The Structure of the Zooplankton Community and the Dynamics of its Biomass in the Lake Jaisamand (Rajasthan: India)

Zooplankton of the lake Jaisamand was represented by 50 taxa out of which 22 were Rotifera, 18 Cladocera, 5 Protozoa, 3 Copepoda and 2 Ostracoda. The total zooplankton exhibited a bimodal pattern with the first peak occurring in December and the second of a little less magnitude in June. The perennial zooplankters were Keratella valga, Brachionus falcatus from Rotifera, Ceriodaphnia spec. from Cladocera and Mesocyclops and Heterocyclops spp. from Copepoda. Considering surface zooplankton as a whole, Rotifera dominated the planktonic biomass followed by Copepoda, Cladocera, Ostracoda, Protozoa and Insecta. The species composition of the mid-stratum zooplankton was not much different from that of the surface. Interestingly, there was a presence of Cladocera in the anoxic bottom waters. The low and occasional presence of Calanoid copepods, the abundance of Cyclopoids and Cladocerans point to the eutrophication in the lake.     

The Structure of the Phytoplankton Community and the Dynamics of its Biomass in the Lake Jaisamand,Rajasthan

Phytoplankton in the lake Jaisamand consists of 52 taxa, out of which 25 belong to Chlorophyceae, 12 to Bacillariophyceae, 2 to Euglenophyceae, 1 to Xanthophyceae and 12 to Myxophyceae. The highest phytoplankton density occurred in July, i.e. in the beginning of monsoon, and the lowest in November. The dominant Chlorophyceae were Spirogyra elliptica, Closterium and Hydrodictyon. Navicula lanceolata, Pinnularia viridis and Synedra ulna were dominant amongst Diatoms. Xanthophyceae was represented by a single species of the genus Botryococcus and Euglenophyceae by Phacus longicauda and Euglena viridis. The dominant Myxophyceae were Microcystis aeruginosa and M. flosaquae. Under the stratified conditions, the near bottom waters got depleted of phytoplankton. The overall trend in the quality and quantity of phytoplankton indicated that temperature and nutrients had an influence on the rate of plankton production.     

Seasonal Variation of Temperature,Alkalinity and Dissolved Oxygen in the Sagar Lake

The present study deals with the seasonal variation of temperature, alkalinity and dissolved oxygen in the Sagar lake. Different abiotic and biotic factors were investigated and a diurnal study was made, too. The investigation shows that the surface water values were always higher than the bottom water values. The water temperature ranged from 16.0 to 31.0 °C, carbonate alkalinity ranged from 0.0 to 46.0 mg/1, bicarbonate alkalinity ranged from 62.0 to 138.0 mg/1, dissolved oxygen ranged between 1.6 and 13.2 ppm. The water temperature was found to be positively correlated with carbonate alkalinity while an inverse correlation existed with bicarbonate alkalinity. Dissolved oxygen had a significant positive correlation with carbonate alkalinity, while a negative correlation was observed with bicarbonate alkalinity during all the seasons.     

太湖梅梁湾中碱性磷酸酶的活性及其与藻类生长的关系

通过对1998年5月-1999年5月的太湖梅梁湾水体中碱性磷酸酶活性及其它水化学因子的同步实地监测,初步探讨了富营养化较严重的太湖梅梁湾湖区的碱性磷酸酶活性的时空变化规律及其与藻类水华的相关性.研究表明,水体中各种形态磷之间的转化非常快.在磷的循环、转化过程中,碱性磷酸酶的作用至关重要.太湖梅梁湾各采样点水体中碱性磷酸酶的最大反应速率(Vmax)的年际变化有着显著的规律性,各点位在春季(3-4月)及夏季(7-8月)均分别出现峰值,与水体中水华出现的峰值相吻合.尤其在水体中水华暴发前的4月份,各采样点中的碱性磷酸酶的活性急剧增加,其Vmax均为年内的最大值或接近最大值,预示着水体中其它形态磷的转化速率加快,为水华的形成提供了充足的活性磷.水体中特异性碱性磷酸酶活性(总碱性磷酸酶活性/Chl.a)与水体中的PO43-存在着较好的负相关.尤其是在春季相关性更加显著,可达-0.9以上;夏季太湖梅梁湾水华暴发时,水体中的磷酸盐浓度远低于碱性磷酸酶的激发阈值,藻类体中的酶被诱导大量产生,从而使得水体中碱性磷酸酶的数量、活性急剧增加,达到较高的水平.这种短时间的有机质快速降解以及由此导致的营养盐释放,维持了水体中藻类的生长.     

