Constraints and Priorities for Conducting Experimental Exposures of Marine Organisms to Microplastics

Marine plastic pollution is a major environmental issue. Given their ubiquitous nature and small dimensions, ingestion of microplastic (MP) and nanoplastic (NP) particles and their subsequent impact on marine life are a growing concern worldwide. Transfers along the trophic chain, including possible translocation, for which the hazards are less understood, are also a major preoccupation. Effects of MP ingestion have been studied on animals through laboratory exposure, showing impacts on feeding activity, reserve depletion and inflammatory responses, with consequences for fitness, notably reproduction. However, most experimental studies have used doses of manufactured virgin microspheres that may not be environmentally realistic. As for most ecotoxicological issues, the environmental relevance of laboratory exposure experiments has recently been debated. Here we review constraints and priorities for conducting experimental exposures of marine wildlife to microplastics based on the literature, feedback from peer reviewers and knowledge gained from our experience. Priorities are suggested taking into account the complexity of microplastics in terms of (i) aggregation status, surface properties and interactions with organic and inorganic materials, (ii) diversity of encountered particles types and concentrations, (iii) particle bioavailability and distribution in experimental tanks to achieve reproducibility and repeatability in estimating effects, and (iv) strict experimental procedures to verify the existence of genuine translocation. Relevant integrative approaches encompass a wide spectrum of methods from -omics to ecophysiological approaches, including modeling, are discussed to provide novel insights on the impacts of MP/NP on marine ecosystems from a long-term perspective. Knowledge obtained in this way would inform stakeholders in such a way as to help them mitigate impacts of the micro- and nano-plastic legacy.

Ika Paul-Pont, Kevin Tallec, Carmen Gonzalez-Fernandez and al., Front. Mar. Sci., 18 July 2018

The article

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Do Microplastics in the Ocean Affect Scallops ? A conversation with WHOI scientist Scott Gallager

WHOI scientist Scott Gallager is making field observations and conducting lab experiments to explore the possible effects of microplastics in the ocean on marine organisms. Specifically, he’s looking at sea scallops at different life stages to determine if the tiny plastic fragments they ingest when filtering seawater stunt their growth. The work is part of WHOI’s Marine Microplastics Initiative, which is aimed at understanding the fate of “hidden” microplastics in the ocean and their impacts on marine life and human health.  (whoi.edu, Oceanus Magazine, 24/01/2019)

The article

Identification and quantitation of semi-crystalline microplastics using image analysis and differential scanning calorimetry

There are several techniques used to analyze microplastics. These are often based on a combination of visual and spectroscopic techniques. Here we introduce an alternative workflow for identification and mass quantitation through a combination of optical microscopy with image analysis (IA) and differential scanning calorimetry (DSC). We studied four synthetic polymers with environmental concern: low and high density polyethylene (LDPE and HDPE, respectively), polypropylene (PP), and polyethylene terephthalate (PET). Selected experiments were conducted to investigate (i) particle characterization and counting procedures based on image analysis with open-source software, (ii) chemical identification of microplastics based on DSC signal processing, (iii) dependence of particle size on DSC signal, and (iv) quantitation of microplastics mass based on DSC signal. We describe the potential and limitations of these techniques to increase reliability for microplastic analysis. Particle size demonstrated to have particular incidence in the qualitative and quantitative performance of DSC signals. Both, identification (based on characteristic onset temperature) and mass quantitation (based on heat flow) showed to be affected by particle size. As a result, a proper sample treatment which includes sieving of suspended particles is particularly required for this analytical approach.

Mauricio Rodríguez Chialanza, Ignacio Sierra, Andrés Pérez Parada, Laura Fornaro, Environmental Science and Pollution Research, pp 1–9, April 2018

Histopathological and molecular effects of microplastics in Eisenia andrei Bouché

The ocean has been assumed as the main sink of microplastics (MPs), however, soils may also receive MPs from different sources and through different pathways, which may affect the biota and their role in soil functions. To the best of our knowledge, only one study, until now, reported the effects of MPs on the survival and fitness of soil organisms (Lumbricus terrestris). In our study, epigeic earthworms, of the species E. andrei, were exposed to different concentrations of MPs (0, 62.5, 125, 250, 500 and 1000 mg/kg soildw) in an OECD artificial soil and tested for reproduction, survival and growth of adults, following a standard protocol. The size of the polyethylene MPs to which earthworms were exposed ranged between 250 and 1000 μm. No significant effects were recorded on survival, number of juveniles and, in the final weight of adult earthworms after 28d of exposure, to the different concentrations of MPs. Nevertheless, FTIR-ATR of earthworms and histopathological analysis of the gut provided evidences of damages and immune system responses to MPs.

A. Rodriguez-Seijo, J. Lourenço, T.A.P. Rocha-Santos, J. da Costa, A.C. Duarte, H. Vala, R. Pereira, Environmental Pollution, Volume 220, Part A, January 2017, Pages 495–503

The article

Extraction, enumeration and identification methods for monitoring microplastics in the environment

There is much research on the occurrence, pollution characteristics and impacts of microplastics in the marine environment but this omits factors which play important roles in the analysis of microplastics. This review summarizes the methods and techniques in the extraction from sediment, seawater and organisms, and assesses their advantages and limitations according to different experimental conditions, such as salt solution and reagents added to remove organic matter. Similarly, this overview includes the enumeration methods of microplastics by many kinds of microscopes (e.g. stereomicroscope, fluorescent microscope, scanning electron microscope). Advantages and challenges of using micro-FTIR, ART-FTIR, FPA-FTIR, Pry-GC/MS, and Raman spectroscopy in the identification methods are also discussed. This review suggests that monitoring microplastics needs standardized protocols for extraction, identification and quantification and that further research on the effects of microplastics to human health is needed.

Qiongxuan Qiu, Zhi Tan, Jundong Wang, Jinping Peng, Meimin Li, Zhiwei Zhan, Estuarine, Coastal and Shelf Science, Volume 176, Pages 102–109, 5 July 2016

The article

A Procedure for Measuring Microplastics using Pressurized Fluid Extraction

A method based on Pressurized Fluid Extraction (PFE) was developed for measuring microplastics in environmental samples. This method can address some limitations of the current microplastic methods and provide laboratories with a simple analytical method for quantifying common microplastics in a range of environmental samples. The method was initially developed by recovering 101% to 111% of spiked plastics on glass beads and was then applied to a composted municipal waste sample with spike recoveries ranging from 85% to 94%. The results from municipal waste samples and soil samples collected from an industrial area demonstrated that the method is a promising alternative for determining the concentration and identity of microplastics in environmental samples.

Stephen George Fuller and Anil Gautam, Environ. Sci. Technol., 2016, 50 (11), pp 5774–5780

The article

Assessing the impact of exposure to microplastics in fish

(…) Collectively, these experiments demonstrate that fish will actively take up microplastics from the water column, as well as ingesting them via their diet. Although ingestion of the micron-sized plastics does not appear to adversely impact the survival or health of adult fish, at least in the short term, there is evidence to support negative changes in the body condition of larval fish. Furthermore, there was evidence that MPs have the potential to partition an organic pollutant and act as a vector to transport this chemical into the food chain. These results highlight the need for longer-term studies that can more fully evaluate the environmental impacts of plastic ingestion for aquatic organisms.

Environment Agency UK, T. Katzenberger and K.Thorpe, March 2015

The report