Species-specific phytoplankton growth rates via diel DNA synthesis cycles. III. Accuracy of growth rate measurements in the dinoflagellate Prorocentrum minimum.

Abstract

The accuracy of species-specific phytoplankton growth rates estimated by cell cycle analysis was tested with the dinoflagellate Prorocentrum minimum (Pav.) Sch. under conditions of altered nitrogen and phosphorus availability. Reduced nutrient availability caused major changes in the duration of cell cycle phases. At the nutrient level of complete f/2 media, the length of the combination of S, G2, and M phases was about 8 h at growth rates of 0.53 to 0.56 d-' A decrease in ~ 0 ,o~r N-O3 concentration extended the S+G2+M phase to about 15.5 to 17.7 h at growth rates ranging from 0.41 to 0.30 d-' Changes in phase durations dld not significantly affect growth rate estimates. In addition, a minimum growth rate, calculated from the maximum values on phase fraction curves, was shown to be usable as an error detector in some cases. Results support the validity of cell cycle analysis to measure in situ growth rates