Plastic and natural inorganic microparticles do not differ in their effects on adult mussels (Mytilidae) from different geographic regions

Thea Hamm,Jonas Barkhau,Daphne Houiller,Mark Lenz,Maria Greulich,Paulo Vasconcelos,Zanna Chase,Corrine Almeida,Abril Sanchez Leon,Leo L Gottschalck,Uki Kawata,Gil Rilov,Lukas Novaes Tump,Anna-Louise Gabriel,Catriona L Hurd,Masahiro Nakaoka,Jennifer L Lavers,Jeffrey T Wright,Martín Thiel ,Vincent H.s Yap

doi:10.1016/j.scitotenv.2021.151740

Abstract

Microplastics are ubiquitous in the marine environment and studies on their effects on benthic filter feeders at least partly revealed a negative influence. However, it is still unclear whether the effects of microplastics differ from those of natural suspended microparticles, which constitute a common stressor in many coastal environments. We present a series of experiments that compared the effects of six-week exposures of marine mussels to two types of natural particles (red clay and diatom shells) to two types of plastic particles (Polymethyl Methacrylate and Polyvinyl Chloride). Mussels of the family Mytilidae from temperate regions (Japan, Chile, Tasmania) through subtropical (Israel) to tropical environments (Cabo Verde) were exposed to concentrations of 1.5 mg/L, 15 mg/L and 150 mg/L of the respective microparticles. At the end of this period, we found significant effects of suspended particles on respiration rate, byssus production and condition index of the animals. There was no significant effect on clearance rate and survival. Surprisingly, we observed only small differences between the effects of the different types of particles, which suggests that the mussels were generally equally robust towards exposure to variable concentrations of suspended solids regardless of whether they were natural or plastic. We conclude, that microplastics and suspended solids elicit similar effects on the tested response variables, and that both types of microparticles mainly cause acute responses rather than more persistent carry-over effects.

Highlights

Microplastic particles are smaller than 5mm and ubiquitous in the marine environment today (Eriksen et al, 2014; Wang and Wang, 2018)
Respiration rates of all mussels that were exposed to natural microparticles were 9% higher than of those individuals that were kept in the presence of plastic microparticles (Fig. 2)
Respiration rates were significantly different between the groups of mussels that received different particle types, while the particle concentration had no significant effect on the oxygen consumption

Summary

Introduction

Microplastic particles are smaller than 5mm and ubiquitous in the marine environment today (Eriksen et al, 2014; Wang and Wang, 2018) They occur from urbanized and polluted coastal areas (Zhao, 2015) to remote and pristine ecosystems (Horton and Barnes, 2020) including the deep sea (Cunningham et al, 2020) and polar regions (Waller et al, 2017). There are studies that did not establish negative effects of microplastics on mussels (Browne et al, 2008; Santana et al, 2018; Van Cauwenberghe et al, 2015) These conflicting findings suggest that the effects of microplastics on filter-feeding mussels and their relevance as an environmental pollutant is still not well understood and may be highly context dependent

Methods

Results

Conclusion