Coastal Sediments Research Articles

Distribution and characteristics of microplastics in sediment at representative dredged material ocean dumping sites, China

Dredged material ocean dumping activities are likely an important source of microplastics (MPs) in coastal areas but have received little attention globally. In this study, we investigated the spatiotemporal distribution and characteristics of MPs in sediments at eight dredged material dumping sites of China. MPs were separated from sediment through density flotation, and polymer types were identified using μ-FTIR. The results showed that the average MP abundance was 112.82 ± 109.68 items/kg d.w. The MPs were more abundant at nearshore dumping sites than at distant dumping sites. Dumping activities may be the main contributor of MPs to Site BD1, the farthest dumping site from shore, but only a minor source of MPs at the other dumping sites. The characteristics of MPs were dominated by transparent PET fibers <1 mm. Overall, sediments at the dumping sites exhibited relatively low to moderate concentrations of MPs in comparison to most other coastal sediments.

WITHDRAWN: Sediment pollution in coastal and marine environments

Sediment pollution in coastal and marine environments has emerged as a pressing concern due to its far-reaching ecological, environmental, and human health impacts. This Special Issue of the Marine Pollution Bulletin assembles a diverse range of studies investigating sediment pollution, its causes, and potential mitigation strategies, covering topics such as geophysical assessment of anthropogenic activities, biological responses to pollution, contamination, and ecological risk assessments, and microplastics in coastal sediments. The findings emphasize the need for effective monitoring, management, and interdisciplinary research to address the multifaceted challenges posed by sediment pollution. As the global population grows and human activities expand, it is essential to prioritize sustainable practices and policies to minimize anthropogenic impacts on coastal and marine ecosystems. By advancing collective knowledge and sharing best practices, we can work towards ensuring a healthier and more resilient future for these crucial ecosystems and the lives they support.

How to distinguish between marine and lacustrine sedimentary environments? —A case study of Lishui Sag, East China Sea Shelf Basin

The identification and characterization of marine versus lacustrine sedimentary environments can aid in the assessment of source and reservoir rock distribution, which is important for hydrocarbon exploration. Analysis of sedimentary facies, trace fossils, micropaleontology, geochemical characteristics, and relative water-levels was conducted in this study. Analysis of the core revealed typical sedimentary structures, including fourteen lithofacies and eleven lithofacies associations, which are indicative of wave-influenced origins and tidal processes. The sediments of the Yueguifeng Formation and upper Mingyuefeng Formation were deposited in shallow water settings, which later transitioned into the semi-deep water environments of the Lingfeng Formation and lower Mingyuefeng Formation. Sediments of the lower Mingyuefeng Formation and Lingfeng Formation were deposited in semi-brackish water or brackish water environments, whilst from the lower Mingyuefeng Formation to upper Mingyuefeng Formation and lower Lingfeng Formation to Yueguifeng Formation, the environment was semi-brackish to freshwater. The Lishui Sag experienced a large-scale and rapid relative water-level increase from the Yueguifeng Formation to the lower Mingyuefeng Formation and a decrease during the upper Mingyuefeng Formation. The relative water-level of the Lingfeng Formation and the lower Mingyuefeng Formation was consistent with the inferred eustatic global sea-level, and the relative water-level of the Yueguifeng Formation and the upper Mingyuefeng Formation deviated from the inferred global eustatic sea-level. The typical lithofacies associations, micropaleontology, and geochemical characteristics are identified as the key indicators to determine the sedimentary environments. The sedimentary environment analysis results show that the Lingfeng Formation to the lower Mingyuefeng Formation developed in a marine setting, whereas the Yueguifeng Formation and the upper Mingyuefeng Formation developed in a lacustrine sedimentary environment. The sediments deposited within shallow marine settings form good source rocks, the coastal sediments form good reservoirs, sediments of shallow lacustrine can generate source rock, and the deep-lacustrine sediments form good source rocks that produce waxy crude. Therefore, accurately distinguishing the difference between marine and lacustrine basins is important in terms of the overall understanding of the basin and the hydrocarbon play elements contained within it.

