Towards assessing the impact of plastic debris on the Mediterranean Sea ecosystem
Project Summary. The accumulation of plastic debris in nature is “one of the most ubiquitous and long-lasting recent changes to the surface of our planet” (Barnes, et al., 2009) and one of the most pervasive environmental concerns of our time. Yet, too little is known about the fate of this plastic and its role in ecosystem dynamics to predict the inevitable impacts on our world’s oceans.
To address this critical knowledge gap, TARA Méditerranée will take the first large-scale expedition and cross-disciplinary approach to better understand the ecosystem-level impacts of surface plastics in the Mediterranean Sea, a vital cultural and economic asset where plastics have already been documented at high numbers (Collignon, et al., 2012). We will quantify and identify surface plastics and plastic-bound organic pollutants, document the interaction between plastics and ecosystem members (e.g., plankton, fish), and explore the community dynamics and function of microscopic plastic-dwelling life forms (including potential alien and toxin species). Finally, we will employ a novel -potentially high-impact- approach to link plastic fragment distribution to circulation and physico-chemical properties of water masses at the basin scale, thereby informing future attempts to model and predict the spatial fate of plastic in the Mediterranean Sea.
Motivation. Reports of the “Great Pacific Garbage Patch”, an amalgam of human-generated trash in the North Pacific Gyre, have brought attention to the accumulation of plastic in the world’s oceans, with even our most remote polar seas inundated with plastic debris (Tara Oceans, press release, 2011). With the first reports of ocean plastic nearly half a century ago (Carpenter and Smith, 1972), prevalence has continued to rise as our societal dependence on disposable plastic products increases annually (Thompson, et al., 2004), since most plastics used are not biodegradable. In 2008 alone, EU-27, Norway and Switzerland produced about 24.9 megatons of plastic waste (Mudgal et al., 2011), but its abundance, distribution, and ecosystem impacts in physically dynamic marine habitats are difficult to predict without coordinated comprehensive assessment efforts (Galgani, et al., European Commission Joint Research Center report, 2010).
Historically, the best-documented impacts of plastic on marine ecosystems are entanglement and ingestion of relatively large debris by wildlife. Lesser-known effects include the physical alteration of habitats and the transport of alien and harmful species (Fig. 1; Derraik, 2002; Barnes, 2002; Masó, et al., 2003), and socioeconomic costs, as visible debris disrupts. The vast majority of aquatic plastic is small, nearly invisible “microplastic” (< 5 mm). These are produced from weathering or enter water directly as pre-consumer plastic before molding or from use in abrasives (e.g., sand-blasting) and cosmetics (e.g., microbead face scrubs).
Plastic-Associated Toxins. Not only are microplastics the most abundant size class, they also represent the greatest total plastic surface area and serve as veritable sponges of ambient persistent organic pollutants (POPs; Teuten, et al., 2007; Hirai, et al., 2011), most of which are highly toxic and have a wide range of chronic effects, including endocrine disruption, mutation and cancer. POPs detected on marine microplastics include PCBs (polychlorinated biphenyls) and PAHs (polyaromatic hydrocarbons), as well as organo-chlorine pesticides, such as DDT (dichlorodiphenyltrichloroethane) (Rios et al., 2007). Furthermore, plastic additives that leach from plastics as they degrade (e.g., phthalates, BPA), induce toxic effects in aquatic organisms, even at low levels (ng l-1 to µgl-1) (Oehlmann, et al., 2009) and bioaccumulate in plastic-ingesting organisms (Boerger, et al., 2010; Wright, et al., 2013), with unknown consequences on the marine food web, human and environmental health.
The “Plastic Microbiome.” The surface of ocean plastic debris is teeming with microscopic life forms (Fig. 2). The role of microbes (bacteria, archaea, picoeukaryotes, viruses) in the fate of aquatic plastics and associated toxins, and vice-a-versa, has not been well studied. We will characterize the microbiome of this contemporary man-made habitat by addressing “who is there?” and “what are they doing?” Microbial communities on ocean plastics are unique from background seawater and non-plastic controls, already suggesting a degree of plastic specificity (M. Duhaime, TARA Oceans). Of further concern, we will assess the extent to which plastics serve as vectors of pathogenic and toxic microbes, as Vibrio spp. colonizing ocean plastics (Zaikab, 2011) and toxic algae on Mediterranean plastics (Masó, et al., 2003) have been reported.
