. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. Figure 6. Dinoflagellate species identified from the Pelican Cays sampling area (scanning electron micrographs; refer to the Appendix): a, Protoperidinium sp. cf. steinii; b, Pyrodinium bahamense var. bahamense. dissolved organic nutrient enrichments could originate from numerous sources in addition to microalgal assemblages: the mangrove forest, corals, seagrass beds, macroalgal meadows, and peat walls dominated by filter-feeding invertebrates and macroalgae (Rutzler and Feller, 1996). In selected enclosed la
. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. Figure 6. Dinoflagellate species identified from the Pelican Cays sampling area (scanning electron micrographs; refer to the Appendix): a, Protoperidinium sp. cf. steinii; b, Pyrodinium bahamense var. bahamense. dissolved organic nutrient enrichments could originate from numerous sources in addition to microalgal assemblages: the mangrove forest, corals, seagrass beds, macroalgal meadows, and peat walls dominated by filter-feeding invertebrates and macroalgae (Rutzler and Feller, 1996). In selected enclosed lagoons such as Manatee Cay, dissolved nutrients retained within the pond result in high dinoflagellate proliferation. In contrast, in semi-enclosed ponds such as those at Douglas and Elbow Cays, brown pelicans provide the organic enrichment needed for dinoflagellate blooms to develop. Here benthic dinoflagellate species G. polygramma can form populations >106 cells/L that may dominate the waters (Morton and Villareal, 1999). Nutrients generated after a "bloom" would be retained because of the very low daily tides (20-25 cm) and calm wind conditions (Ellison et al., 1996; Villareal et al., this volume). Toxic G. polygramma red tides are known to cause extensive fish and shellfish kills (Taylor, 1962). At Manatee Cay, mixotrophy was observed in an autotrophic species, Gymnodinium sanguineum, which engulfed smaller prey organisms (ciliates, pigmented nannoplankton, and microalgae). Here, G. sanguineum cells compete with heterotrophic grazers for the same food source (Bochstahler and Coats, 1993), as do harmful benthic species {Gamblerdiscus, Ostreopsls and Prorocentrum) at South Water Cay (Faust, 1998). Mixotrophy is a recently described phenomenon (Jacobson and Anderson, 1986) that provides energy for cell growth, a potential advantage for dinoflagellates in nutrient-limited marine waters. As observed in this study, dinoflagellates can form "blooms" in ocean
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