Environmental Concentrations of Herbicide Prometryn Render Stress-Tolerant Corals Susceptible to Ocean Warming.

Global warming has caused the degradation of coral reefs around the world. While stress-tolerant corals have demonstrated the ability to acclimatize to ocean warming, it remains unclear whether they can sustain their thermal resilience when superimposed with other coastal environmental stressors. We report the combined impacts of a photosystem II (PSII) herbicide, prometryn, and ocean warming on the stress-tolerant coral Galaxea fascicularis through physiological and omics analyses. The results demonstrate that the heat-stress-induced inhibition of photosynthetic efficiency in G. fascicularis is exacerbated in the presence of prometryn. Transcriptomics and metabolomics analyses indicate that the prometryn exposure may overwhelm the photosystem repair mechanism in stress-tolerant corals, thereby compromising their capacity for thermal acclimation. Moreover, prometryn might amplify the adverse effects of heat stress on key energy and nutrient metabolism pathways and induce a stronger response to oxidative stress in stress-tolerant corals. The findings indicate that the presence of prometryn at environmentally relevant concentrations would render corals more susceptible to heat stress and exacerbate the breakdown of coral Symbiodiniaceae symbiosis. The present study provides valuable insights into the necessity of prioritizing PSII herbicide pollution reduction in coral reef protection efforts while mitigating the effects of climate change.

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.

Natural and Induced Mitochondrial Phosphate Carrier Loss: DIFFERENTIAL DEPENDENCE OF MITOCHONDRIAL METABOLISM AND DYNAMICS AND CELL SURVIVAL ON THE EXTENT OF DEPLETION.

The relevance of mitochondrial phosphate carrier (PiC), encoded by SLC25A3, in bioenergetics is well accepted. However, little is known about the mechanisms mediating the cellular impairments induced by pathological SLC25A3 variants. To this end, we investigated the pathogenicity of a novel compound heterozygous mutation in SLC25A3 First, each variant was modeled in yeast, revealing that substituting GSSAS for QIP within the fifth matrix loop is incompatible with survival on non-fermentable substrate, whereas the L200W variant is functionally neutral. Next, using skin fibroblasts from an individual expressing these variants and HeLa cells with varying degrees of PiC depletion, PiC loss of ∼60% was still compatible with uncompromised maximal oxidative phosphorylation (oxphos), whereas lower maximal oxphos was evident at ∼85% PiC depletion. Furthermore, intact mutant fibroblasts displayed suppressed mitochondrial bioenergetics consistent with a lower substrate availability rather than phosphate limitation. This was accompanied by slowed proliferation in glucose-replete medium; however, proliferation ceased when only mitochondrial substrate was provided. Both mutant fibroblasts and HeLa cells with 60% PiC loss showed a less interconnected mitochondrial network and a mitochondrial fusion defect that is not explained by altered abundance of OPA1 or MFN1/2 or relative amount of different OPA1 forms. Altogether these results indicate that PiC depletion may need to be profound (>85%) to substantially affect maximal oxphos and that pathogenesis associated with PiC depletion or loss of function may be independent of phosphate limitation when ATP requirements are not high.

Marivirga lumbricoides sp. nov., a marine bacterium isolated from the South China Sea.

A novel, aerobic, heterotrophic, orange-pigmented, Gram-staining-negative, rod-shaped, gliding bacterial strain, designated JLT2000(T), was isolated from surface water of the South China Sea. The strain was oxidase- and catalase-positive. The major cellular fatty acids of strain JLT2000 T: were C12 : 0, iso-C15 : 1 G, iso-C15 : 0, iso-C17 : 0 3-OH, summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c), C16 : 0 and C18 : 0. MK-7 was the major respiratory quinone and the major polar lipids were phosphatidylcholine and phosphatidylethanolamine. The genomic DNA G+C content of strain JLT2000(T) was 37.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain JLT2000(T) formed a branch within the genus Marivirga, but was clearly separated from the two established species of this genus, Marivirga tractuosa and Marivirga sericea. The 16S rRNA gene sequence similarity of strain JLT2000(T) with the type strains of these two species was 95.8 % and 96.1 %, respectively. Strain JLT2000(T) had a shorter cell length and wider growth range in different temperatures and salinities than those of Marivirga tractuosa NBRC 15989(T) and Marivirga sericea NBRC 15983(T). In addition, strain JLT2000(T) could utilize more carbon sources and hydrolyse more polymers than Marivirga tractuosa NBRC 15989(T) and Marivirga sericea NBRC 15983(T). Based on this polyphasic analysis, strain JLT2000(T) represents a novel species of the genus Marivirga, for which the name Marivirga lumbricoides sp. nov. is proposed. The type strain is JLT2000(T) ( = JCM 18012(T) = CGMCC 1.10832(T)).