Drilling 1100-km-long seafloor ridges reveals how palaeoshorelines control carbonate shelf morphologies (North West Shelf, Australia)

The Rowley Shelf, the southern half of the tropical, carbonate-dominated, North West Shelf of Australia, is covered with linear ridges that can be tracked parallel to the coast over 1100 km between the modern coast and the 140 m isobath. Here, we investigate the origin and nature of these ridges based on the integration of extensive borehole data, high-resolution geophysical data, age dating and compaction analysis.Our investigation reveals that each ridge consists of now-submerged relict coastal deposits that were formed over the last 200,000 years through wave, tidal, fluvial and aeolian processes. These features were dominantly preserved through early diagenesis and illustrate the longest continuous submerged palaeoshorelines reported to date.The distribution of relict coastal features, and therefore early diagenesis, controls the morphology of the continental shelf. First, relict coastal features tend to be stacked on top of each other, resulting in the formation of composite diachronous coastal deposits that form distinctive steps on the seabed, up to 10s m high. Second, relict coastal features form a hard substrate that controls the location of coral reefs along the shelf. Reefs, including a 20-m-thick MIS 3 drowned coral reef described here for the first time, as well as modern reefs of the Muiron Islands, Montebello Islands and Dampier Archipelago, are all developed on top of relict coastal features.The distribution, size and mineralogy of relict coastal features highlight climatic changes along the Rowley Shelf. High relative sea levels (RSL) are associated with low carbonate production and up to 50% of terrigenous grains, while low RSL deposits exhibit increased carbonate production and reduced terrigenous grain content. This asymmetry is interpreted to reflect the onset of the monsoon associated with increased fluvial runoffs during interglacial periods.Lastly, our work shows that compaction analyses are critical for palaeoenvironment and RSL reconstructions. Indeed, the accumulation of 50 m of sediment on a RSL indicator can result in an offset of the measurement by 12.7 m.

Differential impact of two major polychaete guilds on microbial communities in marine sediments: a microcosm study

Even though sediment macrofauna are widespread in the global seafloor, the influence of these fauna on microbial communities that drive sediment biogeochemical cycles remains poorly understood. According to recent field investigations, macrofaunal activities control bacterial and archaeal community structure in surface sediments, but the inferred mechanisms have not been experimentally verified. Here we use laboratory microcosms to investigate how activities of two major polychaete guilds, the lugworms, represented by Abarenicola pacifica, and the clamworms, represented by Nereis vexillosa, influence microbial communities in coastal sediments. A. pacifica treatments show &amp;gt;tenfold increases in microbial cell-specific consumption rates of oxygen and nitrate, largely due to the strong ventilation activity of A. pacifica. While ventilation resulted in clearly elevated percentages of nitrifying archaea (Nitrosopumilus spp.) in surface sediments, it only minorly affected bacterial community composition. By comparison, reworking – mainly by deposit-feeding of A. pacifica – had a more pronounced impact on microorganismal communities, significantly driving down abundances of Bacteria and Archaea. Within the Bacteria, lineages that have been linked to the degradation of microalgal biomass (e.g., Flavobacteriaceae and Rhodobacteraceae), were especially affected, consistent with the previously reported selective feeding of A. pacifica on microalgal detritus. In contrast, N. vexillosa, which is not a deposit feeder, did not significantly influence microbial abundances or microbial community structure. This species also only had a relatively minor impact on rates of oxygen and nitrogen cycling, presumably because porewater exchanges during burrow ventilation by this species were mainly restricted to sediments immediately surrounding the burrows. Collectively our analyses demonstrate that macrofauna with distinct bioturbation modes differ greatly in their impacts on microbial community structure and microbial metabolism in marine sediments.

