Frequency of Microplastics in Mesopelagic Fishes from the Northwest Atlantic

Alina M Wieczorek,A Louise Allcock,Olivier Savard,Peter L Croot,Eoin Macloughlin,Thomas K Doyle,Hannah Brownlow,Liam Morrison

doi:10.3389/fmars.2018.00039

Abstract

Microplastics are a ubiquitous pollutant in our seas today and are known to have detrimental effects on a variety of organisms. Over the past decade numerous studies have documented microplastic ingestion by marine species with more recent investigations focussing on the secondary impacts of microplastic ingestion on ecosystem processes. However, few studies so far have examined microplastic ingestion by mesopelagic fish which are one of the most abundant pelagic groups in our oceans and through their vertical migrations are known to contribute significantly to the rapid transport of carbon and nutrients to the deep sea. Therefore, any ingestion of microplastics by mesopelagic fish may adversely affect this cycling and may aid in transport of microplastics from surface waters to the deep-sea benthos. In this study microplastics were extracted from mesopelagic fish under forensic conditions and analysed for polymer type utilising micro-Fourier Transform Infrared Spectroscopy (micro-FTIR) analysis. Fish specimens were collected from depth (300 - 600 m) in a warm-core eddy located in the Northwest Atlantic, 1200 km due west of Newfoundland during April and May 2015. In total, 233 fish gut contents from seven different species of mesopelagic fish were examined. An alkaline dissolution of organic materials from extracted stomach contents was performed and the solution filtered over a 0.7 µm borosilicate filter. Filters were examined for microplastics and a subsample originating from 35 fish was further analysed for polymer type through micro-FTIR analysis. 73% of all fish contained plastics in their gut contents with Gonostoma denudatum having the highest ingestion rate (100 %) followed by Serrivomer beanii (93 %) and Lampanyctus macdonaldi (75 %). Overall, we found a much higher occurrence of microplastic fragments, mainly polyethylene fibres, in the gut contents of mesopelagic fish than previously reported. Stomach fullness, species and the depth at which fish were caught at, were found to have no effect on the amount of microplastics found in the gut contents. However, these plastics were similar to those sampled from the surface water. Additionally, using forensic techniques we were able to highlight that fibres are a real concern rather than an artefact of airborne contamination.

Highlights

As a consequence of decades of marine litter entering our seas (Ryan, 2015), microplastics have been found in coastal and pelagic environments around the globe with an ever increasing distribution (Barnes et al, 2009; Galgani et al, 2015)
Overall 73% of fish contained plastics in their stomachs with G. denudatum having the highest frequency of occurrence (100%), followed by S. beanii (93%) and L. macdonaldi (75%) (Table 1)
452 microplastic fragments were extracted from the fish gut contents, with an average of 1.8 microplastic fragments per fish

Summary

Introduction

As a consequence of decades of marine litter entering our seas (Ryan, 2015), microplastics have been found in coastal and pelagic environments around the globe with an ever increasing distribution (Barnes et al, 2009; Galgani et al, 2015). Wright et al (2013) demonstrated how the ingestion of microplastics by the polychaete Arenicola marina (lugworm), an important ecosystem engineer of Northern Europe’s intertidal zones, caused inflammation and decreased feeding and depleted energy reserves. Such studies have prompted researchers to investigate the impact on ecosystem processes. With the increasing evidence that microplastics represent an ecosystem and environmental health concern, UNEP and the EU Commission have established bodies and efforts to guide in decision making and legislation (Galgani et al, 2013; UNEP, 2016). Several governments have taken legislative steps by introducing a ban on microbeads in cosmetics and detergents by 2020 (Sutherland et al, 2017)

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