Growth and uptake kinetics of phosphate by benthic microalga Nitzschia sp isolated from Hiroshima Bay, Japan

In the present study, we experimentally investigated the phosphate uptake kinetics of benthic microalga Nitzschia sp. isolated from Hiroshima Bay, Japan. The maximum uptake rate (?max) obtained by short-term experiments was 6.84 pmol cell-1 h-1 for phosphate. The half-saturation constant for uptake (KS) was 61.2 mu mol cell-1 h-1. Both the ?max and Ks of this species were extremely high, suggesting that Nitzschia sp. is adapted to benthic environments, where nutrient concentrations are much higher than in the water column. The specific maximum growth rate (mu'max) and minimum cell quota (Q0) for the P-limited condition, obtained by a semi-continuous growth experiment, were 0.48 day-1 and 0.045 pmol cell-1, respectively. It is concluded that Nitzschia sp. could be a storage strategist species, meaning it adapts so as to minimize the influence of fluctuations in phosphate conditions resulting from the change in redox conditions of sediment due to bioturbation.