The combined impact of plastic pollution and seawater flooding intensifies the threats to coastal plant species

A new study suggests that two of the planet's more pressing environmental stressors have the potential to alter the growth and reproductive output of plants found along the world's coastlines.

Published in the journal Environmental Pollution, the research is one of the first to examine the combined effects of seawater flooding and microplastic pollution on coastal plants.

The study found that both stressors impacted the species tested, with microplastics affecting the plants reproduction and flooding causing greater tissue death. However, exposure to both microplastics and flooding together—an increasing threat due to climate change and plastic use—had a more pronounced impact on the plants resource allocation. This led to altered growth and short-term suppression of photosynthetic efficiency, affecting the plants ability to capture water, nutrients, and sunlight, and contributing to ecosystem wellbeing.

Led by experts in plastic pollution and plant biology from the University of Plymouth's School of Biological and Marine Sciences and International Marine Litter Research Unit, the study highlights the potential for microplastics to present an elevated risk when combined with other stressors like seawater flooding. Establishing the threats posed by multiple co-occurring stressors on ecosystem resilience is a priority.

Dr. Winnie Courtene-Jones, the study's lead author, said: "This research highlights the potential for microplastics, composed of conventional and biodegradable plastic, to detrimentally affect plant functioning. Moreover, it indicates that the effect of microplastics can be magnified by other environmental factors such as rising sea levels and coastal flooding. Studies like this help us appreciate the potential harm posed by microplastics to a range of organisms, and ecosystem resilience generally."

The study was part of BIO-PLASTIC-RISK, a £2.6 million project led by the University and supported by the Natural Environment Research Council. It focused on buck's horn plantain (Plantago coronopus), a low-growing perennial native to Europe, Asia, and North Africa, but also found in the United States, Australia, and New Zealand, commonly growing in sand dune and beach shingle coastal habitats.

Plants were grown in soil containing conventional or biodegradable plastics for 35 days before being flooded with seawater for 72 hours, replicating the flooding events increasingly associated with storms and coastal storm surges. They were then grown for a further 24 days, with scientists monitoring plant survival, plant size, photosynthetic efficiency, and flower production.

Dr. Mick Hanley, Associate Professor in Plant-Animal Interactions and senior author of the study, added: "On a global scale, habitats such as coastal dunes and grasslands help protect communities through coastal defenses and wind protection. They also play a critical role in supporting biodiversity but are under increasing threat from climate change and other environmental factors. This study emphasizes that we should not view these threats in isolation, as their combined impacts can be more pronounced. This is particularly worrying given that both microplastic pollution and coastal flooding are projected to worsen and intensify over the coming decades unless ambitious global actions are implemented."

Original source: https://www.sciencedaily.com/releases/2024/08/240802132907.htm