Table 1.
Mean carbonate chemistry conditions (± standard error) in the experimental system.
Shown are mean values of dissolved organic carbon (DIC), total alkalinity, pH (total scale), pCO2, and temperature.
Table 2.
Summary of the range of exposure duration, acclimation time, time per trial, recovery period, and sample size for copper and blue rockfish used to test behavioral and physiological responses to elevated pCO2.
Note: Individual fish were used successively in the different trials to enable tracking of performance measures. Data from fish that did not behave normally in a particular trial were excluded (e.g., refusal to swim in the Ucrit test). In addition, 2 of 12 blue rockfish individuals that were sequenced had low quality reads and were subsequently excluded from the differential gene expression analysis.
Fig 1.
Changes in behavioral lateralization, critical swimming speed, and aerobic scope of juvenile copper and blue rockfish as a function of pCO2 treatment exposure history.
(A, B) Behavioral lateralization is measured using the relative lateralization index (negative values = right turn bias in a detour test). (C,D) Critical swimming speed (Ucrit) is the maximum sustained speed in body lengths per second. (E,F) Aerobic scope represents the difference between maximum and resting metabolic rates (measured as oxygen consumption) and is a proxy for the capacity for aerobic activity. Bars are mean values (± SE). Letters over bars represent results of Tukey HSD post-hoc tests; significantly different means do not share letters in common. Note: Due to logistical constraints all behavioral and physiological trials occurred in control seawater (pCO2 ~550 μatms).
Fig 2.
Principal components analysis depicting correlations amongst the suite of behavioral and physiological performance variables measured for (A) copper rockfish and (B) blue rockfish throughout the course of the experiment as a function of pCO2 exposure history.
Filled symbols indicate fish from the two highest pCO2 treatments and open symbols signify fish from the two lowest pCO2 treatments. Fish were tagged to allow tracking of individuals across all performance measures and are plotted based on their multivariate combined performance history in behavioral and physiological challenges. Axes show the percent of variation explained by each principal component.
Fig 3.
Gene expression profiles (A) and Gene Ontology (GO) functional categories (B) for copper and blue rockfish muscle tissue as a function of pCO2 treatment.
(A) Heatmaps display significant differential gene expression (DE) for copper (n = 147) and blue (n = 358) rockfish (FDR<0.001) among pCO2 treatments; green = up-regulation, red = down-regulation. Each column represents an individual fish (n = 15 copper rockfish and n = 10 blue rockfish). Genes are ordered by similarity in gene expression profile and differ in both order and identity between the two species (only 14 DE genes were in common between the two species). Hierarchical (Euclidean) clustering was used to group similar gene expression profiles, labeled along the right side of each heatmap and listed in S2 and S3 Tables. (B) GO categories show relative differences between copper and blue rockfish in the percentage of annotated genes that were differentially expressed, as classified by GO molecular function or biological process. Broken out pie wedges highlight GO categories that were more expressed in one species than the other. Copper rockfish show significant up-regulation of genes involved in transcription and biological regulation at high pCO2 and down-regulation at low pCO2. In contrast, blue rockfish differentially express muscle structural genes across pCO2 treatments.
Fig 4.
Enzyme activity ratios for lactate dehydrogenase and citrate synthase (LDH:CS) in white muscle tissue of (A) copper and (B) blue rockfish following chronic exposure to extreme pCO2 (~2800 μatms) or control (~550 μatms) treatments.
Copper rockfish exhibited a significant increase in aerobic enzyme activity relative to anaerobic activity (i.e., lower LDH:CS ratio) from the control to extreme high pCO2 treatments (two-way ANOVA; Species×Treatment: F1,24 = 4.46, P = 0.045), whereas blue rockfish did not differ in LDH:CS activity among treatments.