Oceans cover more than 70% of our planet, are home to an estimated 80% of all life and play a vital role in the Earth’s climate, due largely to the activities of marine microorganisms. Yet human activities are increasingly subjecting marine life, including microbes, to a barrage of stressors. Currently little known about how this will impact ecosystem functionality.
Plastic pollution in the marine realm is a major cause for concern. Plastic production has increased ~650% in the last 40 years and waste mismanagement currently results in a significant proportion of this ending up in our oceans. It is predicted that by 2025 the cumulative mass of plastic marine debris will be somewhere between 100 and 250 million metric tons. One understudied risk related to such pollution is that plastic debris can leach a variety of potentially toxic chemicals, including chemicals added or produced during the manufacturing process.
Prochlorococcus species are significant players in oceanic primary production and global carbon cycling. Exposure to plastic leachate from common plastic debris items: plastic bags (HDPE) and plastic matting (PVC), impacted in vitro growth and primary productivity of Prochlorococcus marinus strains. The strains tested, MIT 9312 and NATL2A (model high light and low light-adapted ecotypes), showed distinct differences in their sensitivity to each leachate. Genome-wide transcriptomic analyses revealed a suite of genes were differentially expressed following leachate exposure, including many linked to primary production and stress responses. Understanding how key marine primary producers are affected by plastic leachate is critical to determining potential future impacts of plastic pollution on marine ecosystems as a whole.