Marine macrophytes retain microplastics

Microplastics in seawater and fish acquired from the corresponding fishing zones of the Baltic Sea

Microplastics in seawater and fish from the Baltic Sea were analyzed. The significant contribution of the study is due to extensive collection of fish and surface water samples from corresponding fishing zones. Microplastics were detected in 100 % of seawater and 61 % of fish samples. The abundances of microplastics were 19,984 ± 8858 items/m3 (seawater) and 3.3 items/fish in the fish organs. The average dimension was 1.08 ± 1.19 mm (seawater), and 0.77 ± 0.84 mm (fish). In 106 out of 178 specimens (61 %), MPs were found in the gills (46 %), digestive tract (38 %), or liver (16 %). Fiber was the most dominant shape found in seawater (91.7 %) and fish (68.3 %), while the dominant color of items was blue. Items were mostly composed of polyethylene (21 %), polypropylene (20 %), cellophane (16 %), polyamide (9 %), and polyacrylate (8 %).

Optimising microplastic polyethylene terephthalate fibre extraction from sediments: Tailoring a density-separation procedure for enhanced recovery and reliability

Despite the presence of microplastics in sediments being widely acknowledged, the absence of standardised processing methods in extracting microplastics can compromise reliable and comparable results. Density separation is a predominant method for extracting microplastics from sediments. In this study, Sodium Polytungstate (ρ = 1.6 g cm-3) was selected as the density separation agent for three key factors: i) optimal density for extracting common plastic polymers, ii) low toxicity, and iii) recycling potential of the solution. It is therefore cost-effective, and the risk of solution dispersal is minimal. The solution was tested through four separation procedures, extracting PET fibres from three artificial sediment mixtures (i.e., pure sand, pure mud, and 50 % sand and 50 % mud). The results indicate that the solution employed in this work is highly effective for extracting microplastic fibres from sediments, with recovery rates up to 99 %. However, the results highlight differences in the recovery among the four procedures and in terms of the sediment characteristics. Specifically, extracting microplastics was easier in sandy sediment samples than in mud-rich ones. The complexity of extracting microplastics from mud-rich sediments results from i) the creation of microplastic-sediment aggregates forming denser structures, that settle down trapping microplastics in sediments; ii) the development of a clay sediment cap that hinders the rise of microplastics to the surface. Reducing the risk of underestimation of microplastic content in mud-rich samples can be accomplished by applying a procedure that involves placing the samples with the Sodium Polytungstate solution on a stirring plate while progressively lowering the rotation velocity. Using this method, cohesive sediments lose their ability to trap microplastics while aggregating, consequently reducing their ability to drag microplastics to the bottom. This facilitated microplastics to reach the liquid surface, thereby enabling an efficient retrieval even in mud-rich samples.

Natural sorting of sediments in the wave run-up zone works for microplastics as well

The distribution of plastic pollution in the marine environment is highly variable in time and space, making it difficult to assess pollution levels. This study shows that mixing and natural sorting of material in the wave run-up zone of a sandy beach results in a relatively stable abundance of microplastics in the size range 0.5-2 mm (S-MPs). Based on 175 samples collected over 14 months during 42 monitoring surveys at 6 stations along the shore of the Vistula Spit (Baltic Sea), the mean abundance of S-MPs was found to be 64 ± 36 items/kg DW (98.6 % fibers), with a coefficient of variation of only 56 % over more than one year. Statistical tests confirmed its independence from current wind speed, significant wave height, mean sediment grain size, sediment sorting, percentage of certain sand fractions, month, season, or location along the shore. It can therefore be used as a suitable indicator for long-term monitoring of increasing plastic pollution in the marine environment.

Effects of microplastics on typical macrobenthos in sargassum ecosystems

Recently, microplastics (MPs) have attracted extensive attention to their wide distribution and potential toxicity in ecosystems. However, there was a lack of research focused on MPs in seaweed bed ecosystems. This study investigated the distribution and toxicity of MPs in macrobenthos in Sargassum ecosystem. According to the in-situ investigation results, the abundance of MPs in the sediment was 0.9-2.3 items/g, the indoor microcosmic experiment was constructed. After exposure to MPs (0, 2, and 20 items/g) for 30 days, the abundance of MPs in macrobenthos exhibits a concentration-dependent increase. However, there was no significant bioaccumulation of MPs at the trophic level. The indoor toxicity test revealed that MPs induced oxidative stress and altered intestinal microflora composition in macrobenthos, even at actual environmental concentrations (2 items/g). It may result in a perturbation of the organism's homeostatic equilibrium. High-concentration (20 items/g) MPs had a greater impact on alkaline phosphatase (AKP) in Mollusks. The increase in AKP activity could be indicative of an adaptive mechanism in some macrobenthos while the decline in AKP activity might signal a decrease in their survival. These results elucidated the fate of MPs in ecosystem and the ecological risks of MPs to large benthic animals on model environmental conditions.

