Effects of temperature, nitrogen and phosphorous limitation on the physiological and toxigenic characteristics of harmful benthic dinoflagellate Prorocentrum lima isolated from South China Sea

This study evaluated the potential risk for a harmful benthic dinoflagellate Prorocentrum lima (strain HN45), which was isolated from the South China Sea. In this experiment, P. lima was cultured in laboratory under different temperatures（20 ℃, 25 ℃, 30 ℃）and nitrogen phosphorous limitation conditions (nitrogen-to-phosphorus ratio, N/P: 4.08, 8.17, 16.3, 24.5, 73.5, 147). Then the physiological characteristics, including cell density, growth rate and pigments, as well as the production characteristics of diarrhetic shellfish toxins (DSTs) were investigated and analyzed. Based on the multi-factor analysis of variance, the results showed that the temperature and phosphorus-limited levels had significant effect on cell density, peridinins (the typical pigments of dinoflagellates) and intracellular toxin of P. lima. The DSTs production ability of single cells reached to the highest value (11.34 pg/cell) at the temperature of 25 ℃ and phosphorus concentration of 6 μM. Phosphorus deficiency reduced cells density and specific growth rate of P. lima, but significantly increased their ability to produce DSTs. Moreover, esterified toxins accounted for 3% to 14% of intracellular total toxins in P. lima, which was much lower than the free content toxins. In addition, chlorophyll a concentration of P. lima was negatively correlated with DSTs content. Which further confirmed the competition of the production of chlorophyll a and DSTs. Further research was needed to study the survival selective strategies of Prorocentrum lima under the ambient pressures.