三种鱼的磷排泄及其在微型生态系统磷再循环中的作用

在考查罗非鱼或鲢、鳙下行影响的微型生态系统实验后期 ,对三种鱼的特定正磷酸盐 (PO4 P)排泄率进行了测定 ,并且估算了系统中实验鱼的PO4 P排泄率。结果表明 ,在个体大小相同的情况下 ,罗非鱼的特定PO4 P排泄率明显地高于链、鳙 ,似乎同它们的食物含磷量无关而由其体组织含磷量所决定 ;放养罗非鱼的系统中鱼的PO4 P排泄率比放养链、鳙的系统平均高 2倍多 ,其磷排泄对浮游植物的PO4 P供给率分别为 10 0 %— 15 8%和 6 1%—7 5 %。根据有鱼系统中PO4 P的供求关系和实验结束时磷分布的观测结果推断 ,沉积物的磷释放是系统中磷再生的主要途径 ,而实验鱼调节系统磷再循环的主要机制是排粪。     

保安湖沉积物和间隙水中氮和磷的含量及其分布

保安湖沉积物中氮(N)的含量平均为5.20mg/g,平面分布以桥墩湖区含量最高。沉积物中磷(P)的含量平均为0.75mg/g,平面分布以扁担塘湖区含量最高。沉积物间隙水中总氮的平均含量为3.63mg/L,无机氮中以氨氮的含量最高,占总氮的57.2%;间隙水中总磷的含量平均为0.098mg/L,磷酸盐占总磷的50.0%.间隙水中氮和磷含量的平面分布差异不明显。间隙水中氮和磷的含量比湖水中含量高,但除氨氮外,一般不超过5倍,表明湖水和沉积物间隙水之间营养交换十分强烈。       

EVALUATIONS OF THE AVAILABILITY OF SOURCES OF NITROGEN AND PHOSPHORUS FOR ALGAE1

Techniques are compared for the evaluation of nutrient sources in which the potential nutrients are in contact with algae over their entire culture period versus relatively short-term exposure tests. Different nitrogen and phosphorus compounds were shown to be utilized in darkness as well as in light and were equally available at pH 7 and 9. The availability of relatively insoluble nutrients–iron-phosphorus compounds and teeth for phosphorus, hair for nitrogen iron pyrites for iron, and marble for carbon–indicates that in many cases the equilibrium between soluble and insoluble forms allows algae to compete successfully with insoluble forms for nutrients. Apparently, factors other than mere insolubility prevent algae from obtaining available nitrogen or phosphorus from phosphate rock or lake muds. Live algae or aquatic weeds with adequate or surplus nitrogen or phosphorus were shown to not share their nutrients with nitrogen- or phosphorus-limited algae, whereas the nutrients of killed algae or aquatic weeds were readily used by nutrient-limited algae. The facts–(1) that live algae and aquatic weeds do not share their adequate or surplus nutrients with nutrient-limited algae and (2) that lake muds do not provide readily available nitrogen or phosphorus–indicate that once lake waters are stripped of available nutrients by plant production, further plant production will depend upon nutrients from continuous sources of nutrients, such as wastewater effluents.     

鲢、鳙在东湖生态系统的氮、磷循环中的作用

我们研究了鲢、鳙在停食状况下氮、磷的排泄量及在有鱼及无鱼的水环境中鱼类及微囊藻的氮、磷释放率。结合有关参数进行换算,从量的方面评价了鲢、鳙在东湖生态系统物质循环中所起作用:①鲢、鳙摄食过程加速了水体氮、磷释放进程(有鱼水体氮、磷释放率分别为无鱼水体的1.88和1.41倍),但其释放量(粪便的氮、磷释放量分别为水体氮、磷总含量的11.45％和3.4％)不足以左右东湖水体初级生产量的变动;②鲢、鳙摄食过程一方面提高了对初级生产量的利用率,而另一方面却通过鱼体积贮从水体中移出大量氮(52.20吨)、磷(11.36吨),分别占水体浮游物总氮、磷的3.01％和5.28％;③鲢、鳙大量摄食浮游动物,降低了被摄食种群的密度,缩短被摄食种群生物量周转期(1982年被摄食种群的生产量为1981年的1.05倍,鲢、鳙放养量为1981年的7倍;这两年鱼摄食量分别占其被摄食种群产量的31.73％及0.63％,被摄食种群的ρ/B系数分别为67.92及48.01);这样水体中浮游动物产量的相对稳定,也就促使浮游植物产量相对平衡。     