Abundance and mass of plastic litter on sandy shore: Contribution of stormy events

The accumulation of marine litter on beaches has a detrimental impact on the environment, human health, and recreational activities. A total of 116 monitoring surveys were conducted along the shore of the Kaliningrad region between 2019 and 2023. Sampling of anthropogenic and plastic litter (>0.5 cm) was carried out under various meteorological conditions on eight sandy beaches. The greatest abundance and mass of plastic marine litter (mean ± SE: 13.75 ± 8.61 items/m2 and 19.97 ± 5.92 gDW/m2, correspondingly) were observed in the aftermath of storms within beach-cast accumulation stains at the shoreline, where it was intermixed with organic debris. This is two orders of magnitude greater than the plastic litter contamination obtained using the OSPAR methodology at the same beach during fine weather (0.11 ± 0.01 items/m2, 0.33 ± 0.02 gDW/m2). The results suggest that the most effective strategy for beach cleaning is to implement it in the post-storm period.

Kelp forest food webs as hot spots for the accumulation of microplastic and polybrominated diphenyl ether pollutants

Kelp forests (KFs) are one of the most significant marine ecosystems in the planet. They serve as a refuge for a wide variety of marine species of ecological and economic importance. Additionally, they aid with carbon sequestration, safeguard the coastline, and maintain water quality. Microplastic (MP) and polybrominated diphenyl ethers (PBDEs) concentrations were analyzed across trophic levels in KFs around Todos Santos Bay. Spatial variation patterns were compared at three sites in 2021 and temporal change at Todos Santos Island (TSI) in 2021 and 2022. We analyzed these MPs and PBDEs in water, primary producers (Macrocystis pyrifera), grazers (Strongylocentrotus purpuratus), predators (Semicossyphus pulcher), and kelp detritus. MPs were identified in all samples (11 synthetic and 1 semisynthetic polymer) and confirmed using Fourier-transform infrared microspectroscopy-attenuated total reflectance (μ-FTIR-ATR). The most abundant type of MP is polyester fibers. Statistically significant variations in MP concentration were found only in kelps, with the greatest average concentrations in medium-depth kelps from TSI in 2022 (0.73 ± 0.58 MP g-1 ww) and in the kelp detritus from TSI in 2021 (0.96 ± 0.64 MP g-1 ww). Similarly, PBDEs were found in all samples, with the largest concentration found in sea urchins from Punta San Miguel (0.93 ± 0.24 ng g-1 ww). The similarity of the polymers can indicate a trophic transfer of MPs. This study shows the extensive presence of MP and PBDE subtropical trophic web of a KF, but correlating these compounds in environmental samples is highly complex, influenced by numerous factors that could affect their presence and behavior. However, this suggests that there is a potential risk to the systems and the services that KFs offer.

In-depth analysis of microplastics reported from animal and algae seafood species: Implications for consumers and environmental health

Macroalgae are able to retain environmental microplastics (MPs). The potential ingestion of MP through Atlantic agar Gelidium corneum and different animal species (hake, glass eels, mussels, topshells, anemones, sea cucumbers) that are seafood resources in Spain, was estimated from published MPs data calculating daily dose and annual ingestion rate. The study region was Asturias (SW Bay of Biscay). Lower MP ingestion rate from algae than from any animal analysed revealed a reduced risk of MP intake, probably because the alga is harvested from quite clean subtidal zones. However, MP bioconcentration in Atlantic agar was higher than in sea cucumbers, mussels or glass eels. Compared with other algae, G. corneum ranked the highest for MP retention rate, perhaps for its intricate branching and gelatinous surface, suggesting a possible use in MP bioremediation. More experimental studies in MP uptake by macroalgae are recommended to understand their implication in the accumulation of this pollutant.

