A new study suggests that two of the planet’s most pressing environmental stressors – plastic pollution and seawater flooding – have the potential to alter the growth and reproductive output of coastal plants.
The study is one of the first to examine the combined effects of seawater flooding and microplastic pollution on coastal plants.
It showed that both stressors had some effects on the species tested, with microplastics impacting the plants’ reproduction while flooding caused greater tissue death.
The research is published in Environmental Pollution.
BIO-PLASTIC-RISK: Assessing the impact of environmental stressors
The study was carried out as part of BIO-PLASTIC-RISK, a £2.6m project led by the University of Plymouth and supported by the Natural Environment Research Council.
It focused on buck’s horn plantain, a low-growing coastal plant native to Europe, Asia and North Africa – but also found in the United States, Australia, and New Zealand – which commonly grows in sand dune and beach shingle coastal habitats.
Coastal plants were grown in soil containing conventional or biodegradable plastics for 35 days before being flooded with seawater for 72 hours, replicating the kinds of flooding events increasingly associated with storms and coastal storm surges.
They were then grown for a further 24 days with scientists monitoring plant survival in addition to factors such as plant size, photosynthetic efficiency and flower production.
“On a global scale, habitats such as coastal dunes and grasslands help protect communities in the form of coastal defences and wind protection.
“They also play a critical role in supporting biodiversity but are coming under increasing threat from climate change and a number of other environmental factors,” explained Dr Mick Hanley, Associate Professor in Plant-Animal Interactions and senior author of the study
Exposure to combined stressors further affects coastal plants
Being exposed to microplastics and flooding together—a threat likely to increase due to climate change and plastic use—had a more pronounced impact on the resource allocation of coastal plants.
This led to coastal plants exhibiting altered growth and experiencing a short-term suppression in their photosynthetic efficiency.
These responses affect the plant’s ability to capture water, nutrients and sunlight and contribute to ecosystem wellbeing.
The researchers said this signposts the potential for microplastics to present an elevated risk when in combination with additional stressors like seawater flooding. As a result, establishing the threats presented 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.
“It also indicates that the effect of microplastics can be magnified by other environmental factors, such as rising sea levels and coastal flooding.
“Studies such as this help us appreciate the potential harm posed by microplastics to a range of organisms and ecosystem resilience generally.”
Dr Hanley concluded: “This study emphasises that we should not be looking at those threats in isolation as put together, their impacts can be more pronounced.
“That 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.”
