磷在羊草草地植物－土壤中积累、分布及转移规律

本文在研究磷素几种形态的动态变化基础上,运用生态系统理论,利用系统分析的方法,分析了磷在植物－土壤系统中的流通、积累和归还的特点,得出如下结果：１．磷素在系统内９９％以上分布在土壤中。２．群落内磷的再利用量为３．６７５５ｋｇ·ｈａ￣（－１）·ｙｒ￣（－１）。３．群落每年吸收的磷为３．４０６３ｋｇ·ｈａ￣（－１）·ｙｒ￣（－１）,地上部归还土壤为０．１４４７ｋｇ·ｈａ￣（－１）·ｙｒ￣（－１）,地下部归还土壤为１．８１１１ｋｇ·ｈａ￣（－１）·ｙｒ￣（－１）,输出仅占吸收量的４２．２４％,磷素在群落中每年净积累为０．３５ｋｓ·ｈａ￣（－１）·ｙｒ￣（－１）。４．磷在各库内的周转时间是：地上植物活体为１．３３６４年,立枯体为６．４３５０年,活根为１．０８８７年,死根为２．４３７８年,有机磷为８３３．３年。     

斜生栅藻对振荡和磷胁迫的生理生化响应

为了探讨水文条件的变化对常见绿藻水华发生的潜在影响,实验以斜生栅藻为材料,研究了不同水流状态及磷浓度对其生长及磷利用策略的影响。实验分别设置静止条件(0 r/min)、低振荡条件(90 r/min)和高振荡条件(120 r/min),同时设置磷限制(0.2 mg/L)和磷充足(2 mg/L)两组磷浓度,整个实验过程为3周。实验过程测定的指标为:比生长速率、胞外碱性磷酸酶活性、叶绿素a含量以及磷吸收动力学参数。实验结果表明:(1)同静止条件相比,低振荡和高振荡条件均能显著降低斜生栅藻的比生长速率,但是两种不同磷浓度下其比生长速率却无显著性差异。(2)在实验第21天时,振荡条件培养下,斜生栅藻的胞外碱性磷酸酶活性显著高于静止条件培养,与此相反,胞内磷浓度却显著高于静止条件。(3)在磷限制条件下斜生栅藻的叶绿素a含量显著降低,同时两种振荡条件培养均使其在磷充足条件下叶绿素a含量降低。(4)通过磷吸收动力学参数的比较,静止条件培养的斜生栅藻对磷的亲和力高于其在振荡条件下。由此可见,斜生栅藻适应于静止无扰动且磷营养丰富的水体,随着水体中磷浓度进一步升高,静止和水流缓慢的水体存在导致像斜生栅藻这一类绿藻发生水华的风险。       

PHOSPHORUS AND NITROGEN NUTRITION IN CHONDRUS CRISPUS (RHODOPHYTA): EFFECTS ON TOTAL PHOSPHORUS AND NITROGEN CONTENT,CARRAGEENAN PRODUCTION,AND PHOTOSYNTHETIC PIGMENTS AND METABOLISM1

The existence of a phenomenon in phosphorus (P) nutrition comparable to the “Neish effect” in nitrogen (N) nutrition (an inverse relation between seawater N enrichment and carrageenan content) was investigated in the temperate red alga Chondrus crispus Stackhouse. Plants were preconditioned for 17 d and then cultured under varying enrichments of P (0, 3, 6, 10, 15 μM P·wk^?1) and a constant N enrichment (53.5 μM N·wk^?1) for 5 wk. Tissue total P, tissue total N, and carrageenan contents were then determined. Identical experiments were performed using C. crispus collected during the fall, winter, spring, and summer seasons. The procedure was repeated using material collected during the following fall season and cultured under constant P (6 μM P·wk^?1) and varying N enrichments (0, 3, 6, 10, 25 μM N·wk^?1). In the fall (P) experiment, carrageenan content was the highest [53.1 ± 0.3% DW (dry weight)], and tissue total P content was the lowest (1.71 ± 0.27 mg P·g DW^?1) in plants that received no P enrichment. Carrageenan content was stable (46.1 ± 1.8% DW) for plants given enrichments of 3 μM P·wk^?1 and greater. Thus, a decrease in carrageenan content, concomitant with an increase in tissue total P content, was observed, but only at tissue total P levels below 2 mg P·g DW^?1. As these levels were always higher than 2 mg P·g DW^?1 in the winter, spring, and summer experiments, carrageenan content remained constant within each season at 46.2 ± 1.3, 43.1 m 0.7, and 44.5 ± 0.6% DW, respectively. Nitrogen enrichment of plants collected in the fall did not affect carrageenan content, which was stable at 49.3 ± 0.9% DW. When these plants were compared with those of the previous fall experiment (6 μM P·wk^?1 and 53.5 μM N·wk^?1), a slight increase in carrageenan content was noted. Thus, at sufficiently high concentration, N also decreased carrageenan content in C. crispus. Phosphorus nutrition had no significant effect on photosynthesis versus irradiance parameters (P_max, α, R_d, I_c, and I_k), the contents of the photosynthetic pigments chlorophyll-a, phycoerythrin (PE), phycocyanin (PC), and allophycocyanin (APC), and the ratios PE:APC and PC:APC. In contrast, N nutrition affected both P_maxand the photosynthetic pigment contents. The data indicate that N limitation reduces the number of phycobilisomes but not their size. The greater reduction in phycobiliprotein than chlorophyll-acontent corroborates the natural bleaching phenomenon regularly observed in C. crispus populations during summer when N levels are generally low in seawater. These results suggest that C. crispus in the temperate waters of the Bay of Fundy may experience N limitation, but P limitation is unlikely.     

