Widespread distribution of microplastics in subsurface seawater in the NE Pacific Ocean

https://doi.org/10.1016/j.marpolbul.2013.12.035Get rights and content

Highlights

  • Microplastic abundance and distribution were characterized in NE Pacific seawater samples.

  • Microplastic particles (62–5000 μm) were found in seawater at all stations.

  • Microplastic concentrations were highest nearshore, consistent with land-based sources.

  • Low microplastic levels SW of Vancouver Island are consistent with La Perouse Bank upwelling.

  • This assessment provides a basis to evaluate the in-coming debris from Tohoku Tsunami.

Abstract

We document the abundance, composition and distribution of microplastics in sub-surface seawaters of the northeastern Pacific Ocean and coastal British Columbia. Samples were acid-digested and plastics were characterized using light microscopy by type (fibres or fragments) and size (<100, 100–500, 500–100 and >1000 μm). Microplastics concentrations ranged from 8 to 9200 particles/m3; lowest concentrations were in offshore Pacific waters, and increased 6, 12 and 27-fold in west coast Vancouver Island, Strait of Georgia, and Queen Charlotte Sound, respectively. Fibres accounted for ∼75% of particles on average, although nearshore samples had more fibre content than offshore (p < 0.05). While elevated microplastic concentrations near urban areas are consistent with land-based sources, the high levels in Queen Charlotte Sound appeared to be the result of oceanographic conditions that trap and concentrate debris. This assessment of microplastics in the NE Pacific is of interest in light of the on-coming debris from the 2011 Tohoku Tsunami.

Introduction

The marine environment is host to increasing quantities of waste debris from human activities in and around the ocean (Arthur and Baker, 2011). Any persistent or manufactured solid material discarded in the marine or coastal environment is termed marine debris, of which a large fraction (60–80%) consists of plastic (GESAMP, 2010, UNEP, 2005). An estimated 1.3 plastic items can be found for every m2 of shoreline worldwide, based on a review of 201 beach surveys on five continents (Bravo et al., 2009). This debris is increasingly recognized as a threat to marine biota. For instance, through ingestion or entanglement, more than 267 species worldwide are estimated to be impacted by marine debris, including the majority of sea turtle species and almost 50% of all seabird and marine mammal species (Derraik, 2002).

Over the past decade, efforts to document microplastics in the marine environment have increased. Microplastics have been defined as plastic particles <5 mm and typically over 333 μm, while smaller particles (>1 μm) are also included but less often detected (Arthur et al., 2009). Several plastic classes exist, but the most commonly found micro-debris particles include polyethylene (PE), polypropylene (PP), and polystyrene (PS) (Andrady, 2011). Microplastics are now ubiquitous in the marine environment, having been found in seawater at the surface and at depth, and in oceans and coastlines from the equator to the poles (Barnes et al., 2009). Despite the growing number of publications on the topic, large gaps still remain in our understanding of the source, transport and fate of microplastics in the marine environment.

Microplastics consist of either deliberately manufactured commercial micro-particles, including scrubbers, abrasives, and precursor pellets (primary sources), or as fragments and fibres derived from the deterioration of larger products (secondary sources) (Hidalgo-Ruz et al., 2012). Plastic debris can originate from marine-based sources (i.e. fishing, aquaculture, shipping, etc.) or land-based sources (i.e. wastewater effluent, run-off, rivers), but the majority is believed to derive from the latter (Andrady, 2011). Regardless of origin, plastics are manufactured to be durable and thus persist in the environment, particularly in water where degradation can occur over decades (Hidalgo-Ruz et al., 2012). The abundance and distribution of microplastics in the marine environment are believed to be governed by prevailing surface circulation and winds, plastic density, colour and shape, and proximity to urban centres (Andrady, 2011, Browne et al., 2011, Browne et al., 2010, Doyle et al., 2011).

Although the harmful effects of large plastic debris on marine wildlife have been well documented (i.e. Derraik, 2002), little is known about the effects of microplastics. Potential threats to biota may include physical harm from ingestion, leaching of toxic additives, and desorption of persistent, bioaccumulative and toxic (PBT) chemicals (GESAMP, 2010). Small plastic fragments are available to organisms at the base of the food web as they may be in the same size-range as natural food items. Recent studies have shown that plankton and several classes of invertebrates and vertebrates can ingest and accumulate microplastics (see review by Wright et al., 2013). Furthermore, microplastics have been found to concentrate a wide-range of organic contaminants in the aquatic environment due to their hydrophobic nature. Contaminants that have been adsorbed include polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dichlorodiphenyltrichloroethane (DDT), polybrominated diphenylethers (PBDEs), and bisphenol A (BPA) (Mato et al., 2001, Rios et al., 2007, Teuten et al., 2009). Few studies have examined the bioaccumulation of PBT chemicals from plastics, although some studies suggest that PCB concentrations rose in lugworms (Arenicola marina) and seabirds (Puffinus gravis, Calonectris leucomelas) exposed to contaminated plastic particles (Ryan et al., 1988, Teuten et al., 2009, Teuten et al., 2007).

The aim of this study was to investigate the abundance, composition and distribution of marine microplastics in the NE Pacific Ocean in areas in and near the coastal waters of British Columbia (BC), Canada. Microplastics were quantified according to size (62–5000 μm) and shape (fibres or fragments) in sub-surface seawater. This study is particularly timely given the present movement of marine debris across the Pacific as a result of the 2011 Tohoku earthquake and resulting tsunami.

Section snippets

Sampling

Sampling was conducted aboard two oceanographic research cruises: the CCGS John P. Tully cruise of the Line P time series program in August 2012, and the La Perouse Monitoring Program cruise of September 2012 conducted by the Institute of Ocean Sciences (Fisheries and Oceans Canada). The sampling regime was developed to create a low cost, long-term monitoring program that is integrated into existing oceanographic programs. As such, sampling was conducted during standard cruise operations at

Microplastic abundance

Microplastics were detected at 34 stations, but concentrations varied considerably and ranged from 8 to 9180 particles/m3 (Table 1, Fig. 1). The concentration of microplastics was 4–27 times greater at sites nearshore (SoG, WCVI, and QCS) than sites offshore in the NE Pacific Ocean (Fig. 1, Table 1). Locally, the inland waters of QCS and the SoG had higher microplastic levels than the WCVI (p = 0.015 and p = 0.007 respectively, Table 1). A localized area of low concentrations southwest of Vancouver

Discussion

Microplastics (62–5000 μm) were abundant in all samples in our study area, confirming the presence of plastic micro-debris throughout the subsurface waters of the NE Pacific Ocean. The mean abundance of plastic estimated here is several orders of magnitude greater than that reported in other regions of the North Pacific region, including the North Pacific Gyre, the west coast of the United States, and the Bering Sea (Doyle et al., 2011, Lattin et al., 2004, Moore et al., 2002, Moore et al., 2001

Acknowledgements

Thanks to the crew of the CCGS John P. Tully and the sea-going scientific staff of the Institute of Ocean Sciences (Fisheries and Oceans Canada); especially Doug Yelland and Marie Robert, chief scientists for the La Pérouse Zooplankton Monitoring Program and Line P Monitoring Program respectively. The authors kindly acknowledge the helpful discussions with Olga Lukyanova, Joel Baker and participants of the workshop on “Trends in Marine Contaminants” held at the 2011 Annual Conference of the

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