New study suggests ocean’s plankton under greater threat from acidification

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 has previously been thought.

Kevin FlynnProf Kevin Flynn The work, into ocean acidification and the changes it causes in the pH levels at the exterior surface of plankton, is led by Professor Kevin Flynn (pictured) of Swansea University’s Centre for Sustainable Aquatic Research, in collaboration with colleagues in the UK at Plymouth Marine Laboratory, the Marine Biological Association, Plymouth, and the University of Dundee, and in Australia at the University of Technology, Sydney, and Monash University, Victoria.

Professor Flynn, the lead author of the paper, which is published online by leading journal Nature Climate Change, said: “Human impact on the environment means carbon dioxide (CO2) is dissolving in the ocean, which is naturally alkaline, and causing a decrease in seawater pH levels – an event termed ocean acidification.

“Previous projections indicate that the pH level will drop 0.3 units from its present value by 2100.  This change in pH equates to more than a doubling in acidity, but it is unclear how the growth of plankton is likely to respond to this increase in acidification.

“However, given the important role these organisms play in the Earth’s biogeochemical cycles, and for example as a food source for many fish species, the impact that ocean acidification-induced changes in the chemical composition of seawater will have on plankton is a major concern.”

The work indicates that experimental approaches used in most previous studies, such as shaking of samples, disturbs natural plankton assemblages and therefore affects pH gradients next to cells.

Dr Mark Baird, a Senior Research Fellow with the Climate Change Cluster (C3), University of Technology, Sydney, 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 when starting at seawater pH levels indicative of future ocean acidification levels, changes in the pH at the cell surface of plankton could adversely affect cellular homeostasis, 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,” added Professor Flynn. “They suggest scope for a more serious impact of oceanic acidification upon marine plankton than previously thought.”

The next stages in the research include an investigation of the affects of pH on the early stages of finfish and shellfish; stages which are microscopic and hence subject to the same types of events noted in the team’s paper.

“We are currently leading a project funded by the Natural Environment Research Council (NERC) and the Department for the Environment, Food and Rural Affairs (Defra) on the impact of ocean acidification on commercial fisheries, together with colleagues in the universities of Exeter and Strathclyde, and Plymouth Marine Laboratory,” added Professor Flynn, who is the Head of the Department of Biosciences at Swansea University.

“The question is whether the success of these early stages, which are particularly susceptible to environmental change, are damaged by ocean acidification.”

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 (until July 18, 2012) at Changes in pH at the exterior surface of plankton with ocean acidification.

The team’s work was primarily financially supported by the Natural Environment Research Council (NERC), with the additional support of NERC Oceans 2025, the Biotechnology and Biological Sciences Research Council, and the European Project on Ocean Acidification.

This news item forms part of Swansea University’s support for Universities UK (UUK) Universities Week, which runs from Monday, April 30 until Monday, May 7, 2012. Visit www.universitiesweek.org.uk.

Posted by Bethan Evans <b.w.evans@swansea.ac.uk >
Thursday 3 May 2012 00.00 GMT
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