南京玄武湖浮游细菌群落结构的季节变化及其与环境因子的关系

应用16S rRNA基因末端限制性片段长度多态性技术和多元统计方法,探究了南京玄武湖浮游细菌群落结构的季节性变化,并找出了浮游细菌群落组成分布的主要影响因子.结果表明,玄武湖4个季节中夏季Invsimpson指数、Shannon-Wiener指数和Pielou指数最高,而春季最低.非度量多维尺度分析结果显示浮游细菌群落结构存在着明显的季节性变化.Mantel检验、典范对应分析、变量分割分析表明影响玄武湖细菌群落结构最显著的环境因子为温度,其次为pH.营养盐浓度对玄武湖细菌群落结构的影响不显著.总的来说,本研究将有助于更好地理解富营养化水体中的浮游细菌群落组成的季节变化规律.     

Limnological Studies in a Subtropical System (Lake Sattal,India)

A limnological study was carried out in the subtropical Lake Sattal (Kumaun Himalaya) during 1979. The lake was thermally stratified during warm months and a low percentage saturation of dissolved oxygen occurred in the bottom waters. Two maxima of phytoplankton occurred in the Eastern basin in contrast to only one in the Western basin. The peak in the latter developed more than a month (October) after the second peak in the former (August). Bacillariophyceae contributed highest in the Western basin (43.2%) whereas the Dinophyceae had the least share in the Eastern basin (8.0%). Most of the dominant phytoplankters were: Synedra ulna, Fragilaria, Gymnodinium, Crucigenia and Closteridium siamensis. Interestingly, blue-green alga Nostoc, dominated for some time in autumn. A total of 12 genera of rotifers, 6 genera of cladocerans and 1 genus of copepods were found in Lake Sattal basins. Dominant zooplankters included Keratella, Cyclops, Anuraeopsis, Polyarthra and Trichocerca, and there is a high ratio of rotifers to copepods and cladocerans. On comparing the averaged values of both the basins, the Eastern basin showed a 64% larger population of zooplankton than the Western basin. A comparison is made with the plankton of the other subtropical lake-systems of this region.     

Seasonal dynamics of zooplankton in Lake Huetzalin, Xochimilco (Mexico City, Mexico)

We quantified the seasonal changes in the zooplankton abundances collected from the Huetzalin Lake (Mexico City, Mexico) for two years (February 2003–January 2004 and then March 2005–February 2006). Selected physicochemical variables (Secchi depth, temperature, pH, conductivity, dissolved oxygen, phosphorus, nitrogen, carbon and chlorophyll a concentration) were also measured at the time of zooplankton collection. The data on zooplankton abundances and the physicochemical variables were subjected to multiple correlation analysis and we also derived Shannon–Wiener species diversity index. Secchi depth ranged from 9 to 65 cm. Generally the lake was alkaline (pH 7–12). The conductivity ranged from 500–1000 mS cm⁻¹, while the mean water temperature was 20.5 °C. Dissolved oxygen levels were generally >3 mg L⁻¹ and were higher in the winter than warmer months. Nitrates (90–95 μg L⁻¹) and phosphates (.2–.5 mg L⁻¹) indicated that the water was eutrophic. Chlorophyll a levels ranged from 143 to 696 μg L⁻¹ during the study period. The zooplankton community was dominated by rotifers (46 species), followed by cladocerans (9 species) and there were only two copepod species. The dominant rotifer species were Brachionus angularis, Brachionus calyciflorus, Brachionus havanaensis, Brachionus quadridentatus, Lecane bulla and Polyarthra vulgaris. Rare rotifer species in Lake Huetzalin were Lecane ohioensis, Dicranophorus forcipatus, Lecane pyriformis, Lindia torulosa, Pleurotrocha petromyzon and Brachionus durgae. Highest densities (occasional peaks of 400 ind L⁻¹) of B. quadridentatus occurred between April and December, while B. havanaensis reached peak densities, during June to October. B. calyciflorus reached densities higher than 1240 ind L⁻¹ during May–September. Cladoceran and copepod densities in Lake Huetzalin were much lower than that of the rotifers. This study confirmed the earlier findings that Xochimilco system of canals is dominated by rotifers and the crustacean zooplankton have much lower abundances possibly due to predation from fish.     