Microplastics associated with stranded macroalgae on an impacted estuarine beach, Rio de Janeiro, Brazil

Microplastics (MPs) are contaminants widely distributed in marine ecosystems. Only few studies approached MP interactions with marine plants, which are considered potential traps for MPs. Here, we determined MPs' densities and types associated with stranded macroalgae on a eutrophic beach in Guanabara Bay. Our results showed that red algae exhibited higher MP densities (1.48 MPs g-1), possibly due to their more branched thalli, than green algae (0.27 MPs g-1). The predominant MP types were blue and white fragments <3 mm in size and polymers were classified as polyethylene and polyvinyl chloride in fragments, and polypropylene in fibers. The higher densities of MPs in algae seemed to be influenced by the inner bay waters. The densities of MPs associated with algae from Guanabara Bay surpassed those reported in other studies. High MPs densities increase the chances that organisms associated with algae entangle or ingest MPs, impacting their health and survival.

Seaweeds as a major source of dietary microplastics exposure in East Asia

Microplastics (MPs) occurrence in marine ecosystems is well known, but their accumulation in seaweeds and subsequent human exposure remain understudied. This research quantifies MPs presence in two commonly consumed seaweeds, kelp (Saccharina japonica) and nori (Pyropia yezoensis), in East Asia, revealing widespread contamination dominated by microfibers (<500 μm). Based on dietary patterns, human uptake through seaweed consumption was estimated and quantified. Notably, Chinese people consume an estimated 17,034 MPs/person/year through seaweed consumption, representing 13.1% of their total annual MPs intake. This seaweeds-derived exposure surpasses all other dietary sources, contributing up to 45.5% of overall MPs intake. The highest intake was in South Korea, followed by North Korea, China, and Japan. This research identifies seaweeds as a major, previously overlooked route of dietary MPs exposure. These findings are crucial for comprehensive risk assessments of seaweed consumption and the development of mitigation strategies, particularly for populations in East Asian countries.

Algae polysaccharide-induced transport transformation of nanoplastics in seawater-saturated porous media

This study examined the distinct effects of algae polysaccharides (AP), namely sodium alginate (SA), fucoidan (FU), and laminarin (LA), on the aggregation of nanoplastics (NP) in seawater, as well as their subsequent transport in seawater-saturated sea sand. The pristine 50 nm NP tended to form large aggregates, with an average size of approximately 934.5 ± 11 nm. Recovery of NP from the effluent (Meff) was low, at only 18.2 %, and a ripening effect was observed in the breakthrough curve (BTC). Upon the addition of SA, which contains carboxyl groups, the zeta (ζ)-potential of the NP increased by 2.8 mV. This modest enhancement of electrostatic interaction with NP colloids led to a reduction in the aggregation size of NP to 598.0 ± 27 nm and effectively mitigated the ripening effect observed in the BTC. Furthermore, SA's adherence to the sand surface and the resulting increase in electrostatic repulsion, caused a rise in Meff to 27.5 %. In contrast, the introduction of FU, which contains sulfate ester groups, resulted in a surge in ζ-potential of the NP to -27.7 ± 0.76 mV. The intensified electrostatic repulsion between NP and between NP and sand greatly increased Meff to 45.6 %. Unlike the effects of SA and FU, the addition of LA, a neutral compound, caused a near disappearance of ζ-potential of NP (-3.25 ± 0.68 mV). This change enhanced the steric hindrance effect, resulting in complete stabilization of particles and a blocking effect in the BTC of NP. Quantum chemical simulations supported the significant changes in the electrostatic potential of NP colloids induced by SA, FU and LA. In summary, the presence of AP can induce variability in the mobility of NP in seawater-saturated porous media, depending on the nature of the weak, strong, or non-electrostatic interactions between colloids, which are influenced by the structure and functionalization of the polysaccharides themselves. These findings provide valuable insights into the complex and variable behavior of NP transport in the marine environment.

