The effects of small-scale turbulence on the physiology of marine dinoflagellates

Field observations and the results of previous laboratory studies on the effects of turbulence on dinoflagellates have led to a paradigm in phytoplankton ecology that the growth of dinoflagellates is negatively affected by turbulence. To test this paradigm, a representative group of ten dinoflagellate species were exposed to quantified three-dimensional turbulence. Turbulence was generated in culture tanks by oscillating cylindrical rods and quantified (as the turbulence dissipation rate, ϵ) using an acoustic doppler velocimeter. Dinoflagellates were exposed to high turbulence (∼10−4 m2 s−3), low turbulence (∼10−8 m2 s−3), and a non-turbulent control. The response to turbulence was species-specific. The division rates of Alexandrium tamarense, Pyrocystis fusiformis, and a Gyrodinium sp. were unchanged across treatments. However, the division rates of Alexandrium fundyense, Gymnodinium catenatum, and Lingulodinium polyedrum were faster in high turbulence and the division rates of Ceratium tripos, Ceratium fusus, Pyrocystis noctiluca, and Alexandrium catenella were slower in high turbulence.; Lingulodinium polyedrum and A. catenella were exposed to six turbulence intensities (spanning 10−8 m2 s−3 to 10−3 m 2 s−3). These experiments revealed functional relationships between turbulence, division rate, cell size, and morphology. Several years of field observations of A. catenella blooms in East Sound, Washington USA demonstrated that natural populations of dinoflagellates may have adapted strategies to exist in areas of high turbulence even if they are negatively affected by turbulence.; Turbulence can mechanically stimulate bioluminescence in dinoflagellates. Four species of dinoflagellates were grown at various turbulence intensities to determine its affect on their bioluminescence capacity (BCAP). The BCAP of A. catenella did not change at any turbulence intensity. However, the BCAP of L. polyedrum, P. fusiformis, and P. noctiluca was reduced 70–90% at high turbulence intensities.; In most dinoflagellates, bioluminescence is not stimulated by turbulence forces during the day due to the photoinhibition of mechanically stimulable bioluminescence (MSL). This phenomenon was examined in P. noctiluca and had an action spectrum with peak wavelength at 440 nm. The mechanism of photoinhibition of MSL in P. noctiluca appeared to be the light-stimulated movement of bioluminescence organelles away from the cell periphery, where turbulent forces might be more likely to stimulate the bioluminescence organelles.