@article{schaeffer_kamykowski_sinclair_mckay_milligan_2009, title={Diel vertical migration thresholds of Karenia brevis (Dinophyceae)}, volume={8}, ISSN={["1878-1470"]}, DOI={10.1016/j.hal.2009.01.002}, abstractNote={Light and nutrient availability change throughout dinoflagellate diel vertical migration (DVM) and/or with sub-population location in the water column along the west Florida shelf. Typically, the vertical depth of the shelf is greater than the distance a sub-population can vertically migrate during a diel cycle, limiting the ability of a sub-population to photosynthetically fix carbon toward the surface and access nutrients sub-surface. This project investigated changes of Karenia brevis (C.C. Davis) G. Hansen et Moestrup intracellular carbon, nitrogen, internal nitrate (iNO3), free amino acid (FAA), and total lipid concentrations in high-light, nitrate-replete (960 μmol quanta m−2 s−1, 80 μM NO3), and high-light, nitrate-reduced (960 μmol quanta m−2 s−1, <5 μM NO3) mesocosms. The nitrate-reduced mesocosm had a slowed cell division rate when compared to the nitrate-replete mesocosm. Minimum intracellular carbon, nitrogen, iNO3, FAA, and total lipid concentrations during the largest surface sub-population aggregations led to the conclusion that daughter cells resulting from cell division received unequal shares of the parental resources and that this inequality influenced migration behavior. Nutrient reduced daughter cells were more strongly influenced by light and phototaxis for carbon production than their replete same cell division sister cells during vertical migration thus rapidly increasing the fulfillment of constituents through photosynthesis. Vertical migration was consistent with an optimization scheme based on threshold limits through utilization or formation of photosynthate. We propose a simplified conceptual model describing how K. brevis is transported along the benthos of the west Florida shelf from off-shore to on-shore. Dynamic carbon thresholds are also suggested for future DVM modeling efforts on K. brevis populations transported between nitrogen replete and nitrogen reduced environmental conditions.}, number={5}, journal={HARMFUL ALGAE}, author={Schaeffer, Blake A. and Kamykowski, Daniel and Sinclair, Geoff and McKay, Laurie and Milligan, Edward J.}, year={2009}, month={Jun}, pages={692–698} }
 @article{schaeffer_kamykowski_mckay_sinclair_milligan_2009, title={LIPID CLASS, CAROTENOID, AND TOXIN DYNAMICS OF KARENIA BREVIS (DINOPHYCEAE) DURING DIEL VERTICAL MIGRATION}, volume={45}, ISSN={["1529-8817"]}, DOI={10.1111/j.1529-8817.2008.00627.x}, abstractNote={The internal lipid, carotenoid, and toxin concentrations of Karenia brevis (C. C. Davis) Gert Hansen and Moestrup are influenced by its ability to use ambient light and nutrients for growth and reproduction. This study investigated changes in K. brevis toxicity, lipid class, and carotenoid concentrations in low‐light, nitrate‐replete (250 μmol quanta · m−2 · s−1, 80 μM NO3); high‐light, nitrate‐replete (960 μmol quanta · m−2 · s−1, 80 μM NO3); and high‐light, nitrate‐reduced (960 μmol quanta · m−2 · s−1, <5 μM NO3) 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.}, number={1}, journal={JOURNAL OF PHYCOLOGY}, author={Schaeffer, Blake A. and Kamykowski, Daniel and McKay, Laurie and Sinclair, Geoff and Milligan, Edward}, year={2009}, month={Feb}, pages={154–163} }
 @article{schaeffer_kamykowski_mckay_sinclair_milligan_2007, title={A comparison of photoresponse among ten different Karenia brevis (Dinophyceae) isolates}, volume={43}, ISSN={["1529-8817"]}, DOI={10.1111/j.1529-8817.2007.00377.x}, abstractNote={Many laboratories have solely used the Wilson isolate to physiologically characterize the harmful algal bloom (HAB) dinoflagellate Karenia brevis (C. C. Davis) G. Hansen et Moestrup. However, analysis of one isolate may lead to misinterpretations when extrapolating measurements to field populations. In this study, pulse‐amplitude‐modulated chlorophyll fluorometer (PAM‐FL) relative electron transport rate (ETR), Fv/Fm, and chl were compared with traditional techniques, such as 14C photosynthesis versus irradiance (P–E) curves, DCMU [3‐(3′,4′‐dichlorophenyl)‐1,1‐dimethyl urea] Fv/Fm, and extracted chl. The DCMU and PAM‐FL values of Fv/Fm (r2 = 0.51) and chl (r2 = 0.58) were in good agreement. There was no correlation between 14C and PAM‐FL α, Pmax, and β parameters because PAM‐FL ETR was only a relative measurement. The PAM‐FL techniques were then used to investigate P–E curves, quantum yield of PSII (Fv/Fm), and chl from 10 K. brevis isolates to determine whether one or all isolates would better represent the species. Comparisons were made with a radial photosynthetron, which allowed for controlled conditions of light and temperature. Isolate α, Pmax, and β varied between 0.097 and 0.204 μmol e− · m−2 · s−1 · (μmol quanta · m−2 · s−1)−1, 80.41 and 241 μmol e− · m−2 · s−1, and 0.005 and 0.160 μmol e− · m−2 · s−1 · (μmol quanta · m−2 · s−1)−1, respectively. Either carbon limitation and/or bacterial negative feedback were implicated as the cause of the P–E parameter variability. Furthermore, these results directly contradicted some literature suggestions that K. brevis is a low‐light‐adapted dinoflagellate. Results showed that K. brevis was more than capable of utilizing and surviving in light conditions that may be present on cloudless days off Florida.