Bioturbation transports secondary microplastics to deeper layers in soft marine sediments of the northern Baltic Sea

Microplastics (MPs) are observed to be present on the seafloor ranging from coastal areas to deep seas. Because bioturbation alters the distribution of natural particles on inhabited soft bottoms, a mesocosm experiment with common benthic invertebrates was conducted to study their effect on the distribution of secondary MPs (different-sized pieces of fishing line < 1 mm). During the study period of three weeks, the benthic community increased MP concentration in the depth of 1.7–5.1 cm in the sediment. The experiment revealed a clear vertical gradient in MP distribution with their abundance being highest in the uppermost parts of the sediment and decreasing with depth. The Baltic clam Macoma balthica was the only study animal that ingested MPs. This study highlights the need to further examine the vertical distribution of MPs in natural sediments to reliably assess their abundance on the seafloor as well as their potential impacts on benthic communities.

Pinja Näkki, Outi Setälä, Maiju Lehtiniemi, Marine Pollution Bulletin, Available online 25 April 2017, In Press

The article

A review of analytical techniques for quantifying microplastics in sediments

In this review the analytical techniques for measuring microplastics in sediment have been evaluated. Four primary areas of the analytical process have been identified that include (1) sampling, (2) extraction, (3) quantitation and (4) quality assurance/quality control (QAQC). Each of those sections have their own subject specific challenges and require further method development and harmonisation. The most common approach to extracting microplastics from sediments is density separation. Following extraction, visual counting with an optical microscope is the most common technique for quantifying microplastics; a technique that is labour intensive and prone to human error. Spectroscopy (FTIR; Raman) are the most commonly applied techniques for identifying polymers collected through visual sorting. Improvements and harmonisation on size fractions, sampling approaches, extraction protocols and units for reporting plastic abundance would aid comparison of data generated by different research teams. Further, we advocate the development of strong QAQC procedures to be adopted like other fields of analytical chemistry. Finally, inter-laboratory proficiency testing is recommended to give an indication of the variation and reliability in measurements reported in the scientific literature that may be under- or overestimations of environmental burdens.

Joanne S. Hanvey, Phoebe J. Lewis, Jennifer L. Lavers, Nicholas D. Crosbie, Karla Pozo and Bradley O. Clarke, Analytical Methods, 2017, 9, 1369-1383

The article

Microplastics in sediments of the Changjiang Estuary, China

Microplastics are plastics that measure less than 5 mm in diameter. They enter the marine environment as primary sources directly from industrial uses, as well as secondary sources resulting from the degradation of large plastic debris. To improve the knowledge of microplastic pollution in China, we investigated samples from 53 estuarine sediment locations collected with a box corer within the Changjiang Estuary. Microplastics (<5 mm) were extracted from sediments by density separation, after which they were observed under a microscope and categorized according to shape, color and size. Identification was carried out using Micro-Fourier-Transform Infrared Spectroscopy (μ-FT-IR).

The abundance of microplastics in the Changjiang Estuary was mapped. The mean concentration was 121 ± 9 items per kg of dry weight, varying from 20 to 340 items per kg of dry weight. It was found that the concentration of microplastics was the highest on the southeast coast of Shanghai. The distribution pattern of microplastics may be affected by the Changjiang diluted water in summer. All of the microplastics collected were categorized according to shape, color and size. Among which fiber (93%), transparent (42%) and small microplastics (<1 mm) (58%) were the most abundant types. No clear correlation between microplastics and the finer sediment fraction was found. Rayon, polyester, and acrylic were the most abundant types of microplastics identified, indicating that the main source of microplastics in the Changjiang Estuary was from washing clothes (the primary source). It is possible to compare microplastic abundance in this study with the results of other related studies using the same quantification method. The identification of microplastics raises the awareness of microplastic pollution from drainage systems. The prevalence of microplastic pollution calls for monitoring microplastics at a national scale on a regular basis.

Guyu Peng, Bangshang Zhu, Dongqi Yang, Lei Su, Huahong Shi, Daoji Li, Environmental Pollution, Volume 225, June 2017, Pages 283–290

The article

Plastic litter in sediments from the coasts of south Tuscany (Tyrrhenian Sea)

This study estimated the total loads of plastic litter (macro-meso- and micro-plastics) in sediments from a wide stretch of marine and coastal environment of Tyrrhenian Sea. The prevailing category of debris was microplastic. The results obtained, in terms of average amount of microplastic per kilogram of dry sediment, are in agreement with data reported by various Authors internationally. The study area resulted to be uniform for plastic items levels. Particularly evident was the influence of a flood, occurred in November 2012 in Talamone, on sediments collected at the harbour of this locality: in this area, a difference in levels and quality of plastic debris, attributable to periods before and after the flood, was observed in sediments. In addition to focusing on the effect of this phenomenon, this study gives an important overview, for what concerns the presence of plastic litter, of a significant naturalistic area.