The retention of plastic particles by macrophytes in the Amazon River, Brazil

This study evaluated the presence of plastics and microplastics in macrophytes in an urbanized sector of the Amazon River. A total of 77 quadrats in 23 macrophyte banks were sampled during the dry (September 2020) and rainy (June 2021) season. Five species were identified: Paspalum repens, Pontederia rotundifolia, Pistia stratiotes, Salvinia auriculata and Limnobium laevigatum, with P. repens being dominant during the dry season (47.54%) and P. rotundifolia during the rainy season (78.96%). Most of the plastic particles accumulated in Paspalum repens (49.3%) and P. rotundifolia (32.4%), likely due to their morphological structure and volume. The dry season showed a higher accumulation of plastic particles than the rainy season. Microplastics were found in most samples, during both the dry (75.98%) and rainy seasons (74.03%). The upstream macrophyte banks retained more plastic particles compared to the downstream banks. A moderate positive correlation was observed between the presence of plastic particles and macrophyte biomass, and a weak positive correlation between the occurrence of microplastics and mesoplastics. White and blue fragments, ranging from 1 to 5 mm were the most common microplastics found in the macrophyte banks. Green fragments and green and blue fibers were identified as polypropylene, blue and red fragments as polyethylene, and white fragments as polystyrene. Therefore, the results of this study highlight the first evidence of the retention of plastic particles in macrophytes of the Amazon and highlight a significant risk due to the harmful effects that this type of plastic can cause to the fauna and flora of aquatic ecosystems.

Effective removal of microplastics by filamentous algae and its magnetic biochar: Performance and mechanism

In recent years, filamentous algae blooms and microplastics (MPs) pollution have become two major ecological and environmental problems in urban water systems. In order to solve these two problems at the same time, this study explored the loading capacity of MPs on fresh filamentous algae, and successfully synthesized magnetic filamentous algae biochar loading with Fe3O4 by hydrothermal method, with the purpose of removing MPs from water. The magnetic filamentous algal biochar was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and so on. Experiments on adsorption kinetics, adsorption isotherms and optimum pH were carried out to explore the adsorption mechanism of MPs on magnetic filamentous algal biochar. The adsorption kinetics and adsorption isotherm models were evaluated, and the selection criterion for the appropriate model was determined by using the residual sum of squares (RSS) and Bayesian information criterion (BIC). Microscope images revealed that fresh filamentous algae could interact with MPs in the form of entanglement, adhesion and encapsulation. The average load of MPs in filamentous algae samples was 14.1 ± 5 items/g dry weight. The theoretical maximum adsorption capacities of polystyrene MPs (PS-MPs) by raw biochar (A500) and magnetic biochar with Fe3O4 (M2A500) were 176.99 mg/g and 215.58 mg/g, respectively. The adsorbent materials gave better reusability because they could be reused up to five times. Overall, these findings have provided new insights into the use of filamentous algae for in situ remediation of fluvial MPs pollution, as well as feasible strategies for the recycling of algal waste.

Biomonitoring of microplastics, anthropogenic microfibres and glass retroreflective beads by marine macroalgae

Microplastics and other microscopic debris are a concern in the coastal environment but measurements in the water column and sediment are often problematic and rely on non-standardised and highly variable methodologies. To this end, we explore the potential of different species of temperate-cold marine macroalgae as passive biomonitors of anthropogenic microparticles at three contrasting locations in southwest England. Specifically, fronds from samples of fucoids and Ulva lactuca (n = 9 in total, and three from each location) have been sectioned and analysed directly under a microscope and anthropogenic microparticles counted and subsequently characterised for chemical composition. Microparticles were heterogeneously distributed throughout sections from the same sample. However, on a dry weight basis, combined microparticle concentrations for each sample ranged from about 7.5 g-1 to 110 g-1, and from about 0.2 cm-2 to 0.9 cm-2, and for a given species were higher in samples from a semi-enclosed harbour and urban beach than in samples from a protected beach facing the open sea. These values compare with published concentrations of microplastics and microfibres reported for the regional water column on the order of 0.1 m-3. Most particles were cellulosic (e.g., rayon) and petroleum-based (mainly polyester and polyethylene terephthalate) fibres but plastic fragments were also present on most samples. Glass retroreflective beads derived from road markings were also present at up to 18 g-1 on fucoids from the urban beach because of its proximity to a stormwater effluent. Most microparticles were adhered to the smooth parts of the macroalgal surface but some displayed wrapping around edges and creases or entrapment by appendages. The practical and environmental implications of macroalgae passively capturing significant quantities of anthropogenic microparticles are discussed.

Microplastics - A major contaminant in marine macro algal population: Review

Microplastics (MPs) are a significant concern in this modern environment, and the marine environment is a sink for them now. Researchers have taken an interest in marine microplastic studies recently, which has opened the door to research in macroalgae and microalgae. Macroalgae are the primary producers in maritime ecosystems and are economically significant. This review aimed to identify the microplastic interactions with marine macroalgae and the impacts of microplastics on macroalgae based on existing literature while also recognizing knowledge gaps. MPs were mostly fibers and polymers with notable production and application levels; their abundance differed among species. More MPs were found in filamentous species than in other types. The results of this study indicated that, in maritime environments, macroalgae contribute to MP biomagnification and bioaccumulation. Adequate studies are needed to fill the research gaps in this area of MPs in macroalgae and their effects.

