For seventy years, mass plastic production and waste mismanagement have resulted in huge pollution of the environment, including the marine environment. The first mention of seafood contaminated by microplastics was recorded in the seventies, and to date numerous studies have been carried out on shellfish, fish and crustaceans. Based on an ad hoc corpus, the current review aims to report on the numerous practices and methodologies described so far. By examining multiple aspects including problems related to the definition of the term microplastic, contamination at the laboratory scale, sampling and isolation, and quantification and identification, the aim was to point out current limitations and the needs to improve and harmonise practices for future studies on microplastics in seafood. A final part is devoted to the minimum information for publication of microplastics studies (MIMS). Based on the aspects discussed, MIMS act as a starting point for harmonisation of analyses.
Pollution and Marine Debris
Much marine litter comes from land-based sources, with a significant amount coming from activities on bathing beaches. Thus, the overall focus of this exploratory research is to identify elements important for the design of beach infrastructure (i.e., trash cans (TCs)) to reduce littering behaviors. We base our investigation on principles of a relatively new approach, called Design for Sustainable Behavior. In doing so, we consider design for two user groups: bathing beachgoers and beach managers. We examined these users' perceptions of beach TCs through the use of an on-line survey of beachgoers, in-depth interviews with Israeli beach managers, a survey of international Blue Flag beach managers and a design ‘ideation’ workshop. Most importantly, we found that there is interest on the part of beach managers and other stakeholders in applying design principles to improve TCs. The findings of this study have implications for further interdisciplinary – and multidisciplinary – research on this topic.
Microplastics are widespread contaminants, virtually present in all environmental compartments. However, knowledge on sources, fate and environmental concentration over time and space still is limited due to the laborious and varied analytical procedures currently used. In this work we critically review the methods currently used for sampling and detection of microplastics, identifying flaws in study design and suggesting promising alternatives. This work provides insights on bulk sample collection, separation, digestion, identification and quantification, and mitigation of cross-contamination. The sampling of microplastics will improve in representativeness and reproducibility through the determination of bulk sample volume, filter's pore size, density separation and digestion solutions, but also through use of novel methods, such as the enhancement of visual identification by staining dyes, and the generalized use of chemical characterization.
Types of plastic waste in different aquatic environments were assessed to obtain a global framework of plastic waste transport and accumulation, relevant for plastic pollution mitigation strategies in aquatic environments. Packaging and consumer products were the most encountered product categories in rivers, while fishery items dominated in the oceanic environment. Plastics from electronics, building and construction, and transport were barely observed. For polymers, polyethylene and polypropylene contributed most to pollution in all environments. The highest diversity in polymer composition was found in oceanic and freshwater sediments. It is therefore argued that a large fraction of plastic waste accumulates here. This confirms that plastic waste transport and accumulation patterns were most affected by the density, surface area, and size of plastics. Only thick-walled, larger plastic debris from low-density polymers are transported through currents from rivers to ocean, while the larger fraction of plastic litter is likely retained in sediments or beaches.
Global estimations state that between 0.5 and 12.7 million metric tons of plastic enter the oceans each year. They are, however, associated with great uncertainties due to methodological difficulties to accurately quantify land-based plastic fluxes into the oceans. New studies at basin scale are thus needed for better model calibrations. Here, a modeling approach based on Jambeck’s statistical method and a field approach are compared in order to (i) quantify plastic fluxes in the Seine River and (ii) characterize and constrain uncertainties of both approaches. Despite the simplicity of the statistical approach and rough extrapolations, both methods yield similar results, i.e., between 1,100 and 5,900 t/yr of plastic litter flowing into the Sea of which about 88–128 t/yr are removed by cleaning operations. According to the marine strategy framework directive (2008/56/EC), actions are required to quantify plastic fluxes entering the oceans. Among different methods, a better use of the data from the waste collection should be considered. The development of a national and homogenous platform listing all the collects would be a first step in that direction.
We performed an environmental risk assessment for microplastics (<5 mm) in the marine environment by estimating the order of magnitude of the past, present and future concentrations based on global plastic production data. In 2100, from 9.6 to 48.8 particles m−3 are predicted to float around in the ocean, which is a 50-fold increase compared to the present-day concentrations. From a meta-analysis with effect data available in literature, we derived a safe concentration of 6650 buoyant particles m−3 below which adverse effects are not likely to occur. Our risk assessment (excluding the potential role of microplastics as chemical vectors) suggests that on average, no direct effects of free-floating microplastics in the marine environment are to be expected up to the year 2100. Yet, even today, the safe concentration can be exceeded in sites that are heavily polluted with buoyant microplastics. In the marine benthic compartment between 32 and 144 particles kg−1 dry sediment are predicted to be present in the beach deposition zone. Despite the scarcity of effect data, we expect adverse ecological effects along the coast as of the second half of the 21st century. From then ambient concentrations will start to outrange the safe concentration of sedimented microplastics (i.e. 540 particles kg−1sediment). Additional ecotoxicological research in which marine species are chronically exposed to realistic environmental microplastic concentration series are urgently needed to verify our findings.