Susanna Cannas, Paolo Fastelli, Cristiana Guerranti, Monia Renzi, Marine Pollution Bulletin, Available online 12 April 2017, In Press

The article

Sources and fate of microplastics in marine and beach sediments of the Southern Baltic Sea-a preliminary study

Microplastics’ (particles size ≤5 mm) sources and fate in marine bottom and beach sediments of the brackish are strongly polluted Baltic Sea have been investigated. Microplastics were extracted using sodium chloride (1.2 g cm−3). Their qualitative identification was conducted using micro-Fourier-transform infrared spectroscopy (μFT-IR). Concentration of microplastics varied from 25 particles kg−1 d.w. at the open sea beach to 53 particles kg−1 d.w. at beaches of strongly urbanized bay. In bottom sediments, microplastics concentration was visibly lower compared to beach sediments (0–27 particles kg−1 d.w.) and decreased from the shore to the open, deep-sea regions. The most frequent microplastics dimensions ranged from 0.1 to 2.0 mm, and transparent fibers were predominant. Polyester, which is a popular fabrics component, was the most common type of microplastic in both marine bottom (50%) and beach sediments (27%). Additionally, poly(vinyl acetate) used in shipbuilding as well as poly(ethylene-propylene) used for packaging were numerous in marine bottom (25% of all polymers) and beach sediments (18% of all polymers). Polymer density seems to be an important factor influencing microplastics circulation. Low density plastic debris probably recirculates between beach sediments and seawater in a greater extent than higher density debris. Therefore, their deposition is potentially limited and physical degradation is favored. Consequently, low density microplastics concentration may be underestimated using current methods due to too small size of the debris. This influences also the findings of qualitative research of microplastics which provide the basis for conclusions about the sources of microplastics in the marine environment.

Bożena Graca, Karolina Szewc, Danuta Zakrzewska, Anna Dołęga, Magdalena Szczerbowska-Boruchowska, Environ Sci Pollut Res (2017) 24: 7650

The article

Influence of environmental and anthropogenic factors on the composition, concentration and spatial distribution of microplastics: A case study of the Bay of Brest (Brittany, France)

The concentration and spatial distribution of microplastics in the Bay of Brest (Brittany, France) was investigated in two surveys. Surface water and sediment were sampled at nine locations in areas characterized by contrasting anthropic pressures, riverine influences or water mixing. Microplastics were categorized by their polymer type and size class. Microplastic contamination in surface water and sediment was dominated by polyethylene fragments (PE, 53–67%) followed by polypropylene (PP, 16–30%) and polystyrene (PS, 16–17%) microparticles. The presence of buoyant microplastics (PE, PP and PS) in sediment suggests the existence of physical and/or biological processes leading to vertical transfer of lightweight microplastics in the bay. In sediment (upper 5 cm), the percentage of particles identified by Raman micro-spectroscopy was lower (41%) than in surface water (79%) and may explain the apparent low concentration observed in this matrix (0.97 ± 2.08 MP kg−1 dry sediment). Mean microplastic concentration was 0.24 ± 0.35 MP m−3 in surface water. We suggest that the observed spatial MP distribution is related to proximity to urbanized areas and to hydrodynamics in the bay. A particle dispersal model was used to study the influence of hydrodynamics on surface microplastic distribution. The outputs of the model showed the presence of a transitional convergence zone in the centre of the bay during flood tide, where floating debris coming from the northern and southern parts of the bay tends to accumulate before being expelled from the bay. Further modelling work and observations integrating (i) the complex vertical motion of microplastics, and (ii) their point sources is required to better understand the fate of microplastics in such a complex coastal ecosystem.

L. Frère, I. Paul-Pont, E. Rinnert, S. Petton, J. Jaffré, I. Bihannic, P. Soudant, C. Lambert, A. Huvet, Environmental Pollution, Volume 225, June 2017, Pages 211–222

The article

Who cares about dirty beaches? Evaluating environmental awareness and action on coastal litter in Chile

Coastal litter is a source of environmental, economic and health-related problems in many parts of the world, but local responses are not necessarily related to the severity of the impacts. In particular, it is unclear how environmental perception of community members and government bodies relate to active engagement on coastal pollution. The present study analyses the coastal litter situation and evaluates the willingness of citizens to engage at four sites (three regions of mainland Chile, and Easter Island; henceforth Rapa Nui) that feature differences in culture, economy sectors and landscape characteristics. Data on coastal litter were obtained from citizen science campaigns and assessments of large litter accumulations on beaches and rocky shores. The willingness to engage was evaluated qualitatively, considering municipal planning documents and the perception of residents on coastal litter and general waste management. We found very large quantities of litter in northern Chile, posing a hazard to marine wildlife and human health, and moderate quantities in the other regions. The region with the most severe case of coastal pollution does not feature the highest engagement, possibly a result of underlying factors such as an unsustainable economy and few possibilities for the population to connect with the natural environment. On mainland Chile, municipal engagement is low to moderate while on Rapa Nui there exist integrated waste-management strategies that address coastal pollution. Inhabitants of Rapa Nui seem to have a better conduct in the coastal environment (picking up litter, littering less), and show more engagement in waste-reduction strategies (recycling, volunteering for beach clean-ups). We suggest that the unique cultural history of the island, a landscape that allows meaningful interaction with nature and an economy based on sustainable tourism and high international visibility facilitates engagement on environmental issues. We advise managers to consider respective underlying variables, to create environments that allow contact with nature (e.g. public access to parks), and to encourage bottom-up initiatives, preferably by local actors (e.g. by promoting already engaged individuals or organisations).

Tim Kiessling, Sonia Salas, Konar Mutafoglu, Martin Thiel, Ocean & Coastal Management, Volume 137, 1 March 2017, Pages 82–95

The article