Marine Pollution Bulletin xxx (2015) xxx–xxx
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Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul
Review
Microplastics in the marine environment: Current trends and future perspectives Luís Gabriel Antão Barboza a,⇑, Barbara Carolina Garcia Gimenez b a
CAPES Foundation, Ministry of Education of Brazil, 70040-020 Brasília, DF, Brazil Federal University of Paraná (UFPR), Center for Marine Studies (CEM), Coastal and Oceanic Systems Graduate Program (PGSISCO), Av. Beira-Mar, s/n, 83255-976 Pontal do Paraná, Pontal do Sul, Paraná, Brazil b
a r t i c l e
i n f o
Article history: Available online xxxx Keywords: Microplastic Plastic pollution Marine debris Emerging pollutants
a b s t r a c t Over the last decade, the presence of microplastics on marine environments has become an important environmental concern and focus of interest of many researches. Thus, to provide a more integrated view of the research trends regarding this topic, we use a scientometric approach to systematically assess and quantify advances in knowledge related to microplastics in the marine environment. The papers that we used for our assessment were obtained from the database Thomson Reuters (ISI Web of Science), between 2004 and 2014. Our results reveal the overall research performance in the study area of microplastics present in the marine environment over the past decade as a newly developed research field. It has been recognized that there are several important issues that should be investigated. Toward that end, based on the suggested directions on all papers reviewed, we point out areas/topics of interest that may guide future work in the coming years. Ó 2015 Elsevier Ltd. All rights reserved.
Contents 1. 2. 3.
4.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. Characteristics of publication outputs, distribution of subject categories, and journals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. Geographic distribution of the authors and productivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3. Distribution of educational/research institutes and collaborative networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Final considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix A. Supplementary material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1. Introduction The accumulation of plastic and its debris in marine and coastal environments is due to the intense and continuous release of this pollutant into the environment (Possatto et al., 2011; de Sá et al., 2015). The improper disposal of this waste combined with its growing production and inefficiency management, leaves no doubt about its potential impact and threat to these environments. ⇑ Corresponding author. E-mail address: [email protected] (L.G.A. Barboza).
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Recently, research on the environmental impact of plastic waste has added a new dimension with the discovery and investigation of microplastic particles (Law and Thompson, 2014). The presence of small plastic fragments in the open ocean was pointed out for the first time in the 1970s (Carpenter and Smith, 1972). In the following decades, with accumulating data on ecological consequences of such debris, the topic has received increasing research interest (Andrady, 2011). However, it was not until 2004 that R.C. Thompson and collaborators coined the term ‘‘microplastics.’’ In their paper, ‘‘Lost at sea: Where is all the plastic?,’’ Thompson et al. (2004) were the first researchers to use that term in the
http://dx.doi.org/10.1016/j.marpolbul.2015.06.008 0025-326X/Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
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scientific literature, to describe microscopic plastic particles in the marine environment. Since then, growing efforts have been made to document the presence of microplastics and their impact on this ecosystem. Although the defined size of these microparticles has varied between different studies over the past decade, the National Oceanic and Atmospheric Administration (NOAA) now defines the term ‘‘microplastic’’ as fragments smaller than 5 mm in diameter (Arthur et al., 2009). In the marine environment, microplastics can be generated from primary sources and enter directly into the environment as plastic pellets that were used as raw material in the plastic industry and/or in hygiene and personal care products (Fendall and Sewell, 2009; Cole et al., 2011). They may also enter indirectly from secondary sources, such as fragments and fibers obtained from the fragmentation of larger plastic debris, resulting from photothermal degradation, oxidation, and/or mechanical abrasion (Andrady, 2011). Regardless of their origin, plastics have been manufactured to be durable, a fact that allows them to remain for years in the environment. This is particularly true in the marine environment, where the plastic degradation may take decades (Hidalgo-Ruz et al., 2012). In the marine environment, the existence of microplastic debris, including primarily classes of polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) (Andrady, 2011), proliferate, migrate, and accumulate in natural habitats from pole to pole and from the ocean surface to the bottom of the sea (Ivair do Sul and Costa, 2014). With a quick and remarkable trajectory of interest shown by the academic community, and by non-governmental and regional maritime organizations – that have developed programs and guidelines for assessing marine litter, including microplastics – the research in this area has been accompanied by an almost exponential increase in the number of publications. Despite this, large gaps still need to be elucidated, particularly those referring to the origin, transport, interactions, and fate of microplastics in the marine environment (Cole et al., 2011; Oliveira et al., 2013). Therefore, we present herein a scientometric analysis that is aimed at systematically evaluating and quantifying advances in knowledge of microplastics in the marine environment over the past ten years of investigations (2004–2014), thus providing a more integrated view of the research trends regarding this topic. Our aim was to answer the following questions: (i) To what extent did the scientific literature on microplastics in the marine environment grow over the past decade? (ii) In which journals were these studies published? (iii) What have been the questions addressed in the studies published so far? (iv) From which part of the world are the researchers working in this area? (v) What is the proportion of independent and collaborative studies in the past ten years? (vi) How many educational/research institutes are involved in research on microplastics in the marine environment? (vii) How is the international collaborative network organized between countries and educational/research institutes? (viii) What are the gaps and/or future research perspectives in this area? Answering these questions will enable us to construct a research profile related to the presence of microplastics in the marine environment, which may serve as a potential guide for future investigations.
the term in both singular and plural forms. We considered publications on marine environments in journals covered by the ISI Web of Science, in which the aforementioned term appeared in the title and/or keywords of the manuscripts. Therefore, in this review we not included technical reports and academic theses. Conventional analysis of the scientific results, subject categories, journals, authors, countries, and educational/research institutes was performed by using descriptive statistics, and it was processed with Microsoft Excel software. The geographical worldwide distribution of the authors was plotted using QGIS software version 2.6.1 (Sherman et al., 2014). In order to observe the temporal trends in relation to the focus of researches, the variable ‘‘keywords’’ was ordered over time by the Principal Components Analysis (PCA). To achieve this goal, in addition to the keywords of the authors, also was used as unit of analysis ‘‘Keywords Plus’’ obtained through the ISI Web of Science platform. In total 365 keywords were related. Of these, we selected 24 for analysis that had a frequency equal or greater than five, considering all years (2006 to 2014). The years 2004 and 2005 were removed, because at the first there was no minimum frequency of keywords and at the second were unpublished papers related to the topic. To remove the influence of the number of studies in different periods (current periods have more published papers), we organized the matrix as follows: proportion of number of papers with a keyword in a given period by total number of papers in the same period. The PCA was based on the correlation matrix (Legendre and Legendre, 1998), and was performed using the PC-Ord 5.01 (McCune and Mefford, 1999). The type of collaboration was determined based upon the affiliation of the authors. The term ‘‘national collaborative articles’’ was assigned when researcher affiliations belonged to the same country/institute, whereas the term ‘‘international collaborative articles’’ was assigned when articles were co-written by researchers from multiple countries/institutes. As visualization tools for network analysis, UCINET software version 6.5 (Borgatti et al., 2013) and NetDraw version 2.1 (Borgatti, 2002) were used to assess the correlation with regard to the international collaboration between countries and educational/research institutes.