Phytoremediation: A promising approach to remove microplastics from the aquatic environment

Due to the increasing amount of microplastics (MPs) in the environment, various technologies for their removal have been investigated. One of the possible technologies are phytoremediation methods, but insufficient understanding of the interactions between MPs and aquatic macrophytes limits their further development. In this context, the aim of this study was to investigate the interactions between polyethylene MPs and the floating aquatic macrophyte Lemna minor in terms of the extent and time frame of MPs adhesion to the plant biomass, the stability of the interactions under water movement and understanding the nature of the adsorption process through the adsorption isotherm models. The results showed that the maximum number of adhered MPs was reached after 24 h. With increased amount of plant biomass the number of adhered MPs increased as well. Slow movement of water had no statistically significant effect on the adhesion of MPs. Among several adsorption models, the Freundlich adsorption isotherm model was the best fit to the experimental data, which assumes weak binding of MPs to plant biomass. Finally, 79% of MPs was removed during 15 cycles of phytoremediation (i.e., the biomass was removed and replaced with new biomass 15 times) and it was calculated that 53 cycles would be needed to remove all MPs from the water phase under test conditions.

The bioadhesion and effects of microplastics and natural particles on growth, cell viability, physiology, and elemental content of an aquatic macrophyte Elodea canadensis

Microplastics in the aquatic environment can interact with aquatic plants, but the consequences of these interactions are poorly understood. Therefore, the aim of this study was to investigate the effects of microplastics commonly found in the environment, namely polyethylene (PE) fragments, polyacrylonitrile (PAN) fibres, tire wear (TW) particles under a relevant environmental concentration (5000 particles/L) on the growth, cell viability, physiology, and elemental content of the aquatic macrophyte Elodea canadensis. The effects of microplastics were compared to those of natural wood particles. The results showed that all types of microplastics adhered to plant tissues, but the effect on leaves (leaf damage area) was greatest at PE > PAN > TW, while the effect of natural particles was comparable to that of the control. None of the microplastics studied affected plant growth, lipid, carbohydrate, or protein content. Electron transport system activity was significantly higher in plants exposed to PAN fibres and PE fragments, but also when exposed to natural particles, while chlorophyll a content was negatively affected only by PE fragments and TW particles. Elemental analysis of plant tissue showed that in some cases PAN fibres and TW particles caused increased metal content. The results of this study indicated that aquatic macrophytes may respond differently to exposure to microplastics than to natural particles, likely through the combined effects of mechanical damage and chemical stress.

Trophic transfer increases the exposure to microplastics in littoral predators

Predators in aquatic environments can be exposed to microplastics (MPs) directly through water and indirectly through prey. Laboratory experiments were conducted to study the potential of MP trophic transfer in Baltic Sea littoral food chains of different lengths. The longest studied food chain had three trophic levels: zooplankton, chameleon shrimp (Praunus flexuosus) and rockpool prawn (Palaemon elegans). 10 μm fluorescence microspheres were used as tracer MP particles and MP ingestion was verified with epifluorescence microscopy. Transfer of MPs occurred up to both second and third trophic level. The number of ingested microspheres in both chameleon shrimp and rockpool prawn was higher when the animals were exposed through pre-exposed prey in comparison to direct exposure through the water. The results show that trophic transfer may be an important pathway of and increase the microplastic exposure for some animals at higher trophic levels in highly polluted areas.

The influences of spatial-temporal variability and ecological drivers on microplastic in marine fish in Hong Kong

This study examined microplastic (MP) occurrence and abundance in marine fish collected from the western and eastern waters of Hong Kong during the wet and dry seasons. Over half (57.1%) of the fish had MP in their gastrointestinal (GI) tracts, with overall MP abundance ranging from not detected to 44.0 items per individual. Statistical analysis revealed significant spatial and temporal differences in MP occurrence, with fish from more polluted areas having a higher likelihood of MP ingestion. Additionally, fish collected in the west during the wet season had significantly higher MP abundance, likely due to influence from the Pearl River Estuary. Omnivorous fish had significantly higher MP counts than carnivorous fish, regardless of collection location or time. Body length and weight were not significant predictors of MP occurrence or abundance. Our study identified several ecological drivers that affect MP ingestion by fish, including spatial-temporal variation, feeding mode, and feeding range. These findings provide a foundation for future research to investigate the relative importance of these factors in governing MP ingestion by fish in different ecosystems and species.