N、P营养盐胁迫对两株布朗葡萄藻生长的影响

采用批次培养方法,在光照强度60、110mol/m2s下分别设置了7个不同的氮、磷浓度(N:0-3500g/L,P:15-775g/L),研究两株布朗葡萄藻(Botryococcus braunii)对氮、磷胁迫的敏感性差异,筛选高营养利用效率的优良藻株。结果表明:两株藻对氮磷营养胁迫的耐受性存在差异,B.braunii764株对氮胁迫具有较高耐受性,而B.braunii765株对磷胁迫具有较高耐受性。光照强度110mol/m2s,不同氮浓度下B.braunii764株其平均生长速率均显著高于其他各处理组;不同磷浓度下B.braunii765株其平均生长速率显著高于B.braunii764株。在试验设定的光照强度条件下,适当增加光照强度能够显著降低氮胁迫对布朗葡萄藻生长的抑制效应。在光照强度110mol/m2s下,氮浓度3500g/L时两株布朗葡萄藻平均生长速率与在正常Chu-10培养基条件下无显著差异。磷浓度775g/L时两株布朗葡萄藻的平均生长速率均显著低于正常Chu-10培养基条件,增加光照强度对磷胁迫下藻细胞的生长无显著作用。两株布朗葡萄藻在第2天时磷吸收与初始磷浓度呈正相关关系,氮吸收在3500g/L时出现饱和现象。布朗葡萄藻的生长更容易受到培养基中磷营养胁迫的影响。       

武汉东湖磷含量的变动及其分布

本文总结了武汉东湖水体中磷含量（均以PO4计算）的周年逐月季节和年际变动及其分布上的差异（1973－1985年）。按面积加权法计算总磷的平均含量为0．244毫克／升（1983－1985年）,总溶解磷和溶解活性磷的平均含量分别为0．121毫克／升和0．051毫克／升（1981－1984年）,总磷和总溶解磷周年中出现两次高峰含量,即春季（3－5月）和夏末秋初（8－9月）。低含量出现在水温最低的冬季（12－2月）,周年中溶解活性磷高峰含量出现在冬末春初（1－3月）,低含量多数出现在春天夏初（5－7月）。东湖水体中磷含量平面分布有明显的差异,而垂直分布表层和底层差异小,各种形态磷的组成中颗粒磷所占比较最大（1983－1984年平均值）,平均占总磷63．4％,溶解非活性磷所占比较最小,平均占总磷12．0％。     

THE EFFECT OF ORGANOPHOSPHORUS INSECTICIDAL SPRAYS ON THE GROWTH AND PHOSPHORUS CONTENT OF BRUSSELS SPROUTS

No evidence was found that the insecticides schradan or demeton directly increase the growth of plants. The dry weight of Brussels sprouts plants grown in soil supplying little phosphorus was unaffected by spraying six times with schradan or demeton, or with sodium phosphate Solution supplying the same amount of phosphorus as the insecticides. The dry weight of larger plants grown in soil supplying more phosphorus was unaffected by spraying with demeton or inorganic phosphorus Solutions; schradan spray decreased it in one experiment but not in the other.
Spraying with schradan, or with the equivalent amount of phosphorus as sodium phosphate, in one experiment increased the phosphorus content of plants grown in soil supplying little phosphorus. With high phosphorus supply in the same experiment, sodium phosphate Solution, but not schradan, increased phosphorus content of the plants slightly, but not significantly. Phosphorus content was not affected either by schradan sprays in the other experiment or by demeton sprays in both experiments.     

SOME ASPECTS OF THE DISTRIBUTION OF REACTIVE PHOSPHORUS IN LAKE McILWAINE,RHODESIA: PHOSPHORUS LOADING AND ABIOTIC RESPONSES

SUMMARY

This study was designed to investigate the apparent loss from the water column in Lake McIlwaine This study of significant quantities of reactive phosphorus. The Total Reactive Phosphorus mass-balance for the lake for 1977/78 was calculated, and both in situ and laboratory experiments were carried out to determine the effect of the lake sediments on the phosphorus loading of the lake. The experimental results showed that both uptake and release of phosphorus occurs in the lake, but that uptake of phosphorus by the sediments was by far the dominant process, thus accounting for the observed loss of phosphorus from the water column. The availability of the bound phosphorus for algal growth was also studied and it is suggested that algal uptake of bound phosphorus is possible. Various factors affecting phosphorus uptake by the sediments are discussed.     

