EXPERIMENTS ON AQUATIC ECOSYSTEM REGIME SHIFT IN ENCLOSURES NEAR LAKE DIANCHI, CHINA

To discover how a lake converts from a turbid state to clean state, and what drives this process, we constructed controlled enclosure ecosystems and used the ecological remediation method to force ecosystems to convert from the turbid state to the clean state. Our results show that the driving forces include temperature., macrophyte, silver carp and mussel, which form a combined force to drive the controlled ecosystem to switch. There is a threshold existing in treated enclosure ecosystem during the conversion from turbid to clean state. When TP <0.09 mg.L-1, Chl-a <0.036 mg.L-1, transparency >62 cm, TN <2.15 mg.L-1, CODMn <13.7 mg.L-1, tubidity <10, and the number of algal cells <10(6) cells.L-1, the treated ecosystem changes sharply from turbid to clean state. The conversion process can be divided into three phases: turbid state, clean-turbid transitional state as well as clean state, and described with the power function Y = a*X-b (where Y is water parameter, X is time, a and b are constants), which indicates that the shift in the enclosure ecosystem from turbid to clean state is discontinuous.

A simple closed aquatic ecosystem (CAES) for space

A closed aquatic ecosystem (CAES) was developed to stud), the effects of microgravity on the function of closed ecosystems aboard the Chinese retrieved satellite and on the spacecraft SHENZHOU-II. These systems housed a small freshwater snail (Bulinus australianus) and an autotrophic green algae (Chlorella pyrenoidosa). The results of the test on the satellite were that the concentration of algae changed little, but that the snails died during the experiments. We then sought to optimize the function of the control system, the cultural conditions and the data acquisition system and carried out an experiment on the spacecraft SHENZHOU-II. Using various sensors to monitor the CAES, real-time data regarding the operation of the CAES in microgravity was acquired. In addition, all on-board Ig centrifuge was included to identify gravity-related factors. It was found that microgravity is the major factor affecting the operation of the CAES in space. The change in biomass of the primary producer during each day in microgravity was larger than that of the control groups. The mean biomass concentration per day in the microgravity group decreased, but that of the control groups increased for several days and then leveled off. Space effects on the biomass of a primary producer may be a result of microgravity effects leading to increasing metabolic rates of the consumer combined with decreases in photosynthesis. (c) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

空间微重力条件下小型水生闭合生态系统的研究

目的以小球藻和澳洲水泡螺构成二元水生封闭生态系统(closed aquatic ecosystem,CAES),研究微重力对此二元系统运行的影响。方法设定了空间1 G对照、地面1 G和1.4 G(离心机)条件利用遥测方法对搭载于"神舟"2号飞船的CAES系统进行了跟踪,获得微重力及各种对照条件下该系统运行的数据。结果在空间微重力条件下,生产者小球藻的生物量日变化较大,每天的生物量平均值在飞行中表现为递减趋势,而3组对照的生产者生物量日变化较小,2个1 G对照组每天的生物量平均值表现为一定的增长后趋于平衡,

Genetic diversity of plankton community as depicted by PCR-DGGE fingerprinting and its relation to morphological composition and environmental factors in lake donghu

To collect information about the genetic diversity of the plankton community and to study how plankton respond to environmental conditions, plankton samples were collected from five stations representing different trophic levels in a shallow, eutrophic lake (Lake Donghu), and investigated by PCR-DGGE fingerprinting. A total of 100 bands (61 of 16S rDNA bands and 39 of 18S rDNA bands) were detected. The DGGE bands unique to any single station accounted for 38% of the total bands, whereas common bands detected at all five stations accounted for only 11%. Using UPGMA clustering and MDS ordination of DGGE fingerprints, stations I and II were found to initially group together into one cluster, which was later joined by station V. Stations III and IV were isolated into two separate groups of one station each. Some differences in grouping relationships were found when analysis was completed on the basis of chemical characteristics and morphological composition, with zooplankton composition showing the greatest variability. However, the most similar stations (I and II) were always initially grouped into one cluster. Moreover, stations that exhibited the same or similar trophic level (stations III and IV), but different concentrations of heavy metals, were further differentiated by the DGGE method. Results of the present study indicated that PCR-DGGE fingerprinting was more sensitive than the traditional methods, as other studies suggested. Additionally, PCR-DGGE appears to be more appropriate for diversity characterization of the plankton community, as it is more canonical, systematic, and effective. Most importantly, fingerprinting results are more convenient for the comparative analyses between different studies. Therefore, the use of the described fingerprinting analysis may provide an operable and sensitive biomonitoring approach to identify critical, and potentially negative, stress within an aquatic ecosystem.

