武汉东湖星形柄裸藻种群与宿主的关系以及生态因子对它的影响

INTERRELATIONSHIP BETWEEN THE POPULATION OF COLACIUM SIDEROPUS IN DONGHU LAKE, WUHAN AND ITS HOSTS AS WELL AS THE INFLUENCE OF ECOLOGICAL FACTORS ON IT

星形柄裸藻与附生宿主之间的相互作用为:它是偏利者,而对宿主无很大影响;当其在宿主体表大量附着时,才对宿主有偏害作用。它的种群密度(N,个/L)与宿主密度(N_a,个/L)有密切的正相关关系:N=0.0858e^(0.0528N_a)(r=0921,p<0.01)。宿主的蜕皮间隔时间(T,天)对星形柄裸藻的平均附着量(m,个/每个甲壳动物)和附着量(B,个/L)的影响是:在一定的蜕皮间隔时间范围内呈正相关性:m=ae^(bT)和B=ae^(bT)(a和b为方程常数,下同);超过这个范围呈负相关性:m=aT^(-b)和B=aT^(-b)。而宿主蜕皮间隔时间(T,天)对星形柄裸藻附着率(R,％)的影响则仅为正相关性:R=a+blnT。星形柄裸藻对宿主的附生有一定的选择性。水温(t,℃)与星形柄裸藻种群密度(N,个/L)的关系为:在5—12℃时呈正相关性,N=0.309e^(0.624t)(r=0.914,p<0.01);在12—30℃时呈负相关性,N=0.0000617e^((190.2)/t)(r=0.941,p<0.01),12℃左右可能是星形柄裸藻最适生长温度。水温对星形柄裸藻的平均附着量和附着量也有类似的相关性;而对其附着率(R,％)的影响则仅呈负相关关系:R=bln(30—t)—a。水的透明度(d,cm)与星形柄裸藻种群密度(N,个/L)的相关方程为:N=0.020e^(0.037d)(r=0.838,p<0.01)。湖水中氮磷含量及其比值不是星形柄裸藻增长的限制因素,而钙的含量(S,mg/L)与种群密度(N,个/L)有一定的正相关性:N=0.00254e^(0.178S)(r=0.816,p<0.05)。星形柄裸藻种群变动(N,个/L)与4个主要因子:宿主密度(N,个/L),透明度(d,cm),水温(t,℃),含钙量(S,mg/L)的多元回归方程为:N=1.208N_a+0.698d+5.584t+2.942S-357.957(R=0.853,df=11,k=4,p<0.01)。

Colacium sideropus Skuja is one of main algal populations in Donghu lake,Wuhan during winter and spring. It mainly attaches on cladocerca and Copepoda (belonging to Crustaea).Its growth peak appears in March(late winter and early spring). The population growth corresponds to the J-shaped growth form. The interaction between C.sideropus and its hosts:The interaction between them is mostly commensalism, i. e., to the benefit of C.sideropus; but doesn't exert any influence upon its hosts. So both population densities (N) of C. sideropus and host's densities (N_a) have close positive correlation which may be described as N= 0.0858e^(0.0528N_a)(r=0.921,p<0.01,fig. 1). But when the amount of C. sideropus attaching on its hosts is huge, the interaction between them is amensalism, i.e., host's morement will become slow and go so far as to sink (even die). The influence of host's exuviation on C.sideropus: The mean attachment amount (m)~* and the attachment amount (B)^(**) in relation to interval time (T) of host's exuviation may be positive within fixed time range: m=ae^(bT) and B= ae^(bT); or negative beyond the time: m=aT^(-b) and B=aT^(-b) (a and b are costants, see figs. 2 and 3). But the attachment rate (R)~* in relation to interval time (T) of host's exuviation is only positive:R=22.95+30.40lnT(r=0.834,p<0.01, fig. 6) in D.hyalina; R=32.50+37.00lnT (r=0.729, 0.05>p>0.01, fig.4) in C. vicinus Selectively of C. sideropus to its hosts: The attachment ability of C. sideropus is the strongest to Daphina hyalina (Cladocerca); second to Cyclops vicinus (Copepoda) and the weakest to Neutrodiaptomus incongruens (Copepoda) (see table 1). The water temperature exerts an influence on the population of C. sideropus: The correlation between the population densities (N) and the water temperatures (t) may be positive within 5—12℃:N=0.309e^(0.624t)(r=0.914,p<0.01,fig. 8); or negative within 12—30℃:N=0.0000617e^(190·2/t)(r=0.941,p<0.01,fig.5). The growth of C. sideropus is the fastest when the water temperature is 12℃. So 12℃ may be the most suitable temperature for the growth of C.sideropus. Samely, the correlation between the mean attachment amounts(m)and the water temperatures (t) may also be positive within fixed range of the water temperature: m=bt-a; or negative beyond the range: m=ae^(b/t)(a and b are constants, see fig. 6). But the attachment rates (R) of C.sideropus in relation to the water temperatures (t) is only negative (see fig. 7): R=39.37ln(30-t)—20.89(r=0.933, p<0.01) in D.hyalina; R=40.95ln(30-t)-30.61(r=0.939,p<0.01),in C. vicinus; R=31.54ln(30-t)-44.74(r=0.843,p<0.01) in N.incongruens. The influence of trasparency: The population densities (N) of C.sideropus in relation to the transparencies (d) is positive. It may be described as: N=0.020 e^(0.037d)(r=0.838,p<0.01, fig.8). The influence of nutrients: Nitrogen and phosphorus in Donghu lake, Wuhan aren't limiting factors for population growth of C.siderppus because the lake is eutrophic.(fig.9). The population densities (N) of C. sideropus in relation to calcium concentrations (S) may be described as N=0.00254e^(0.178S)(r=0.816, 0.05>p>0.01,fig. 10). Multiple regression analysis of synthetic influence on ecological factors: It is very remarkable that the population growth (N) of C. sideropus in relation to the densities (N_a) of hosts, trasparencies (d), water temperatures (t) and calcium concentrations (S) is analysed by multiple regression. The multiple regression equation may be described as N=1.208N_a+0.698d+5.584t+2.9425-357.957 (R=0.853,df=11,k=4,p<0.01)