3. Results and discussion 3.1. Characteristics of publication outputs, distribution of subject categories, and journals From 2004 to 2014, the annual production of publications showed an increasing trend for studies on microplastics in the marine environment (Fig. 1). This trend was observed mainly in 2011 and 2013, when the annual growth rate of publications
2. Materials and methods The study was conducted in November 2014 through a bibliographic survey using the Thomson Reuters database (ISI Web of Science, apps.webofknowledge.com), and it examined papers published between 2004 and 2014. The keyword ‘‘microplastic⁄’’ was used as search criteria to retrieve valid data records in the database. The asterisk at the end of the word ensured the inclusion of
Fig. 1. Number of papers on microplastics published between 2004 and 2014 and expected growth.
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
L.G.A. Barboza, B.C.G. Gimenez / Marine Pollution Bulletin xxx (2015) xxx–xxx
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Fig. 2. Journals used to publish studies on microplastics in the marine environment over the past decade (2004–2014).
reached 6.5% and 18%, respectively. From these publications, it is clear that this increase was mainly due to the increase in the number of studies carried out in microcosms. The aim of those studies was to understand the correlation between the ecological consequences of microplastics exposure in the marine environment, as well as the relationship between these particles and the adsorption of different pollutants and/or environmental contaminants. Studies on microplastics in the marine environment have been published in a wide range of journals, many of which are considered high-impact journals (Fig. 2). Over the past decade, a large number of publications were found in four main journals, which together were responsible for 62.5% (68 articles) of all published articles. These journals were as follows: Marine Pollution Bulletin (30.3%), Environmental Science & Technology (17.5%), Environmental Pollution (9.2%), and Marine Environmental Research (5.5%). The articles published in these journals sparked interest in approaching different questions over the past ten years of research. Briefly, the subjects that were mainly investigated by researchers were related to the impacts of microplastics on the marine environment, their ability to interact (sorption/desorption) with other environmental contaminants, the quantification and characterization of these plastic microparticles in marine and coastal environments, transport routes of microplastic debris and possible places for their deposition, ingestion of microplastics by marine organisms and their potential transfer between organisms of different trophic levels, and the development of analytical techniques and detection methods for the presence of microplastics in these environments. We observed a temporal trend involving the keywords associated with the analyzed papers (Fig. 3). The interpretation of Fig. 3 is made from the overlap between Fig. 3a and b. As described below, each number refers to a keyword. Fig. 3 shows a segregation of keywords into two distinct groups along the first axis. In the first group (I and IV quadrants), related to the years 2006, 2007, 2009, 2010 and 2012, the keywords are scarce and in general with broad sense (e.g., marine environment). In the second group (II and III quadrants), related to the years 2008, 2011, 2013 and 2014, the
keywords are more diverse and connected to more specific topics (e.g., marine debris and marine litter). This indicates that the more recently developed research involves different areas, with a tendency of multi and interdisciplinary studies. Clearly, this is because of the growing number of publications involving the theme ‘‘microplastics’’, especially in the last two years (2013 and 2014). 3.2. Geographic distribution of the authors and productivity Regarding the research focused on microplastics in the marine environment, researchers from different parts of the world have contributed over the past decade to an increase in scientific knowledge in the area. During this period, articles from 337 authors were published. The main spatial clusters of authors working in this field are spread over 33 countries and 135 different cities, with clearly distinguishable clusters in the United States, Western Europe, Oceania, and East Asia, in addition to several other smaller groups in other parts of the world (Fig. 4). In absolute terms, the United States alone has contributed the most researchers; they can be found in 19 different American cities. In relative terms, Western Europe houses most researchers in the field (50.8%), spread in 66 different cities. The groups of authors from Western European are mainly located in the United Kingdom, France, Germany, Spain, and Italy. Japan and South Korea represent the main areas where authors are located in East Asia. 3.3. Distribution of educational/research institutes and collaborative networks It is clear that collaborative networks between the different institutes play an increasingly important role in scientific research; this is also the case in the research field of microplastics in the marine environment. Of the studies published in the past decade, 35.8% (39) were independent articles, i.e., published by a single institution, while 64.2% (70) were inter-institutional collaborative investigations, including national (44% or 62.9%) and international (26% or 37.1%) collaborations (see Fig. 5).
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
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(a)
(b)
I
1 Mediterranean sea 2 Marine environment
II 3 North Pacific
III 11 Ingestion 12 Plastic debris 13 Debris
4 Persistent organic pollutants (POPs)
14 Transport
5 Sea
15 Mytilus edulis
6 Marine debris
16 Marine Strategy Framework Directive
7 Particles
17 Accumulation
8 Environment
18 Chemicals
9 Pollution
19 Sediment
10 Zooplankton
20 Marine litter 21 Coastal waters IV 22 Microplastics 23 Infrared spectroscopy 24 Plastic(s)
Fig. 3. Principal Components Analysis (PCA) with Pearson correlation coefficients (a) and scores (b), showing the temporal occurrence of keywords. The first and the second axis of PCA accumulated 24.79% and 20.32% of the total variance, respectively.
