Growth and Nitrogen Uptake Kinetics in Cultured Prorocentrum donghaiense

We compared growth kinetics of Prorocentrum donghaiense cultures on different nitrogen (N) compounds including nitrate (NO(3) (−)), ammonium (NH(4) (+)), urea, glutamic acid (glu), dialanine (diala) and cyanate. P. donghaiense exhibited standard Monod-type growth kinetics over a range of N concentraions (0.5–500 μmol N L(−1) for NO(3) (−) and NH(4) (+), 0.5–50 μmol N L(−1) for urea, 0.5–100 μmol N L(−1) for glu and cyanate, and 0.5–200 μmol N L(−1) for diala) for all of the N compounds tested. Cultures grown on glu and urea had the highest maximum growth rates (μ(m), 1.51±0.06 d(−1) and 1.50±0.05 d(−1), respectively). However, cultures grown on cyanate, NO(3) (−), and NH(4) (+) had lower half saturation constants (K(μ), 0.28–0.51 μmol N L(−1)). N uptake kinetics were measured in NO(3) (−)-deplete and -replete batch cultures of P. donghaiense. In NO(3) (−)-deplete batch cultures, P. donghaiense exhibited Michaelis-Menten type uptake kinetics for NO(3) (−), NH(4) (+), urea and algal amino acids; uptake was saturated at or below 50 μmol N L(−1). In NO(3) (−)-replete batch cultures, NH(4) (+), urea, and algal amino acid uptake kinetics were similar to those measured in NO(3) (−)-deplete batch cultures. Together, our results demonstrate that P. donghaiense can grow well on a variety of N sources, and exhibits similar uptake kinetics under both nutrient replete and deplete conditions. This may be an important factor facilitating their growth during bloom initiation and development in N-enriched estuaries where many algae compete for bioavailable N and the nutrient environment changes as a result of algal growth.