Biologically-relevant ocean acidification (OA) thresholds and syntheses are critical for interpreting the growing body of OA monitoring data and guiding ocean conservation actions. Bednaršek et al. (2021a) conducted such a synthesis and developed OA-specific thresholds for decapods, compiling literature data and analyzing 27,000 data points from 55 studies, making it one of the most robust OA decapod meta-analyses. Bednaršek et al. (2021a) related biological responses to OA stress and then convened a working group of experts to develop consensus thresholds based on that evidence, using similar approaches and data analyses as published previously for pteropods and echinoderms (Bednaršek et al., 2019, 2021b).
McElhany and Bush (2024) critiqued the decapod synthesis and suggested a need for re-evaluation. Their primary concerns were with the statistical methods, particularly the use of Least Squares Regression (LSR) and Piecewise Regression (PR). They argued that LSR-derived thresholds are dependent on experimental pH ranges, while PR is criticized because all data points were treated equally, rather than weighing them so each study has an equal influence on the outcome.
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While we disagree with the McElhany and Bush (2024) critiques and assert the thresholds developed by Bednaršek et al. (2021a) through expert consensus are suitable for OA risk assessments, we do want to highlight that these important numbers should be subject to continual refinement. We suggest that the greatest improvements in the threshold estimates in the future will come from more targeted experimental design focusing specifically on deriving biological thresholds. Specifically, increasing the number of exposure levels and the number of species across different habitats will allow for greater species-specific data resolution robustness of their thresholds. Moreover, conducting studies that account for, or better yet quantify, multifactorial stressors, biological variability and adaptations will provide greater value. Reducing the differences in experimental parameters will improve future statistical modelling and help the scientific community advance towards more robust thresholds that can effectively guide conservation efforts.
Bednaršek N., Ambrose R. F., Calosi P., Feely R. A., Litvin S. Y., Long W. C., Spicer J. I., Štrus J., Taylor J., Kessouri F., Roethler M., Sutula M. & Weisberg S. B., 2025. Commentary: synthesis of thresholds of ocean acidification impacts on decapods. Frontiers in Marine Science 12: 1581303. doi: 10.3389/fmars.2025.1581303. Article.
