Reevaluation of experimental data using Hedges d instead of log-transformed response ratios as a metric for effect size. from Robust quantification of fish early life CO₂ sensitivities via serial experimentation.

Despite the remarkable expansion of laboratory studies, robust estimates of single species CO₂ sensitivities remain largely elusive. We conducted a meta-analysis of 20 CO₂ exposure experiments conducted over 6 years on offspring of wild Atlantic silversides (Menidia menidia) to robustly constrain CO₂ effects on early life survival and growth. We conclude that early stages of this species are generally tolerant to CO₂ levels of approximately 2000 µatm, likely because they already experience these conditions on diel to seasonal timescales. Still, high CO₂ conditions measurably reduced fitness in this species by significantly decreasing average embryo survival (−9%) and embryo + larval survival (−13%). Survival traits had much larger coefficients of variation (greater than 30%) than larval length or growth (3–11%). CO₂ sensitivities varied seasonally and were highest at the beginning and end of the species' spawning season (April–July), likely due to the combined effects of transgenerational plasticity and maternal provisioning. Our analyses suggest that serial experimentation is a powerful, yet underused tool for robustly estimating small but true CO₂ effects in fish early life stages.