Effect of nitrogen and phosphorus concentration on interspecific competition between Skeletonema costatum and Scrippsiella trochoidea
氮和磷浓度对中肋骨条藻和锥状斯氏藻种间竞争的影响

Aims Skeletonema costatum and Scrippsiella trochoidea are two algal species that can cause red tides together. Interspecific competition is thought to be a factor in development of algal blooms. Our objective is to study the effect of nitrogen and phosphorus on interspecific competition between Skeletonema costatum and Scrippsiella trochoidea. Methods The experiments were carried out in mono-culture and co-culture. The nitrogen (nitrate) and phosphorus (phosphate) concentrations were 32, 32; 128, 32; 512, 32; 512, 8; 512, 2 μmol·L–1 , respectively. Important findings With increased concentration of nitrogen and phosphorus, the time of Skeletonema costatum as the dominant species was prolonged. Compared with mono-culture, the maximum densities of two species were inhibited in co-culture, and the degree of inhibition increased with higher concentration of nitrogen and phosphorus. The maximum density of Skeletonema costatum was more inhibited than that of Scrippsiella trochoidea. When the concentration of nitrogen and phosphorus was highest, the inhibitory starting point (t p ) of the two species was highest, and with the decline of nutrients, the t p also decreased. Under various nutritional conditions, competitive inhibition parameters of Scrippsiella trochoidea to Skeletonema costatum (β) were higher than α. Scrippsiella trochoidea out-competed Skeletonema costatum when nitrogen was 512 μmol·L–1 and phosphorus was 2 μmol·L–1 . In other nutritional conditions, competition resulted in unstable coexistence of the species.