Meta‐analysis suggests negative, but pCO₂‐specific, effects of ocean acidification on the structural and functional properties of crustacean biomaterials

Abstract

Crustaceans comprise an ecologically and morphologically diverse taxonomic group. They are typically considered resilient to many environmental perturbations found in marine and coastal environments, due to effective physiological regulation of ions and hemolymph pH, and a robust exoskeleton. Ocean acidification can affect the ability of marine calcifying organisms to build and maintain mineralized tissue and poses a threat for all marine calcifying taxa. Currently, there is no consensus on how ocean acidification will alter the ecologically relevant exoskeletal properties of crustaceans. Here, we present a systematic review and meta‐analysis on the effects of ocean acidification on the crustacean exoskeleton, assessing both exoskeletal ion content (calcium and magnesium) and functional properties (biomechanical resistance and cuticle thickness). Our results suggest that the effect of ocean acidification on crustacean exoskeletal properties varies based upon seawater p CO 2 and species identity, with significant levels of heterogeneity for all analyses. Calcium and magnesium content was significantly lower in animals held at p CO 2 levels of 1500–1999 µatm as compared with those under ambient p CO 2 . At lower p CO 2 levels, however, statistically significant relationships between changes in calcium and magnesium content within the same experiment were observed as follows: a negative relationship between calcium and magnesium content at p CO 2 of 500–999 µatm and a positive relationship at 1000–1499 µatm. Exoskeleton biomechanics, such as resistance to deformation (microhardness) and shell strength, also significantly decreased under p CO 2 regimes of 500–999 µatm and 1500–1999 µatm, indicating functional exoskeletal change coincident with decreases in calcification. Overall, these results suggest that the crustacean exoskeleton can be susceptible to ocean acidification at the biomechanical level, potentially predicated by changes in ion content, when exposed to high influxes of CO 2 . Future studies need to accommodate the high variability of crustacean responses to ocean acidification, and ecologically relevant ranges of p CO 2 conditions, when designing experiments with conservation‐level endpoints.

Same data, different analysts: variation in effect sizes due to analytical decisions in ecology and evolutionary biology

“…One possible explana on for the lower heterogeneity among most Eucalyptus Zr effects is that weak rela onships may limit the opportuni es for heterogeneity in analy cal outcome. Some evidence for this idea comes from two sets of "many labs" studies in psychology [4,57]. In these studies, many independent lab groups each replicated a large set of studies, including, for each study, the experiment, data collec on, and sta s cal analyses.…”

“…In these studies, many independent lab groups each replicated a large set of studies, including, for each study, the experiment, data collec on, and sta s cal analyses. These studies showed that, when the metaanaly c mean across the replica ons from different labs was small, there was much less heterogeneity among the outcomes than when the mean effect sizes were large [4,57]. Of course, a weak average effect size would not prevent divergent effects in all circumstances.…”

Narrowed gene functions and enhanced transposon activity are associated with high tolerance to ocean acidification in a juvenile subarctic crustacean

“…Many are capable of maintaining hemolymph pH homeostasis by acid-base regulation [21,22], and have exoskeletons composed of both calcium carbonate and chitin, which may protect against direct dissolution [23,24]. Still, tissue and shell growth [25], molt cycle [26,27], exoskeleton properties [28,29], metabolic activity [30,31], reproduction [22,32], behavior [33,34], and immune function [22,35] can all be altered by OA, particularly at higher pCO 2 concentrations [36]. Effects are most acutely observed in early life stages (larvae, juveniles), and vary greatly by species, severity of OA, life stage, and duration of exposure [20,28,37,38].…”

“…Still, tissue and shell growth [25], molt cycle [26,27], exoskeleton properties [28,29], metabolic activity [30,31], reproduction [22,32], behavior [33,34], and immune function [22,35] can all be altered by OA, particularly at higher pCO 2 concentrations [36]. Effects are most acutely observed in early life stages (larvae, juveniles), and vary greatly by species, severity of OA, life stage, and duration of exposure [20,28,37,38].…”

Parentage influence on gene expression under acidification revealed through single‐embryo sequencing

“…This change alone has resulted in multiple interacting stressors, including acidosis, hypercapnia and reduced saturation of calcium carbonate (Albright et al, 2016; Gattuso et al, 2015; IPCC, 2014). Calcifying organisms, such as coccolithophores, corals and echinoderms, are deemed more sensitive and exhibit negative outcomes when exposed to OA conditions (Leung et al, 2022; Siegel et al, 2022). These detrimental impacts include the elevated metabolic cost to maintain physiological processes (e.g.…”