Beyond ingestion: Adhesion of microplastics to aquatic organisms

The interactions of microplastics with aquatic organisms have been studied primarily using animal species, with dietary ingestion being the most important uptake route. However, recent research indicated that microplastics also interact with biota via bioadhesion. This process has been studied in aquatic macrophytes under laboratory conditions where microplastics adhered to their biomass, but monitoring studies also confirmed that microplastic bioadhesion occurs in other species and in the natural environment. Similarly, microplastics adhere to microorganisms, and in the aquatic environment they can be retained by ubiquitous biofilms. This can occur on a natural substrate such as sediment or rocks, but biofilms are also responsible for enhanced bioadhesion of microplastics to other biotic surfaces such as plant surfaces. Adhesion to these large biotic surfaces could influence the abundance and bioavailability of microplastics in the environment. Only few studies have been conducted on the bioadhesion of microplastics to animals, but their results confirmed that bioadhesion may be even greater than particle ingestion by some animals, such as corals or bivalves. However, the ecotoxicological effects are not yet fully understood and the possible transport of microplastics, e.g. adhered to fish or aquatic insects, also needs to be considered. In summary, bioadhesion seems to be an important process for the interactions of microplastics and biota. Neglecting bioadhesion in an environmental context may limit our understanding of the behavior, fate, and effects of microplastics in the aquatic environment.

Accumulation and re-distribution of microplastics via aquatic plants and macroalgae - A review of field studies

The aquatic plants and macroalgae are primary producers with major roles regarding the maintenance of ecosystems but their interaction with microplastics (MPs) has received less attention than animals. We summarize the methodologies used, the MPs abundances and their characteristics across the literature on MPs pollution in aquatic plants and macroalgae. The sampling and quantification of MPs still lacks consistency between studies, which increased the uncertainty in cross-comparisons. The abundance of MPs varied by orders of magnitude between species and were mostly fibers and polymers with large degrees of production and applications. Filamentous species contained more MPs than others. The average ratio of MPs between vegetated and unvegetated sites reached 3:1. The average ratio of MPs between the biotic and abiotic fractions reached 2193:1, suggesting a high level of retention in fields. Our findings supported that aquatic plants and macroalgae are critical in the plastic flux within the marine environments.

Are seafloor habitats influencing the distribution of microplastics in coastal sediments of a Marine Protected Area?

The marine environment is affected by the increasing presence of microplastics (MPs; < 5 mm), and the seafloor acts as a sink for these particles. Locations with different predominant seafloor habitat and protection level applied were selected from Cabrera Marine-Terrestrial National Park (henceforth, Cabrera MPA) (western Mediterranean Sea) with the aim to assess the distribution of MPs along the sediments of this Mediterranean MPA. A total of 37 samples were collected. A high diversity of sediment between locations was detected according to the Udden-Wentworth classification and locations were clustered into two main groups according to the predominance of different particle size fractions. The identification of MPs was carried out according to the sediment particle size classification. A total of 1431 MPs and a mean value (± SD) of 314.53 ± 409.94 items kg-1 D.W. were identified, and 70% of the particles were fibers. Statistically higher abundances of MPs were found in sediments collected from sandy habitats, with a mean value of 630.80 ± 636.87 items kg-1 D.W., compared to the abundances of MPs found in locations with different predominant seafloor habitats, that ranged from 136.79 ± 156.33 items kg-1 D.W. in habitats with similar predominance of seagrass and sand to 223.02 ± 113.35 items kg-1 D.W. in habitats with similar predominance of rocks and sand. The abundance of MPs regarding each sediment particle size fraction differed between years and locations, and the abundance of MPs according to each identified shape differed between sampling years, particle size fraction, and predominant seafloor habitat. The present study highlights the ubiquitous presence of MPs in seafloor sediments from a MPA. Furthermore, the results suggest that the predominant seafloor habitat can modulate the presence of MPs in marine environments in both general abundances and shape of items.