Characterization of three plastic forms: Plasticoncrete, plastimetal and plastisessiles

Plastic forms, including plastiglomerate, pyroplastic, plasticrusts, anthropoquinas, plastistone and plastitar, were recorded worldwide. These plastic forms derive from geochemical or geophysical interactions such as heat-induced plastic fusion with rock in campfires, incomplete plastic combustion, water motion-driven plastic abrasion in the rocky intertidal zone, plastic deposition in hardened sediments and plastic bonding with tar. Thereby, these interactions can profoundly influence the fate of plastics in the environment. This study characterized three novel plastic forms (plasticoncrete, plastimetal and plastisessiles) discovered on Helgoland island (North Sea). Plasticoncrete consisted of common polyethylene (PE) and polypropylene (PP) fibers hardened in concrete. Plastimetal included PE fibers rusted with metal. Plastisessiles consisted of PE fibers attached to benthic substrates by sessile invertebrates (oysters and polychaetes). Plasticoncrete and plastimetal are the first plastic forms composed of two man-made materials. Plastisessiles show that plastic forms not only result from human- or environment-mediated interactions but also from biological interactions between invertebrates and plastic. All plastic forms (bulk density ≥ 1.4 g/cm3) sunk during floating tests and hardly changed their positions during a 13-day field experiment and 153- to 306-day field monitorings, indicating their local formation, limited mobility and longevity. Still, experimentally detached plastic fibers floated, confirming that the formation of these plastic forms influences the fate of plastic fibers in the environment. Furthermore, the experiment showed that plasticoncrete got deposited in beach sand under wavy and windy conditions, indicating that coastal waves and onshore winds drive plasticoncrete deposition in coastal sediments. We also provide first records of plasticoncrete on Mallorca island (Mediterranean Sea) and plastimetal on Hikoshima island (Sea of Japan), respectively, which show that these plastic forms are no local phenomena. Thereby, our study contributes to the growing fundamental knowledge of plastic forms that is essential to understand the role and fate of these pollutants in coastal habitats worldwide.

Inter-annual sea level change and transgression along a barrier Island coast

On the decadal time scale of coastal planning and management, relative sea-level rise is usually considered a trend or constant rate rather than a dynamic, time varying influence on coastal change. However, the coastal ocean sea level along the east coast of Florida and coastal regions further north is, to a first order, controlled at the interannual and decadal time scale by the dynamics of North Atlantic circulation and Gulf Stream (GS) flow, Every coastal region has its own distinctive annual sea-level cycle, and longer-term intra- and inter-decadal sea-level oscillations. This paper addresses the influence of the strong Florida coastal ocean sea-level signal on topographic evolution of the shoreface, coastal sediment budgets, and potential for coastal transgression at the decadal time scale.

Carbon burial potential of the surface sediment and its associated anthropogenic impacts in the semi-closed area of Bohai Bay

Carbon burial potential in marine sediments plays an important role in global warming. However, they are easily disturbed by human activities in coastal areas. In this study, marine sediment samples were collected from the coastal area of Bohai Bay, and the effects of exogenous inputs on the carbon content and forms were evaluated. Results showed that the carbon content in sediments ranged from 12.45 g/kg to 19.14 g/kg, with an average of 16.23 g/kg ± 2.78 g/kg, and the average organic carbon (C-Org) content is 12.68 ± 1.14 g/kg, which accounts for about 75% of the total carbon storage in sediment. The content of inorganic carbon (CaCO3) did not change significantly, but the content of C-Org in the estuary area was significantly higher than that in other areas. The proportions of active components in C-Org such as light organic carbon (LOC) and neutral organic carbon (NOC) were relatively low, accounting for approximately 9.49% and 18.15% of the total organic carbon, respectively. The spatial distribution characteristics of LOC and NOC were similar to that of C-Org in the study area. This indicates that human activities have increased the content of C-Org and its active components in marine sediments. Although C-Org and its active components are of relatively low abundance, both are easily affected by human activities which increase pollutants associated with the active components of organic carbon in coastal sediments. Therefore, further consideration should be given to reducing the pollutants carried by exogenous inputs, so that cleaner carbon can be buried in the sediments of Bohai Bay.

