Nutrient Compositions of Cultured Thalassiosira rotula and Skeletonema costatum from Jiaozhou Bay

The nutrient compositions of cultured Thalassiosira rotula and Skeletonema costatum from Jiaozhou Bay were measured. Carbon (C), nitrogen (N), phosphorus (P), and silicon (Si) contents in cell were obvious higher in T. rotula than in S. costatum, but the percents of N, P, Si contents in cell dry mass in T. rotula were lower than those in S. costatum. The dry mass concentrations of N, P, Si in S. costatum were much higher than those in T. rotula, particularly Si, the former was 6.4 times of the latter, showing that S. costatum could more assimilate these elements. Especially, S. costatum had competitive dominance for assimilation Si, which is beneficial to its becoming a major dominant species in relative short Si of Jiaozhow Bay. There were some differences in numerical value of nutrient ratios both laboratory-cultured phytoplankton and different-sized suspended particulates (mainly phytoplankton) in Jiaozhou Bay, which was caused by the changes of environment. High contents of C, N and relative low P, Si, high N/P ratio (far higher than Redfield value) and low Si/P and Si/N ratios (far lower than Redfield values) in the two diatoms and different-sized suspended particulates were consistent with those in the seawater. Relative short Si in the seawater and phytoplankton showed that Si was possibly affecting phytoplankton growth in Jiaozhou Bay.