Vertical Migration and Motility Responses in Three Marine Phytoplankton species exposed to solar radiation

PETER R. RICHTER; DONAT P. HADER; RODRIGO J. GONCALVES; M. ALEJANDRA MARCOVAL; VIRGINIA ESTELA VILLAFAÑE; E. WALTER HELBLING

PHOTOCHEMISTRY AND PHOTOBIOLOGY

Año: 2007 vol. 83 p. 810 - 817

0031-8655

Diurnal vertical migration in the water column and the impact ofsolar radiation on motility were investigated in three marinephytoplankton species: Tetraselmis suecica, Dunaliella salinaand Gymnodinium chlorophorum. Cells were exposed to solarradiation either in ultraviolet radiation (UVR, 280–400 nm)transparent Plexiglas tubes (45 cm length, 10 cm diameter) or inquartz tubes under three radiation treatments: PAB (280–700 nm), PA (320–700 nm) and P (400–700 nm). The threespecies displayed different behavior after exposure to solarradiation. Tetraselmis suecica was insensitive to UVR and underhigh solar radiation levels, cells accumulated preferentially nearthe surface. Exposure experiments did not indicate any significantchanges in swimming speed nor in the percentage of motilecells after 5 h of exposure. On the other hand, D. salina wassensitive to UV-B displaying a significant decrease in swimmingspeed and percentage of motile cells after 2–3 h of exposure.Moreover, D. salina cells migrated deep in the water columnwhen irradiance was high. The response of G. chlorophorum wasin between that of the other two species tested, with a slight (butsignificant) decrease in swimming speed and percentage of motilecells in all radiation treatments after 5 h of exposure. While G.chlorophorum cells were more or less homogenously distributedin the water column, a slight (but significant) avoidance responseto high radiation was observed at local noon, with cells migratingdeep in the water column. Our data clearly indicate that thesesub-lethal effects of solar radiation are species-specific and theymight have important implications for the aquatic ecosystem.