Pelagibacterium nitratireducens sp.nov., a marine Alphaproteobacterium isolated from the East China Sea.

A Gram-negative, rod-shaped, non-spore-forming aerobic bacterium, motile with a single polar flagellum, strain JLT2005(T), was isolated from surface seawater collected from the East China Sea and formed ivory white colonies on a rich organic medium. The strain was positive for catalase, oxidase, and urease. It grew in the presence of 0-12 % (w/v) NaCl (optimum 5 %), at 20-35 °C (optimum 25 °C), or at pH 6-10 (optimum pH 9). The major fatty acids (>10 %) were C(18:1)ω7c, C(19:0)ω8c cyclo, C(16:0), and C(18:0). The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol, and five unidentified glycolipids. Ubiquinone-10 and Ubiquinone-11 were present as the major quinones. The DNA G+C content was 74.3 mol%. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain JLT2005(T) belongs to the genus Pelagibacterium in the family Hyphomicrobiaceae, class Alphaproteobacteria. The closest neighbors were Pelagibacterium halotolerans B2(T) (98.7 % similarity) and Pelagibacterium luteolum 1_C16_27(T) (97.1 % similarity). DNA-DNA relatedness values of strain JLT2005(T) with P. halotolerans B2(T) and with P. luteolum 1_C16_27(T) were 31.6 and 25 %. Evidence from genotypic, chemotaxonomic, and phenotypic data shows that strain JLT2005(T) represents a novel species of the genus Pelagibacterium, for which the name Pelagibacterium nitratireducens sp. nov is proposed. The type strain is JLT2005(T) (=CGMCC 1.10829(T) =JCM 17767(T)).

Modeling nutrient flows from land to rivers and seas - A review and synthesis.

Water quality modeling facilitates management of nutrient flows from land to rivers and seas, in addition to environmental pollution management in watersheds. In the present paper, we review advances made in the development of seven water quality models and highlight their respective strengths and weaknesses. Afterward, we propose their future development directions, with distinct characteristics for different scenarios. We also discuss the practical problems that such models address in the same region, China, and summarize their different characteristics based on their performance. We focus on the temporal and geographical scales of the models, sources of pollution considered, and the main problems that can be addressed. Summary of such characteristics could facilitate the selection of appropriate models for resolving practical challenges on nutrient pollution in the corresponding scenarios globally by stakeholders. We also make recommendations for model enhancement to expand their capabilities.

Ecological risk assessment of heavy metals in the sediments and their impacts on bacterial community structure: A case study of Bamen Bay in China.

Heavy metal pollution associated with human activity is of big concern in tropical bays. Microorganisms may be highly sensitive to heavy metals. Nonetheless, little is known about effects of heavy metals on microbial structure in tropical bay sediments. In this study, 16S rRNA gene sequencing and potential ecological risk index analysis were used to analyze the relationships between nine metals (arsenic, lead, cadmium, cobalt, chromium, copper, zinc, manganese, and nickel) and bacterial communities in the sediments of Bamen Bay, China. Our results showed that Bamen Bay was under a considerable ecological risk and cadmium had the highest monomial potential ecological risk. In addition, individual metal contamination correlated with bacterial community composition but not with bacterial α-diversity. Arsenic was the metal influencing bacterial community structure the most. Our findings provide a novel insight into the monitoring and remediation of heavy metal pollution in tropical bays.

Synergistic/antagonistic effects of nitrate/ammonium enrichment on fatty acid biosynthesis and translocation in coral under heat stress.

