LIPID CLASS, CAROTENOID, AND TOXIN DYNAMICS OF KARENIA BREVIS (DINOPHYCEAE) DURING DIEL VERTICAL MIGRATION¹

Abstract

The internal lipid, carotenoid, and toxin concentrations of Karenia brevis (C. , <5 lM NO 3 ) mesocosms. Reverse-phase HPLC quantified the epoxidation state (EPS) of the xanthophyll-cycle pigments diadinoxanthin and diatoxanthin, and a Chromarod Iatroscan thin layer chromatography ⁄ flame ionization detection (TLC ⁄ FID) system quantified changes in lipid class concentrations. EPS did not exceed 0.20 in the low-light mesocosm, but increased to 0.65 in the high-light mesocosms. Triacylglycerol and monogalactosyldiacylglycerol (MGDG) were the largest lipid classes consisting of 9.3% to 48.7% and 37.3% to 69.7% of total lipid, respectively. Both lipid classes also experienced the greatest concentration changes in high-light experiments. K. brevis increased EPS and toxin concentrations while decreasing its lipid concentrations under high light. K. brevis may mobilize its toxins into the surrounding environment by reducing lipid concentrations, such as sterols, limiting competition, or toxins are released because lipids are decreased in high light, reducing any protective mechanism against their own toxins.C

Increased Toxicity of Karenia brevis during Phosphate Limited Growth: Ecological and Evolutionary Implications

“…It affords greater protection against grazers and pathogens to compensate for the reduced rates of growth and reproduction. It also provides the cell with a means disposing of unneeded fixed carbon during the onset of nutrient limitation of growth, thereby protecting the photosynthetic electron transport chain from over reduction and attendant oxidative stress [38]–[40]. The CNB hypothesis predicts a similar increase in cellular PbTx concentrations should also occur under P-limitation.…”

Diel vertical migration thresholds of Karenia brevis (Dinophyceae)

“…6, off-shore cells remain sub-surface because of a higher necessity for nitrogen in oligotrophic nitrogen reduced conditions in the upper water column. Exposure to lower nitrogen concentrations lowers the need for photosynthetic production because essential building blocks containing nitrogen cannot be synthesized (Schaeffer et al, 2009). Reduced availability of nitrogen and carbon fixation under low light led K. brevis to divide at a slower rate as indicated at Step (1) in Fig.…”

“…Lipid extraction and analysis were previously detailed in Schaeffer et al (2009). Briefly, lipids were analyzed with the MK-V Chromarod-Iatroscan (Iatron, Inc., Tokyo, Japan) thin layer chromatography/flame ionization detection (TLC/FID) system.…”

“…The second mesocosm was nitrate-reduced with <5 mM NO 3 , 960 mmol quanta m À2 s À1 PAR at surface, and 100 mmol quanta m À2 s À1 PAR at 90 cm depth; from this point forward this set-up is referred to as high-light, nitrate-reduced (H-N-Reduced). Mesocosm experiments were conducted as described in Schaeffer et al (2009). Briefly, mesocosms were translucent fiberglass columns (155 cm height  44 cm diameter, 225 L volume) housed in a 22 8C temperature-controlled room.…”

Mathematical modeling of cascading migration in a tri-trophic food-chain system

“…Many species of dinoflagellates have also been observed to undertake vertical migration, residing at the surface during the day and residing at depth at night [19][20][21][22][23]. Although the light intensity at surface water and nutrients at deep water play an important role as drivers of dinoflagellate DVM in laboratory studies [24][25][26][27][28][29][30], recent experiments have shown that many of the dinoflagellate species migrate to avoid the predation of copepod and other grazer zooplankton [4,31]. Therefore, it is clear that the motile phytoplankton (dinoflagellate) and its predator zooplankton (copepod) exhibit opposite migration patterns; the zooplankton undertakes a normal DVM (up at night, down during the day), whereas the dinoflagellate undertake a reverse DVM (down at night, up during the day).…”