Phytoplankton primary production, chlorophyll-a and nutrient concentrations in the water column of mountainous Lake Phewa, Nepal

The seasonal patterns of phytoplankton primary production, chlorophyll‐a concentration, cell number and several other limnological variables in Lake Phewa, located in the active monsoon zone in Central Himalaya, Nepal, were studied for a year beginning in April 2001. During the study period, the gross primary production and chlorophyll‐a concentrations were relatively low during the monsoon season. The phytoplankton cell number, represented by 24 genera, also fluctuated seasonally, but tended to increase in the pre‐ and post‐monsoon period. These results suggest that the monsoon plays a crucial role in the primary production and phytoplankton dynamics for Lake Phewa. Among the phytoplankton species, Microcystis aeruginosa, a representative species for eutrophic lakes, was the dominant phytoplankton. At the same time, however, it is clear that the lake is not yet heavily eutrophic. The present study suggests that the exchange of lake water during the monsoon season contributes to maintaining the health of the lake against further degradation. Nevertheless, the silt carried in the monsoon rain run‐off from the lake's catchment area suggests increasingly serious degradation problems for this small mountainous lake.     

Dynamics of photosynthetic pigments in an Andean lake in Colombia

Guatavita Lake is a small, sheltered tropical high mountain lake located in the Colombian Andes, with a closed watershed and a maximum depth of 25 m. It is the freshwater source for human consumption in nearby small towns, as well as being a site of cultural value for the country, as it was a sacred place to indigenous peoples until about five centuries ago. As the structure and function of this aquatic ecosystem is poorly understood, this study provides initial knowledge on its phytoplankton biomass dynamics, which should be useful in designing efficient management plans with environmental baseline information for similar lakes elsewhere. Physical and chemical data, and photosynthetic pigment concentrations, were measured for the period November 1999–November 2000 at the central vertical axis of Guatavita Lake. The vertical profile of the chlorophyll‐a concentration was closely related to the dissolved inorganic nitrogen concentrations and the thermal stratification characteristics. The maximum chlorophyll‐a concentration in the metalimnion was recorded for the thermal stratification period (November 1999–June 2000). Deepening of the maximum chlorophyll‐a concentration began in February, continuing to June, when it reached its lowest value at the 15 m depth. The phytoplankton biomass values showed an increment within the entire water column at the beginning of the mixing period (July). The relation between the metalimnetic peak of chlorophyll‐a and the dissolved inorganic nitrogen concentration suggests the growth of the phytoplankton community is limited mainly by the availability of nitrogen.     

Benefits to 0+ fishes of connecting man‐made waterbodies to the lower River Trent,England

Floodplain waterbodies are reputed to enhance recruitment of riverine fish populations via provision of spawning and nursery habitat, refuge from floods, and increased availability of planktonic food resources compared with main river channels. Notwithstanding, there have been few parallel studies of fishes and their food resources at both main river and floodplain sites. Thus, this study investigated the 0+ fishes, zooplankton and phytoplankton (chlorophyll a) at four main river and four (man‐made) floodplain sites on the lower River Trent, England, between May 1999 and October 2004 inclusive. All sites shared the same key fish species, and there were no consistent differences in the densities, growth or condition of 0+ fishes from main river and floodplain sites. Similarly, all sites shared the same key zooplankton taxa. However, zooplankton densities, notably of large‐bodied cladocerans, and chlorophyll a concentrations, were significantly higher at floodplain sites than at main river sites. Thus, connection of man‐made waterbodies has the potential to enhance recruitment of riverine fish populations via provision of important spawning and nursery habitat, and superior feeding opportunities for 0+ fishes compared with main river channels. Copyright © 2007 John Wiley & Sons, Ltd.     

Evidence for biotic control of Australian reservoir phytoplankton communities and the potential for applied biomanipulation

Although some concerns have been expressed with respect to the applicability of biomanipulation to Australian reservoirs and other inland waters, no major obstacles were found in this review. The previous doubts stimulated research, which has provided evidence for unexpected mechanisms of food web interactions, such as positive effects of small copepods on planktonic algae, higher than usual grazing potential of cladoceran communities, and direct positive effects of planktivores on phytoplankton. Further research into zooplankton-cyanobacteria interactions should indicate how widespread is the previously reported ability of some southern hemisphere crustaceans to benefit at a population level from feeding on cyanobacteria. Quantitative fisheries acoustics, which has not been widely used in biomanipulation trials before, is a promising new tool in the assessment of the biomass of planktivorous fish in the pelagic zone of reservoirs.     

Toxicity of Detroit River Sediment-Bound Contaminants to Ultraplankton

Four sites in the Detroit River/Lake Erie western basin were evaluated for their toxicity. The evaluation was based on 1) bulk chemical characterization of the sediments, 2) chemical composition of the sediment elutriates, and 3) toxicity of the elutriates to ultraplankton and microplankton/net plankton. A sequence of decreasing contamination was determined from the chemical composition of the elutriates based on the elutriation release of metals such as Zn, Mn, Cd, Ni, and Co. Bioassessment of elutriate toxicity was determined by carbon-14 Algal Fractionation Bioassays (AFB's) which were conducted with various dilutions of standard and Chelex-100 treated elutriates. Site A (near Windsor, Ontario) and Site D (western Lake Erie) were found to be toxic to ultraplankton. The observed toxicity was attributed to the bioavailability and synergistic impact of elutriated metals on ultraplankton production. A direct relationship between the water soluble metal fraction and toxicity was observed. These results confirmed that sediment toxicity should not be evaluated solely on bulk chemical composition of the sediments. The AFB's have been proven useful in the bioassessment of sediments due to their rapidity/sensitivity and hence could be routinely used for the screening and early detection of contaminants affecting fast growing organisms which form the basis of the aquatic food chain.     

Phytoplankton as biomonitors: A study of Museum Lake in Government Botanical Garden and Museum,Thiruvananthapuram, Kerala India

An assessment of the pollution status of Museum Lake in the Thiruvananthapuram Botanical Garden and Museum was conducted. Analysis of different community structures of the planktonic taxa in the lake revealed it is organically polluted, attributable to the organic litter from riparian vegetation. A total of 30 most pollution‐tolerant phytoplankton genera and 24 pollution‐tolerant species were identified. Pollution‐tolerant phytoplankton genera in the lake included Chlorophyceae, Bacillariophyceae, Cyanophyceae and Euglenophyceae. Scenedesmus, Pinnularia, Euglena, Ankistrodesmus, Closterium, Crucigenia, Kirchneriella, Merismopedia and Oscillatoria were some of the phytoplankton pollution tolerant genera whereas, Nitzschia palea, Synedra acus, Scenedesmus quadricauda, Pandorina morum and Trachelomonas volvocina were some of the pollution tolerant species noted. