Effects of natural phenolic material (tannin) on phytoplankton growth

Natural phenolic materials were found to influence the growth of two phytoplankton species in Celestún Lagoon, a tropical coastal lagoon on the northern Yucatan Peninsula (Gulf of Mexico). The input of natural phenolic materials from mangrove forests imparts a reddish color to the water column of the lagoon. Natural water from the lagoon and tannic acid were used to assess the effects of natural phenolic material on the growth of two microalgae, Dunaliella salina and Skeletonema costatum. Both species were inhibited by tannic acid concentrations equivalent to those observed in the lagoon during winter (18 mg liter ‒1 ). The pattern was similar in both species, but cultures of S. costatum achieved higher cell numbers (>400 × 10 4 cells ml ‒1 ). However, growth of both species at lower concentrations, equivalent to 3 mg liter ‒1 of tannic acid in the natural water, was similar to growth in the control assay, suggesting a positive effect of other organic substances on phytoplankton growth. The climatic conditions during the nortes season (November–February) result in high concentrations of natural phenolic materials in the inner zone of the lagoon, which can play an important role in controlling the seasonal changes in phytoplankton and could control the response of the lagoon ecosystem to climate change.