Objectives of the TARA Méditerranée expedition
1- Assess spatial distribution of floating plastic fragments (0.3 – 50 mm) in the Mediterranean Sea
2- Chemical characterization of the different plastic types
3- Scanning electron microscopy, stereomicroscopy and genomic analysis of the attached microbial communities
4- Ecosystem structure of plankton in contact with plastic fragments – day/night variability
5- Acquisition of environmental descriptors – T, S, turbidity, pigments, ocean color
This approach will allow:
(1) spatial quantification and polymer-type characterization of plastic across the Mediterranean Sea,
(2) identification of prolific point sources or plastic accumulation zones,
(3) analysis of plastic-bound POPs,
(4) linkage of plastic fragments to discreet water masses and related ecosystems.
Work at sea. Each sample will consist of at least 3 daytime Manta tows and one night tow, 30 min each. Sample will be stored according to different protocols. Simultaneously, water samples will be taken for water column microbial community and phytoplankton pigment analyses. The physic-chemical sampling will be done underway using a SBE thermosalinograph and a hyperspectral ACs. A SBE CTD will be deployed vertically to determine the depth of the mixed layer. Ocean Colour satellite images supplied by ACRI-ST and the Mercator circulation model will be used to determine the zones of interest for the field sampling. Short supplementary net tows will provide living material for live stereomicroscopy of the surface plankton in different Mediterranean regions. When possible, neuston tows will be performed to collect small planktonivorous fish. The stomach contents of collected fish will be examined for microplastics.
Work on land. Non-destructive Fourier Transform-Infrared Spectroscopy (FT-IR) will be used to determine polymer types. A database of FT-IR spectra representing dominant marine microplastic families will be established per Mediterranean region. The plastic-attached metazoans and microbial biofilm communities will be characterized using different imaging techniques, scanning electron microscopy (SEM) and community genomic sequencing. Organic pollutants will be extracted from bulk plastic samples and identified using a combination of gas chromatography mass spectroscopy (GC-MS) and liquid chromatography. The biodiversity determined using the ZooScan method (Gorsky, et al., 2010) on day and night zooplankton samples will be compared with the plastic fragments distribution patterns and with water mass physical characteristics. Stomach content of fish collected at night on the surface will be used for the bioaccumulation studies.
List of scientists involved in alphabetical order:
Emmanuel Boss, University of Maine, USA, with the support of NASA : marine optics
Stéphane Bruzaud, University of Bretagne Sud, France : classification of plastic
Melissa Duhaime, University of Michigan, USA : plastic colonisation – SEM, genomics; chemistry
Ma Luz Fernandez des Puelles, IEO, Centro Oceanográfico de Baleares, Spain : zooplankton
Francois Galgani, IFREMER Corse, France : data base of Mediterranean plastic
Marie Garrido, Université de Corse, France : phytoplankton
Jean-Francois Ghiglione, CNRS/UPMC, Observatoire Océanographique de Banyuls, France : bacteria & archea
Gaby Gorsky, UPMC/CNRS, Observatoire Océanologique de Villefranche sur mer, France : PI
Jean-Louis Jamet, Université Toulon Var, France : zooplankton diversity
Maria Grazia Mazzocchi, Stazione Zoologica Anton Dohrn, Naples, Italy : zooplankton diversity
Anne Molcard, MIO Université Toulon Var, France : physical oceanography
Maria-Luiza Pedrotti, CNRS and Stéphanie Petit, UPMC, France: attached microbial and macrobial communities
Mathias Ricking, Free University Berlin, Germany : pollutants chemistry
Richard Sempéré, Aix Marseille Université, France : phthalates
Lars Stemmann and Amanda Elineau, UPMC, Observatoire Océanologique de Villefranche sur mer, France : distribution of plastic and plankton in relation to the hydrodynamics
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16 Zaikab, G.D. (2011). Marine microbes digest plastic. Nature News. doi:10.1038/news.2011.191