Distribution of phytoplankton in the Three-Gorge Reservoir during rainy and dry seasons

After damming of the Yangtze River, in order to explore the impacts of the Three-Gorge Dam (TGD) on the aquatic ecosystem, phytoplankton composition, abundance and biomass spatial distribution were studied in the Three-Gorge Reservoir (TGR), and the closest upstream anabranch Xiangxi River, which is 38 kin away from the Three-Gorge Dam (TGD) during August (rainy season) 2004 and April (dry season) 2005. In surveys, 6 transects (2 downstream and 4 cross-stream) and 25 stations have been investigated and 314 samples were collected from the surface to the river bed with water samplers. In TGR, 63 taxa and 60 taxa were identified in the rainy and dry seasons, respectively. In the Xiangxi River, 39 taxa were observed in the rainy and dry seasons. Algal blooms occurred in the Xiangxi River and at the influx region of the Yangtze and Xiangxi in both seasons, but had not occurred prior to damming. In the rainy season, the dominant species was Chroomonas acuta with 1.84 x 10(7) cells l(-1), and in the dry season the dominant species were Asterionella formosa and Cryptomonas ovata with 1.34 x 10(7) cells l(-1) and 1.79 x 10(6) cells(.)l(-1), respectively. In the main channel of TGR, there were no significant correlations between phytoplankton abundance and the concentrations of the main soluble nutrients. In the Xiangxi River, significant negative correlations were observed between phytoplankton abundance and nitrate (Spearman, p < 0.01, n=21), phosphate (Spearman, p < 0.05, n=21) and silicate (Spearman, p < 0.01, n=21) in the rainy season, and similar correlations were also observed with nitrate (Spearman, p < 0.05, n=28) and silicate (Speannan, p < 0.01, n=28), but not with phosphate in the dry season. Since the damming of the Yangtze River, eutrophication in the anabranch within the backwater has occurred and become severe, and the frequency of algal bloom within TGR and anabranches is expected to increase. (c) 2006 Elsevier B.V. All rights reserved.

Optimization of an effective extraction procedure for the analysis of microcystins in soils and lake sediments

Microcystin analysis in sediments and soils is considered very difficult due to low recovery for extraction. This is the primary limiting factor for understanding the fate of toxins in the interface between water and sediment in both the aquatic ecosystem as well as in soils. In the present study, a wide range of extraction solvents were evaluated over a wide range of pH, extraction approaches and equilibration time to optimize an effective extraction procedure for the analysis of microcystins in soils and lake sediments. The number of extractions required and acids in extraction solutions were also studied. In this procedure, EDTA-sodium pyrophosphate solution was selected as an extraction solvent based on the adsorption mechanism study. The optimized procedure proved to be highly efficient and achieved over 90% recovery. Finally, the developed procedure was applied to field soil and sediment sample collected from Chinese lakes during bloom seasons and microcystins were determined in six of ten samples. (c) 2005 Elsevier Ltd. All rights reserved.