Superimposed on ocean warming, nitrogen enrichment caused by human activity puts corals under even greater pressure. Biosynthesis of fatty acids (FA) is crucial for coral holobiont survival. However, the responses of FA biosynthesis pathways to nitrogen enrichment under heat stress in coral hosts and Symbiodiniaceae remain unknown, as do FA translocation mechanisms in corals. Herein, we used the thermosensitive coral species Acropora hyacinthus to investigate changes in FA biosynthesis pathways and polyunsaturated FA translocation of coral hosts and Symbiodiniaceae with respect to nitrate and ammonium enrichment under heat stress. Heat stress promoted pro-inflammatory FA biosynthesis in coral hosts and inhibited FA biosynthesis in Symbiodiniaceae. Nitrate enrichment inhibited anti-inflammatory FA biosynthesis in Symbiodiniaceae, and promoted pro-inflammatory FA biosynthesis in coral hosts and translocation to Symbiodiniaceae, leading to bleaching after 14 days of culture. Intriguingly, ammonium enrichment promoted anti-inflammatory FA biosynthesis in Symbiodiniaceae and translocation to hosts, allowing corals to better endure heat stress. We constructed schematic diagrams of the shift in FA biosynthesis and translocation in and between A. hyacinthus and its Symbiodiniaceae under heat stress, heat and nitrate co-stress, and heat and ammonium co-stress. The findings provide insight into the mechanisms of coral bleaching under environmental stress from a fatty acid perspective.

Oceanitalea nanhaiensis gen. nov., sp. nov., an actinobacterium isolated from seawater.

A Gram-positive, motile, short-rod-shaped bacterium, designated strain JLT1488(T), was isolated from the South China Sea and investigated in a taxonomic study using a polyphasic approach. The peptidoglycan type determined for strain JLT1488(T) was A4α with lysine as the diagnostic cell-wall diamino acid and an interpeptide bridge of L-Lys-L-Glu. The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides, an unknown glycolipid and an unknown phospholipid. The only detected menaquinone was MK-8(H(4)), and the major fatty acids were summed feature 8 (C(18 : 1)ω7c/C(18 : 1)ω6c) , C(16 : 0) and summed feature 3 (C(16 : 1)ω7c/C(16 : 1)ω6c); significant amounts of C(12 : 0) 3-OH, C(10 : 0) and C(19 : 0) cyclo ω8c were also present. The G+C content of the genomic DNA was 62.3 mol%. Comparison of the 16S rRNA gene sequence of strain JLT1488(T) with those of related type strains demonstrated that it represented a novel lineage within the family Bogoriellaceae, suborder Micrococcineae, being closely related to species of the genera Georgenia, Bogoriella and Cellulomonas (94.6-96.8 % sequence similarity). These results demonstrate that strain JLT1488(T) is a member of a new genus, for which the name Oceanitalea nanhaiensis gen. nov., sp. nov. is proposed. The type strain of the type species is JLT1488(T) ( = JCM 17755(T) = CGMCC 1.10826(T)).

Oceaniovalibus guishaninsula gen. nov., sp. nov., a marine bacterium of the family Rhodobacteraceae.

The alphaproteobacterial strain JLT2003(T) was isolated from surface seawater off the coast of Guishan island, Taiwan. The strain was Gram negative, ovoid or coccoid, non-motile and formed pink colonies on marine agar 2216 (MA; DIFCO) medium. The dominant fatty acids were C(18:1)ω7c, cyclo C(19:0)ω8c, and C(16:0). The polar lipid profile consisted of diphosphatidylglycerol and phosphatidylglycerol. The major respiratory ubiquinone was Q-10. The DNA G+C content was 62.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that the strain was most closely related to Pontibaca methylaminivorans GRP21(T) with 94.8% similarity. The isolate was distinguishable from members of the family Rhodobacteraceae based on phenotypic and biochemical characteristics. On the basis of the taxonomic data presented, strain JLT2003(T) is considered to represent a novel species of a new genus, for which the name Oceaniovalibus guishaninsula gen. nov., sp. nov. is proposed. The type strain of Oceaniovalibus guishaninsula is JLT2003(T) (=JCM 17765(T) = CGMCC 1.10827(T)).

