AME 63:255-264 (2011)  -  DOI: https://doi.org/10.3354/ame01498

ABSTRACT: Increasing precipitation and surface water temperature due to global change may strengthen the salinity gradient in coastal regions, which could influence the behaviour of dinoflagellate migration. We studied diel vertical migration (DVM) behaviour in the dinoflagellates Prorocentrum minimum and Heterocapsa triquetra using vertically stratified laboratory columns with 3 different salinity gradients (difference of 6, 11 and 16 psu). With nutrient-depleted conditions at the surface, and with nutrients added below the halocline, P. minimum remained mainly concentrated in the bottom water, while H. triquetra performed DVM under all 3 salinity treatments. H. triquetra migrated through a salinity difference of 6 and 11 psu, concentrated at the surface at noon, then migrated to the nutrient-rich bottom water during the night. A salinity gradient of 16, however, stopped H. triquetra cells from moving through the gradient and resulted in a concentration of cells in the cline during the night. At midday, cells were again found at the surface. P. minimum and H. triquetra grown in 4 different salinities (10, 15, 20, 26 psu) and at 3 different temperatures (10, 15, 20°C) showed higher specific growth rates with increasing temperature only in the 2 highest salinity treatments. At 10°C, specific growth rates were not affected by different salinities.

KEY WORDS: Dinoflagellate · Stratification · Vertical distribution · Global change · Salinity · ­Temperature · Growth rate · Heterocapsa triquetra · Prorocentrum minimum