Enzymatic preparation and potential applications of agar oligosaccharides: a review

Oligosaccharides derived from agar, that is, agarooligosaccharides and neoagarooligosaccharides, have demonstrated various kinds of bioactivities which have been utilized in a variety of fields. Enzymatic hydrolysis is a feasible approach that principally allows for obtaining specific agar oligosaccharides in a sustainable way at an industrial scale. This review summarizes recent technologies employed to improve the properties of agarase. Additionally, the relationship between the degree of polymerization, bioactivities, and potential applications of agar-derived oligosaccharides for pharmaceutical, food, cosmetic, and agricultural industries are discussed. Engineered agarase exhibited general improvement of enzymatic performance, which is mostly achieved by truncation. Rational and semi-rational design assisted by computational methods present the latest strategy for agarase improvement with greatest potential to satisfy future industrial needs. Agarase immobilized on magnetic Fe3O4 nanoparticles via covalent bond formation showed characteristics well suited for industry. Additionally, albeit with the relationship between the degree of polymerization and versatile bioactivities like anti-oxidants, anti-inflammatory, anti-microbial agents, prebiotics and in skin care of agar-derived oligosaccharides are discussed here, further researches are still needed to unravel the complicated relationship between bioactivity and structure of the different oligosaccharides.

Microplastics in the first-year sea ice of the Novik Bay, Sea of Japan

Sea ice is heavily contaminated with microplastics particles (MPs, <5 mm). First-year sea ice cores (38-41 cm thick) were taken in the beginning of spring in a narrow populated bay of the Sea of Japan. Two ice cores were examined (layer-by-layer, excluding surface) for MPs content: one using μ-FTIR for 25-300 μm (SMPs), and another one - with visual+Raman identification for 300-5000 μm particles (LMPs). The integral (25-5000 μm) bulk mean abundance of MPs was found to be 428 items/L of meltwater, with fibers making 19 % in SMPs size range and 59 % in LMPs. Integral mean mass of MPs was estimated in 34.6 mg/L, with 99.6 % contribution from fragments of LMPs. Comparison with simple fragmentation models confirms deficit of SMPs (especially of fibers in size range 150-300 μm), suggested to result from their leakage with brine. Multivariate statistical analysis indicates strong positive correlation of large fiber (>300 μm) counts and ice salinity.

Microplastics and linear alkylbenzene levels in oysters Crassostrea gigas driven by sewage contamination at an important aquaculture area of Brazil

The levels of linear alkylbenzenes (LABs) and the occurrence of microplastics (MPs) in the oysters Crassostrea gigas were evaluated in six farming areas in southern Brazil. The results revealed higher concentrations of LABs in oyster tissue from the Serraria (1977 ± 497.7 ng g^-1) and Imaruim (1038 ± 409.9 ng g^-1) sites. Plastic microfibers were found in oysters from all locations with values from 0.33 to 0.75 MPs per oyster (0.27-0.64 MPs per gram) showing the ubiquitous presence of this contaminant in the marine environment, which could be considered a threat to farming organisms. In addition, elements such as Ti, Al, Ba, V, Rb, Cr, and Cu were found in the chemical composition of the microfibers, suggesting MPs as vectors of inorganic compounds. A positive correlation between LABs and thermotolerant coliforms suggests that sewage discharges are the main source of contamination in these oysters cultured for human consumption. The present study highlights the need for efficient wastewater treatment plants and the implementation of depuration techniques in oysters from farming areas.

Macroalgal morphology mediates microplastic accumulation on thallus and in sediments

The accumulation process of microplastics (MPs) is a key to understanding their fate in the environment. However, there is limited information about the short-term accumulation of MPs on macrophytes. The ability of macrophyte to attenuate wave and reduce current velocity is potentially facilitating MPs deposition. We hypothesize that the macroalgae retain MPs with their morphologies (filamentous and non-filamentous) being one of the factors to govern retention. Our hypothesis was tested by field observation during the dry season in Hong Kong when the macroalgae communities were the most diverse. MPs per biomass, surface area, or interstitial volume were used to represent the abundances on macroalgae. We found that filamentous algae retained a 2.35 times higher number of MPs when compared with non-filamentous algae if unit per biomass was considered. Other units, however, showed insignificant differences in MPs abundances between algal morphologies. Fibre was the most dominant shape of MPs with no significant difference in their abundances between filamentous and non-filamentous algae, suggesting fibres were retained regardless of the algal morphologies. To further evaluate the potential accumulation in the environment, sediment samples were also collected under the algal mat and immediate vicinity (~50 cm) of the algal mat. We found that sediment collected under the vegetated area contained significantly higher MPs. This was 3.39 times higher than the unvegetated area. Sediment collected under/near filamentous algae retained much higher abundances of MPs than those of non-filamentous algae. Provided that the observed retention of MPs on macroalgae, we speculate macrophyte system is one of the short-term MPs accumulation hotspots where the temporal increase of MPs depends on the seasonality of macrophyte in a given region.

