Growth and Nitrogen Uptake Kinetics in Cultured Prorocentrum donghaiense

We compared growth kinetics of Prorocentrum donghaiense cultures on different nitrogen (N) compounds including nitrate (NO3-), ammonium (NH4+), 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 mu mol NL-1 for NO3- and NH4+ , 0.5- 50 mu mol N L-1 for urea, 0.5-100 mu mol N L-1 for glu and cyanate, and 0.5-200 mu mol N L-1 for diala) for all of the N compounds tested. Cultures grown on glu and urea had the highest maximum growth rates (mu(m), 1.51=0.06 d(-1) and 1.50=0.05 d(-1), respectively). However, cultures grown on cyanate, NO3- , and NH4+ had lower half saturation constants (K-mu, 0.28-0.51 mu mol N L-1). N uptake kinetics were measured in NO3--deplete and -replete batch cultures of P. donghaiense. In NO3--deplete batch cultures, P. donghaiense exhibited Michaelis-Menten type uptake kinetics for NO3(-), NH4+, urea and algal amino acids; uptake was saturated at or below 50 mu mol N L-1. In NO3--replete batch cultures, NH4+, urea, and algal amino acid uptake kinetics were similar to those measured in NO3--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.