Pollution of the world's oceans by marine debris has direct consequences for wildlife, with fragments of plastic <10 mm the most abundant buoyant litter in the ocean. Seabirds are susceptible to debris ingestion, commonly mistaking floating plastics for food. Studies have shown that half of petrel species regularly ingest anthropogenic waste. Despite the regularity of debris ingestion, no studies to date have quantified the dimensions of debris items ingested across petrel species ranging in size. We excised and measured 1694 rigid anthropogenic debris items from 348 petrel carcasses of 20 species. We found that although the size of items ingested by petrels scale positively with the size of the bird, 90% of all debris items ingested across species fall within a narrow “danger zone” range of 2–10 mm, overlapping with the most abundant oceanic debris size. We conclude that this globally profuse size range of marine plastics is an ingestion hazard to petrels.
Deep sea sediments have emerged as a potential sink for microplastics in the marine environment. The discovery of microplastics in various environmental compartments of the Arctic Central Basin (ACB) suggested that these contaminants were potentially being transported to the deep-sea realm of this oceanic basin. For the first time, the present study conducted a preliminary assessment to determine whether microplastics were present in surficial sediments from the ACB. Gravity and piston corers were used to retrieve sediments from depths of 855–4353 m at 11 sites in the ACB during the Arctic Ocean 2016 (AO16) expedition. Surficial sediments from the various cores were subjected to density flotation with sodium tungstate dihydrate solution (Na 2 WO 4 ·2H 2 O, density 1.4 g cm −3 ). Potential microplastics were isolated and analysed by Fourier Transform Infrared (FT-IR) spectroscopy. Of the surficial samples, 7 of the 11 samples contained synthetic polymers which included polyester (n = 3), polystyrene (n = 2), polyacrylonitrile (n = 1), polypropylene (n = 1), polyvinyl chloride (n = 1) and polyamide (n = 1). Fibres (n = 5) and fragments (n = 4) were recorded in the samples. In order to avoid mis-interpretation, these findings must be taken in the context that (i) sampling equipment did not guarantee retrieval of undisturbed surficial sediments, (ii) low sample volumes were analysed (~10 g per site), (iii) replicate sediment samples per site was not possible, (iv) no air contamination checks were included during sampling and, (v) particles <100 µm were automatically excluded from analysis. While the present study provides preliminary indication that microplastics may be accumulating in the deep-sea realm of the ACB, further work is necessary to assess microplastic abundance, distribution and composition in surficial sediments of the ACB.
This study aims to examine the composition and the spatial/tidal changes of marine debris caught with a fishing net during a fishery survey in two different areas of a sand beach at the northeast of Brazil. Samples were conducted weekly, at each moon phase, for two months using a beach seine net in the surf zone. Abundance of debris were estimate by swept area (items·km−1 and g·km−1). A total of 12 categories of debris were recorded. Plastic – both hard and soft types - was the most abundant debris category. Most fragments were classified as macro (20–100 mm) and mega debris (>100 mm). Significant differences (P < 0.05) between areas and tides were registered for plastic, metal and cloth. Spring tides were responsible for the high rates of marine debris found in the surf zone of Miramar beach. The results demonstrate the occurrence and abundance of litter in this fish nursery area and reinforce the need and importance of environmental protection and educational programs.
Plastic debris is a major global threat to marine ecosystems and species. However, our knowledge of this issue may be incomplete due to a lack of a standardized method for quantifying ingested ultrafine particles (1 μm – 1 mm) in wildlife. This study provides the first quantification of ultrafine plastic in seabirds using chemical and biological digestion treatments to extract plastic items from seabird gizzards. The alkaline agent, potassium hydroxide, outperformed the enzyme corolase, based on cost and efficiency (e.g., digestion time). Ultrafine plastics were observed in 7.0% of Flesh-footed Shearwater (Ardenna carneipes) gizzards collected from Lord Howe Island, Australia and accounted for 3.6% of all plastic items recovered (13 out of 359 items). Existing methods for extracting ingested plastic from seabirds do not account for ultrafine particles, therefore our results indicate current seabird plastic loads, and the associated physical and biological impacts, are underestimated.