Roseibacterium beibuensis sp. nov., a novel member of roseobacter clade isolated from Beibu Gulf in the South China Sea.

A novel aerobic, bacteriochlorophyll-containing bacteria strain JLT1202r(T) was isolated from Beibu Gulf in the South China Sea. Cells were gram-negative, non-motile, and short-ovoid to rod-shaped with two narrower poles. Strain JLT1202r(T) formed circular, opaque, wine-red colonies, and grew optimally at 3-4 % NaCl, pH 7.5-8.0 and 28-30 °C. The strain was catalase, oxidase, ONPG, gelatin, and Voges-Proskauer test positive. In vivo absorption spectrum of bacteriochlorophyll a presented two peaks at 800 and 877 nm. The predominant cellular fatty acid was C(18:1) ω7c and significant amounts of C(16:0), C(18:0), C(10:0) 3-OH, C(16:0) 2-OH, and 11-methyl C(18:1) ω7c were present. Strain JLT1202r(T) contained Q-10 as the major respiratory quinone and the genomic DNA G+C content was 76.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences of various species with validly published names showed that strain JLT1202r(T) fell within the genus Roseibacterium, family Rhodobacteraceae, sharing the highest similarity with Roseibacterium elongatum OCh 323(T) (97.9 % similarity), followed by Dinoroseobacter shibae DFL 12(T) (95.4 % similarity). The phylogenetic distance of pufM genes between strain JLT1202r(T) and R. elongatum OCh 323(T) was 9.4 %, suggesting that strain JLT1202r(T) was distinct from the only strain of the genus Roseibacterium. Based on the variabilities of phylogenetic and phenotypic characteristics, strain JLT1202r(T) stands for a novel species of the genus Roseibacterium and the name R. beibuensis sp. nov. is proposed with JLT1202r(T) as the type strain (=JCM 18015(T) = CGMCC 1.10994(T)).

Changes in bacterial community structures in soil caused by migration and aging of microplastics.

Microplastics (MPs) are classified as emerging pollutants and greatly threatens soil ecosystems. To determine the impact of microplastic migration on soil bacterial diversity, we conducted a 90-day indoor soil column simulation test. Soil and microplastic (granular polystyrene, polypropylene MPs) samples were collected from different soil layers on days 30, 60, and 90. The downward migration trend of MPs was obvious, and its surface functional groups, hydrophobic properties, and crystallinity changed. Bacterial diversity was significantly higher in the surrounding soil than on microplastic surfaces. Also, the topsoil has more bacterial diversity than the middle soil. A higher number of OTUs were detected on microplastic surfaces for the middle soil than in the topsoil. Proteobacteria abundance on microplastic surfaces in the topsoil gradually increased over the course of the experiment, while an opposite trend was observed for the middle soil. Nevertheless, Proteobacteria abundances in both layers were higher than in the surrounding soils. MPs alters the bacterial community composition of soils and provides unique substrates for colonization. The impacts of MPs on soil bacterial communities were better understood in this study. Our findings highlighted the relevance of MPs in soil ecosystems as well as the potential threats they pose.

Paracoccus oceanense sp. nov., isolated from the West Pacific.

A Gram-negative, short ovoid- to coccus-shaped, aerobic, motile, non-spore-forming bacterium (designated strain JLT1679(T)) was isolated from West Pacific. Cells have subpolar flagella, dividing by binary fission. Phylogenetic analyses based on 16S rRNA gene sequences showed that the strain belongs to branch of the evolutionary radiation occupied by the genus Paracoccus, family Rhodobacteraceae, order Rhodobacterales, class Alphaproteobacteria. The closest neighbours were Paracoccus stylophorae KTW-16(T) (97.1% similarity), Paracoccus caeni strain MJ17(T) (96.5% similarity), Paracoccus homiensis DD-R11(T) (96.0% similarity) and Paracoccus alcaliphilus JCM 7364(T) (95.8% similarity). The predominant cellular fatty acids of strain JLT1679(T) were summed feature 8 (18:1ω6c) (38.8%), C(18:0) (27.7%), C(16:0) (22.5%), and significant amounts of C(18:1) ω9c (5.1%), C(14:0) (3.8%) and C(18:1) ω7c 11-methyl (2.1%), were present. The predominant respiratory ubiquinone of strain JLT1679(T) was Q-10 and the DNA G + C content of strain JLT1679(T) was 59.5 mol%. The polar lipid profile consisted of a mixture of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine and sphingoglycolipid. The isolate was distinguishable from members of the genus Paracoccus on the basis of phenotypic and biochemical characteristics. It is evident from the genotypic, chemotaxonomic and phenotypic data that strain JLT1679(T) represents a novel species of the genus Paracoccus, for which the name Paracoccus oceanense sp. nov. is proposed. The type strain is JLT1679(T) (= JCM 17768(T) = CGMCC 1.10831(T)).