呼伦湖浮游植物群落季节动态及其与环境因子的关系

为探究呼伦湖浮游植物群落的季节变化特征及其与环境因子的关系,本研究分别于2019年3、5 10月对呼伦湖浮游植物的种类、细胞密度和生物量及湖水水质进行调查.结果显示,共鉴定出120种浮游植物,隶属于7门72属.从浮游植物群落季节组成差异上来看,春季绿藻门种类数最多,其次是硅藻门、蓝藻门;夏秋季绿藻门种类数最多,蓝藻门次之;冬季硅藻门种类数最多,绿藻门次之.呼伦湖浮游植物优势种主要为硅藻门的梅尼小环藻(Cyclotella meneghiniana)、蓝藻门的卷曲长孢藻(Anabaena circinalis)和细小平裂藻(Merismopedia minima),种类数在春季最多,秋冬季最少.浮游植物细胞密度在春季(123.52×10⁴cells/L)和冬季(16.41×10⁴cells/L)较夏季(280.80×10⁴cells/L)和秋季(380.63×10⁴cells/L)低,春冬季绿藻门细胞密度最高,夏秋季蓝藻门细胞密度最高.就浮游植物生物量而言,夏季(0.38mg/L)最大,其次是秋季(0...     

Variation of reference evapotranspiration and its contributing climatic factors in the Poyang Lake catchment,China

By using linear regression (parametric), Mann–Kendall (nonparametric) and attribution analysis methods, this study systematically analysed the changing properties of reference evapotranspiration (ETr) calculated using the Penman–Monteith method over the Poyang Lake catchment during 1960–2008 and investigated the contribution of major climatic variables to ETr changes and their temporal evolution. Generally, a significant decreasing trend of annual ETr is found in the catchment. The decrease of annual ETr in the Poyang Lake basin is mostly affected by the decline of summer ETr. Over the study period, climatic variables, i.e. sunshine duration (SD), relative humidity (RH), wind speed (WS) and vapour pressure all showed decreasing trends, whereas mean daily temperature (DT) increased significantly. Multivariate regression analysis indicated that SD is the most sensitive climatic variable to the variability of ETr on annual basis, followed by RH, WS and DT, whereas the effect of vapour pressure is obscure. Although recent warming trend and decrease of relative humidity over the catchment could have increased ETr, the combined effect of shortened SD and reduced WS negated the effect and caused significant decrease of ETr. Our investigation reveals that the relative contributions of climatic variables to ETr are temporally unstable and vary considerably with large fluctuation. In consideration of the changes of climatic variables over time, further analysis indicated that changes of mean annual ETr in 1970–2008 were primarily affected by SD followed by WS, RH and DT with reference to 1960s. However, WS became the predominant factor during the period 2000–2008 compared with reference period 1960s, and followed by SD. Copyright © 2013 John Wiley & Sons, Ltd.     

Seasonal changes in vertical distribution of zooplankton in an oligotrophic, subarctic lake (Lake Takvatn, Norway)

Zooplankton vertical distribution was studied in Lake Takvatn (69°07′ N) by discrete sampling of the water column during the open water season. Attention was focused on predation risk and competition to understand when, where and to what degree a given species should aggregate along the water column. Temperature profiles and phytoplankton abundance and composition were recorded to assess degree of heterogeneity and food availability in the pelagic zone. Vertical segregation was evident during thermal stratification. Rotifers partitioned the water column, with species less susceptible to predation (e.g. Conochilus unicornis) in the epilimnion, where they overlapped with the predators Asplanchna priodonta and Polyphemus pediculus, and species more vulnerable to these predators (e.g. Keratella cochlearis) in the hypolimnion. Cladocerans remained in the epilimnion, in a year when predation by fish was limited. The copepodites of Eudiaptomus graciloides and Cyclops scutifer maintained different depths staying respectively near surface and in the meta-hypolimnion. A broader distribution with increasing density was evident among rotifers and C. scutifer nauplii. Density-dependent habitat selection behaviour is considered as a mechanism explaining the observed distribution of predators and competing prey and promoting species coexistence.     

洞庭湖流域常德柳叶湖及其邻近水体轮虫群落结构变化及其对环境因子的响应

城市河-湖连通使不同水文特征的水体连通构成多样化水环境,环境异质性为提高浮游动物多样性提供了多样性生境条件.为了解湖南常德柳叶湖及其邻近水体轮虫群落结构变化对不同水体连通性和异质性的响应,于2018年对柳叶湖、穿紫河和沅江常德市区河段共15个站点进行了每季度1次的轮虫群落结构和环境特征调查分析.调查期间,不同水体的营养水平呈现:穿紫河柳叶湖沅江,穿紫河和柳叶湖呈富营养化状态,沅江呈中营养状态.本研究共检出轮虫88种(包括亚种8种和变种1种),其中,长肢多肢轮虫(Polyarthra dolichoptera)为水系第一优势种.轮虫最高丰度为2535ind./L,全年平均丰度空间分布呈现:柳叶湖穿紫河沅江;季节分布呈现:6月 9月 3月 12月.轮虫群落对水体连通性的响应表现为:柳叶湖、穿紫河和沅江3个水体轮虫种类组成具有一定的相似性且第一优势种相同.对异质性的响应表现为:不同水体轮虫群落年平均丰度和多样性指数存在空间差异.典范对应分析表明水温是影响轮虫群落结构变化的主要环境因子.     