}, number={4}, journal={JOURNAL OF PHYCOLOGY}, author={Schaeffer, Blake A. and Kamykowski, Daniel and McKay, Laurie and Sinclair, Geoff and Milligan, Edward J.}, year={2007}, month={Aug}, pages={702–714} }
 @article{mckay_kamykowski_milligan_schaeffer_sinclair_2006, title={Comparison of swimming speed and photophysiological responses to different external conditions among three Karenia brevis strains}, volume={5}, ISSN={["1878-1470"]}, DOI={10.1016/j.hal.2005.12.001}, abstractNote={Behavior, growth, and production are integral in the life history of Karenia brevis, an autotrophic, dinoflagellate HAB species, and are important variables in modeling blooms in the Gulf of Mexico. This study compares swimming speeds, growth rates, and photosynthetic responses of recent isolates of K. brevis (specifically the Apalachicola – APA, Manasota – MAN, and Jacksonville – JAX strains) over a range of light intensities and temperatures. Strain swimming speeds were similar and remained fairly constant from 17 to 30 °C, but decreased markedly at 13 °C. Photosynthetic responses of the strains to different acclimated temperatures had opposite trends with APA exhibiting higher electron transport rates (ETR) at higher temperatures and MAN exhibiting higher ETR at lower temperatures. In the light experiments, the cells’ internal physiological state (represented by photosynthetic yield, ETR, and neutral lipid reserves) and swimming capabilities were examined in the dark after 6 h incubations in the radial photosynthetron. For all strains, at initial incubation light intensities swimming speed decreased and ETR increased. As incubation light intensities increased, ETR decreased and swimming speed increased. At the highest incubation light intensities, ETR and swimming speed decreased. Neutral lipids followed a pattern similar to ETR, only lipids peaked after ETR at a light intensity that corresponded to the increase in swimming speed. The results suggest that cells may partition energy selectively depending on the needs of the cell. Information was combined to characterize a generalized species response to light and temperature ranges.}, number={6}, journal={HARMFUL ALGAE}, author={McKay, Laurie and Kamykowski, Daniel and Milligan, Ed and Schaeffer, Blake and Sinclair, Geoff}, year={2006}, month={Dec}, pages={623–636} }
 @article{sinclair_kamykowski_milligan_schaeffer_2006, title={Nitrate uptake by Karenia brevis. I. Influences of prior environmental exposure and biochemical state on diel uptake of nitrate}, volume={328}, ISSN={["1616-1599"]}, DOI={10.3354/meps328117}, abstractNote={The ability of a Karenia brevis population to persist in an oligotrophic water column depends on how cell physiology and cell behavior contribute to the acquisition of light and nutrients that often are separated in space. We hypothesized that an aggregation of K. brevis, observed under- going a diel vertical migration (DVM) in the bottom half of a 22 m water column on the West Florida Shelf, used the sediments as a nutrient source. We tested how the physiology of K. brevis contributed to the acquisition of nitrate by evaluating how nitrate uptake changed with prior environmental exposure. The experimental conditions simulated the extremes that cells might endure during DVM when migrating up into an oligotrophic water column versus cells that remained near the sediment- water interface. The first culture, representing cells that attained the maximum apex of their migra- tion away from the sediments, was grown under relatively high light (350 μmol quanta m -2 s -1 ) and reached nitrate-depleted conditions (<0.5 μM NO3 - ) prior to the experiment. The second culture, rep- resenting cells that remained near the sediment-water interface, was grown under relatively low light (60 μmol quanta m -2 s -1 ) and nitrate-replete conditions (~20 μM NO3 - ) prior to the experiment. Cells exposed to nitrate-depleted environments for 12 h prior to the experiment enhanced nocturnal uptake compared to cells continuously exposed to nitrate-replete conditions. Changes in cell physi- ology may contribute to nitrate acquisition after descent from oligotrophic environments to areas with elevated nitrate concentrations.}, journal={MARINE ECOLOGY PROGRESS SERIES}, author={Sinclair, Geoffrey A. and Kamykowski, Daniel and Milligan, Edward and Schaeffer, Blake}, year={2006}, pages={117–124} }
