title: Comparing the diel vertical migration of Karlodinium veneficum (dinophyceae) and Chattonella subsalsa (Raphidophyceae): PSII photochemistry, circadian control, and carbon assimilation.
abstract: Diel vertical migration (DVM) is thought to provide an adaptive advantage to some phytoplankton, and may help determine the ecological niche of certain harmful algae. Here we separately compared DVM patterns between two species of harmful algae isolated from the Delaware Inland Bays, Karlodinium veneficum and Chattonella subsalsa, in laboratory columns. We interpreted the DVM patterns of each species with Photosystem II (PSII) photochemistry, rates of carbon assimilation, and specific growth rates. Each species migrated differently, wherein K. veneficum migrated closer to the surface each day with high population synchrony, while C. subsalsa migrated near to the surface from the first day of measurements with low population synchrony. Both species appeared to downregulate PSII in high light at the surface, but by different mechanisms. C. subsalsa grew slower than K. veneficum in low light intensities (≈bottom of columns), and exhibited maximal rates of C-assimilation (Pmax) at surface light intensities, suggesting this species may prefer high light, potentially explaining this species' rapid surface migration. Contrastingly, K. veneficum showed declines in carbon assimilation at surface light intensities, and exhibited a smaller reduction in growth at low (bottom) light intensities (compared to C. subsalsa), suggesting that this species' step-wise migration was photoacclimative and determined daily migration depth. DVM was found to be under circadian control in C. subsalsa, but not in K. veneficum. However, there was little evidence for circadian regulation of PSII photochemistry in either species. Migration conformed to each species' physiology, and the results contribute to our understanding each alga's realized environmental niche.
authors.affiliation: University of Delaware, 700 Pilottown Road, Lewes, DE 19958, USA. Electronic address: ctilney@gmail.com.
authors.forename: Charles L
authors.initials: CL
authors.lastname: Tilney
authors.affiliation: University of Delaware, 700 Pilottown Road, Lewes, DE 19958, USA.
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Hoadley
authors.affiliation: University of Delaware, 700 Pilottown Road, Lewes, DE 19958, USA.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Warner
mesh_terms: D056893:Alveolata / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects; D002244:Carbon / Q000378:metabolism*; D057906:Circadian Clocks; D002940:Circadian Rhythm; D008027:Light; D055668:Photochemical Processes; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism*; D058009:Stramenopiles / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects
chemical_list: D045332:Photosystem II Protein Complex; D002244:Carbon