The Investigation On Allelopathy And Allelochemicals Of Several Red Tide Species

Algal allelopathy is a manifold ecological/physiological phenomenon and it plays a crucial role in explaining microalgae distribution, community structure and the dynamics of the populations within an ecosystem.In this article,the experiments was conducted under stable environmental conditions (temperature,light and illuminating periodicity, etc.) and sufficient nutrition supply by f/2 enrichment every day, thus excluding the effects of variations in environmental factors.The results showed that the growth of S.costatum was not only notly inhibited when cultured with A.carterae (S.costatum:A.carterae=1:1, P=0.04940<0.05;S.costatum:A.carterae=1:5,P=0.04971<0.05),P.micans(S.costatum:A.cart erae=1:1,P=0.01489<0.05;S.costatum:A.carterae=1:10,P=0.03093<0.05)or P.minimum (P=0.00000<0.05) in different cell densities, respectively,but also suppressed in the filtrate of A. carterae (Growth StageⅠ:P=0.00298<0.05;StageⅡ:P=0.03149<0.05)and P.micans (Growth StageⅠ:P=0.02374<0.05;StageⅡ:P=0.04790<0.05),and the cell-contact is not necessiry for the allelopathy. And in S. trochoidea filtrate, the S.costatum growth is not significantly different compared to the control (Growth Stage I:P=0.73391>0.05; StageⅡ: 0.90756> 0.05).When was cultured with two-two, A. carterae,P. micans and S. trochoidea, are restrained by other algae, respectively,in different degree. The inhibitory strength of P. micans on S. trochoidea was about 1.6 times higher than it was inhibited by P. micans; and the inhibitory strength on A.carterae was about 33.3 times higher than it was inhibited by P. micans. The inhibitory strength of S. trochoidea on A.carterae was about 30.5 times higher than it was inhibited by S. trochoidea.The filtrate from different phases of A. carterae,P. micans and S. trochoidea were cultured with 5 algae. It is noted that the enriched filtrate of A. carterae could weakly stimulated itself(Growth StageⅠ:P=0.75099>0.05; StageⅡ:P=0.77627>0.05),and the growth ofⅠ. golbana remained almost unchanged; And the growth of P. micans was weakly suppressed in its enriched filtrate(Growth StageⅠ:P=0.40681>0.05; StagⅠ:P= 0.35286> 0.05). The growth of A. carterae was not affected by enriched filtrate of S. trochoidea,but S. trochoidea was weakly suppressed (StagⅠ:P=0.60516>0.05; StageⅡ:P=0.33872>0.05). The growth of algae was more inhibited in enriched filtrate of growth phaseⅡthan in phase I, it means when cell densities of A. carterae,P. micans and S. trochoidea are 6×105cells ml-1,1.1×104cells ml-1 and 1×105cells ml-1, respectively, growth of 5 algae was reduced obviously. While the filtrate was diluted to 1/2,1/4 and 1/8,the inhibition effect was losing, or the growth was stimulated at low concentrations. The marine algae filtrate, A. carterae,P. micans and S. trochoidea, depending on growth stage influenced other's growth. And in the filtrate of exponential phase S.costatum, the 5 algae growth were not significantly different compared to the control.Extracts from cell-free filtrates of A. carterae,P. micans and S. trochoidea were bioassayed.It is noted that the crude extraction has the function of dissolving algae. Then the extraction were finally analyzed by gas chromatography coupled to mass spectrometry (GC/MS). The results of GC/MS showed that the major potential allelochemicals were phenolic compounds, and different algae have different allelochemicals.Benzyl butyl phthalate is the only one they all have.This paper provides theoretical basis to deeply research the allelopathy between those microalgae.