Assessing the Toxicity of Leachates From Weathered Plastics on Photosynthetic Marine Bacteria Prochlorococcus

Indrani Sarker,Sasha G Tetu,Ian T Paulsen,Lisa R Moore

doi:10.3389/fmars.2020.571929

Abstract

Marine plastic pollution is a well-recognized, global problem. Research addressing plastic pollution has largely focused on investigating impacts on macroorganisms, with few studies investigating effects on marine microbes. We previously showed that marine Prochlorococcus, which are important contributors to oceanic primary production, suffer declines in growth and photosynthetic activity following exposure to leachates from new plastic bags (HDPE) and plastic matting (PVC). However, as such plastics reside in the environment they will be subject to weathering processes, so it is also important to consider how these may alter the composition and amounts of substances available to leach. Here we report on how plastic leachate toxicity is affected by environmental weathering (17- and 112-days in estuarine water) of these common plastic materials. We found that while toxicity was reduced by weathering, materials weathered for up to 112-days continued to leach substances that negatively affected Prochlorococcus growth, photophysiology and membrane integrity. Weathered plastics were found to continue to leach zinc, even after up to 112-days in the environment. The two Prochlorococcus strains tested, NATL2A and MIT9312, showed differences in the sensitivity and timing of their responses, indicating that exposure to leachate from weathered plastics may affect even closely related strains to different degrees. As many marine regions inhabited by Prochlorococcus are likely to be subject to continued accumulation of plastic pollution, our findings highlight the potential for ongoing impacts on these important primary producers.

Highlights

Plastics play an important role in human society (Andrady and Neal, 2009) due to their relatively low cost and strong, durable, lightweight nature (Thompson et al, 2009b)
Plastic aging experiments performed in marine waters showed that weathering processes involves both adsorption and desorption of different organic and inorganic substances and found that different changes occur with different plastic items and polymer types (Kedzierski et al, 2018). These findings indicate that multiple issues would benefit from further exploration, including how specific physical conditions during weathering affect leachate toxicity through to how different plastic types are affected by weathering in terms of leachate toxicity, the latter being a focus of this work
To investigate how environmental weathering of plastics affected leachate toxicity, PVC and HDPE plastics were weathered in estuarine waters for 17- and 112-days, placed in artificial seawater to generate sterile-filtered, particle-free leachate stocks which were added to Prochlorococcus MIT9312 and NATL2A cultures at a range of dilutions

Summary

Introduction

Plastics play an important role in human society (Andrady and Neal, 2009) due to their relatively low cost and strong, durable, lightweight nature (Thompson et al, 2009b). Plastic leachates can include substances added during manufacturing (Browne et al, 2007; Thompson et al, 2009a) and other compounds accumulated from the surrounding marine environments (Mato et al, 2001; Teuten et al, 2009). Additives used in plastic manufacture include polymerization solvents, plasticizers, metals, dyes, flameretardants, UV stabilizers and antioxidants (Hahladakis et al, 2018). Some of these additives are thought to have the potential to enter the marine food web and adversely affect marine ecosystems (Avio et al, 2017)

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