Photosynthetic activity of Prorocentrum donghaiense Lu acclimated to phosphorus limitation and its photosynthetic responses to nutrient depletion

Prorocentrum donghaiense blooms periodically occur in late spring and early summer in the phosphorus (P)-limited East China Sea; however, few studies have been conducted in nutrient conditions that resembled those in the East China Sea. To study the actual photosynthetic status of P. donghaiense in P-limited conditions, we established stable P-limited conditions using semi-continuous culture at two dilution rates (0.1 and 0.3day(-1)). When the external nutrient concentrations remained steady after 26days, time did not affect the maximum quantum yield (F-v/F-m), normalized Stern-Volmer quenching (NPQ(NSV)), maximum light use efficiency (), maximum relative electron transport rate (rETR(max)), and light saturation intensity (I-k). Prorocentrum donghaiense acclimated to P limitation, and the high actual quantum yield of photosystem II (phi(PSII)) and rETR(max), low NPQ(NSV) at 0.3day(-1), and increased phi(PSII) with time at 0.3 day(-1) indicated the photosynthetic advantages of P. donghaiense at a high growth rate. To test the responses of P-limitation-acclimated P. donghaiense to nutrient inputs, nutrient-addition experiments were conducted. Nitrate and phosphate addition thoroughly depleted P or nitrogen (N). Greater decreases in F-v/F-m, phi(PSII), and rETR(max), and higher NPQ(NSV) derived from rapid light curves (RLCs) were found under the P-depletion condition than under the N depletion condition. These results showed that the P-limitation-acclimated P. donghaiense had a weaker photosynthetic tolerance to P depletion. Given the differences in the photosynthetic tolerance of P. donghaiense to nutrient depletion, our results suggested that reduced P inputs should be considered during the management of P. donghaiense blooms.