryotoxicity characterization of the flame retardant tris(1-chloro-2-propyl)phosphate (TCPP) in the invertebrate chordate Ciona intestinalis

Tris(1-chloro-2-propyl)phosphate (TCPP) is the most common chlorinated organophosphorus flame retardant in seawater. Due to its chemical features and abundance, TCPP has been classified as a high hazard, and restrictions of use have been set in multiple countries. Despite TCPP being highly present in the marine environment, only a few studies have explored the TCPP impact on the development of marine invertebrates. Ascidians are important invertebrate members of benthic marine communities and reliable model systems for ecotoxicological research. The aim of this study was to assess the adverse effects of TCPP exposure on the embryogenesis of the ascidian Ciona intestinalis. Our results showed that this pollutant affected both muscles and nervous system development. Malformations appeared similar to those reported in other animal models for other flame retardants, suggesting that these molecules could share a common mechanism of action and induce a mixture effect when simultaneously present in the aquatic environment even at sub-teratogenic concentrations.

Risks of floating microplastic in the global ocean

Despite the ubiquitous and persistent presence of microplastic (MP) in marine ecosystems, knowledge of its potential harmful ecological effects is low. In this work, we assessed the risk of floating MP (1 μm-5 mm) to marine ecosystems by comparing ambient concentrations in the global ocean with available ecotoxicity data. The integration of twenty-three species-specific effect threshold concentration data in a species sensitivity distribution yielded a median unacceptable level of 1.21 ∗ 10⁵ MP m^-³ (95% CI: 7.99 ∗ 10³-1.49 ∗ 10⁶ MP m^-³). We found that in 2010 for 0.17% of the surface layer (0-5 m) of the global ocean a threatening risk would occur. By 2050 and 2100, this fraction increases to 0.52% and 1.62%, respectively, according to the worst-case predicted future plastic discharge into the ocean. Our results reveal a spatial and multidecadal variability of MP-related risk at the global ocean surface. For example, we have identified the Mediterranean Sea and the Yellow Sea as hotspots of marine microplastic risks already now and even more pronounced in future decades.

Toxicity of nanoplastics during the embryogenesis of the ascidian Ciona robusta (Phylum Chordata)

Nanoplastics are considered contaminants of emerging concern at the global scale. The recent evidence of their occurrence in seawater from the Mediterranean Sea calls for a thorough evaluation of their impact on marine life and in particular on vulnerable life stages such as planktonic embryos. Here, we investigated the impact of increasing nominal concentrations of 50 nm amino-modified (PS-NH₂) and 60 nm carboxy-modified (PS-COOH) polystyrene nanoparticles (PS NPs) on the embryonic development of the ascidian Ciona robusta (phylum Chordata), a common benthic invertebrate living in Mediterranean coastal areas with the peculiarity of being an early chordate developmental model. A strong agglomeration of PS-COOH (approx. 1 µm) was observed in natural sea water (NSW) already at time 0, while PS-NH₂ resulted still monodispersed (approx. 130 nm) but largely aggregated after 22 h with a microscale dimension similar to those negatively charged. However, their effect on C. robusta embryos development largely differed at 22 h: PS-COOH did not affect larvae phenotypes nor their development, while PS-NH₂ caused a dose-dependent effect (EC₅₀ (22 h) of 7.52 μg mL^-1) with various degrees of phenotype malformations (from mild to severe) and impairment of larval swimming. Embryos (up to 30%) exposed to 15 µg mL^-1PS-NH₂ resulted not developed and the majority was unable to hatch. Calculated PS-NH₂ EC₅₀ resulted higher than those available for other marine invertebrate species, suggesting a protective role of the egg envelopes surrounding C. robusta embryos toward nanoplastics exposure.

Foamed Polystyrene in the Marine Environment: Sources, Additives, Transport, Behavior, and Impacts

Foamed polystyrene (PS) that may be either expanded (EPS) or extruded (XPS) is a rigid, lightweight insulating thermoplastic that has a variety of uses in the consumer, packaging, construction, and marine sectors. The properties of the material also result in waste that is readily generated, dispersed, and fragmented in the environment. This review focuses on foamed PS in the marine setting, including its sources, transport, degradation, acquisition of contaminants, ingestion by animals, and biological impacts arising from the mobilization of chemical additives. In the ocean, foamed PS is subject to wind-assisted transport and fracturing via photolytic degradation. The material may also act as a substrate for rafting organisms while being exposed to elevated concentrations of natural and anthropogenic surface-active chemicals in the sea surface microlayer. In the littoral setting, fragmentation is accentuated by milling in the swash zone and abrasion when beached, with wind transport leading to the temporary burial of significant quantities of material. Ingestion of EPS and XPS has been documented for a variety of marine animals, but principally those that feed at the sea surface or use the material as a habitat. As well as risking injuries due to gastro-intestinal blockage, ingestion of foamed PS exposes animals to harmful chemicals, and of greatest concern in this respect is the presence of the historical, but still recycled, flame-retardant, hexabromocyclododecane. Because foamed PS is particularly difficult to retrieve as a constituent of marine litter, means of reducing its presence and impacts will rely on the elimination of processes that generate foamed waste, modification of current storage and disposal practices, and the development of more durable and sustainable alternatives.