Abstract
Microplastics receive significant societal and scientific attention due to increasing concerns about their impact on the environment and human health. Marine mammals are considered indicators for marine ecosystem health and many species are of conservation concern due to a multitude of anthropogenic stressors. Marine mammals may be vulnerable to microplastic exposure from the environment, via direct ingestion from sea water, and indirect uptake from their prey. Here we present the first systematic review of literature on microplastics and marine mammals, composing of 30 studies in total. The majority of studies examined the gastrointestinal tracts of beached, bycaught or hunted cetaceans and pinnipeds, and found that microplastics were present in all but one study, and the abundance varied between 0 and 88 particles per animal. Additionally, microplastics in pinniped scats (faeces) were detected in eight out of ten studies, with incidences ranging from 0% of animals to 100%. Our review highlights considerable methodological and reporting deficiencies and differences among papers, making comparisons and extrapolation across studies difficult. We suggest best practices to avoid these issues in future studies. In addition to empirical studies that quantified microplastics in animals and scat, ten studies out of 30 (all focussing on cetaceans) tried to estimate the risk of exposure using two main approaches; i) overlaying microplastic in the environment (water or prey) with cetacean habitat or ii) proposing biological or chemical biomarkers of exposure. We discuss advice and best practices on research into the exposure and impact of microplastics in marine mammals. This work on marine ecosystem health indicator species will provide valuable and comparable information in the future.
Highlights
IntroductionMarine mammals play key roles in influencing the structure and function of the marine environment and are sentinels for ecosystem health (Burek et al, 2008; Moore, 2008).due to an increase in anthropogenic activities, including fishing (Barcenas-De laCruz et al, 2018; Ocampo Reinaldo et al, 2016), shipping (Halliday et al, 2017; Riley &Hollich, 2018), pollution (Brown et al, 2018; Frouin et al, 2012) and climate change (Albouy et al, 2020; Sanderson & Alexander, 2020), many marine mammals species are of conservation concern (Nelms et al, In prep; Davidson et al, 2012; Pompa et al, 2011).Journal Pre-proof Plastic pollution is known to affect marine mammals, through entanglement (Kraus, 2018), ingestion (Alexiadou et al, 2019; De Stephanis et al, 2013; Unger et al, 2016) and potential habitat degradation (Gall & Thompson, 2015; Pawar et al, 2016)
2018), pollution (Brown et al, 2018; Frouin et al, 2012) and climate change (Albouy et al, 2020; Sanderson & Alexander, 2020), many marine mammals species are of conservation concern (Nelms et al, In prep; Davidson et al, 2012; Pompa et al, 2011)
Most of the scat and gut studies on microplastics and marine mammals were conducted in Europe (47%; n=10) – mostly in the United Kingdom and in Italy, followed by North America
Summary
Marine mammals play key roles in influencing the structure and function of the marine environment and are sentinels for ecosystem health (Burek et al, 2008; Moore, 2008).due to an increase in anthropogenic activities, including fishing (Barcenas-De laCruz et al, 2018; Ocampo Reinaldo et al, 2016), shipping (Halliday et al, 2017; Riley &Hollich, 2018), pollution (Brown et al, 2018; Frouin et al, 2012) and climate change (Albouy et al, 2020; Sanderson & Alexander, 2020), many marine mammals species are of conservation concern (Nelms et al, In prep; Davidson et al, 2012; Pompa et al, 2011).Journal Pre-proof Plastic pollution is known to affect marine mammals, through entanglement (Kraus, 2018), ingestion (Alexiadou et al, 2019; De Stephanis et al, 2013; Unger et al, 2016) and potential habitat degradation (Gall & Thompson, 2015; Pawar et al, 2016). One area of specific concern is the exposure of marine mammals to microplastics. These small (< 5mm), pervasive and persistent synthetic particles (Moore, 2008) are bioavailable to marine organisms, through direct ingestion and/or via trophic transfer (Cole et al, 2011; Eriksson & Burton, 2003; Nelms, et al, 2019a). Mysticetes (baleen-whales), for example, are megafilter feeders that engulf large volumes of water alongside their prey, and are potentially exposed to microplastics via both pathways; direct uptake of microplastics from the environment Germanov et al, 2018; Guerrini et al, 2019), and indirect ingestion, from consuming contaminated prey (trophic transfer exposure, e.g. BurkhardtHolm & N’Guyen, 2019; Desforges et al, 2015). Studies on other taxa indicate that microplastics may present a number of potential impacts, acting as a vector for pathogens or chemical contaminants (Prinz & Korez, 2020)
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