Identification of Hypoxia Signature to Assess the Tumor Immune Microenvironment and Predict Prognosis in Patients with Ovarian Cancer.

BACKGROUND: The 5-year overall survival rate of ovarian cancer (OC) patients is less than 40%. Hypoxia promotes the proliferation of OC cells and leads to the decline of cell immunity. It is crucial to find potential predictors or risk model related to OC prognosis. This study aimed at establishing the hypoxia-associated gene signature to assess tumor immune microenvironment and predicting the prognosis of OC. METHODS: The gene expression data of 378 OC patients and 370 OC patients were downloaded from datasets. The hypoxia risk model was constructed to reflect the immune microenvironment in OC and predict prognosis. RESULTS: 8 genes (AKAP12, ALDOC, ANGPTL4, CITED2, ISG20, PPP1R15A, PRDX5, and TGFBI) were included in the hypoxic gene signature. Patients in the high hypoxia risk group showed worse survival. Hypoxia signature significantly related to clinical features and may serve as an independent prognostic factor for OC patients. 2 types of immune cells, plasmacytoid dendritic cell and regulatory T cell, showed a significant infiltration in the tissues of the high hypoxia risk group patients. Most of the immunosuppressive genes (such as ARG1, CD160, CD244, CXCL12, DNMT1, and HAVCR1) and immune checkpoints (such as CD80, CTLA4, and CD274) were upregulated in the high hypoxia risk group. Gene sets related to the high hypoxia risk group were associated with signaling pathways of cell cycle, MAPK, mTOR, PI3K-Akt, VEGF, and AMPK. CONCLUSION: The hypoxia risk model could serve as an independent prognostic indicator and reflect overall immune response intensity in the OC microenvironment.

Where are we? Towards an understanding of the selective accumulation of microplastics in mussels.

Mussels are suggested as bioindicators of marine microplastic pollution. However, they are selective in regards to accumulation of microplastics. To make studies more targeted and comparable, ultimately helping to determine the suitability of the mussel as a bioindicator species for microplastic exposure, we review the published literature that has directly or indirectly demonstrated particle selection in mussels. The reported difference between microplastic levels in mussel tissues and environmental matrices provides evidence for their selective uptake characteristics. Both the organ-specific fate characteristics of microplastics, and the different movement patterns of microplastics in the same organ, show that selective translocation processes take place. The selective elimination is reflected in multiple aspects which include (1) the different characteristics of microplastics in excretion and mussel body; (2) the different retention time of various microplastics in mussels; and (3) the tissue-specific change in the numbers of microplastics during the depuration process. This selectivity is affected by the characteristics of the microplastics, the environmental, or laboratory exposure concentrations, feeding status, and other factors. There are still many research gaps and contradictory viewpoints in this field due to this complexity. The current methodology needs improvement and a breakthrough in standardization.

Microplastics in the commercial seaweed nori.