Over the past decade, 132 educational/research institutes published studies on microplastics in the marine environment. The collaborative network of active institutes established by the NetDraw program showed a complex collaborative relationship. The node size represents the degree of specific importance of a given institute within a collaborative network (Fig. 6a). In this way, the results show that the University of Plymouth – UK (A1) was, in the past decade, the flagship within the network, having a strong correlation with 30 other research institutes (Fig. 6b). The University of Exeter – UK (A46), IFREMER– FRA (A25), the University of Edinburgh – UK (A13), ALGALITA – USA (A4), North Carolina State University – USA (A45), the University of Western
Australia – AUS (A12), and AWI – Alfred Wegener Institute – DEU (A59) were the main institutes that also exhibited the tendency to collaborate with other research centers. The publication outputs showed that 81.3% (26) of the countries established collaborative networks among themselves. China, South Korea, Romania, Finland, Singapore, and the Netherlands were the only countries in which the authors were not part of a collaboration. As shown in Fig. 7, the UK was the main cooperation partner with other countries, collaborating with 17 countries. This was followed by the United States, which cooperated with 13 countries. In the last decade, mainly in the past five years, the term ‘‘microplastics’’ entered in the popular lexicon (GESAMP, 2015). Even so, we recognize that the history of these small plastic particles present in ocean, dates back to early 1970s [see, e.g., Carpenter et al. (1972) and Wong et al. (1974)], and that other term derivations may be found in the literature, such as ‘‘neustonic plastic particles’’ (used by the researchers cited above and others). Although we consider in our analysis, only journal papers covered by the ISI Web of Science, worth pointing out that the consideration of microplastics by international agreements (e.g., RIO+20 and MSFD) as a specific indicator of litter pollution, and more generally the consideration of pollution by marine litter as a real concern (e.g., Honolulu strategy, UNEP regional actions plans, MSFD and GESAMP working group) has supported a number of studies in the recent years (on distribution, methods, implementation of monitoring, etc.). This clearly may explain the increase of publications. Therefore, it is important to highlight the role of political decisions as a major factor in increased efforts of research and activities, which aimed at minimizing the real problem of the presence of microplastics in marine environment. Such decisions and/or initiatives must act to understand the dynamics and impacts of the presence of this type of marine litter, and preventing further inputs or reducing total amounts in the environment (Eerkes-Medrano et al., 2015). As demonstrated in this study, there is an increased interest in research on microplastics in the marine environment. The concentrations of these microparticles in the environment are being reported worldwide (Claessens et al., 2013), including in areas that are naturally protected [see, e.g., Batzan et al. (2014)], as well as more remote ones (Obbard et al., 2014). Although scientific evidence has quickly been reported in the literature regarding the fate of microplastics and their impact on these environmental systems, many critical issues are still poorly understood (Ivair do Sul and Costa, 2014). Therefore, it is implicit that important questions regarding production, transport, fate, and the physical and chemical effects of microplastics present in the marine environment should be investigated (Zarfl et al., 2011). Due to their small size and presence in both pelagic and benthic ecosystems, a growing number of studies show that microplastics are potentially bioavailable for ingestion by a wide range of organisms (Browne et al., 2008; Cole et al., 2011). Several studies report that these particles may be ingested by invertebrates, e.g., polychaetes, crustaceans, echinoderms, bryozoans, and bivalves, as well as vertebrates such as fishes and birds, in addition to plankton and zooplankton organisms (Von Moos et al., 2012; Cole et al., 2013; Ivair do Sul and Costa, 2014). Thus, it has been suggested that the intake of these microparticles can cause direct physical injuries and also facilitate the transfer of chemicals to organisms, including those intentionally incorporated during the manufacturing process, as well as environmental contaminants that could be absorbed on the plastic surface (Oliveira et al., 2013). Therefore, microplastics can absorb persistent, bioaccumulative, and toxic substances (PBT), including persistent organic pollutants (POPs) and metals (Rios et al., 2007; Gouin et al., 2011). Once ingested, the absorbed pollutants may be transferred to marine
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
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Fig. 4. Spatial distribution of the authors of papers published in the past decade (2004–2014).
areas/topics of interest for future research on microplastics in the marine environment, as bellows:
Fig. 5. Independent and collaborative production of articles per year (2004–2014).
organisms. The interactions between these compounds inside the bodies of these marine organisms may alter the distribution, biotransformation, and/or toxicity of environmental contaminants. This may lead to an increase in the concentration of contaminants and the potential risk for these to be incorporated into superior trophic chains, thus threatening the health of animals including humans (Teuten et al., 2009; Hidalgo-Ruz et al., 2012; Oliveira et al., 2013). However, many of these effects and processes involving the presence and accumulation of microplastics in the marine environment still remain to be elucidated, and the long-term consequences are still unknown (Moore, 2008; Wright et al., 2013). Therefore, the challenge of understanding all these issues is left to future research. Based on the suggested directions in the discussions of the all papers reviewed, in particular on the papers of Cole et al. (2011), Ballent et al. (2013), Depledge et al. (2013), Wright et al. (2013) and Lusher et al. (2014), we made a synthesis of
(1) Understand which are the marine organisms that are most affected by the presence of microplastics. (2) Evaluate the presence and effects of microplastics in the marine environment through organisms used as sentinel species, and apply new integrated monitoring tools. (3) Determine the impact (mortality, morbidity, and/or reproduction) caused by microplastic ingestion by the marine biota and evaluate what is the influence and impact of the different forms and types of microplastics in marine organisms. (4) Understand the capacity and transport mechanisms of microplastics and their contaminants through the marine food chain via trophic interactions, as well as to estimate the associated impact of these processes at the level of the population and the ecosystem. (5) Optimize and implement methodologies of high throughput sampling of microplastics to better compare the results of different studies and to develop methods to detect microplastics present in the water and sediments. (6) Evaluate what are the ecological consequences of exposure to microplastics in marine environments, especially in critical areas such as biodiversity hotspots. (7) Evaluate the consequences of microplastics for human health. (8) Increase the knowledge about the origin, path, fate, and microplastic behavior in the water, including the effects of fragmentation and bio-incrustation. (9) Increase knowledge of the effects resulting from the concentration of additives in microplastics over time, their bioavailability, and the associated toxicological impact and the persistence time of microplastics in the environment (Fig. 8). 4. Final considerations The presence and accumulation of these microparticles in the marine environment is a current and growing concern. In recent
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
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Fig. 6a. Collaborative network between the educational/research institutes in studying microplastics in the marine environment (2004–2014). ⁄The complete list of educational/research institutes can be found in Supplementary Material.
Fig. 6b. Collaborative network of the institute more active in studying microplastics in the marine environment over the past decade (2004–2014).
years, plastic pollution in the ocean, including microplastics, has become a relevant environmental concern for scientists, non-governmental organizations, rulers, and even for the lay people. Scientometric analysis showed the overall research performance in the study area of microplastics in the marine environment over the past decade (2004–2014), as a newly
developed research field. This shows that this field has had a continuous growth of publications. Nevertheless, despite the great scientific advances that were made over this period, more advanced and in-depth studies are required to understand the majority of the questions and processes that remain unknown. Therefore, the contribution of the scientific community by way of additional
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
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Fig. 7. International collaborative network between countries in the past decade (2004–2014).
Fig. 8. Research aspects of interest future with regard to marine environment microplastics.
investigations to be carried out in the coming years will be fundamental in trying to understand the real impact of these emerging micro-contaminants that are present in coastal and oceanic systems.
Borders programme. The authors would like to thank the anonymous reviewers for their valuable comments and suggestions to improve the quality of the paper. Appendix A. Supplementary material
Acknowledgments The first author acknowledges financial support from CAPES/Scholarship No. Bex 13568/13-2, under the Science without
Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.marpolbul.2015. 06.008.
