Carbohydrate, Lipid, and Protein Composition of Zooxanthellae and Animal Fractions of the Coral Pocillopora damicornis Exposed to Ammonium Enrichment

Abstract

The carbohydrate, lipid, and protein composition of coral tissue and zooxanthellae were compared in Hawaiian Pocillopora damicornis (Linnaeus) colonies kept at different ammonium levels. Corals were maintained at two levels of ammonium enrichment (20 uM and 50 uM), in locally drawn seawater with < 1 uM ammonium, and in water stripped of ammonium by running over a flume with macroalgae. No significant differences due to the treatment were found in the biochemical composition of the coral tissue. The values from control corals were 900, 275, and 170 ug/cm2 for protein, carbohydrates, and lipids, respectively. Under all treatments the carbohydrate levels of zooxanthellae were inconsistent, but did not differ much from the control value of about 650 pg per cell. Lipid content in the control of nonenriched algae remained at ca. 140 pg per cell. However, in the 20-uM treatment algal lipid content increased to about 200 pg per cell during the second and fourth weeks, decreased slightly at 6 weeks, and remained at 164 pg per cell after 8 weeks. In the 50-uM ammonium treatment, there was a decrease to levels of about 40 pg lipids per cell for the entire period. Protein content increased from a control value of 590 pg per cell to ca. 950 pg per cell after 2 and 4 weeks of 20-uM ammonium enrichment and then after 6 weeks dropped back to the control level. At 50-uM ammonium the algal protein content increased after 2 weeks and remained at about 900 pg per cell after 6 and 8 weeks. The preliminary nature of this study is emphasized.