Plastic and rising carbon dioxide levels could pose a combined threat to the marine environment

The combined environmental threat of plastic pollution and ocean acidification is having a significant impact on the species living in our oceans, according to new research.

An international team of scientists found that after three weeks of immersion in the ocean, the bacterial diversity on the plastic bottles was double that of samples collected from the surrounding seawater.

However, in areas of high carbon dioxide, a large number of taxonomic groups, including bacteria that play an important role in the carbon cycle, were negatively affected.

Conversely, other species, including those that have previously been shown to thrive in areas of deep ocean plastic and potentially cause disease on coral reefs, have been enriched by them.

The research also showed that while many groups of bacteria were shared among plastic, free-living, particle-associated samples, nearly 350 were found solely on the plastic.

Writing in the diary Marine Pollution Bulletin, the researchers say the study adds to growing evidence that the growing presence of plastic marine debris is providing a new habitat for bacteria.

However, their findings highlight that local environmental conditions and ecological processes will play an important role in determining its wider impact in the coming decades.

The study was conducted by the University of Tsukuba (Japan) and the University of Plymouth (UK), in collaboration with Keimyung University (Korea), Kyungpook National University (Korea) and Nanjing University (China).

Scientists dipped a series of plastic bottles in the seas off the Japanese island of Shikine, a region renowned for its CO₂ filters where the escaping gas dissolves in seawater and creates conditions similar to those that are expected to occur around the world in the coming years.

They then used a combination of DNA sequencing and statistical techniques to analyze how the bacteria colonize the plastic relative to the surrounding natural environment and whether the increase in CO₂ levels would cause changes in the distribution of bacteria.

Lead author Dr Ben Harvey, assistant professor at Tsukuba University’s Shimoda Marine Research Center and graduate of Plymouth’s BSc (Hons) Ocean Science program, said: “Discarded plastic bottles have become a common sight. in our oceans and we expected to see them colonized by different types of bacteria. We also predicted it would increase CO₂ the levels would have caused significant changes in bacterial colonies, but it was still surprising to see the extent of that change and how the increased levels affected the species differently. Seeing beneficial species dwindle while pests thrive is an obvious cause for concern now and in the future. “

Researchers from Tsukuba, Plymouth and other collaborators have published several studies over the past decade showing the threats posed by ocean acidification in terms of habitat degradation and biodiversity loss.

It is also the latest research from the University of Plymouth on plastics, which was awarded the Queen’s Anniversary Prize for higher education in 2020 and continues for its groundbreaking research and the impact of policies on microplastic pollution in the oceans.

Jason Hall-Spencer, professor of marine biology at the University of Plymouth and senior author of the study, added: “Up to 13 million tons of plastic from the earth ends up in the oceans every year and has been shown to affect all types and sizes. marine species Combine that with the increase in CO₂ levels and the threat posed to the global ocean is severe. It reinforces the importance of taking steps to meet the standards required by international climate treaties in order to reduce the impact of ocean acidification and warming. It is also in our power to change cultures so that the waste created on earth does not become an environmental hazard in our oceans, both now and for future generations. ”