No evidence of light inhibition on aerobic methanotrophs in coastal sediments using eDNA and eRNA

AbstractIt is estimated that up to half of global methane (CH4) emissions are derived from microbial processes in aquatic ecosystems. However, it is not fully understood which factors explain the spatial and temporal variability of these emissions. For example, light has previously been shown to both inhibit and stimulate aerobic methane‐oxidizing bacteria (i.e., methanotrophs) in the water column. These contrasting results indicate that the mechanisms that light has on CH4 oxidation are not yet clearly known, even less so for benthic aerobic methanotrophs. Here, we tested whether light reaching the seafloor can inhibit methanotrophic activity on the sediment surface. We sampled and distributed over 40 intact sediment cores from two coastal sites (illuminated 10 m, and a dark site at 33 m water depth) into 0, 50, and 100 PAR light treatments. After 10 days, we found no difference between treatments for each site in pore‐water CH4 concentrations, relative abundance of aerobic methanotrophs, or the number of RNA transcripts related to methane oxidation. Our results suggest that light attenuation in coastal waters does not significantly affect aerobic methanotrophs in coastal sediments.

Quantifying microplastics in fjords along the Western Antarctic Peninsula

Microplastics are ubiquitous around the world. Microplastics have been documented around the Southern Ocean, in coastal sediments and in Antarctic marine organisms, however microplastics data for Antarctic waters remain scarce. Microplastics concentrations were characterized from fjord habitats on the Western Antarctic Peninsula where most glaciers are rapidly retreating. Water samples were collected from 2017 to 2020 from surface and benthos, vacuum-filtered, quantified to determine the classification of microplastic, color, and size. Micro-FTIR spectrophotometry was utilized to confirm chemical composition. Comparisons over time and location were made for average microplastic per liter. Despite the new emergent youth and remoteness of these habitats, it was determined that all fjord habitats had microplastics present each year sampled and increased from 2017 to 2020 in each fjord. Despite physical ‘barriers’ such as the Antarctic Circumpolar Current (and particularly its strongest jet, the Polar Front), microplastics are clearly present and increasing in even recent habitats.

A consistent multi-resolution particle method for fluid-driven granular dynamics

Granular dynamics driven by fluid flow is ubiquitous in many industrial and natural processes, such as fluvial and coastal sediment transport. Yet, their complex multiphysics and multi-scale nature challenge numerical models’ accuracy and efficiency. Here, we develop a new multi-resolution mesh-free particle method, based on an enhanced weakly-compressible Moving Particle Semi-implicit (MPS) method, to study the dynamics of rapid fluid-driven granular erosion. We propose and validate a novel multi-resolution multiphase MPS formulation for the consistent and conservative form of the governing equations, including particle stabilization techniques. First, we discuss the numerical accuracy and convergence of the proposed approximation operators through two numerical benchmark cases: the multi-viscosity Poiseuille flow and the multi-density hydrostatic pressure. Then, coupling the developed model with a generalized rheology equation, we investigate the water dam-break waves over movable beds. The particle convergence study confirms that the proposed multi-resolution formulation predicts the analytical solutions with acceptable accuracy and order of convergence. Validating the multiphase granular flow reveals that the mechanical behavior of this fluid-driven problem is highly sensitive to the water-sediment density ratio; the bed with lighter grains experiences extreme erosion and interface deformations. For the bed with a heavier material but different geometrical setups, the surge speed, and the transport layer thickness remain almost identical (away from the gate). Furthermore, while the multi-resolution model accurately estimates the global sediment dynamics, the single-resolution model underestimates the flow evolution. Overall, the qualitative and quantitative analysis of results emphasizes the importance of multi-scale multi-density interactions in fluid-driven modeling.