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
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References Andrady, A.L., 2011. Microplastics in the marine environment. Mar. Pollut. Bull. 62 (8), 1596–1605. Arthur, C., Baker, J., Bamford, H., (Eds.), 2009. Proceedings of the International Research Workshop on the Occurrence, Effects and Fate of Microplastic Marine Debris, Sept. 9–11, 2008, NOAA Technical Memorandum NOS-OR&R-30, 2009. Ballent, A., Pando, S., Purser, A., Juliano, M.F., Thomsen, L., 2013. Modelled transport of benthic marine microplastic pollution in the Nazaré Canyon. Biogeosciences 10, 7957–7970. Batzan, J., Carrasco, A., Chouinard, O., Cleaud, M., Gabaldon, J.E., Huck, T., Jaffrés, L., Jorgensen, B., Miguelez, A., Paillard, C., Vanderlinden, J.-P., 2014. Protected areas in the Atlantic facing the hazards of micro-plastic pollution: first diagnosis of three islands in the Canary Current. Mar. Pollut. Bull. 80 (1–2), 302–311. Borgatti, S.P., 2002. NetDraw: Graph Visualization Software. Analytic Technologies, Harvard. Borgatti, S.B., Everett, M.G., Johnson, J.C., 2013. Analyzing Social Networks. Sage Publications, United Kingdon. Browne, M.A., Dissanayake, A., Galloway, T.S., Lowe, D.M., Thompson, R.C., 2008. Ingested microscopic plastic translocates to the circulatory system of the mussel, Mytilus edulis (L.). Environ. Sci. Technol. 42 (13), 5026–5031. Carpenter, E.J., Smith, K.L., 1972. Plastics on the Sargasso sea surface. Science 175 (4027), 1240–1241. Carpenter, E.J., Anderson, S.J., Harvey, G.R., Miklas, H.P., Peck, B.B., 1972. Polystyrene spherules in coastal waters. Science 175, 749–750. Claessens, M., Cauwenberghe, L.V., Vandegehuchte, M.B., Janssen, C.R., 2013. New techniques for the detection of microplastics in sediments and field collected organisms. Mar. Pollut. Bull. 70 (1–2), 227–233. Cole, M., Lindeque, P., Halsband, C., Galloway, T.S., 2011. Microplastics as contaminants in the marine environment: a review. Mar. Pollut. Bull. 62 (12), 2588–2597. Cole, M., Lindeque, P., Fileman, E., Halsband, C., Goodhead, R., Moger, J., Galloway, T.S., 2013. Microplastic ingestion by zooplankton. Environ. Sci. Technol. 47 (12), 6646–6655. de Sá, L.C., Luís, L.G., Guilhermino, L., 2015. Effects of microplastics on juveniles of the common goby (Pomatoschistus microps): confusion with prey, reduction of the predatory performance and efficiency, and possible influence of developmental conditions. Environ. Pollut. 196, 359–362. Depledge, M.H., Galgani, F., Panti, C., Caliani, I., Casini, S., Fossi, M.C., 2013. Plastic litter in the sea. Mar. Environ. Res. 92, 279–281. Eerkes-Medrano, D., Thompson, R.C., Aldridge, D.C., 2015. Microplastics in freshwater systems: a review of the emerging threats, identification of knowledge gaps and prioritisation of research needs. Water Res. 75 (15), 63–82. Fendall, L.S., Sewell, M.A., 2009. Contributing to marine pollution by washing your face: microplastics in facial cleansers. Mar. Pollut. Bull. 58 (8), 1225–1228. GESAMP, 2015. Sources, fate and effects of microplastics in the marine environment: a global assessment. In: Kershaw, P.J. (Ed.), (IMO/FAO/UNESCOIOC/UNIDO/WMO/IAEA/UN/UNEP/UNDP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection). Rep. Stud. GESAMP No. 90, 96p. Gouin, T., Roche, N., Lohmann, R., Hodges, G., 2011. A thermodynamic approach for assessing the environmental exposure of chemicals absorbed to microplastic. Environ. Sci. Technol. 45 (4), 1466–1472.
Hidalgo-Ruz, V., Gutow, L., Thompson, R.C., Thiel, M., 2012. Microplastics in the marine environment: a review of the methods used for identification and quantification. Environ. Sci. Technol. 46 (6), 3060–3075. Ivair do Sul, J.A., Costa, M.F., 2014. The present and future of microplastic pollution in the marine environment. Environ. Pollut. 185, 352–364. Law, K.L., Thompson, R.C., 2014. Microplastics in the seas. Science 345 (6193), 144– 145. Legendre, P., Legendre, L., 1998. Numerical Ecology, second ed. Elsevier, Amsterdam. Lusher, A.L., Burke, A., O’Connor, I., Officer, R., 2014. Microplastic pollution in the Northeast Atlantic Ocean: validated and opportunistic sampling. Mar. Pollut. Bull. 88 (1–2), 325–333. McCune, B., Mefford, M.J., 1999. Multivariate analysis of ecological data version 5.01. PC-Ord for Windows. MjM Software, Gleneden Beach, Oregon Moore, C.J., 2008. Synthetic polymers in the marine environment: a rapidly increasing, long-term threat. Environ. Res. 108 (2), 131–139. Obbard, R.W., Sadri, S., Wong, Y.Q., Khitun, A.A., Baker, I., Thompson, R.C., 2014. Global warming releases microplastic legacy frozen in Arctic Sea ice. Earth’s Future 2 (6), 315–320. Oliveira, M., Ribeiro, A., Hylland, K., Guilhermino, L., 2013. Single and combined effects of microplastics and pyrene on juveniles (0+ group) of the common goby Pomatoschistus microps (Teleostei, Gobiidae). Ecol. Indic. 34, 641–647. Possatto, F.E., Barletta, M., Costa, M.F., Ivair do Sul, J.A., Dantas, D.V., 2011. Plastic debris ingestion by marine catfish: an unexpected fisheries impact. Mar. Pollut. Bull. 62 (5), 1098–1102. Rios, L.M., Moore, C., Jones, P.R., 2007. Persistent organic pollutants carried by synthetic polymers in the ocean environment. Mar. Pollut. Bull. 54 (8), 1230– 1237. Sherman, G.E., Sutton, T., Blazek, R.E, Luthman, L. Quantum GIS User Guide – Version 2.6.1 ’Brighton’, 2014. . Teuten, E.L., Saquing, J.M., Knappe, D.R.U., Barlaz, M.A., Jonsson, S., Bjorn, A., Rowland, S.J., Thompson, R.C., Galloway, T.S., Yamashita, R., Ochi, D., Watanuki, Y., Moore, C., Pham, H.V., Tana, T.S., Prudente, M., Boonyatumanond, R., Zakaria, M.P., Akkhavong, K., Ogata, Y., Hirai, H., Iwasa, S., Mizukawa, K., Hagino, Y., Imamura, A., Saha, M., Takada, H., 2009. Transport and release of chemicals from plastics to the environment and to wildlife. Philos. Trans. Soc. B 364 (1526), 2027–2045. Thompson, R.C., Olsen, Y., Mitchell, R.P., Davis, A., Rowland, S.J., John, A.W.G., McGonigle, D., Russel, A.E., 2004. Lost at sea: where is all the plastic? Science 304 (5672), 838. Von Moos, N., Burkhardt-Holm, P., Kohler, A., 2012. Uptake and effects of microplastics on cells and tissue of the blue mussel Mytilus edulis L. after an experimental exposure. Environ. Sci. Technol. 46 (20), 11327–11335. Wong, C.S., Green, D.R., Cretney, W.J., 1974. Quantitative tar and plastic waste distributions in Pacific Ocean. Nature 247, 30–32. Wright, S.L., Thompson, R.C., Galloway, T.S., 2013. The physical impacts of microplastics on marine organisms: a review. Environ. Pollut. 178, 483–492. Zarfl, C., Fleet, D., Fries, E., Galgani, F., Gerdts, G., Hanke, G., Matthies, M., 2011. Microplastics in oceans. Mar. Pollut. Bull. 62 (8), 1589–1591.