 @article{sinclair_kamykowski_milligan_schaeffer_2006, title={Nitrate uptake by Karenia brevis. II. Behavior and uptake physiology in a nitrate-depleted mesocosm with a bottom nutrient source}, volume={328}, ISSN={["1616-1599"]}, DOI={10.3354/meps328125}, abstractNote={Karenia brevis may optimize growth by alternately maximizing exposure to light, migrating up into an oligotrophic water column during the day, and to nutrients (nitrate), by migrat- ing down to the sediment-water interface at night. Understanding how cell behavior contributes to the acquisition of light and nutrients that are separated in space is critical to understanding how K. brevis populations persist in oligotrophic environments. In response to previous modeling efforts that parameterized cell physiology and behavior in nitrate-replete conditions, we examined similar cellular characteristics in a stratified 1.5 m deep mesocosm. The upper 2/3 of the mesocosm, encom- passing the surface and middle samples, was nitrate depleted (<0.5 µM NO3 - ) and simulated an oligotrophic water column. The lower 1/3 of the mesocosm contained 10 µM NO3 - corresponding to elevated nutrient levels near the sediment-water interface. We sampled uptake rates at 3 depths during the day at light levels of 350, 125 and 60 µmol quanta m -2 s -1 and again at night in the dark. Nocturnal uptake of nitrate in the mesocosm was significantly less than diurnal uptake. Nocturnal uptake rates in the mesocom were intermediate between cells exposed to prolonged nitrate-depleted and nitrate-replete conditions. Both migration, as indicated by diel aggregation patterns, and cell physiology indicate that descent to regions of higher nutrient concentrations were sufficient to main- tain average growth rates of 0.3 div d -1 . Thus, both the physiology and behavior of K. brevis may sup- port populations near the sediment-water interface, where they may grow undetected in offshore oligotrophic water columns.}, journal={MARINE ECOLOGY PROGRESS SERIES}, author={Sinclair, Geoffrey A. and Kamykowski, Daniel and Milligan, Edward and Schaeffer, Blake}, year={2006}, pages={125–131} }
 @article{kamykowski_milligan_reed_liu_1999, title={Geotaxis/phototaxis and biochemical patterns in Heterocapsa (=Cachonina) illdefina (Dinophyceae) during diel vertical migrations}, volume={35}, ISSN={["1529-8817"]}, DOI={10.1046/j.1529-8817.1999.3561397.x}, abstractNote={Two separate experiments with Heterocapsa (=Cachonina) illdefina Herman et Sweeney, one with and the other without water volume replacement, were performed in a 250‐L laboratory mesocosm (45‐cm diameter × 150‐cm height) to examine how diel vertical migration (DVM) relates to taxis sign and strength and to cellular biochemical state. Although only the cell population grown with water volume replacement maintained a division per day over the course of the experiment, periodic measurements during both experiments demonstrated that cells aggregating at the surface during the light period generally were deficient in all measured biochemical constituents compared to cells obtained from a midcolumn depth. More specifically, H. illdefina cells that aggregated at the surface during the light period in both experiments exhibited weakened positive geotaxis but strengthened positive phototaxis and were very deficient in lipid and free amino acid compared to midcolumn cells. Cells sampled at midcolumn during the light period exhibited similar but weaker taxes changes compared to surface samples, and geotaxis strength was inversely correlated with cell diameter, cellular DNA and protein content, and RNA/DNA ratio. In comparison, published data on Gymnodinium breve Davis, a harmful algal bloom species, showed that cells aggregating at the surface during the light period generally exhibited weakened negative geotaxis and strengthened positive phototaxis and were very deficient in lipid and chl a compared to midcolumn cells. Although the persistent tendency toward negative geotaxis was weaker in midcolumn subpopulations throughout the day, its strength was inversely correlated with cell diameter and cellular lipid content. The combined results for both species support a revised conceptual model of optimized DVM in autotrophic marine dinoflagellates incorporating generalized expressions of taxis and biochemical state of individual cells.}, number={6}, journal={JOURNAL OF PHYCOLOGY}, author={Kamykowski, D and Milligan, EJ and Reed, RE and Liu, WC}, year={1999}, month={Dec}, pages={1397–1403} }