三峡水库上游长寿湖浮游藻类的季节变化特征及关键环境影响因子

基于2013年3月-2014年2月的长寿湖浮游藻类以及水质的监测结果,分析浮游藻类物种组成、密度以及多样性指数的季节动态,利用非度量多维尺度和相似性分析检验不同季节浮游藻类群落差异,同时利用典范对应分析法确定影响不同季节浮游藻类群落结构的关键环境因子.结果表明:泽丝藻(Limnothrix sp.)、小尖头藻(Raphidiopsis sp.)、汉斯冠盘藻(Stephanodiscus hantzschii)、具尾逗隐藻(Komma caudata)、鞘丝藻(Lyngbya sp.)和马索隐藻(Cryptomonas marssonii)为长寿湖优势种群,不同季节间浮游藻类群落组成结构存在较大差异.浮游藻类群落结构以春季最为简单,夏季次之,秋、冬季最为复杂.不同季节影响浮游藻类群落结构的环境因子差异较大,水温和营养盐是影响浮游藻类群落结构最重要的环境因子,光照强度、高锰酸盐指数、氧化还原电位、溶解有机碳在秋、冬季节同样成为影响浮游藻类群落结构的关键环境因子.     

2010-2017年太湖总磷浓度变化趋势分析及成因探讨

近年来,太湖流域各省市政府加大治理力度,流域水体水质取得明显好转,氨氮浓度和总氮浓度呈大幅度下降趋势,然而太湖水体总磷浓度呈上升趋势.为探讨太湖总磷浓度升高的原因,采用太湖流域管理局2010年以来的水质水量实测数据、遥感监测数据等,分别从太湖入湖河流污染负荷量、水生植被和蓝藻与总磷浓度的关系3个方面进行相关性分析.结果表明,入湖河流总磷浓度高于太湖水体总磷浓度,且磷不易出湖,逐年总磷净入湖量持续累积与太湖总磷浓度有明显的正相关性,入湖污染负荷量大是太湖总磷浓度居高不下的根本原因;水生植被可吸收湖泊沉积物中的营养盐,并抑制底泥再悬浮从而降低内源性营养盐的释放,东太湖水生植被的大量减少,一方面减少了沉水植物对磷元素的吸收,另一方面增加了风浪对底泥的扰动再悬浮,造成磷元素释放,是造成湖水总磷浓度升高的重要因素;近年来太湖蓝藻密度呈上升趋势,受其影响,总磷浓度也有上升,蓝藻水华加快湖体磷循环,藻类密度增加也是太湖总磷浓度升高的影响因素之一.     

基于MODIS数据的博斯腾湖流域植被变化及其与气候因子的关系

以博斯腾湖流域为研究区,基于2001-2016年时间序列的MODIS NDVI数据分析了研究区植被的时空变化趋势,并结合流域气象站点的气温、降水、日照时数和相对湿度数据分析了植被生长季累积NDVI和16天NDVI与气候因子之间的响应特征.结果表明:(1)流域植被覆盖变化呈改善趋势,生长季累积NDVI年变化率为0.014 a-1,16天NDVI变化率均为正值,植被改善趋势显著区域主要分布在高山草原湿地和农业灌溉区边缘的新增农田.(2)植被生长季累积NDVI主要受降水和相对湿度影响,植被总体生产力与水分条件关系最密切,生长季逐16天NDVI与同期气温和日照时数在植被生长初期和末期关系显著,而与降水没有显著的相关性,说明植被短期瞬时长势对热量条件更为敏感.(3)在植被生长不同阶段对气候变化具有不同的滞后效应,其中植被生长初期和末期对气温有0.5~1个月的滞后,生长盛期对降水有0.5~3个月的滞后、日照时数有1.5~2.5个月的滞后、相对湿度有0.5~2.5个月的滞后,揭示了植被不同生长阶段水热条件对其生长韵律的控制差异.     

