UWA Oceans Institute

Helping solve the complex issue in ocean acidification research

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OCEANS ONLINE     ISSUE 3. SEPTEMBER 2015

 

Ocean acidification, caused by the introduction of massive amounts of CO2 into our seas, has been identified as a major risk to our marine ecosystems. Not only is it altering water chemistry, these gases are also affecting the life cycles of many marine organisms, particularly those at the lower end of the food chain.

New Oceans Institute member Dr Christopher Cornwall (from UWA’s School of Earth and Environment & ARC Centre of Excellence in Coral Reef Studies) and Associate Professor Catriona Hurd (Institute for Marine and Antarctic Studies, University of Tasmania) have identified solutions to commonly encountered problems in ocean acidification research. 

Their work is in a new publication in ICES Journal of Marine Science, however Chris dropped in to tell us more.

A lot of scientific effort has gone in to investigating the effects of ocean acidification, mostly in laboratory experiments. However, performing manipulations in a lab can be logistically difficult. Accurately designing experiments is also complex, in part because of the rigorous requirements for controlling and monitoring seawater carbonate chemistry involved in such work. 

For tens of millions of years, Earth's oceans have maintained a relatively stable acidity level leading to the rich and varied web of life in our seas. However research shows this ancient balance is being undone by a recent and rapid drop in surface pH that could have devastating consequences. 

We reviewed all past long-term laboratory research investigating the impacts of ocean acidification (465 studies) during an exhaustive search.  We found the majority of published studies were unrepeatable because of lack of details (~45%), or that they had used inappropriate methods where spatial or temporal effects could be confused with the effects of ocean acidification (~50%). 

Ocean acidification is a major threat to marine ecosystems, through its potential to reduce the growth rates of calcareous species such as corals, shellfish and many species of phytoplankton and seaweed, as well as by altering the behaviour of marine fishes and invertebrates.  

For many types of organisms we know the direction in which they will respond to ocean acidification, but better understanding of the exact magnitude of these responses will allow us to more accurately predict changes in future ecosystems. 

We hope that this publication will be used by the scientific community to maximise the conclusions that can be made from future research. In our paper we not only highlight several problems relating to experimental design or the lack of reporting of details in published work, but importantly discuss ways in which this can be improved.

It’s essential that ocean acidification experiments are correctly replicated so that the effects of time and space cannot be confused with treatments.The goal here was not to undermine any previous research.  On the contrary, past research examining the effects of ocean acidification has revealed vast amounts of information at an unprecedented rate. While our paper focused on replication in experiments, experimental design now needs to improve across the board.  This field of research needs to move away from measuring the responses of species to acid additions in single jars, and towards multi-tank systems that employ conditions that as closely as possible independently simulate future CO2, light and water motion.

A guide for best practices in manipulating and measuring seawater carbonate chemistry was published in 2010.  This guide stated that additions of acid (not CO2 or its chemical equivalent) where not useful in ocean acidification research. Additionally, guidelines for appropriate measurements of seawater carbonate chemistry were also outlined. Our research found that this guide all but eliminated the practice of using acid only additions, and also significantly reduced inappropriate measurement of carbonate chemistry. Hopefully the solutions outlined in our paper will have a similar positive impact on replication in ocean acidification research.

Read more about this month's activities at Oceans Online.