In controlled experiments mimicking future ocean conditions, scientists found that phytoplankton – microscopic organisms responsible for producing half the world’s oxygen and capturing vast amounts of carbon – suffered significant losses in both growth and diversity when exposed to both higher temperatures and projected microplastic levels.
Diatoms, a key group of phytoplankton and major carbon fixers, were particularly hard hit.
The climate and plastic crises are not separate issues – they’re deeply connected. Together they could create a hostile environment for the very organisms that help stabilise our planet’s climate. If phytoplankton suffer, we all do.
The findings suggest that this dual threat could reduce the ocean’s ability to sequester carbon by over 10 billion tonnes a year – a third of annual current fossil fuel emissions.
But the study also points to hope in the form of Nature-based Solutions (NbS).
When seagrass fronds were added to the experimental setups, phytoplankton fared far better.
Seagrasses appear to trap microplastics, preventing them from harming marine life.
This is a wake-up call, but also a call to action. We need urgent global action to cut plastic pollution and carbon emissions – but we must also invest in restoring ecosystems like seagrass meadows. They’re not just beautiful and full of marine life; they’re frontline climate defenders. The research highlights the urgent need to tackle interconnected environmental crises together – and to recognise the powerful role nature can play in the fight back.
If you’d like to learn about Nature-based Solutions and what we can do to improve our environment, then Bangor University offers a range of related degrees.
The report is available to read here: The combined effects of ocean warming and microplastic pollution on marine phytoplankton community dynamics. Marine Pollution Bulletin, 2025.