云南程海和阳宗海季节性分层及其消退对冬季水华的潜在影响

基于2014年10月2016年7月在云南程海和阳宗海开展了4个季度(秋季,10月;冬季,1月;春季,4月;夏季,7月)的调查,研究了两个湖泊的水体分层特征,探讨了热力分层及其变化与其他环境因子对浮游植物生物量的潜在影响,结果显示:程海和阳宗海水体分层的特征均为冬季混合、春季形成分层、夏秋季分层稳定,两湖均属暖单次混合型湖泊;程海分层期温跃层的平均深度(顶界)、厚度和强度分别为17.70±3.89 m、5.54±4.44 m和0.67±0.43℃/m,阳宗海的分别为12.53±3.35 m、8.25±4.85 m和0.53±0.43℃/m.在热力分层稳定期,两湖底层达到缺氧甚至厌氧状态,底层的电导率总体较表层高.调查期间,两个湖泊水柱表层浮游植物生物量(以叶绿素a浓度表征)均在冬季出现峰值,程海和阳宗海的分别为19.22±11.08和45.82±9.41μg/L;进一步分析发现,热力分层的消退可能是导致水体表层无机营养盐升高(底层供给)的重要原因,加之适宜的光热条件可诱导两湖冬季水华的发生;在其他季节转化期间,浮游植物生物量变化的主要影响因子亦具有一定的共性及湖泊与季节异质性.     

Some results of induced polarisation surveys for sulphide mineralisation in parts of Rajasthan and Gujarat,India

Some results of induced polarisation surveys carried out for the exploration of sulphide mineralisation in parts of Rajasthan and Gujarat, employing both frequency-domain and time-domain techniques, are presented. A few typical examples of I.P. results along with borehole sections and results of conventional geophysical surveys have been incorporated. Frequency-domain and time-domain I.P. data have been compared for selected areas.Borehole data pertaining to several areas investigated have corroborated the I.P. results fairly well.     

Linking human-biophysical interactions with the trophic status of Dal Lake,Kashmir Himalaya,India

The study analyses the long-term biophysical and demographic changes in Dal lake, located in the heart of Srinagar city, Kashmir India, using a repository of historical, remote sensing, socio-economic and water quality data supported by the extensive field observations. The lake faces multiple pressures from the unplanned urbanization, high population growth, nutrient load from intensive agriculture and tourism. The data showed that the lake has shrunk from 31 km² in 1859–24 km² in 2013. Significant changes were observed in the land use and land cover (LULC) within the lake (1859–2013) and in the vicinity of the lake (1962–2013). Analysis of the demographic data indicates that the human population within the lake has shown more than double the national growth rate. Additionally, 7 important water quality parameters from 82 well distributed sites across the lake were analyzed and compared with the past data to determine the historical changes in the water quality from 1971 to 2014. The changes in the LULC and demography have adversely affected the pollution status of this pristine lake. Ortho-phosphate phosphorous concentration has increased from 16.75 μg L⁻¹ in 1977–45.78 μg L⁻¹ in 2014 and that of the nitrate-nitrogen from 365 μg L⁻¹ to 557 μg L⁻¹, indicating nutrient enrichment of the lake over the years. Built-up area within the lake has increased 40 times since 1859, which, together with the changes in the population and settlements, have led to the high discharge of untreated nutrient-rich sewage into the lake. Similarly the expansion of floating gardens within the lake and agriculture lands in the catchment has contributed to the increased nutrient load into the lake due to the increasing use of fertilizers. The information about the existing land cover, demography and water quality was integrated and analyzed in GIS environment to identify the trophic status of the lake. The analysis indicated that 32% of the lake falls under sever degradation, 48% under medium degradation while as 20% of the lake waters are relatively clean. It is believed that the results provide improved knowledge and insights about the lake health and causal factors of its degradation necessary for effectively restoring its ecological and hydrological functionality.     

Reservoir induced seismicity in the vicinity of Lake Bhatsa,Maharashtra, India

The township of Khardi, located 7 km northwest of the Bhatsa dam, in the western part of the Deccan Volcanic Province, was subjected to earthquakes of magnitudes 4.0 and 4.8 on August 17, 1983 and September 15, 1983, respectively. The Khardi-Bhatsa area is located to the east of the Panvel flexure axis and on a northwest-southeast trending belt, forming an extension of the Ghod lineament of the Deccan Plateau. The earth tremors at Khardi followed impoundment of water, during June–July 1983, behind the recently constructed Bhatsa dam, and the rise in lake-level from about 92 to 110 m above MSL. It is suggested that percolation of water during this period along fractures led to a build-up of pore-fluid pressure which was transmitted down to a stress zone with a potential to slip. Consequent reduction in effective stress (tectonic stress-pore fluid pressure) induced the earthquakes. Available seismic data for the Khardi-Bhatsa area suggest that b-values can also be used as a ‘short term’ precursor for detecting impending, strong reservoir-induced earth tremors in the area.