Lack of behavioral effect of surgical mask leachate on the Asian shore crab Hemigrapsus sanguineus: Implications for invasion success in polluted coastal waters.

The COVID-19 pandemic generated a new source of plastic mass pollution, i.e. surgical masks, that preferentially accumulate in intertidal environments. Made of polymers, surgical masks are likely to leach additives and impact local intertidal fauna. As typical endpoints of complex developmental and physiological functions, behavioral properties are non-invasive key variables that are particularly studied in ecotoxicological and pharmacological studies, but have, first and foremost, adaptive ecological significance. In an era of ever-growing plastic pollution, this study focused on anxiety behaviors, i.e. startle response, scototaxis (i.e. preference for dark or light areas), thigmotaxis (i.e. preference for moving toward or away from physical barriers), vigilance and level of activity, of the invasive shore crab Hemigrapsus sanguineus in response to leachate from surgical masks. We first showed that in the absence of mask leachates H. sanguineus is characterized by a short startle time, a positive scototaxis, a strong positive thigmotaxis, and an acute vigilance behavior. Specifically, a significantly higher level of activity was observed in white areas, in contrast to the lack of significant differences observed in black areas. Noticeably, the anxiety behaviors of H. sanguineus did not significantly differ after a 6-h exposure to leachate solutions of masks incubated in seawater for 6, 12, 24, 48 and 96 h. In addition, our results were consistently characterized by a high inter-individual variability. This specific feature is discussed as an adaptive behavioral trait, which - through the observed high behavioral flexibility - increases H. sanguineus resilience to contaminant exposures and ultimately contribute to its invasion success in anthropogenically-impacted environments.

A whale of a plastic tale: A plea for interdisciplinary studies to tackle micro- and nanoplastic pollution in the marine realm.

Plastic is one of the most ubiquitous sources of both contamination and pollution of the Anthropocene, and accumulates virtually everywhere on the planet. As such, plastic threatens the environment, the economy and human well-being globally. The related potential threats have been identified as a major global conservation issue and a key research priority. As a consequence, plastic pollution has become one of the most prolific fields of research in research areas including chemistry, physics, oceanography, biology, ecology, ecotoxicology, molecular biology, sociology, economy, conservation, management, and even politics. In this context, one may legitimately expect plastic pollution research to be highly interdisciplinary. However, using the emerging topic of microplastic and nanoplastic leachate (i.e., the desorption of molecules that are adsorbed onto the surface of a polymer and/or absorbed into the polymer matrix in the absence of plastic ingestion) in the ocean as a case study, we argue that this is still far from being the case. Instead, we highlight that plastic pollution research rather seems to remain structured in mostly isolated monodisciplinary studies. A plethora of analytical methods are now available to qualify and quantify plastic monomers, polymers and the related additives. We nevertheless show though a survey of the literature that most studies addressing the effects of leachates on marine organisms essentially still lack of a quantitative assessment of the chemical nature and content of both plastic items and their leachates. In the context of the ever-increasing research effort devoted to assess the biological and ecological effects of plastic waste, we subsequently argue that the lack of a true interdisciplinary approach is likely to hamper the development of this research field. We finally introduce a roadmap for future research which has to evolve through the development of a sound and systematic ability to chemically define what we biologically compare.

Plastic leachates: Bridging the gap between a conspicuous pollution and its pernicious effects on marine life.

With 4 to 12 million tons of plastic entering the marine environment each year, plastic pollution has become one of the most ubiquitous sources of pollution of the Anthropocene threatening the marine environment. Beyond the conspicuous physical damages, plastics may release a cocktail of harmful chemicals, i.e. monomers, additives and persistent organic pollutants. Although known to be highly toxic, plastic leachates seemingly appear, however, as the "somewhat sickly child" of the plastic pollution literature. We reviewed the only 26 studies investigating the impact of plastic leachates on marine microbes and invertebrates, and concluded that the observed effects essentially depend on the species, polymer type, plastic composition, accumulated contaminants and weathering processes. We identified several gaps that we believe may hamper progress in this emerging area of research and discussed how they could be bridged to further our understanding of the effects of the compounds released by plastic items on marine organisms. We first stress the lack of a consensus on the use of the term 'leachate', and subsequently introduce the concepts of primary and secondary leachates, based on the intrinisic or extrinsic origin of the products released in bulk seawater. We discuss how methodological inconsistencies and the discrepancy between the polymers used in experiments and their abundance in the environment respectively limit comparison between studies and a comprehensive assessment of the effects leachate may actually have in the ocean. We also discuss how the imbalanced in the variety of both organisms and polymers considered, the mostly unrealistic concentrations used in laboratory experiments, and the lack of investigation on key ecosystem engineers may considerably narrow the spectrum of our understanding of the plastic leachates' effects. We finally discuss how increasing multi-disciplinarity through collaborations between different research fields may benefit to an area of research which is still in its early infancy.

Effects of temperature on the behaviour and metabolism of an intertidal foraminifera and consequences for benthic ecosystem functioning.

Heatwaves have increased in intensity, duration and frequency over the last decades due to climate change. Intertidal species, living in a highly variable environment, are likely to be exposed to such heatwaves since they can be emerged for more than 6 h during a tidal cycle. Little is known, however, on how temperature affects species traits (e.g. locomotion and behaviour) of slow-moving organisms such as benthic foraminifera (single-celled protists), which abound in marine sediments. Here, we examine how temperature influences motion-behaviour and metabolic traits of the dominant temperate foraminifera Haynesina germanica by exposing individuals to usual (6, 12, 18, 24, 30 °C) and extreme (high; i.e. 32, 34, 36 °C) temperature regimes. Our results show that individuals reduced their activity by up to 80% under high temperature regimes whereas they remained active under the temperatures they usually experience in the field. When exposed to a hyper-thermic stress (i.e. 36 °C), all individuals remained burrowed and the photosynthetic activity of their sequestered chloroplasts significantly decreased. Recovery experiments subsequently revealed that individuals initially exposed to a high thermal regime partially recovered when the hyper-thermic stress ceased. H. germanica contribution to surface sediment reworking substantially diminished from 10 mm3 indiv-1 day-1 (usual temperature) to 0 mm3 indiv-1 day-1 when individuals were exposed to high temperature regimes (i.e. above 32 °C). Given their role in sediment reworking and organic matter remineralisation, our results suggest that heatwaves may have profound long-lasting effects on the functioning of intertidal muddy ecosystems and some key biogeochemical cycles.