New research from the UK and Australia suggests that changes in the ocean's chemistry, as a result of global warming, could threaten organisms such as marine plankton to a greater extent than previously thought.
Dr Mark Baird, a Research Fellow with The Plant Functional Biology and Climate Change Cluster (C3) is a member of the international team researching ocean acidification and the changes it causes in the pH levels at the exterior surface of plankton.
The work is led by Professor Kevin Flynn of Swansea University's Centre for Sustainable Aquatic Research, in collaboration with colleagues in the UK and Professor John Beardall from Monash University.
Professor Flynn said, "Human impact on the environment means carbon dioxide is dissolving in the ocean, which is naturally alkaline, and causing a decrease in seawater pH levels – an event termed ocean acidification."
He added that although ocean acidity could double from its present value by 2100 it was unclear how the growth of plankton would respond.
"However, given the important role these organisms play in the Earth's biogeochemical cycles, the impact that ocean acidification-induced changes in the chemical composition of seawater will have on plankton is a major concern," Professor Flynn said.
The work indicates that experimental approaches used in most previous studies, such as shaking of samples, disturbs natural plankton communities and thus affects pH gradients next to cells.
Dr Mark Baird said, "Numerical models allow us to isolate one phenomenon, such as how cell size alters plankton susceptibility to ocean acidification. This is difficult to do using laboratory experiments."
However, using simulations, the team has presented and discussed mechanisms by which many marine plankton will experience a substantially more acidic environment than currently suggested by ocean acidification scenarios – experiencing pH conditions which are completely outside their recent historical range.
Their results suggest that changes in the pH at the cell surface of plankton could adversely affect cellular equilibrium, leading to poor growth if not death.
Importantly, the team's work suggests that some of the most critical organisms to the Earth's biogeochemical cycles, such as planktonic calcifiers (coccolithophorids and forams), will be disproportionately affected by this mechanism.
These changes could represent a powerful driving force, shaping the composition of plankton communities of the future ocean.
"The implications of our research are profound," said Professor Flynn. "They suggest scope for a more serious impact of oceanic acidification upon marine plankton than previously thought."
Professor Beardall added, "In Australia we propose to apply this research to understand the synergistic effects of ocean acidification and other aspects of climate change on key Australian phytoplankton species."
The team's paper, Changes in pH at the exterior surface of plankton with ocean acidification, is published online by leading journal Nature Climate Change.
The full paper can be read at this link until July 18.
The research was primarily funded by the Natural Environment Research Council.