Temporal and Spatial Trends in Benthic Infauna and Potential Drivers, in a Highly Tidal Estuary in Atlantic Canada

Infaunal invertebrate communities of coastal marine sediments are often impacted by human activities, particularly in harbours and estuaries. However, while many studies have attempted to identify the key factors affecting benthic infauna, few have done so for highly energetic tidal estuaries. Samples were collected over a decade (2011–2020) from a series of reference sites in Saint John Harbour (45.25° N, 66.05° W), a highly tidal estuary in the Bay of Fundy, Canada. These data were used to examine spatial and temporal trends in infaunal invertebrate communities and sediment properties and to determine the extent to which the biological patterns were driven by measured physical and chemical variables. There were substantial differences among sites in infaunal invertebrate abundance (median ranging from 688 to 13,700 individuals per square meter), infaunal species richness (median ranging from 8 to 22), and Shannon diversity (median ranging from 1.26 to 2.34); multivariate analysis also revealed variation in species composition among sites. Sediment contaminant concentrations also varied among sites, but differences tended to be smaller (e.g. median chromium concentrations ranging from 21.6 to 27.6 mg/kg). Sample contaminant concentrations were all below probable effect levels, and almost all below threshold effect levels (Canadian interim sediment quality guidelines), but relationships with biological data were still detectable. However, physical variables (depth, sediment characteristics) were better predictors of biological variables and community composition. These results confirm the importance of physical factors in shaping infaunal communities in soft-sediment habitats in tidally influenced coastal waters.

Microbial Dimethylsulfoniopropionate Cycling in Deep Sediment of the Mariana Trench.

Dimethylsulfoniopropionate (DMSP) and related organic sulfur compounds play key roles in global sulfur cycling. Bacteria have been found to be important DMSP producers in seawater and surface sediments of the aphotic Mariana Trench (MT). However, detailed bacterial DMSP cycling in the Mariana Trench subseafloor remains largely unknown. Here, the bacterial DMSP-cycling potential in a Mariana Trench sediment core (7.5 m in length) obtained at a 10,816-m water depth was investigated using culture-dependent and -independent methods. The DMSP content fluctuated along the sediment depth and reached the highest concentration at 15 to 18 cm below the seafloor (cmbsf). dsyB was the dominant known DMSP synthetic gene, existing in 0.36 to 1.19% of the bacteria, and was identified in the metagenome-assembled genomes (MAGs) of previously unknown bacterial DMSP synthetic groups such as Acidimicrobiia, Phycisphaerae, and Hydrogenedentia. dddP, dmdA, and dddX were the major DMSP catabolic genes. The DMSP catabolic activities of DddP and DddX retrieved from Anaerolineales MAGs were confirmed by heterologous expression, indicating that such anaerobic bacteria might participate in DMSP catabolism. Moreover, genes involved in methanethiol (MeSH) production from methylmercaptopropionate (MMPA) and dimethyl sulfide (DMS), MeSH oxidation, and DMS production were highly abundant, suggesting active conversions between different organic sulfur compounds. Finally, most culturable DMSP synthetic and catabolic isolates possessed no known DMSP synthetic and catabolic genes, and actinomycetes could be important groups involved in both DMSP synthesis and catabolism in Mariana Trench sediment. This study extends the current understanding of DMSP cycling in Mariana Trench sediment and highlights the need to uncover novel DMSP metabolic genes/pathways in extreme environments. IMPORTANCE Dimethylsulfoniopropionate (DMSP) is an abundant organosulfur molecule in the ocean and is the precursor for the climate-active volatile gas dimethyl sulfide. Previous studies focused mainly on bacterial DMSP cycling in seawater, coastal sediment, and surface trench sediment samples, but DMSP metabolism in the Mariana Trench (MT) subseafloor sediments remains unknown. Here, we describe the DMSP content and metabolic bacterial groups in the subseafloor of the MT sediment. We found that the tendency for vertical variation of the DMSP content in the MT was distinct from that of the continent shelf sediment. Although dsyB and dddP were the dominant DMSP synthetic and catabolic genes in the MT sediment, respectively, both metagenomic and culture methods revealed multiple previously unknown DMSP metabolic bacterial groups, especially anaerobic bacteria and actinomycetes. The active conversion of DMSP, DMS, and methanethiol may also occur in the MT sediments. These results provide novel insights for understanding DMSP cycling in the MT.

