Better understanding of effect of plastics in the ocean
Alan Williams, University of Plymouth
An
international team of scientists found that after three weeks of being
submerged in the ocean, the bacterial diversity on plastic bottles was twice as
great as on samples collected from the surrounding seawater.
However,
in areas of elevated carbon dioxide, a large number of taxonomic groups –
including bacteria that play an important role in carbon cycling – were
negatively impacted.
Conversely,
other species – including those that have previously been shown to thrive in
areas of high ocean plastics and to potentially cause disease on coral reefs –
were enriched by it.
The
research also showed that while many groups of bacteria were shared between
plastic, free-living and particle-associated samples, almost 350 were found
uniquely on plastics.
Writing in the journal Marine Pollution Bulletin, researchers say the study adds to growing evidence that the increasing presence of plastic marine debris is providing a novel habitat for bacteria.
However,
their results highlight that environmental conditions and local ecological
processes will play an important role in determining its broader impact over
the coming decades.
The
study was led by the University of Tsukuba (Japan) and the University of
Plymouth (UK), in collaboration with Keimyung University (South Korea),
Kyungpook National University (South Korea) and Nanjing University (China).
Scientists
submerged a number of plastic bottles in seas off the Japanese Island of
Shikine-jima, a region renowned for its CO2 seeps, where the escaping gas
dissolves into the sea water and creates conditions similar to that expected to
occur worldwide in coming years.
They
then used a combination of DNA sequencing and statistical techniques to analyse
how bacteria colonise the plastic in comparison to the surrounding natural
environment, and whether the increased CO2 levels would cause changes in the
bacteria’s distribution.
Lead
author Dr Ben Harvey, Assistant Professor at the
University of Tsukuba’s Shimoda Marine Research Center and a graduate of the
BSc (Hons) Ocean Science programme in Plymouth, said:
"Discarded
plastic drinking bottles have become a common sight in our oceans and we were
expecting to see them being colonised by different types of bacteria. We
also predicted that raised CO2 levels would cause significant changes in the
bacterial colonies, but it was still surprising to see the extent of that
change and how the raised levels affected species differently. To see
beneficial species dwindling while harmful species thrive is an obvious present
and future cause for concern.”
Jason Hall-Spencer, Professor of Marine
Biology at the University of Plymouth and senior author on the study, added:
“Up
to 13 million tons of plastics from land end up in the oceans each year and
they have been shown to affect all types and sizes of marine species. Combine
that with rising CO2 levels and the threat posed to the global ocean is stark.
It reinforces the importance of taking steps to meet the standards demanded by
international climate treaties so as to reduce the impact of ocean
acidification and warming. It is also within our power to change cultures so
that litter created on land does not become an environmental hazard in our
oceans, both now and for future generations.”
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 a loss of biodiversity.
It
is also the latest research by the University of Plymouth into plastics, with
it being awarded a Queen’s Anniversary Prize for Higher and Further Education
in 2020 for its ground-breaking research and policy impact on microplastics
pollution in the oceans.
The
full study – Harvey et al. (2020): Ocean acidification alters bacterial
communities on marine plastic debris – is published in Marine
Pollution Bulletin, DOI: 10.1016/j.marpolbul.2020.111749.