青藏高原东缘几种树苗对增强紫外线-B和氮供应的响应

大气臭氧的损耗导致了地球表面具有生物学效应的紫外线-B(UV-B)辐射增强。同时，大气成分变化中除了UV-B辐射增强外，氮沉降是一个新近出现而又令人担忧的环境问题，其来源和分布正在迅速扩展到全球范围，并不断向陆地和水生生态系统沉降。本试验在四川省境内的中国科学院茂县生态站内进行，以云山、冷杉、色木槭和红椋子幼苗为模式植物，从生长形态、光合作用、抗氧化能力和矿质营养等方面研究了青藏高原东缘4种树苗对全球变化－增强UV-B辐射和氮供应(氮沉降)的响应。该试验为室外盆栽试验，包括四个处理：(1)大气UV-B辐射+无额外的氮供应(C)；(2)大气UV-B辐射+额外的氮供应(N)；(3)增强UV-B辐射+无额外的氮供应(UV-B)；(4)增强UV-B辐射+额外的氮供应(UV-B+N)。其目的：一方面有助于丰富我国对全球变化及区域响应研究的全面认识，进一步完善在全球气候变化条件下臭氧层削减和氮沉降对陆地生态系统影响的内容；另一方面，在一定程度上有助于我们更好的理解在全球变化下森林更新的早期过程。具体结果如下： 增强的UV-B辐射在生长形态、光合、抗氧化能力、活性氧和矿质营养方面对4种幼苗都有显著的影响。UV-B辐射增强对幼苗的影响不仅与物种有关，而且，还与氮营养水平相关。总体表现为，高的UV-B辐射导致了色木槭和红椋子幼苗叶片的皱缩和卷曲，并降低了色木槭幼苗的叶片数和叶重，在额外的氮供应下，云杉、冷杉和红椋子的叶重也显著地降低了；色木槭和红椋子幼苗叶片的解剖结构受到了增强的UV-B辐射的影响，增强的UV-B辐射显著地降低了色木槭叶片的栅栏组织厚度，提高了红椋子叶片的厚度；增强的UV-B辐射显著地降低了4种幼苗的单株总生物量、植物地下部分的生长、总叶绿素含量 [Chl (a + b)]、净光合速率和最大量子产量(Fv/Fm)，提高了4种幼苗叶片的膜脂过氧化(MDA含量)，改变了植物体不同器官中的矿质元素含量；增强的UV-B辐射提高了冷杉、色木槭和红椋子叶片中的过氧化氢含量(H2O2)、超氧负离子(O2-)生成速率，在额外的氮供应下，云杉叶片中的活性氧含量也显著地提高了；在无额外的氮供应条件下，增强的UV-B辐射显著地提高了4种幼苗叶片中的UV-B吸收物质、脯氨酸含量和抗氧化酶的活性(SOD、POD、CAT、GR和APX)。在额外的氮供应条件下，UV-B辐射的增强却显著地降低了冷杉叶片中脯氨酸含量和红椋子叶片中UV-B吸收物质含量，但是，在4种幼苗叶片中，5种抗氧化酶的活性对UV-B辐射的增强没有明显的规律性，增强的UV-B辐射显著地提高了云杉叶片中的POD、SOD和GR的活性，提高了冷杉叶片中的POD和GR活性，提高了色木槭叶片中的POD、SOD和CAT活性和红椋子幼苗叶片中的POD和SOD活性。从这些结果可知，植物在遭受高的UV-B辐射导致的过氧化胁迫时，植物体内形成了一定的保护机制，但是，这种保护不能抵抗高的UV-B辐射对植物的伤害。 额外的氮供应在生长形态、光合、抗氧化能力、活性氧和矿质营养方面对4种幼苗都有一定的影响，不同幼苗对额外的氮供应响应不同，并且受到UV-B辐射水平的影响。在当地现有的UV-B辐射水平下，额外的氮供应显著地提高了幼苗的单株总生物量、植物地下部分的生长、Chl (a + b)、净光合速率(红椋子除外)、UV-B吸收物质(冷杉除外)、脯氨酸含量(红椋子除外)和部分抗氧化酶的活性，降低了H2O2的含量、O2-的生成速率和MDA含量(红椋子除外)，改变了植物体内部分矿质元素含量，显著地提高了云杉和冷杉叶片中的Fv/Fm。这些指标总体表明，在当地现有大气UV-B辐射水平下，额外的氮供应对植物的生长和发育是有利的。在增强的UV-B辐射水平下，4种幼苗的生长形态和光合大部分指标都没有受到额外氮供应的影响，额外的氮供应提高了红椋子幼苗的单株总生物量和Chl (a + b)含量，提高了冷杉和色木槭叶片中的活性氧含量和MDA含量，却降低了红椋子叶片中的活性氧含量；额外的氮供应也提高了云杉、色木槭和红椋子叶片中UV-B吸收物质和脯氨酸含量，降低了冷杉叶片中UV-B吸收物质和脯氨酸含量；在抗氧化酶活性方面，额外的氮供应降低了云杉、冷杉叶片中5种抗氧化酶的活性和红椋子叶片中POD和GR的活性，提高了色木槭叶片中的POD和SOD的活性；4种幼苗植物体内的矿质元素含量对额外的氮供应没有显著的规律性。从这些结果可知，在高的UV-B辐射下，额外的氮供应提高了云杉、冷杉和色木槭幼苗对高的UV-B辐射的敏感性，然而，额外的氮供应却促进了红椋子幼苗的生长，原因可能是，在高的UV-B辐射下，额外的氮供应增加了红椋子叶片的厚度、叶重和叶片数，降低了叶片中活性氧含量的结果。表明在高的UV-B辐射水平下，额外的氮供应降低了红椋子幼苗对高的UV-B辐射的敏感性。 在全球变化的趋势下，UV-B辐射增强和氮沉降可能同时存在，我们的研究表明，与大气UV-B辐射+无额外的氮供应处理相比，增强UV-B辐射+额外的氮供应处理显著地降低了幼苗的单株总生物量(红椋子除外)、Chl (a + b)、净光合速率、Fv/Fm(冷杉除外)和MDA含量(红椋子除外)，提高了活性氧含量 (云杉除外)、UV-B紫外吸收物质含量(冷杉除外)、脯氨酸含量和部分抗氧化酶的活性，改变了植物体不同器官中的矿质元素含量。结果表明，在当地现有条件下，全球变化(UV-B辐射增强和氮沉降)对云杉、冷杉和色木槭幼苗的生长是不利，尽管植物体内一些抗氧化性指标提高了，然而，却对红椋子幼苗的单株总生物量的累积没有显著的影响。 The depletion of the ozone led to the increase of ultraviolet-B (UV-B) with biological effects in the earth’s surface. At the same time, except for enhanced UV-B radiation, nitrogen deposition was an anxious environmental problem at present, rapidly expanding to the global scope and continuously depositing to land and aquatic ecosystem. The experiment was conducted in Maoxian Ecological Station of Chinese Academy of Sciences, Sichuan province, China. Picea asperata, Abies faxoniana, Acer mono Maxim and Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings were selected as model plants to assess the effects of enhanced UV-B radiation and supplemental nitrogen supply on growth, morphological, photosynthesis, antioxidant and mineral nutrient traits of 4 species seedlings in east Qinghai-Tibetan Plateau. The experiment was potted outdoor, including 4 treatments: (1) ambient UV-B without supplemental nitrogen (control, C); (2) ambient UV-B with supplemental nitrogen (N); (3) enhanced UV-B without supplemental nitrogen (UV-B); (4) enhanced UV-B with supplemental nitrogen (UV-B+N). One hand, it was helpful for enriching our country to comprehensive understanding of the researches in the global change and the region response, further perfecting the effects of the depleted ozone layer and nitrogen deposition