Figure 1. Growth response of fleshy and calcareous algae to treatment conditions.

The eleven species of algae exposed to CO₂ enrichment experiments on Palmyra Atoll. Algae were separated by functional group. The species of fleshy macroalgae included: (A) Acanthophora spicifera, (B) Avrainvillea amadelpha, (C) Caulerpa serrulata, (D) Dictyota bartayresiana, (E) Hypnea pannosa. The upright calcareous algae included: (F) Dichotomaria marginata, (G) Galaxaura rugosa, (H) Halimeda taenicola, (I) Halimeda opuntia, and the CCA included: (J) Lithophyllum sp., (K) Lithophyllum prototypum. (L) The mean (±SE) change in either fleshy or calcareous biomass (highlighted in gray) following exposure to either present-day ambient air controls (open circles) or predicted OA treatments (closed circles). Fleshy macroalgae are shown in brown, upright calcareous algae in green, and CCA in red. Species tested in multiple experiments were pooled across years. * Indicates a significant difference between treatments as determined by independent t-tests (results reported in Table 2).