Diel vertical migration and luminescent activity of bioluminescent dinoflagellates in Bonaire, Dutch Caribbean
Bioluminescence is a cold-light produced by chemical reactions and has been observed in over 90% of marine organisms. The largely speculated adaptive significance behind bioluminescent activity includes defense against predators, prey distraction, and communication. Bioluminescent photosynthetic dinoflagellates play a major role in the ocean’s primary production. Daily vertical migrations (DVMs) through the water column are phototactic movements, where photosynthetic dinoflagellates return to the surface during daylight to photosynthesize. It was hypothesized that dinoflagellates migrate to the surface in daylight and to depth (4 m) in darkness. It was also hypothesized that chemically provoked luminescent activity would be greater after prolonged exposure to daylight rather than darkness. Samples were collected at am and pm intervals using a 30 cm diameter plankton tow with 20 µm netting. Density of dinoflagellates were estimated under a compound microscope using a Neubauer-improved haemocytometer. Luminescent assays were performed by adding 5% acetic acid to the samples and timing the duration of luminescence in s. A two-way ANOVA with depth and time as factors revealed a significant interaction: at night 4 m density was significantly higher than 0 m density, and in the morning 0 m density was significantly higher than 4 m density. Luminescent activity in the morning was significantly higher than in the evening. A DVM of bioluminescent dinoflagellates was exhibited as a result of a phototactic movement. This study aimed to understand the relatively unknown bioluminescent dinoflagellate activity of one shallow coastal area in Bonaire, Dutch Caribbean.