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Experimental design in ocean acidification research: problems and solutions


Cornwall, CE and Hurd, CL, Experimental design in ocean acidification research: problems and solutions, ICES Journal of Marine Science, 73, (3) pp. 572-581. ISSN 1054-3139 (2016) [Refereed Article]

Copyright Statement

Copyright 2015 International Council for the Exploration of the Sea

DOI: doi:10.1093/icesjms/fsv118


Ocean acidification has been identified as a risk to marine ecosystems, and substantial scientific effort has been expended on investigating its effects, mostly in laboratory manipulation experiments. However, performing these manipulations correctly can be logistically difficult, and correctly designing experiments is complex, in part because of the rigorous requirements for manipulating and monitoring seawater carbonate chemistry. To assess the use of appropriate experimental design in ocean acidification research, 465 studies published between 1993 and 2014 were surveyed, focusing on the methods used to replicate experimental units. The proportion of studies that had interdependent or non-randomly interspersed treatment replicates, or did not report sufficient methodological details was 95%. Furthermore, 21% of studies did not provide any details of experimental design, 17% of studies otherwise segregated all the replicates for one treatment in one space, 15% of studies replicated CO2 treatments in a way that made replicates more interdependent within treatments than between treatments, and 13% of studies did not report if replicates of all treatments were randomly interspersed. As a consequence, the number of experimental units used per treatment in studies was low (mean = 2.0). In a comparable analysis, there was a significant decrease in the number of published studies that employed inappropriate chemical methods of manipulating seawater (i.e. acid–base only additions) from 21 to 3%, following the release of the "Guide to best practices for ocean acidification research and data reporting" in 2010; however, no such increase in the use of appropriate replication and experimental design was observed after 2010. We provide guidelines on how to design ocean acidification laboratory experiments that incorporate the rigorous requirements for monitoring and measuring carbonate chemistry with a level of replication that increases the chances of accurate detection of biological responses to ocean acidification.

Item Details

Item Type:Refereed Article
Keywords:ocean acidification, experimental design, manipulation experiments, pseudoreplication, replication
Research Division:Environmental Sciences
Research Group:Climate change impacts and adaptation
Research Field:Ecological impacts of climate change and ecological adaptation
Objective Division:Environmental Policy, Climate Change and Natural Hazards
Objective Group:Adaptation to climate change
Objective Field:Ecosystem adaptation to climate change
UTAS Author:Cornwall, CE (Dr Chris Cornwall)
UTAS Author:Hurd, CL (Professor Catriona Hurd)
ID Code:104208
Year Published:2016
Web of Science® Times Cited:159
Deposited By:Ecology and Biodiversity
Deposited On:2015-11-04
Last Modified:2022-08-24

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