Influence of El Niño on the variability of global shoreline position

Coastal zones are fragile and complex dynamical systems that are increasingly under threat from the combined effects of anthropogenic pressure and climate change. Using global satellite derived shoreline positions from 1993 to 2019 and a variety of reanalysis products, here we show that shorelines are under the influence of three main drivers: sea-level, ocean waves and river discharge. While sea level directly affects coastal mobility, waves affect both erosion/accretion and total water levels, and rivers affect coastal sediment budgets and salinity-induced water levels. By deriving a conceptual global model that accounts for the influence of dominant modes of climate variability on these drivers, we show that interannual shoreline changes are largely driven by different ENSO regimes and their complex inter-basin teleconnections. Our results provide a new framework for understanding and predicting climate-induced coastal hazards.

Spatial distribution of trace elements in coastal sediments of Ha Tinh province, Vietnam

Sediment compositions and trace element (Cu, Pb, Zn, Cr, Fe, Mn, As, and Hg) concentrations were analyzed to assess the sediment quality and the factors affecting the trace elements’ concentration in Ha Tinh province’s coastal sediments. Results revealed that the concentration of trace elements in the coastal sediments was generally lower than in other coastal areas in Vietnam. The significantly positive correlation of the fine sediment composition with Cu, Pb, Zn, Cr, and Fe indicated that the silt and clay sediments could absorb these trace elements. The highly positive correlation among Cu, Pb, Zn, Cr, and Fe suggested that the trace elements likely originated from similar sources. The sediment quality assessment showed that trace element concentrations were lower than the limited values in the sediment quality guideline (QCVN 43:2017/BTNMT). According to the Igeo index, the sediments were not polluted by Cu, Pb, Zn, Cr, Fe, and As but were likely polluted by Hg and Mn in some sampling sites. Therefore, it is necessary to invest the future studies to assess the Hg and Mn concentration levels in these sites to protect the marine environment.

When microplastics are not plastic: Chemical characterization of environmental microfibers using stimulated Raman microspectroscopy

The abundance of anthropogenic debris dispersed in the environment is exponentially growing, raising concerns about marine life and human exposure to microplastics. Microfibers are the most abundant microplastic type in the environment. However, recent research suggests that most microfibers dispersed in the environment are not made of synthetic polymers. In this work, we systematically tested this assumption by determining the man-made or natural origin of microfibers found in different environments, including surface waters, sediments at depths >5000 m and highly sensitive habitats like mangroves and seagrass, and treated water using stimulated Raman scattering (SRS) microscopy. Our findings show that ¾th of analyzed microfibers are of natural origin. One plastic fiber is estimated per every 50 L in surface seawater, every 5 L in desalinated drinking water, every 3 g in deep sea sediments and every 27 g in coastal sediments. Synthetic fibers were significantly larger in surface seawaters compared to organic fibers due to higher resistance to solar radiation. These results emphasize the necessity of using spectroscopical methods to assess the origin of environmental microfibers to accurately estimate the abundance of synthetic materials in the environment.

Textural Characteristics of Coastal Sediments Between Bhavanapadu and Baruva Villages in Srikakulam District, East Coast of India

The texture of a rock or sediment is the size, shape, and arrangement of the grains. The microgeometry of sediments deals with intergranular relationship of grains, their size and shape. In the present study, a total of sixty surficial sediment samples were collected from the study area (foreshore-20, berm-7, backshore-13, and dunes-20) with an interval of 1 km. The geology, geomorphology, drainage pattern, climate, waves, and currents are discussed. The grain size parameters viz., mean grain size, standard deviation, skewness, and kurtosis are discussed extensively. Sand is the predominant component in all the sediment samples (99.82–99.93%) whereas silt and clay contents are less than 1% from the four environments. The mean grain size of the sediment samples shows that medium grained sands are followed by fine grained sands indicating a low energy environment of deposition. The standard deviation values reveal that the sediments are well to moderately sorted. The average values of skewness indicate that all the sediment samples are negatively skewed to positively skewed representing an environment of deposition of low to moderate energy conditions. Most of the kurtosis values indicate that the sediments are of platykurtic to leptokurtic in nature. The platykurtic nature of sediments indicates the sorting of tail portions of sediment populations.

