Experimental design in ocean acidification research: problems and solutions

摘要

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 correctlydesigning 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 interspersedtreatment replicates, or did not report sufficient methodological details was 95. Furthermore, 21 of studies did not provide any details ofexperimental design, 17 of studies otherwise segregated all the replicates for one treatment in one space, 15 of studies replicatedCO_2 treatmentsin away that made replicates more interdependent within treatments than between treatments, and 13 of studies did not report if replicates of alltreatments 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 ofmanipulating seawater (i.e. acid–base only additions) from 21 to 3, following the release of the “Guide to best practices for ocean acidificationresearch and data reporting” in 2010; however, no such increase in the use of appropriate replication and experimental design was observed after2010. Weprovide guidelines on how to design ocean acidification laboratory experiments that incorporate the rigorous requirements for monitoringand measuring carbonate chemistry with a level of replication that increases the chances of accurate detection of biological responses to oceanacidification.