At second glance: The importance of strict quality control – A case study on microplastic in the Southern Ocean key species Antarctic krill, Euphausia superba

The stomach content of 60 krill specimens from the Southern Ocean were analyzed for the presence of micro-plastic (MP), by testing different sample volumes, extraction approaches, and applying hyperspectral imaging Fourier-transform infrared spectroscopy (μFTIR). Strict quality control was applied on the generated results. A high load of residual materials in pooled samples hampered the analysis and avoided a reliable determination of putative MP particles. Individual krill stomachs displayed reliable results, however, only after re-treating the samples with hydrogen peroxide. Before this treatment, lipid rich residues of krill resulted in false assignments of polymer categories and hence, false high MP particle numbers. Finally, MP was identified in 4 stomachs out of 60, with only one MP particle per stomach. Our study highlights the importance of strict quality control to verify results before coming to a final decision on MP contamination in the environment to aid the establishment of suitable internationally standardized protocols for sampling and analysis of MP in organisms including their habitats in Southern Ocean and worldwide

Quantification of microplastics in the stomach content of krill in the Southern Ocean

Microplastics (< 5 mm) have become ubiquitous in global oceans, posing a threat for a wide range of marine species. Recent publications have described the presence of microplastics in the water column and sediments in the Southern Ocean. This study aimed to investigate the occurrence of microplastics in the gut content of the keystone species Antarctic Krill (Euphausia superba). Specimens were collected around the Antarctic Peninsula during the PS112 expedition (March to May 2018) in three regions: Elephant Island, Bransfield Strait West and the Weddell Sea. Twenty krill stomachs were analysed per region: 10 pooled, 5 pooled and 5 single stomachs. Microplastics were extracted through a 24-hour 10% potassium hydroxide (KOH) digestion step and the particles were identified using focal plane array (FPA) Fourier transform infrared (FTIR) microscopy. Abundance, chemical nature, and size distribution of the microplastics were also analysed. All analysed samples contained microplastics except one individual in the Bransfield Strait West region that did not show any plastic contamination. Krill collected in Elephant Island showed a higher number of plastic particles per stomach than the two other regions. Twelve polymer types were found across the three areas. The main polymers identified were polyethylene (34.47%), polypropylene (27.68%) and polyamide (26.51%) in Elephant Island, polyamide (64.52%) in Bransfield Strait West, and polyamide (66.65%) and polycarbonate (23.51%) in the Weddell Sea. All microplastics were below 100 μm in size, with 98.14% smaller than 50 μm

Analysis of small microplastics and nanoplastics in complex matrices

Plastic pollution is ubiquitous and persistent in the aquatic environment. Its distribution is heterogeneous in terms of both physical (e.g. size, shape, density, porosity, colour) and chemical properties (e.g. polymer type, surface charge, polarity, presence of additives or persistent organic pollutants). A strong international research effort has been made over the past 15 years, notably on methods development, to collect, prepare, and thus analyse plastic items with dimensions between 10 µm and 5 mm denoted as microplastics (MPs). However, MPs will eventually degrade in the environment - with a concomitant modification of their initial characteristics - to successively smaller entities, eventually reaching the nano-size range: they are then denoted as nanoplastics (< 1 µm; NPs). Nanoplastics are expected to be widely present in the environment and to represent an hazard for the ecosystem and ultimately for humans, but there is a paucity of reliable data on the concentration and distribution of small MPs (< 10 µm ; sMPs) and NPs in environmental matrices. Furthermore, there is currently a knowledge gap on these particles notably because of sampling and analytical challenges with methods that need to diverge from the ones developed at present for MPs. The current lack of relevant and standardized methods for sampling, preparing, and then quantifying and characterizing sMPs and NPs precludes the development of robust environmental risk assessment strategies. Indeed, by knowing their realistic distribution in the environment, it will be possible to set ecotoxicological studies with notably relevant concentration and particles types of plastics. The end goal of the present work is to identify reliable and relevant methods applicable for sampling, preparing, and determining the concentration and distribution of sMPs and NPs in complex environmental matrices (water, sediment and fauna) including information on their physical and/or chemical characteristics. The developed analytical toolbox will provide the means to establish realistic input values for further ecotoxicological studies and risk assessment regarding plastic particles with size smaller than 10 µm. [Acknowledgements: This research is supported by the Fonds Wetenschappelijk Onderzoek – Vlaanderen (FWO, Research Foundation Flanders) via SB PhD fellowship (grant no.1S03922N) and FWO project (grant no.G053320N).