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
Contents lists available at ScienceDirect
Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul
Review
Microplastics in the marine environment: Current trends and future perspectives Luís Gabriel Antão Barboza a,⇑, Barbara Carolina Garcia Gimenez b a
CAPES Foundation, Ministry of Education of Brazil, 70040-020 Brasília, DF, Brazil Federal University of Paraná (UFPR), Center for Marine Studies (CEM), Coastal and Oceanic Systems Graduate Program (PGSISCO), Av. Beira-Mar, s/n, 83255-976 Pontal do Paraná, Pontal do Sul, Paraná, Brazil b
a r t i c l e
i n f o
Article history: Available online xxxx Keywords: Microplastic Plastic pollution Marine debris Emerging pollutants
a b s t r a c t Over the last decade, the presence of microplastics on marine environments has become an important environmental concern and focus of interest of many researches. Thus, to provide a more integrated view of the research trends regarding this topic, we use a scientometric approach to systematically assess and quantify advances in knowledge related to microplastics in the marine environment. The papers that we used for our assessment were obtained from the database Thomson Reuters (ISI Web of Science), between 2004 and 2014. Our results reveal the overall research performance in the study area of microplastics present in the marine environment over the past decade as a newly developed research field. It has been recognized that there are several important issues that should be investigated. Toward that end, based on the suggested directions on all papers reviewed, we point out areas/topics of interest that may guide future work in the coming years. Ó 2015 Elsevier Ltd. All rights reserved.
Contents 1. 2. 3.
4.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. Characteristics of publication outputs, distribution of subject categories, and journals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. Geographic distribution of the authors and productivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3. Distribution of educational/research institutes and collaborative networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Final considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix A. Supplementary material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1. Introduction The accumulation of plastic and its debris in marine and coastal environments is due to the intense and continuous release of this pollutant into the environment (Possatto et al., 2011; de Sá et al., 2015). The improper disposal of this waste combined with its growing production and inefficiency management, leaves no doubt about its potential impact and threat to these environments. ⇑ Corresponding author. E-mail address: [email protected] (L.G.A. Barboza).
00 00 00 00 00 00 00 00 00 00
Recently, research on the environmental impact of plastic waste has added a new dimension with the discovery and investigation of microplastic particles (Law and Thompson, 2014). The presence of small plastic fragments in the open ocean was pointed out for the first time in the 1970s (Carpenter and Smith, 1972). In the following decades, with accumulating data on ecological consequences of such debris, the topic has received increasing research interest (Andrady, 2011). However, it was not until 2004 that R.C. Thompson and collaborators coined the term ‘‘microplastics.’’ In their paper, ‘‘Lost at sea: Where is all the plastic?,’’ Thompson et al. (2004) were the first researchers to use that term in the
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Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
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scientific literature, to describe microscopic plastic particles in the marine environment. Since then, growing efforts have been made to document the presence of microplastics and their impact on this ecosystem. Although the defined size of these microparticles has varied between different studies over the past decade, the National Oceanic and Atmospheric Administration (NOAA) now defines the term ‘‘microplastic’’ as fragments smaller than 5 mm in diameter (Arthur et al., 2009). In the marine environment, microplastics can be generated from primary sources and enter directly into the environment as plastic pellets that were used as raw material in the plastic industry and/or in hygiene and personal care products (Fendall and Sewell, 2009; Cole et al., 2011). They may also enter indirectly from secondary sources, such as fragments and fibers obtained from the fragmentation of larger plastic debris, resulting from photothermal degradation, oxidation, and/or mechanical abrasion (Andrady, 2011). Regardless of their origin, plastics have been manufactured to be durable, a fact that allows them to remain for years in the environment. This is particularly true in the marine environment, where the plastic degradation may take decades (Hidalgo-Ruz et al., 2012). In the marine environment, the existence of microplastic debris, including primarily classes of polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) (Andrady, 2011), proliferate, migrate, and accumulate in natural habitats from pole to pole and from the ocean surface to the bottom of the sea (Ivair do Sul and Costa, 2014). With a quick and remarkable trajectory of interest shown by the academic community, and by non-governmental and regional maritime organizations – that have developed programs and guidelines for assessing marine litter, including microplastics – the research in this area has been accompanied by an almost exponential increase in the number of publications. Despite this, large gaps still need to be elucidated, particularly those referring to the origin, transport, interactions, and fate of microplastics in the marine environment (Cole et al., 2011; Oliveira et al., 2013). Therefore, we present herein a scientometric analysis that is aimed at systematically evaluating and quantifying advances in knowledge of microplastics in the marine environment over the past ten years of investigations (2004–2014), thus providing a more integrated view of the research trends regarding this topic. Our aim was to answer the following questions: (i) To what extent did the scientific literature on microplastics in the marine environment grow over the past decade? (ii) In which journals were these studies published? (iii) What have been the questions addressed in the studies published so far? (iv) From which part of the world are the researchers working in this area? (v) What is the proportion of independent and collaborative studies in the past ten years? (vi) How many educational/research institutes are involved in research on microplastics in the marine environment? (vii) How is the international collaborative network organized between countries and educational/research institutes? (viii) What are the gaps and/or future research perspectives in this area? Answering these questions will enable us to construct a research profile related to the presence of microplastics in the marine environment, which may serve as a potential guide for future investigations.
the term in both singular and plural forms. We considered publications on marine environments in journals covered by the ISI Web of Science, in which the aforementioned term appeared in the title and/or keywords of the manuscripts. Therefore, in this review we not included technical reports and academic theses. Conventional analysis of the scientific results, subject categories, journals, authors, countries, and educational/research institutes was performed by using descriptive statistics, and it was processed with Microsoft Excel software. The geographical worldwide distribution of the authors was plotted using QGIS software version 2.6.1 (Sherman et al., 2014). In order to observe the temporal trends in relation to the focus of researches, the variable ‘‘keywords’’ was ordered over time by the Principal Components Analysis (PCA). To achieve this goal, in addition to the keywords of the authors, also was used as unit of analysis ‘‘Keywords Plus’’ obtained through the ISI Web of Science platform. In total 365 keywords were related. Of these, we selected 24 for analysis that had a frequency equal or greater than five, considering all years (2006 to 2014). The years 2004 and 2005 were removed, because at the first there was no minimum frequency of keywords and at the second were unpublished papers related to the topic. To remove the influence of the number of studies in different periods (current periods have more published papers), we organized the matrix as follows: proportion of number of papers with a keyword in a given period by total number of papers in the same period. The PCA was based on the correlation matrix (Legendre and Legendre, 1998), and was performed using the PC-Ord 5.01 (McCune and Mefford, 1999). The type of collaboration was determined based upon the affiliation of the authors. The term ‘‘national collaborative articles’’ was assigned when researcher affiliations belonged to the same country/institute, whereas the term ‘‘international collaborative articles’’ was assigned when articles were co-written by researchers from multiple countries/institutes. As visualization tools for network analysis, UCINET software version 6.5 (Borgatti et al., 2013) and NetDraw version 2.1 (Borgatti, 2002) were used to assess the correlation with regard to the international collaboration between countries and educational/research institutes.
