Fig. 1.

Growth and morphometrics of sea urchin larvae cultured at control pCO₂ (400 µatm; black bars) vs. elevated pCO₂ (900 µatm; gray bars). Results are from larvae collected on days 11, 13, 15, and 17 (postfertilization) of trial 1. Responses to CO₂ seldom differed among the four populations (ANOVA, CO₂ × population; P > 0.05), so results shown are for responses pooled across populations (n = 12–14 culture jars per CO₂ level). Drawings (based on ref. 49) illustrate the morphological features quantified. (A) Postoral rod length. (B) Postoral rod and body rod length. (C) Anterolateral rod length. (D) Body length at midline. (E) Stomach area. Error bars are +1 SE. *P < 0.05; **P < 0.005 (significant differences between CO₂ levels; ANOVA).