on land ecosystem under the global change; the other hand, it was favorable for us to better understanding of the early process of forest renews under the global change. The results were as follows: Enhanced UV-B radiation had significant effects on 4 species seedlings in growth, morphological, photosynthesis, antioxidant and mineral nutrient traits of 4 species seedlings. The effects of enhanced UV-B on plants were not only related with species, but also related with nitrogen nutrient level. Generally, the increase of UV-B radiation led to the shrinkage and curl of leaves in Acer mono Maxim and Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings, and reduced the number of leaf and leaf weight of Acer mono Maxim seedlings, under supplemental nitrogen supply, leaf weight of Picea asperata, Abies faxoniana and Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings significantly also reduced; the anatomical features of leaf in Acer mono Maxim and Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings affected by enhanced UV-B radiation, the increase of UV-B radiation markedly reduced the palisade tissue thickness of Acer mono Maxim leaf and enhanced the leaf thickness of Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings; the enhanced UV-B radiation significantly reduced total biomass per plant of 4 species seedlings, the growth of the underground parts, Chl (a + b), net photosynthetic rate and maximum potential quantum yield of photosynthesis (Fv/Fm), and increased the degree of lipid peroxidation (MDA content) and changed the content of mineral elements in different parts of plants; the enhanced UV-B radiation also increased the rate of superoxide radical (O2-) production and hydrogen peroxide (H2O2) content in leaves of Abies faxoniana, Acer mono Maxim, Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings, under supplemental nitrogen supply, the reactive oxygen species in leaves of Picea asperata seedlings also significantly increased by enhanced UV-B radiation; under without supplemental nitrogen supply, enhanced UV-B radiation evidently induced an increase in UV-B absorbing compounds, proline content and the activities of antioxidant enzymes (SOD, POD, CAT, GR and APX) of leaves in 4 species seedlings. Under supplemental nitrogen supply, enhanced UV-B radiation induced a decrease in proline content of leaves in Abies faxoniana seedlings and UV-B absorbing compounds of leaves in Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings, but, there were no obvious rules in the activities of five antioxidant enzymes of 4 species seedling leaves to enhanced UV-B radiation, enhanced UV-B radiation significantly increased the activities of POD, SOD and GR in Picea asperata leaves, the activities of POD and GR in Abies faxoniana leaves and the activities of POD, SOD and CAT in Acer mono Maxim leaves. The results indicated that some protective mechanism was formed when plants were exposed to enhanced UV-B radiation, but the protection could not counteract the harm of high UV-B radiation on plants. Supplemental nitrogen supply had some effects on 4 species seedlings in growth, morphological, photosynthesis, antioxidant and mineral nutrient traits. The response of 4 species seedlings was different to supplemental nitrogen supply, and was affected by UV-B levels. Under local ambient UV-B radiation, supplemental nitrogen supply significantly increased the total biomass per plant, the growth of underground parts, Chl (a + b), net photosynthetic rate (except for Acer mono Maxim seedlings), UV-B absorbing compounds (except for Abies faxoniana seedlings), proline content (except for Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings) and the activities of some antioxidant enzymes, and reduced H2O2 content, the rate of O2- production and MDA content (except for Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings) and changed the content of mineral elemental in different parts; supplemental nitrogen supply also evidently increased Fv/Fm in Picea asperata and Abies faxoniana seedlings. These results indicated that supplemental nitrogen supply was favorable for the growth of plants under local ambient UV-B radiation. Under enhanced UV-B radiation, mostly parameters in growth and morphology of 4 species seedlings were not affected by supplemental nitrogen supply. Supplemental nitrogen supply increased the total biomass per plant and Chl (a + b) of Swida hemsleyi (Schneid. et Wanger.) Sojak seedling, increased the reactive oxygen species and MDA content in Abies faxoniana and Acer mono Maxim leaves, and reduced the reactive oxygen species in Swida hemsleyi (Schneid. et Wanger.) Sojak leaves; supplemental nitrogen supply also increased UV-B absorbing compounds and proline content in Picea asperata, Acer mono Maxim and Swida hemsleyi (Schneid. et Wanger.) Sojak leaves, decreased UV-B absorbing compounds and proline content in Abies faxoniana leaves; in the activities of antioxidant enzymes, supplemental nitrogen supply significantly reduced the activities of antioxidant enzymes in Picea asperata and Abies faxoniana leaves and the activities of POD and GR in Swida hemsleyi (Schneid. et Wanger.) Sojak leaves, and increased the activities of POD and SOD in Acer mono Maxim leaves; the content of mineral elements in 4 species seedlings was no significantly rule to supplemental nitrogen supply. We knew from the results, under enhanced UV-B radiation, supplemental nitrogen supply made Picea asperata, Acer faxoniana and Acer mono Maxim seedlings more sensitivity to enhanced UV-B radiation, however, accelerated the growth of Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings. The reason was probably that supplemental nitrogen supply increased the leaf thickness, leaf weight and leaf number, reduced the reactive oxygen content of leaf in Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings grown under high UV-B radiation. This showed that supplemental nitrogen supply reduced the sensitivity of Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings to high UV-B radiation. Under the tendency of the global change, enhanced UV-B radiation and nitrogen deposition may probably coexist. The results showed, compared with the treatment of ambient UV-B radiation without supplemental nitrogen supply, the treatment of enhanced UV-B radiation with supplemental nitrogen supply significantly reduced the total biomass per plants (except for Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings), Chl (a + b), net photosynthetic rate, Fv/Fm and MDA content (except for Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings), and increased reactive oxygen content (except for Picea asperata seedlings), UV-B absorbing compounds (except for Abies faxoniana seedlings), proline content and part antioxidant enzymes, and changed the content of mineral elements of different parts. The results indicated that the global change (enhanced UV-B and nitrogen deposition) were not favorable for the growth of plants under local ambient UV-B radiation and nitrogen nutrient level,, though increased some antioxidant indexes, however, the treatment of enhanced UV-B with supplement nitrogen supply did not significantly affect on the biomass accumulation of Swida hemsleyi (Schneid. et Wanger.) Sojak seedlings.