3. Results and discussion 3.1. Characteristics of publication outputs, distribution of subject categories, and journals From 2004 to 2014, the annual production of publications showed an increasing trend for studies on microplastics in the marine environment (Fig. 1). This trend was observed mainly in 2011 and 2013, when the annual growth rate of publications
2. Materials and methods The study was conducted in November 2014 through a bibliographic survey using the Thomson Reuters database (ISI Web of Science, apps.webofknowledge.com), and it examined papers published between 2004 and 2014. The keyword ‘‘microplastic⁄’’ was used as search criteria to retrieve valid data records in the database. The asterisk at the end of the word ensured the inclusion of
Fig. 1. Number of papers on microplastics published between 2004 and 2014 and expected growth.
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
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Fig. 2. Journals used to publish studies on microplastics in the marine environment over the past decade (2004–2014).
reached 6.5% and 18%, respectively. From these publications, it is clear that this increase was mainly due to the increase in the number of studies carried out in microcosms. The aim of those studies was to understand the correlation between the ecological consequences of microplastics exposure in the marine environment, as well as the relationship between these particles and the adsorption of different pollutants and/or environmental contaminants. Studies on microplastics in the marine environment have been published in a wide range of journals, many of which are considered high-impact journals (Fig. 2). Over the past decade, a large number of publications were found in four main journals, which together were responsible for 62.5% (68 articles) of all published articles. These journals were as follows: Marine Pollution Bulletin (30.3%), Environmental Science & Technology (17.5%), Environmental Pollution (9.2%), and Marine Environmental Research (5.5%). The articles published in these journals sparked interest in approaching different questions over the past ten years of research. Briefly, the subjects that were mainly investigated by researchers were related to the impacts of microplastics on the marine environment, their ability to interact (sorption/desorption) with other environmental contaminants, the quantification and characterization of these plastic microparticles in marine and coastal environments, transport routes of microplastic debris and possible places for their deposition, ingestion of microplastics by marine organisms and their potential transfer between organisms of different trophic levels, and the development of analytical techniques and detection methods for the presence of microplastics in these environments. We observed a temporal trend involving the keywords associated with the analyzed papers (Fig. 3). The interpretation of Fig. 3 is made from the overlap between Fig. 3a and b. As described below, each number refers to a keyword. Fig. 3 shows a segregation of keywords into two distinct groups along the first axis. In the first group (I and IV quadrants), related to the years 2006, 2007, 2009, 2010 and 2012, the keywords are scarce and in general with broad sense (e.g., marine environment). In the second group (II and III quadrants), related to the years 2008, 2011, 2013 and 2014, the
keywords are more diverse and connected to more specific topics (e.g., marine debris and marine litter). This indicates that the more recently developed research involves different areas, with a tendency of multi and interdisciplinary studies. Clearly, this is because of the growing number of publications involving the theme ‘‘microplastics’’, especially in the last two years (2013 and 2014). 3.2. Geographic distribution of the authors and productivity Regarding the research focused on microplastics in the marine environment, researchers from different parts of the world have contributed over the past decade to an increase in scientific knowledge in the area. During this period, articles from 337 authors were published. The main spatial clusters of authors working in this field are spread over 33 countries and 135 different cities, with clearly distinguishable clusters in the United States, Western Europe, Oceania, and East Asia, in addition to several other smaller groups in other parts of the world (Fig. 4). In absolute terms, the United States alone has contributed the most researchers; they can be found in 19 different American cities. In relative terms, Western Europe houses most researchers in the field (50.8%), spread in 66 different cities. The groups of authors from Western European are mainly located in the United Kingdom, France, Germany, Spain, and Italy. Japan and South Korea represent the main areas where authors are located in East Asia. 3.3. Distribution of educational/research institutes and collaborative networks It is clear that collaborative networks between the different institutes play an increasingly important role in scientific research; this is also the case in the research field of microplastics in the marine environment. Of the studies published in the past decade, 35.8% (39) were independent articles, i.e., published by a single institution, while 64.2% (70) were inter-institutional collaborative investigations, including national (44% or 62.9%) and international (26% or 37.1%) collaborations (see Fig. 5).
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
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(a)
(b)
I
1 Mediterranean sea 2 Marine environment
II 3 North Pacific
III 11 Ingestion 12 Plastic debris 13 Debris
4 Persistent organic pollutants (POPs)
14 Transport
5 Sea
15 Mytilus edulis
6 Marine debris
16 Marine Strategy Framework Directive
7 Particles
17 Accumulation
8 Environment
18 Chemicals
9 Pollution
19 Sediment
10 Zooplankton
20 Marine litter 21 Coastal waters IV 22 Microplastics 23 Infrared spectroscopy 24 Plastic(s)
Fig. 3. Principal Components Analysis (PCA) with Pearson correlation coefficients (a) and scores (b), showing the temporal occurrence of keywords. The first and the second axis of PCA accumulated 24.79% and 20.32% of the total variance, respectively.
Over the past decade, 132 educational/research institutes published studies on microplastics in the marine environment. The collaborative network of active institutes established by the NetDraw program showed a complex collaborative relationship. The node size represents the degree of specific importance of a given institute within a collaborative network (Fig. 6a). In this way, the results show that the University of Plymouth – UK (A1) was, in the past decade, the flagship within the network, having a strong correlation with 30 other research institutes (Fig. 6b). The University of Exeter – UK (A46), IFREMER– FRA (A25), the University of Edinburgh – UK (A13), ALGALITA – USA (A4), North Carolina State University – USA (A45), the University of Western
Australia – AUS (A12), and AWI – Alfred Wegener Institute – DEU (A59) were the main institutes that also exhibited the tendency to collaborate with other research centers. The publication outputs showed that 81.3% (26) of the countries established collaborative networks among themselves. China, South Korea, Romania, Finland, Singapore, and the Netherlands were the only countries in which the authors were not part of a collaboration. As shown in Fig. 7, the UK was the main cooperation partner with other countries, collaborating with 17 countries. This was followed by the United States, which cooperated with 13 countries. In the last decade, mainly in the past five years, the term ‘‘microplastics’’ entered in the popular lexicon (GESAMP, 2015). Even so, we recognize that the history of these small plastic particles present in ocean, dates back to early 1970s [see, e.g., Carpenter et al. (1972) and Wong et al. (1974)], and that other term derivations may be found in the literature, such as ‘‘neustonic plastic particles’’ (used by the researchers cited above and others). Although we consider in our analysis, only journal papers covered by the ISI Web of Science, worth pointing out that the consideration of microplastics by international agreements (e.g., RIO+20 and MSFD) as a specific indicator of litter pollution, and more generally the consideration of pollution by marine litter as a real concern (e.g., Honolulu strategy, UNEP regional actions plans, MSFD and GESAMP working group) has supported a number of studies in the recent years (on distribution, methods, implementation of monitoring, etc.). This clearly may explain the increase of publications. Therefore, it is important to highlight the role of political decisions as a major factor in increased efforts of research and activities, which aimed at minimizing the real problem of the presence of microplastics in marine environment. Such decisions and/or initiatives must act to understand the dynamics and impacts of the presence of this type of marine litter, and preventing further inputs or reducing total amounts in the environment (Eerkes-Medrano et al., 2015). As demonstrated in this study, there is an increased interest in research on microplastics in the marine environment. The concentrations of these microparticles in the environment are being reported worldwide (Claessens et al., 2013), including in areas that are naturally protected [see, e.g., Batzan et al. (2014)], as well as more remote ones (Obbard et al., 2014). Although scientific evidence has quickly been reported in the literature regarding the fate of microplastics and their impact on these environmental systems, many critical issues are still poorly understood (Ivair do Sul and Costa, 2014). Therefore, it is implicit that important questions regarding production, transport, fate, and the physical and chemical effects of microplastics present in the marine environment should be investigated (Zarfl et al., 2011). Due to their small size and presence in both pelagic and benthic ecosystems, a growing number of studies show that microplastics are potentially bioavailable for ingestion by a wide range of organisms (Browne et al., 2008; Cole et al., 2011). Several studies report that these particles may be ingested by invertebrates, e.g., polychaetes, crustaceans, echinoderms, bryozoans, and bivalves, as well as vertebrates such as fishes and birds, in addition to plankton and zooplankton organisms (Von Moos et al., 2012; Cole et al., 2013; Ivair do Sul and Costa, 2014). Thus, it has been suggested that the intake of these microparticles can cause direct physical injuries and also facilitate the transfer of chemicals to organisms, including those intentionally incorporated during the manufacturing process, as well as environmental contaminants that could be absorbed on the plastic surface (Oliveira et al., 2013). Therefore, microplastics can absorb persistent, bioaccumulative, and toxic substances (PBT), including persistent organic pollutants (POPs) and metals (Rios et al., 2007; Gouin et al., 2011). Once ingested, the absorbed pollutants may be transferred to marine
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
L.G.A. Barboza, B.C.G. Gimenez / Marine Pollution Bulletin xxx (2015) xxx–xxx
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Fig. 4. Spatial distribution of the authors of papers published in the past decade (2004–2014).
