起始生物量比对3种海洋微藻种间竞争的影响

为深入了解饵料微藻与赤潮微藻间的种间竞争关系,通过微藻共培养的方法,研究了起始生物量比(1:4、1:1和4:1)对3种海洋微藻(塔玛亚历山大藻、蛋白核小球藻和湛江等鞭金藻)两两之间种间竞争的影响,并对其作用机制进行了探讨。结果表明:①3种海洋微藻表现出种间竞争的相互抑制效应;②在与塔玛亚历山大藻(简称A)的种间竞争中,蛋白核小球藻(简称C)和湛江等鞭金藻(简称I)均在竞争中占优势,蛋白核小球藻随自身起始生物量比的提高,其竞争优势越加明显,湛江等鞭金藻在A:I=1:1时竞争优势最为明显;在蛋白核小球藻和湛江等鞭金藻的种间竞争中,当C:I=1:4时,湛江等鞭金藻在竞争中占优势,C:I=1:1时,初期湛江等鞭金藻占竞争优势,随蛋白核小球藻的迅速生长,后期蛋白核小球藻占竞争优势,C:I=4:1时,蛋白核小球藻占绝对竞争优势;③由种间竞争抑制参数比较得出:3种微藻的种间竞争强弱依次为蛋白核小球藻>湛江等鞭金藻>塔玛亚历山大藻。蛋白核小球藻和湛江等鞭金藻在起始比例C:I=1:1时,可共培养利用,在海产经济动物育苗中可对其进行适时采收投喂;两种饵料藻对塔玛亚历山大藻具有明显的抑制作用,可为开发利用饵料藻进行赤潮生物防控提供一定的科学依据。

Effects of initial biomass ratio on the interspecific competition outcome between three marine microalgae species

The investigation of interspecific competition is useful to reveal the mechanism in regulating growth and reproduction of organisms,optimal control of harmful organisms and co-culture of beneficial organisms.The interspecific competition is influenced by either population density or body size,therefore it is important to investigate the effects of biomass on the interspecific competition. A method of co-culturing microalgae was used to examine the effects of initial biomass ratio(1∶4,1∶1 and 4∶1) on interspecific competition between three marine microalgae species,Alexandrium tamarense,Isochrysis zhanjiangensis and Chlorella pyrenoidosa in the present experiment.The mixed algae in the exponential growth phase were cultured to increase cell density in 250 mL erlenmeyer flasks containing 150 mL of f/2 culture medium.The temperature was maintained at(20±1) ℃,and flasks were illuminated in a photoperiod of 12L—12D with a light intensity of approximately 1000 lx.The salinity was(31±0.5) and pH was 8.34.After 20 days culture,the densities of algal cell(algal cells/ml) were measured with OlympusCX21 microscope.Moreover,logistic growth curve was fitted to calculate the competitive inhibition parameters based on the cell densities. The results mainly suggested the following points: 1) the inhibition effect of interspecific competition between three microalgae was significantly related to the environmental carrying capacities(K);2) during the process of competition with A.tamarense(A),both C.pyrenoidosa(C) and I.zhanjiangensis(I) were dominant algae.With the increase of initial biomass,C.pyrenoidosa showed the increasing competition advantage.When the biomass ratio of A to I was held at 1∶1,I.zhanjiangensis was obviously super-dominant.When the ratio of C to I was 1∶4,I.zhanjiangensis was the dominant algae.When the ratio of C to I was 1∶1,I.zhanjiangensis was competitively dominant in the earlier stage,but C.pyrenoidosa grew faster,superseding I.zhanjiangensis in the later stage.When the ratio of C to I was 4∶1,C.pyrenoidosa was predominant;3) based on the competitive inhibition parameters,the interspecies competitive ability of three species of microalgae were as follow: C.pyrenoidosa> I.zhanjiangensis> A.tamarense.Furthermore,their competitive ability significantly depended on the algal cell size. The above results suggested that equal ratio of C.pyrenoidosa to I.zhanjiangensis was suitable to co-culture and then utilize in the marine economic animals aquaculture.Moreover,they could also inhibit the growth of A.tamarense.This might be used to control the harmful algae bloom.It was speculated that the inhibiting effect of C.pyrenoidosa and I.zhanjiangensis on the growth of A.tamarense was mainly due to the competition of nutritional sources,while the inhibiting effect of A.tamarense on the growth of C.pyrenoidosa and I.zhanjiangensis was caused by both the direct contact of cells and secondary secretion of toxic substances.