Microplastics have been reported to attach to the marine macroalgae which act as the vector for microplastic transfer in the marine food web. In this study, the edible seaweed nori (Pyropia spp.) was chosen as a target species. The microplastic contaminant situations in nori were analyzed in both its final commercial products and the intermediate products across different processing stages. The abundance of microplastics ranged from 0.9 to 3.0 items/g (dw) among 24 brands of commercially packaged nori samples. With the development of nori processing stages, an enlarged size fraction of greater microplastics (1-5 mm) was observed. Compared with commercially packaged nori samples, the proportions of polypropylene, polyethylene and poly (ethylene-propylene) copolymers increased, whereas that of polyester decreased in factory-processed nori. Additionally, we further simulated and quantified the number of fluorescent polyester fibers (concentrations: 0, 1000, 5000, 10,000 fibers/L) attach to the algal pieces of Pyropia yezoensis under laboratory conditions. The average abundance of microfibers on the nori was positively and quantitatively related to their abundances in seawater (p < 0.01). To our best knowledge, this is the first work that shows the prevalence of microplastics in the commercial seaweed nori and relates to their potential sources during the processing phase.

Fusion of microplastics into the mussel byssus.

Microplastics have been found to adhere to the surface of specific tissues or organs other than being ingested by the organisms. To further test the hypothesis that microplastics might get into specific body parts of organisms, mussel byssus was chosen as a target subject in the present study. In the field investigation, microplastics were found in mussel byssus, and the abundance of microplastics was 0.85-1.02 items/individual mussel and 3.69-9.16 items/g byssus, but the location of microplastics in byssus was not easily determined. Therefore, we simulated environmental conditions in the laboratory for mussels to form fresh byssus in the presence of microplastics. Three types of man-made microplastics (Polystyrene beads, Polyamide fragments, and Polyester fibers) were found in newly formed byssus of mussels after exposure to these test materials. We observed that microplastics not only adhered to the surface but also fused into the byssus of mussels. Since byssus is important for the well-being of mussels, the incorporation of microplastics into the byssus might impair the function of byssus. To the authors' best knowledge, this is the first study to show that microplastics can contact and fuse with the byssus of mussels during their formation, suggesting possible alternations for mussels to grip and interact with microplastics in the aquatic environments.

The uptake of microfibers by freshwater Asian clams (Corbicula fluminea) varies based upon physicochemical properties.

Microplastic is an umbrella term that covers particles with various physical and chemical properties. However, microplastics with a consistent shape, polymer type and size are generally used in exposure studies (e.g., spherical polyethylene or polystyrene beads 1-100 µm in size). In the present study, we exposed freshwater Asian clams (Corbicula fluminea) to microfibers with different physicochemical properties at concentrations of 100 and 1000 fibers/L. The first experiment in this study exposed clams to microfibers made from six different polymers, demonstrating that Asian clams uptake more polyester (PET) (4.1 items/g) relevant to other polymers. The next experiment exposed clams to PET fibers of different size classes, demonstrating that uptake in the size range 100-250 µm (1.7 items/g) was greater than other size classes. These results suggest that physicochemical properties such as polymer and size play important roles in the uptake of microfibers by organisms. Thus, we strongly suggest that the properties of microplastics used in future laboratory exposure experiments be considered, with the aim of being "environmentally relevant", i.e., similar to what is found in nature.

Using mussel as a global bioindicator of coastal microplastic pollution.

The ubiquity and high bioavailability of microplastics have an unknown risk on the marine environment. Biomonitoring should be used to investigate biotic impacts of microplastic exposure. While many studies have used mussels as indicators for marine microplastic pollution, a robust and clear justification for their selection as indicator species is still lacking. Here, we review published literature from field investigations and laboratory experiments on microplastics in mussels and critically discuss the suitability and challenges of mussels as bioindicator for microplastic pollution. Mussels are suitable bioindicator for microplastic pollution because of their wide distribution, vital ecological niches, susceptibility to microplastic uptake and close connection with marine predators and human health. Field investigations highlight a wide occurrence of microplastics in mussels from all over the world, yet their abundance varies enormously. Problematically, these studies are not comparable due to the lack of a standardized approach, as well as temporal and spatial variability. Interestingly, microplastic abundance in field-collected mussels is closely related to human activity, and there is evidence for a positive and quantitative correlation between microplastics in mussels and surrounding waters. Laboratory studies collectively demonstrate that mussels may be good model organisms in revealing microplastic uptake, accumulation and toxicity. Consequently, we propose the use of mussels as target species to monitor microplastics and call for a uniform, efficient and economical approach that is suitable for a future large-scale monitoring program.