areas/topics of interest for future research on microplastics in the marine environment, as bellows:
Fig. 5. Independent and collaborative production of articles per year (2004–2014).
organisms. The interactions between these compounds inside the bodies of these marine organisms may alter the distribution, biotransformation, and/or toxicity of environmental contaminants. This may lead to an increase in the concentration of contaminants and the potential risk for these to be incorporated into superior trophic chains, thus threatening the health of animals including humans (Teuten et al., 2009; Hidalgo-Ruz et al., 2012; Oliveira et al., 2013). However, many of these effects and processes involving the presence and accumulation of microplastics in the marine environment still remain to be elucidated, and the long-term consequences are still unknown (Moore, 2008; Wright et al., 2013). Therefore, the challenge of understanding all these issues is left to future research. Based on the suggested directions in the discussions of the all papers reviewed, in particular on the papers of Cole et al. (2011), Ballent et al. (2013), Depledge et al. (2013), Wright et al. (2013) and Lusher et al. (2014), we made a synthesis of
(1) Understand which are the marine organisms that are most affected by the presence of microplastics. (2) Evaluate the presence and effects of microplastics in the marine environment through organisms used as sentinel species, and apply new integrated monitoring tools. (3) Determine the impact (mortality, morbidity, and/or reproduction) caused by microplastic ingestion by the marine biota and evaluate what is the influence and impact of the different forms and types of microplastics in marine organisms. (4) Understand the capacity and transport mechanisms of microplastics and their contaminants through the marine food chain via trophic interactions, as well as to estimate the associated impact of these processes at the level of the population and the ecosystem. (5) Optimize and implement methodologies of high throughput sampling of microplastics to better compare the results of different studies and to develop methods to detect microplastics present in the water and sediments. (6) Evaluate what are the ecological consequences of exposure to microplastics in marine environments, especially in critical areas such as biodiversity hotspots. (7) Evaluate the consequences of microplastics for human health. (8) Increase the knowledge about the origin, path, fate, and microplastic behavior in the water, including the effects of fragmentation and bio-incrustation. (9) Increase knowledge of the effects resulting from the concentration of additives in microplastics over time, their bioavailability, and the associated toxicological impact and the persistence time of microplastics in the environment (Fig. 8). 4. Final considerations The presence and accumulation of these microparticles in the marine environment is a current and growing concern. In recent
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
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Fig. 6a. Collaborative network between the educational/research institutes in studying microplastics in the marine environment (2004–2014). ⁄The complete list of educational/research institutes can be found in Supplementary Material.
Fig. 6b. Collaborative network of the institute more active in studying microplastics in the marine environment over the past decade (2004–2014).
years, plastic pollution in the ocean, including microplastics, has become a relevant environmental concern for scientists, non-governmental organizations, rulers, and even for the lay people. Scientometric analysis showed the overall research performance in the study area of microplastics in the marine environment over the past decade (2004–2014), as a newly
developed research field. This shows that this field has had a continuous growth of publications. Nevertheless, despite the great scientific advances that were made over this period, more advanced and in-depth studies are required to understand the majority of the questions and processes that remain unknown. Therefore, the contribution of the scientific community by way of additional
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
L.G.A. Barboza, B.C.G. Gimenez / Marine Pollution Bulletin xxx (2015) xxx–xxx
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Fig. 7. International collaborative network between countries in the past decade (2004–2014).
Fig. 8. Research aspects of interest future with regard to marine environment microplastics.
investigations to be carried out in the coming years will be fundamental in trying to understand the real impact of these emerging micro-contaminants that are present in coastal and oceanic systems.
Borders programme. The authors would like to thank the anonymous reviewers for their valuable comments and suggestions to improve the quality of the paper. Appendix A. Supplementary material
Acknowledgments The first author acknowledges financial support from CAPES/Scholarship No. Bex 13568/13-2, under the Science without
Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.marpolbul.2015. 06.008.
