Fig. 2. The influence of nutrient enrichment in the field on the physiology of the Haliclona—Ceratodictyon symbiosis. (A) The maximum rate of gross photosynthesis (P_max). (B) The dark respiration rate (R). Treated branches (N=10) were placed in either sea water plus 10 µmol l^-1 NaNO₃ (`Nitrate') or sea water only (`Control') for 24 h. Treated branches were compared with branches harvested directly from the field (`Freshly collected'). Values are means ± S.D. Measurements obtained in laboratory-based experiments were similar to those obtained in the field experiments and are therefore not shown.

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