陆地生态系统磷素循环及其影响因素

 磷是生命系统的重要组成成分,其在生态系统内的迁移转化是生态系统结构和功能的决定性因素之一。近20年来,磷在陆地生态系统内的重要性受到越来越多的关注。该文总结了国内外磷循环研究的成果,从磷的来源、在土壤中的存在形态和固定特性、影响因素的复杂性等方面分析了磷素循环的特点;系统阐述了磷在陆地生态系统各库之间及其内部,主要是植被-土壤亚系统内的迁移转化规律及影响因素。陆地生态系统磷素循环主要是系统内部的生物化学循环,由植物自身的遗传特性和土壤的生物、理化性质共同控制,不同控制因素的相对重要性因生态系统类型、时间和空间尺度而异。文章简述了磷循环研究方法的发展及存在的局限性;另外,分析了干旱、半干旱地区磷循环研究的重要性和意义;干旱区生态系统的脆弱性及其植被、土壤特性决定了其磷素循环有其自身的特点及研究的必要性。最后指出了当前陆地生态系统磷循环研究的发展趋势。     

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。     

藻细胞的聚磷作用及其成矿意义

研究了现代蓝藻盐泽螺旋藻（Ｓｐｉｒｕｌｉｎａ ｓｕｂｓａｌｓａ）在富磷环境中细胞的聚磷作用及其与磷块岩形成的关系。实验证明,在富磷环境中盐泽螺旋藻细胞从环境中吸收磷的速度快,并主要用以合成多聚磷酸盐。模拟成矿试验证明,从藻细胞中提取出来的多聚磷酸盐在Ｃａ２＋ －ＨＰＯ２－４ －ＨＣＯ－３ －Ｆ－ －Ｈ２Ｏ 体系中,在常温常压及偏碱性条件下形成的主要成分为碳氟磷灰石、方解石及非晶质磷酸盐的矿物,为藻类成矿提供了新的极有意义的证据     

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.     

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.     

SIZE-DEPENDENT PHOSPHORUS UPTAKE KINETICS AND CELL QUOTA IN PHYTOPLANKTON1

The allometric equation, y = aX^b, described the interspecific variation of phosphate uptake kinetics and cell quota with phytoplankton cell size and showed that smaller cells are superior in uptake rate to large. Species-specific measurements, made by track autoradiography in phosphorus deficient cultures of communities from a phosphorus-limited lake, revealed that eight different species did not differ significantly in the Michaelis-Menten half-saturation constant, K_m. However, both saturated uptake rates (V_max) and the initial slope of the uptake curve (V_max:K_m) decreased per unit biomass with increasing cell size. Biomass-specific cell phosphorus quotas also decreased with increasing cell volume, but less rapidly than did V_max or V_max: K_m. Comparable data from the literature showed that marine species were superior in phosphorus uptake to freshwater species of similar size, but allometric variation of kinetics appeared to exist within both groups. Together with a variable internal stores model of phosphorus-limited growth, the allometric relationships of uptake kinetics and quotas predicted competition to favor smaller cells, with a differential in growth rate diminishing as competitive intensity increased.     

龙须菜对海水氮磷富营养化的响应

龙须菜(Gracilaria lemaneiformis)是红藻门江蓠属大型海藻,已从山东青岛引种到广东省南澳岛等地栽培多年。深入了解其光合作用与环境条件的关系,对龙须菜的合理栽培及其在环境生态中的生物学作用和扩大其开发利用价值,具有重要的理论和现实意义。该文利用人为配置的不同程度N、P污染海水处理龙须菜,研究其生理生态特性对海水氮磷富营养化的响应。结果表明: 处理6 d后,龙须菜叶绿素a及3种藻胆蛋白含量和总抗氧化能力在轻度P(P 0.2 mg·L^-1)及重度N、P复合污染(P 10 mg·L^-1,N 55 mg·L^-1)情况下降低。叶绿素荧光参数的变化也表明上述处理对叶绿体PSⅡ造成不利影响,而在轻度N(N 0.9 mg·L^-1)和轻度N、P复合污染(P 0.2 mg·L^-1,N 0.9 mg·L^-1)海水中上述参数则变化不大,表现出龙须菜对轻度N及轻度N、P复合污染的耐受性。该实验条件下,轻度污染处理后,藻体中不因环境N、P浓度升高而富集N、P。表明龙须菜可以作为轻度富营养化海水水体的净化藻类。