Plastic debris in coastal macroalgae

Macroalgae are the most productive marine macrophytes in the coastal ecosystem. Although plastic debris has been ubiquitously detected in marine animals, little is known about plastic pollution in macroalgae and how they interact with each other. In this study, the occurrence of plastic debris including microplastics was investigated in 5 macroalgae species that are commonly found along the Chinese shorelines. These species consisted of Gracilaria lemaneiformis, Chondrus ocellatus, Ulva lactuca, Ulva prolifera and Saccharina japonica. We categorized the plastic debris into 3 size classes, i.e., macroplastics (>25 mm), mesoplastics (5-25 mm), and microplastics (1 μm-5 mm). It was shown that there were 5 loading patterns of plastic debris interaction with the macroalgae. The 5 patterns included entanglement, adherence, wrapping, embedment, and entrapment by epibionts. According to direct observations through the non-digestion method, all 3 size classes of plastics were found in the macroalgae. The abundances were 0-201.5 (macroplastics), 0-1178.0 (mesoplastics) and 0-355.6 (microplastics) items/kg dry weight, respectively. These plastics were dominated by fibers (52.2%) in shape, 1-5 mm (39.6%) in size, and polystyrene (36.5%) in composition. According to indirect observations through the digestion method, only 2 size classes of plastics were identified in the macroalgae: mesoplastics, 0 to 888.9 items/kg dry weight; microplastics, 148.1 to 5889.0 items/kg dry weight. These plastics were prevailing by fibers (71.5%) in shape, 1-5 mm (52%) in size, and polyester (29.3%) in composition. Furthermore, plastic characteristics in the detected macroalgae were related to their species, sampling regions, and beach types based on the results of similarity and principal component analysis. This study indicated that macroalgae utilized diverse pathways for loading plastics in the coastal environment. Meanwhile, environmental factors significantly influenced the distribution of plastics loaded by macroalgae.

Assessment of the Influence of Size and Concentration on the Ecotoxicity of Microplastics to Microalgae Scenedesmus sp., Bacterium Pseudomonas putida and Yeast Saccharomyces cerevisiae

The harmful effects of microplastics are not yet fully revealed. This study tested harmful effects of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET) microplastics were tested. Growth inhibition tests were conducted using three microorganisms with different characteristics: Scenedesmus sp., Pseudomonas putida, and Saccharomyces cerevisiae. The growth inhibition test with Scenedesmus sp. is relatively widely used, while the tests with Pseudomonas putida and Saccharomyces cerevisiae were, to our knowledge, applied to microplastics for the first time. The influence of concentration and size of microplastic particles, in the range of 50–1000 mg/L and 200–600 µm, was tested. Determined inhibitions on all three microorganisms confirmed the hazardous potential of the microplastics used. Modeling of the inhibition surface showed the increase in harmfulness with increasing concentration of the microplastics. Particle size showed no effect for Scenedesmus with PE, PP and PET, Pseudomonas putida with PS, and Saccharomyces cerevisiae with PP. In the remaining cases, higher inhibitions followed a decrease in particle size. The exception was Scenedesmus sp. with PS, where the lowest inhibitions were obtained at 400 µm. Finally, among the applied tests, the test with Saccharomyces cerevisiae proved to be the most sensitive to microplastics.

Microplastic contamination of sandy beaches of national parks, protected and recreational areas in southern parts of the Baltic Sea

The distribution of small (0.5-2 mm, S-MPs) and large (2-5 mm, L-MPs) microplastics and mesoplastic particles in 51 samples of surface beach sands at 7 locations along the southern shore of the Baltic Sea was investigated. MPs particles (3267 in total) were found at all the sites and in all the beach zones. The bulk mean MPs (0.5-5 mm) contamination is 68 ± 117 (median 33) items/kg DW (n = 51). The results were confirmed by μ-Raman spectroscopy analysis. National park areas did not differ substantially from other beaches. Expanded polystyrene fragments accounted for about 38% of the total collected particles. Fibres were the predominant type of MPs (55%). The highest contamination was found within the current wrack line (60.1 ± 36.6 items/kg DW of S-MPs). A consistent picture for S-MPs was observed at the beach face, where the mean values in different locations varied between 21.0 and 58.1 items/kg DW, with a bulk mean of 30.4 ± 13.7 items/kg DW.