JOURNAL OF PLANKTON RESEARCH | VOLUME 13 | NUMBER 1 | PAGES 61-75 | 1991
© Oxford University Press
research-article |
Comparative nutrient status and competitive interactions of two Antarctic diatoms (Corethron criophilum and Thalassiosira antarctica)
Max-Planck-Institute of Limnology PO Box 165, D-2320 Plön, FRG
Received on January 1, 1990; revised on August 23, 1990 The nutrient status of two common Antarctic diatoms (Corethron criophilum and Thalassiosira cf. antarctica) was analysed by studying the growth response in enrichment bioassays and by estimates of the cell quotas of Si, N and P after size-fractionation of net plankton samples Corethron had higher biomass-specific N-quotas; Si- and P-quotas were quite similar between both species. Corethron was Si-limited in five enrichment experiments and not nutrient limited in five experiments. Thalassiosira was not nutrient limited in six experiments, N-hmited in four experiments and Si-limited in one experiment Droop-kinetics of Si-limited growth of Corethron and of N-hmited growth of Thalassiosira were obtained by combining the growth rates in the bioassays and the cell quotas from the natural populations. The minimal Si-quota of Corethron was 0 041 mol Si/mol C, the saturating cell quota was 0.158 mol Si/mol C respectively The minimal N-quota of Thalassiosira was 0 0223 mol N/mol C, the saturating cell quota was 0.208 mol N/mol C Corethron was N-saturated at cell quotas of >0 106 mol N/mol C; Thalassiosira was Si-saturated at cell quotas of <0 132 mol Si/mol C. As the better competitor for N and the poorer one for Si, Corethron became more important with increasing Si N ratios, while Thalassiosira became more important with decreasing Si:N ratios in the water