Please cite this article in press as: Barboza, L.G.A., Gimenez, B.C.G. Microplastics in the marine environment: Current trends and future perspectives. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.06.008
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References Andrady, A.L., 2011. Microplastics in the marine environment. Mar. Pollut. Bull. 62 (8), 1596–1605. Arthur, C., Baker, J., Bamford, H., (Eds.), 2009. Proceedings of the International Research Workshop on the Occurrence, Effects and Fate of Microplastic Marine Debris, Sept. 9–11, 2008, NOAA Technical Memorandum NOS-OR&R-30, 2009. Ballent, A., Pando, S., Purser, A., Juliano, M.F., Thomsen, L., 2013. Modelled transport of benthic marine microplastic pollution in the Nazaré Canyon. Biogeosciences 10, 7957–7970. Batzan, J., Carrasco, A., Chouinard, O., Cleaud, M., Gabaldon, J.E., Huck, T., Jaffrés, L., Jorgensen, B., Miguelez, A., Paillard, C., Vanderlinden, J.-P., 2014. Protected areas in the Atlantic facing the hazards of micro-plastic pollution: first diagnosis of three islands in the Canary Current. Mar. Pollut. Bull. 80 (1–2), 302–311. Borgatti, S.P., 2002. NetDraw: Graph Visualization Software. Analytic Technologies, Harvard. Borgatti, S.B., Everett, M.G., Johnson, J.C., 2013. Analyzing Social Networks. Sage Publications, United Kingdon. Browne, M.A., Dissanayake, A., Galloway, T.S., Lowe, D.M., Thompson, R.C., 2008. Ingested microscopic plastic translocates to the circulatory system of the mussel, Mytilus edulis (L.). Environ. Sci. Technol. 42 (13), 5026–5031. Carpenter, E.J., Smith, K.L., 1972. Plastics on the Sargasso sea surface. Science 175 (4027), 1240–1241. Carpenter, E.J., Anderson, S.J., Harvey, G.R., Miklas, H.P., Peck, B.B., 1972. Polystyrene spherules in coastal waters. Science 175, 749–750. Claessens, M., Cauwenberghe, L.V., Vandegehuchte, M.B., Janssen, C.R., 2013. New techniques for the detection of microplastics in sediments and field collected organisms. Mar. Pollut. Bull. 70 (1–2), 227–233. Cole, M., Lindeque, P., Halsband, C., Galloway, T.S., 2011. Microplastics as contaminants in the marine environment: a review. Mar. Pollut. Bull. 62 (12), 2588–2597. Cole, M., Lindeque, P., Fileman, E., Halsband, C., Goodhead, R., Moger, J., Galloway, T.S., 2013. Microplastic ingestion by zooplankton. Environ. Sci. Technol. 47 (12), 6646–6655. de Sá, L.C., Luís, L.G., Guilhermino, L., 2015. Effects of microplastics on juveniles of the common goby (Pomatoschistus microps): confusion with prey, reduction of the predatory performance and efficiency, and possible influence of developmental conditions. Environ. Pollut. 196, 359–362. Depledge, M.H., Galgani, F., Panti, C., Caliani, I., Casini, S., Fossi, M.C., 2013. Plastic litter in the sea. Mar. Environ. Res. 92, 279–281. Eerkes-Medrano, D., Thompson, R.C., Aldridge, D.C., 2015. Microplastics in freshwater systems: a review of the emerging threats, identification of knowledge gaps and prioritisation of research needs. Water Res. 75 (15), 63–82. Fendall, L.S., Sewell, M.A., 2009. Contributing to marine pollution by washing your face: microplastics in facial cleansers. Mar. Pollut. Bull. 58 (8), 1225–1228. GESAMP, 2015. Sources, fate and effects of microplastics in the marine environment: a global assessment. In: Kershaw, P.J. (Ed.), (IMO/FAO/UNESCOIOC/UNIDO/WMO/IAEA/UN/UNEP/UNDP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection). Rep. Stud. GESAMP No. 90, 96p. Gouin, T., Roche, N., Lohmann, R., Hodges, G., 2011. A thermodynamic approach for assessing the environmental exposure of chemicals absorbed to microplastic. Environ. Sci. Technol. 45 (4), 1466–1472.
Hidalgo-Ruz, V., Gutow, L., Thompson, R.C., Thiel, M., 2012. Microplastics in the marine environment: a review of the methods used for identification and quantification. Environ. Sci. Technol. 46 (6), 3060–3075. Ivair do Sul, J.A., Costa, M.F., 2014. The present and future of microplastic pollution in the marine environment. Environ. Pollut. 185, 352–364. Law, K.L., Thompson, R.C., 2014. Microplastics in the seas. Science 345 (6193), 144– 145. Legendre, P., Legendre, L., 1998. Numerical Ecology, second ed. Elsevier, Amsterdam. Lusher, A.L., Burke, A., O’Connor, I., Officer, R., 2014. Microplastic pollution in the Northeast Atlantic Ocean: validated and opportunistic sampling. Mar. Pollut. Bull. 88 (1–2), 325–333. McCune, B., Mefford, M.J., 1999. Multivariate analysis of ecological data version 5.01. PC-Ord for Windows. MjM Software, Gleneden Beach, Oregon Moore, C.J., 2008. Synthetic polymers in the marine environment: a rapidly increasing, long-term threat. Environ. Res. 108 (2), 131–139. Obbard, R.W., Sadri, S., Wong, Y.Q., Khitun, A.A., Baker, I., Thompson, R.C., 2014. Global warming releases microplastic legacy frozen in Arctic Sea ice. Earth’s Future 2 (6), 315–320. Oliveira, M., Ribeiro, A., Hylland, K., Guilhermino, L., 2013. Single and combined effects of microplastics and pyrene on juveniles (0+ group) of the common goby Pomatoschistus microps (Teleostei, Gobiidae). Ecol. Indic. 34, 641–647. Possatto, F.E., Barletta, M., Costa, M.F., Ivair do Sul, J.A., Dantas, D.V., 2011. Plastic debris ingestion by marine catfish: an unexpected fisheries impact. Mar. Pollut. Bull. 62 (5), 1098–1102. Rios, L.M., Moore, C., Jones, P.R., 2007. Persistent organic pollutants carried by synthetic polymers in the ocean environment. Mar. Pollut. Bull. 54 (8), 1230– 1237. Sherman, G.E., Sutton, T., Blazek, R.E, Luthman, L. Quantum GIS User Guide – Version 2.6.1 ’Brighton’, 2014. . Teuten, E.L., Saquing, J.M., Knappe, D.R.U., Barlaz, M.A., Jonsson, S., Bjorn, A., Rowland, S.J., Thompson, R.C., Galloway, T.S., Yamashita, R., Ochi, D., Watanuki, Y., Moore, C., Pham, H.V., Tana, T.S., Prudente, M., Boonyatumanond, R., Zakaria, M.P., Akkhavong, K., Ogata, Y., Hirai, H., Iwasa, S., Mizukawa, K., Hagino, Y., Imamura, A., Saha, M., Takada, H., 2009. Transport and release of chemicals from plastics to the environment and to wildlife. Philos. Trans. Soc. B 364 (1526), 2027–2045. Thompson, R.C., Olsen, Y., Mitchell, R.P., Davis, A., Rowland, S.J., John, A.W.G., McGonigle, D., Russel, A.E., 2004. Lost at sea: where is all the plastic? Science 304 (5672), 838. Von Moos, N., Burkhardt-Holm, P., Kohler, A., 2012. Uptake and effects of microplastics on cells and tissue of the blue mussel Mytilus edulis L. after an experimental exposure. Environ. Sci. Technol. 46 (20), 11327–11335. Wong, C.S., Green, D.R., Cretney, W.J., 1974. Quantitative tar and plastic waste distributions in Pacific Ocean. Nature 247, 30–32. Wright, S.L., Thompson, R.C., Galloway, T.S., 2013. The physical impacts of microplastics on marine organisms: a review. Environ. Pollut. 178, 483–492. Zarfl, C., Fleet, D., Fries, E., Galgani, F., Gerdts, G., Hanke, G., Matthies, M., 2011. Microplastics in oceans. Mar. Pollut. Bull. 62 (8), 1589–1591.
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