Do beachrocks affect microplastic deposition on the strandline of sandy beaches?

The strandline is one of the first deposition habitats of microplastics before they are integrated to the beach as a standing stock or finally removed. Beaches, entirely or partially protected by beachrocks, have different sediment dynamics and therefore may present variation in microplastic deposition. The aim of this work was to test if protected and unprotected (i.e., exposed to waves) areas of a sandy beach present different microplastic accumulation on the strandline – a habitat greatly influenced by both water and sediment dynamics. Microplastic (MP) amounts were significantly higher at the protected area (Mprotected = 642.6 ± 514.8 MP m−2, Mexposed = 130.6 ± 126.8 MP m−2, Mann-Whitney U test, U = 14.5, p = 0.0009), showing that beachrocks influence microplastic accumulation on the beach face. Therefore, hard structures parallel to the beach may also affect microplastics deposition on beach sediments, being important to consider these structures on microplastic surveys.

L. M. Pinheiro, R. C.P. Monteiro, J. A. Ivar do Sul and al., Marine Pollution Bulletin, Volume 141, April 2019, Pages 569-572

The article

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Consistent microplastic ingestion by deep-sea invertebrates over the last four decades (1976–2015), a study from the North East Atlantic

Although evidence suggests the ubiquity of microplastics in the marine environment, our knowledge of its occurrence within remote habitats, such as the deep sea, is scarce. Furthermore, long term investigations of microplastic abundances are even more limited. Here we present a long-term study of the ingestion of microplastics by two deep-sea benthic invertebrates (Ophiomusium lymani and Hymenaster pellucidus) sampled over four decades. Specimens were collected between the years 1976–2015 from a repeat monitoring site >2000 m deep in the Rockall Trough, North East Atlantic. Microplastics were identified at a relatively consistent level throughout and therefore may have been present at this locality prior to 1976. Considering the mass production of plastics began in the 1940s – 50s our data suggest the relatively rapid occurrence of microplastics within the deep sea. Of the individuals examined (n = 153), 45% had ingested microplastics, of which fibres were most prevalent (95%). A total of eight different polymer types were isolated; polyamide and polyester were found in the highest concentrations and in the majority of years, while low-density polystyrene was only identified in 2015. This study provides an assessment of the historic occurrence of microplastics on the deep seafloor and presents a detailed quantification and characterisation of microplastics ingested by benthic species. Furthermore these data advance our knowledge on the long-term fate of microplastic in marine systems.

W. Courtene-Jones, B. Quinn, C. Ewins and al., Environmental Pollution, Volume 244, January 2019, Pages 503-512

The article

Dispersion, Accumulation, and the Ultimate Fate of Microplastics in Deep-Marine Environments: A Review and Future Directions

An estimated 8.3 billion tonnes of non-biodegradable plastic has been produced over the last 65 years. Much of this is not recycled or disposed of ‘properly’, has a long environmental residence time and accumulates in sedimentary systems worldwide, posing a threat to important ecosystems and potentially human health. We synthesise existing knowledge of seafloor microplastic distribution, and integrate this with process-based sedimentological models of particle transport, to provide new insights, and critically, to identify future research challenges. Compilation of published data shows that microplastics pervade the global seafloor, from abyssal plains to submarine canyons and deep-sea trenches. However, few studies relate microplastic accumulation to sediment transport and deposition. Microplastics may enter directly into the sea as marine litter from shipping and fishing, or indirectly via fluvial and aeolian systems from terrestrial environments. The nature of the entry-point is critical to how terrestrially-sourced microplastics are transferred to offshore sedimentary systems. We present models for physiographic shelf connection types related to the tectono-sedimentary regime of the margin. Beyond the shelf, the principal agents for microplastic transport are: i) gravity-driven transport in sediment-laden flows; ii) settling, or conveyance through biological processes, of material that was formerly floating on the surface or suspended in the water column; iii) transport by thermohaline currents, either during settling or by reworking of deposited microplastics. We compare microplastic settling velocities to natural sediments to understand how appropriate existing sediment transport models are for explaining microplastic dispersal. Based on this analysis, and the relatively well-known behaviour or deep-marine flow types, we explore the expected distribution of microplastic particles, both in individual sedimentary event deposits and within deep-marine depositional systems. Residence time within certain deposit types and depositional environments is anticipated to be variable, which has implications for the likelihood of ingestion and incorporation into the food chain, further transport, or deeper burial. We conclude that integration of process-based sedimentological and stratigraphic knowledge with insights from modern sedimentary systems, and biological activity within them, will provide essential constraints on the transfer of microplastics to deep-marine environments, their distribution and ultimate fate, and the implications that these have for benthic ecosystems.