Coastal response to global warming during the Paleocene-Eocene Thermal Maximum

Global warming during the Paleocene-Eocene Thermal Maximum (PETM) is hypothesized to have had a profound effect on the paleohydrologic cycle, including enhanced seasonality and increased water and sediment discharge. Although the PETM may represent the closest geologic analog for future global climate changes, the effects of this event on ancient coastal systems are poorly understood. We examined drill core from two locations in eastern Texas that preserve a record of tidally influenced deltaic sedimentation associated with the paleo-Colorado River that drained up to 2 × 106 km2 of central North America, approximately two-thirds of the area of the modern Mississippi River catchment. In these cores, the development of a regionally extensive sand-rich unit (the Carrizo Formation) at the onset of the PETM is identified from a negative carbon isotope excursion and supported by detrital zircon UPb geochronology and pollen occurrence data. The basal Carrizo Formation indicates that the onset of the PETM was characterized by an increase in the delivery of coarser-grained sediments and progradation of the coastline, which occurred despite rising sea level. Using a mass-balance framework for equilibrium deltaic systems, we estimate that sediment delivery to the coastline increased by ca. 46% (2-σ: 13% to 167%). Our findings of enhanced sediment delivery to the coast are consistent with proxy climatic and sedimentologic data indicating heightened precipitation seasonality in the interior of North America during the PETM. Thus, the effects of a regional change in climate forced by greenhouse events were transmitted downstream by large river systems to produce shifts in coastal sediment supply, progradation, and coastline evolution.

Microorganisms in coastal wetland sediments: a review on microbial community structure, functional gene, and environmental potential.

Coastal wetlands (CW) are the junction of the terrestrial and marine ecosystems and have special ecological compositions and functions, which are important for maintaining biogeochemical cycles. Microorganisms inhabiting in sediments play key roles in the material cycle of CW. Due to the variable environment of CW and the fact that most CW are affected by human activities and climate change, CW are severely degraded. In-depth understanding of the community structure, function, and environmental potential of microorganisms in CW sediments is essential for wetland restoration and function enhancement. Therefore, this paper summarizes microbial community structure and its influencing factors, discusses the change patterns of microbial functional genes, reveals the potential environmental functions of microorganisms, and further proposes future prospects about CW studies. These results provide some important references for promoting the application of microorganisms in material cycling and pollution remediation of CW.

Microplastic paint particle production for spiking experiments; silicone rubber as application material provide high yield with low effort

Paint particles are a highly-important but as-yet overlooked type of microplastic commonly found in coastal sediment, although research interest is growing. There is a need for paint particles as laboratory standards for spiking experiments, however, given paint is generally only available for purchase in liquid form, a new method is needed to reliable produce laboratory-grade paint particles. The main distinguishing issue with paint particle production (as opposed to other microplastic production) is the paint must be applied to a surface in layers before then being decoupled to be processed into particles. Since paints, and especially primers, are designed specifically to strongly adhere to surfaces, using the right application material is highly important. This study tests the time and material efficiency of 2 different application materials; laboratory wax film (i.e. Parafilm®) and silicone rubber sheets (i.e. silicone baking sheets). Silicone rubber was on average 36 × more time-efficient than laboratory wax and was also 8 × more material-efficient (8 × more paint particles were produce per liquid paint used). Indeed, silicone rubber provided an essentially-perfect decoupling process, as the paint could be easily peeled away in a solid and complete layer. As such, for the future production of paint particles for laboratory purposes, silicone rubber is highly recommended as an application material.