A machine learning algorithm for high throughput identification of FTIR spectra: Application on microplastics collected in the Mediterranean Sea

The development of methods to automatically determine the chemical nature of microplastics by FTIR-ATR spectra is an important challenge. A machine learning method, named k-nearest neighbors classification, has been applied on spectra of microplastics collected during Tara Expedition in the Mediterranean Sea (2014). To realize these tests, a learning database composed of 969 microplastic spectra has been created. Results show that the machine learning process is very efficient to identify spectra of classical polymers such as poly(ethylene), but also that the learning database must be enhanced with less common microplastic spectra. Finally, this method has been applied on more than 4000 spectra of unidentified microplastics. The verification protocol showed less than 10% difference in the results between the proposed automated method and a human expertise, 75% of which can be very easily corrected

Is it absent or is it present? Detection of a non-native fish to inform management decisions using a new highly-sensitive eDNA protocol

Environmental managers require a sensitive and reliable means to prove, with the highest level of confidence possible, where non-native fish species exist and where they do not. Therefore, a nested PCR (nPCR) protocol was developed to detect the environmental DNA (eDNA) of a case-study species, topmouth gudgeon Pseudorasbora parva, which was recently the subject of a national eradication campaign in the UK. The nPCR protocol was tested in the laboratory and in the field in a series of coordinated surveys (eDNA and conventional sampling with traps) at a commercial angling venue in southern England where an initial eDNA survey, based on conventional PCR (cPCR), found P. parva to be present in one of the seven ponds. In the laboratory, the nPCR protocol was on average 100x more sensitive than cPCR, providing a 100% detection rate at DNA concentrations of 3x10(-8)ng/mu L (8 DNA copies per mu L). In the field, nPCR and conventional trapping both detected P. parva in only one of the seven angling ponds, the same infested pond as in the previous cPCR-based study. Following eradication work on the infested pond, no eDNA of P. parva was detected using nPCR in either the formerly-infested pond or the adjacent pond, which had been used to quarantine large commercially-valuable fishes. In management applications where the veracity of negative results may be of equal importance as confirmation of positive detections, nPCR protocols provide a useful addition to the analytical toolkit available to inform decision makers responsible for non-native species management

Statistical Methodology for Identifying Microplastic Samples Collected During TARA Mediterranean Campaign

International audienc

Chemical composition of microplastics floating on the surface of the Mediterranean Sea

The Mediterranean Sea is one of the most studied regions in the world in terms of microplastic (MP) contamination. However, only a few studies have analysed the chemical composition of MPs at the Mediterranean Sea surface. In this context, this study aims to describe the chemical composition as a function of particle size, mass and number concentrations of MPs collected in the surface waters of the Mediterranean Sea. The chemical composition showed a certain homogeneity at the Mediterranean Sea scale. The main polymers identified by Fourier Transform Infra-Red (FTIR) spectroscopy were poly(ethylene) (67.3 +/- 2.4%), poly(propylene) (20.8 +/- 2.1%) and poly(styrene) (3.0 +/- 0.9%). Nevertheless, discrepancies, confirmed by the literature, were observed at a mesoscale level. Thus, in the North Tyrrhenian Sea, the proportion of poly(ethylene) was significantly lower than the average value of the Mediterranean Sea (57.9 +/- 10.5%). Anthropic sources, rivers, or polymer ageing are assumed to be responsible for the variations observed