Kane I. A., Clare M. A., Front. Earth Sci., 30 April 2019

The article

Qualitative and quantitative assessment of microplastics in three sandy Mediterranean beaches, including different methodological approaches

Microplastics are small plastic particles (<5 mm) that are found in most marine habitats around the world. Currently, several studies are trying to determine their exact effects. Microplastics can be introduced into the marine ecosystem directly as manufactured microplastics, or indirectly through the decomposition of larger plastic particles. They can enter the food chain, and can be found as vectors for the movement of microbial communities and chemical pollutants. In our study, two different ways of measuring microplastics were tested at three Mediterranean beaches, each subject to different types of human pressure. The purpose of the study was to compare different sampling approaches for assessing the microplastics present in sediment, taking into account temporal variability across the summer and winter seasons. Statistically significant differences were found between the beaches, which reflect the distinct uses made of each of them. At the same time, significant differences were found in the contents of microplastics, which were due to seasonal variability. Our analysis showed that microplastics can be found in deeper sediment layers with different concentrations to that of the surface layer. Therefore sampling methods that do not sample the same sediment layer do not seem to produce comparable results. In addition, classic categorizations of microplastics (as microfibers, membranes, etc.) may not always be sufficient. Rather, a classification based on microplastic properties, the specificities of each region and each study’s objectives is recommended.

Odysseas Piperagkas, Nafsika Papageorgiou, Ioannis Karakassis, Estuarine, Coastal and Shelf Science, Volume 219, 5 April 2019, Pages 169-175

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Experimental analysis of microplastics in beach sediment samples by density separation and microscopic examination

This thesis mainly deals with microplastics, its sources and experimental approach to investigate the presence of microplastics in environment. Microplastics are threat to environment in recent years. Its adverse effect is directed towards aquatic animals. This thesis will provide the information about the sources of microplastics and how it ends up to the marine environment. The main objectives of this thesis project are to review the methods to analyze microplastics, develop methods to collect microplastic samples from local terrestrial environment and the procedure to analyze them in Arcada’s laboratory. Sediment samples collected from 4 different locations were examined using microscopic analysis. Two different methods were employed to analyze collected sediments samples. Sodium chloride was used as a density separator to extract microplastics from sample. Results obtained from microscopic analysis showed the presence of colored microplastics and fibers in all the collected sediment samples.

Sharma, Ritesh (2019), Degree thesis

Beached microplastics in the Northwestern Mediterranean Sea

Microplastics are small (<5 mm) fragments of plastic debris that are ubiquitous in coastal areas and in open ocean. We have investigated the occurrence and composition of microplastics in beach sediments from the micro-tidal Northwestern Mediterranean Sea. Samples were collected on two beaches (northern and southern site) of the western Gulf of Lion showing markedly different characteristics. Sampling was performed along depositional lower, mid and upper beaches and repeated after 1 month. Concentrations of microplastics in the northern and southern site were highly variable, ranging from 33 to 798 and from 12 to 187 microplastics per kg of dry sediment, respectively. Highest concentrations were found at three specific locations: nearby a local river mouth, within an accretionary area and in a depositional upper beach. The spatial and temporal distribution of beached microplastics seems to be directly dependent on external forcing such as wind, swell, precipitation, outflow and river mouth proximity.

Constant M., Kerhervé P., Mino-Vercellio-Verollet M. and al., Marine Pollution Bulletin, Volume 142, May 2019, Pages 263-273

The article

Abundance, characteristics and surface degradation features of microplastics in beach sediments of five coastal areas in Tamil Nadu, India

This study undertook to investigate the occurrence of microplastics (MPs) in the high and low-tide sediments of five coastal areas in Tamil Nadu, India. The abundance of microplastics vary from 439 ± 172 to 119 ± 72 (HTL) and 179 ± 68 to 33 ± 30 (LTL) items kg−1 of sediments. The MP polymers found in the study sites are Polyethylene (73.2%), polypropylene (13.8%), nylon (8.2%), polystyrene (2.8%) and polyester (2%). The weathered surfaces might act as high-capacity carriers and this was confirmed by SEM-EDAX. The results of an analysis of the textures of the sediments do not ascribe any influence on microplastic abundance. The recreation, religious and fishing activities are the major contributors to plastic pollution in these beaches, which is borne out by the high abundance of MPs in the study sites. A regular and permanent waste management system should be put in place for the protection of beaches.

Sathish N., Jeyasanta K. I., Patterson J., Marine Pollution Bulletin, Volume 142, May 2019, Pages 112-118

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