THE PREPARATION AND USE OF TOBACCO MOSAIC VIRUS CONTAINING RADIOACTIVE PHOSPHORUS

Normal and tobacco mosaic-diseased Turkish tobacco plants were grown in sand for a period of several weeks, during which they were fed daily a complete nutrient solution to which had been added disodium phosphate containing radioactive phosphorus. Determinations were made of the distribution of radioactive phosphorus in different fractions such as the wash from the sand and roots, the press cake obtained on pressing the juice from the plants, the protein and protein-free portions of the supernatant liquids obtained on ultracentrifugation of the juices, and the purified tobacco mosaic virus isolated from the diseased plants. Chemical analyses as well as radiographs of the normal and diseased leaves indicated that they contained the same amount of phosphorus. Approximately 30 per cent of the radioactive phosphorus absorbed by the diseased plants was found to be combined with the purified tobacco mosaic virus that was isolated from these plants. Following the inoculation of purified tobacco mosaic virus possessing high radioactivity to normal Turkish tobacco plants, most of the radioactivity was found to be associated with non-virus components of which about 40 per cent was in the inoculated and 60 per cent in the uninoculated portions of the plants. Although a small amount of radioactive virus was isolated from the uninoculated portions of the plants, it was impossible, because of a number of complicating factors which have been discussed, to draw from the results any reliable conclusions regarding the mode of reproduction of tobacco mosaic virus.     

CARBON,NITROGEN, AND PHOSPHORUS AND THE EUTROPHICATION OF FRESHWATER LAKES1

The question of nutrients responsible for eutrophication of freshwater lakes is reviewed, and recent additions to the literature on nutrient limitation are discussed. The paper by Lange is criticized on several grounds, including the facts that utilization of HCO₃^? by phytoplankton and the invasion of lake waters by atmospheric CO₂ are ignored as sources of photosynthetic carbon. The phosphorus and nitrogen concentrations used in Lange's experiments are far higher than values published by others for Lakes Erie and Ontario. Preliminary results of fertilizing a small oligotrophic lake with nitrogen and phosphorus are described. The standing crop of phytoplankton increased by 30–50 ×, while the P:N:C ratio in seston did not change from ratios found in unfertilized lakes. Other experiments done in water columns isolated with polyethylene film showed that addition of carbon did not increase the phytoplankton standing crop. Since the fertilized lake was initially lower in total CO₂ than any other recorded in the literature, it is concluded that carbon is unlikely to limit the standing crop of phytoplankton in almost any situation. Measurements of invasion of atmospheric gases to the fertilized lake by the Rn²²² technique were compared with phytoplankton production measurements, revealing that atmospheric invasion of CO₂ is sufficient to support the high phytoplankton standing crop in the epilimnion of the lake. Possible errors in interpretation of culture and bottle-bioassay experiments with respect to eutrophication are discussed.     

PHOSPHORUS CONTENT AND RATE OF GROWTH IN THE DIATOMS CYCLOTELLA NANA AND THALASSIOSIRA FLUVIATILIS

Cyclotella nana and Thalassiosira fluviatilis were grown in chemostat and turbidostat units in 1/3 strength artificial seawater supplemented with nutrients and vitamin B₁₂ in excess except for phosphorus (P) which in concentrations of 50 or 100 μg/liter was limiting. Different chemostat and turbidostat settings produced different cell numbers per unit volume which, since external P was practically nil, corresponded to varying amounts of bound P per cell. Growth rate plotted vs. P per cell follows a saturation curve. While no growth occurs at a certain minimum content of bound P, half the maxi-mum growth rate is observed at twice the minimum level of P,3/4 of the maximum at 3 times the minimum level, etc., the maximum growth rate being defined as that observed during growth unrestricted by P supply at a given set of conditions (light, temperature, salinity, etc.). Temperature and light were varied from 13.5 to 24 C and from 2000 to 6000 lux (continuous and intermittent). An abnormal growth curve was found with C. nana at 24 C and 6000 lux continuous light. Any change in P content of the cells significantly alters cell composition as reflected in P distribution in acid-soluble, lipid, and acid-insoluble fractions and in organic carbon content. External P does not immediately enter our equation for growth rate but is one of the factors deter-mining rate of P uptake and therefore bound P per cell. Conditions governing uptake, however, cannot be adequately controlled in a chemostat and there fore should be determined in a different experimental approach.     

武汉东湖不同湖区底泥总磷含量及变化的研究

以武汉东湖为对象,研究了1998.03—1999.02期间不同营养水平湖区底泥中(0—5cm,5—10cm)总磷的含量及季节动态。6个站平均总磷含量为1.15mg/g,同80年代初相比,Ⅰ、Ⅱ站底泥中总磷含量分别增高1.42倍和1.03倍。受污水排放影响较重的0站磷含量高达2.78mg/g,而受污水排放影响较小的Ⅳ、Ⅴ站仅分别为0.52mg/g和0.50mg/g。东湖底泥中磷年平均含量与湖水中磷年平均浓度相关系数极高(r=0.997,n=5,p＜0.02)。通过对不同湖泊的底泥磷含量、水柱磷含量和外源负荷的比较和相关分析可以看出,水柱中磷含量较高,磷负荷较大的湖泊底泥中磷含量也高。可以预测,即使东湖的外源负荷得以控制,巨大的底泥磷内源负荷将会继续对东湖水质构成威胁。