A published analysis of ocean acidification thresholds for decapod crustaceans highlights data showing the negative effects of low pH on many species. However, the methods used in the paper have substantial flaws that call into question the proposed thresholds. The quantitative metrics calculated for the meta-analysis are uninformative with respect to pH sensitivity, which raises concerns about the validity of the thresholds developed by the expert opinion process. We recommend against using the published thresholds and for a reanalysis of the data to identify new thresholds.
Introduction
Identifying thresholds of biological response to environmental stressors can provide valuable information for marine resource managers (Heinze et al., 2021). In the field of ocean acidification (OA), meta-analysis of species pH exposure experiments have been used to develop thresholds or relative risk metrics for multiple taxa (Bednaršek et al., 2019; Bednaršek et al., 2021b; Hancock et al., 2020; Cornwall et al., 2022). Decapod crustaceans are an important ecological and economic component of marine ecosystems, and species in this group are potentially vulnerable to OA. Using quantitative analysis based on published data from species pH exposure experiments and expert opinion, Bednaršek et al. (2021a) developed pH exposure thresholds for a number of biological responses of decapods. The Bednaršek et al. (2021a) thresholds have been used in other analyses to characterize potential risk of decapod species to OA (Alin et al., 2023; Alin et al., 2024; Hamilton et al., 2023; Zeldis et al., 2022; Siegel et al., 2022). Although there is no doubt that many decapod species are sensitive to elevated CO2 and exhibit thresholds in their sensitivity, the quantitative analysis in Bednaršek et al. (2021a), which informs the expert opinion, has several methodological issues which raise questions about the utility of the recommended thresholds. This brief research report describes the methodological issues and discusses the implications for our current understanding of pH thresholds for decapods. It does not recommend a specific pathway for re-evaluation of the data, but does provide some relevant references that could guide a re-evaluation.
McElhany P. & Busch D. S., 2024. Ocean acidification thresholds for decapods are unresolved. Frontiers in Marine Science 11: 1449345. doi: 10.3389/fmars.2024.1449345. Article.
