Seasonal studies of the dinoflagellate Ceratium longipes (Bailey) Gran in the Bedford Basin, Canada

Abstract

During an extensive bloom the subsurface Ceratium longipes (Bailey) Gran maximum layer was monitored with an attenuance meter and a particle counter in the Bedford Basin, Nova Scotia. This layer was controlled by the density-gradient. The cells absorbed mainly blue light in the region of 450–500 nm. Maximum cell number at the subsurface Ceratium maximum layer was 6.5 × 10 4 cells · 1 −1, and single cell volume 6 × 10 4 μm 3. Maximum total particle volume was 8.8 ppm and dominated by particles with diameters in the range 40–51 μm. The C. longipes made up 70% of total particle volume. A ratio by weight of organic carbon to nitrogen was 8, and the ratio of Ceratium carbon to chlorophyll a 84 ± 16. The growth rate was 0.56 doublings · day −1, which is ≈ 40% of the empirical maximum at 7°C. The maximum quantum yield φm was 0.05 mole C · Einstein −1. The effect of self-shading on φm was confirmed. The maximum light-saturated photosynthetic rate P m B , was 10.4 mg C · [mg Chl a] −1 · h −1 or 0.07 mg C · [mg plant C] −1 · h −1. The maximum index of dark respiration R d B was − 0.25 mg C· [mg Chl a] −1 · h −1 which corresponded to 2.5% of the P m B value. The physiological properties, i.e., φm, P m B and R d B of the dinoflagellate C. longipes are similar to diatoms even though their chemical properties are quite different.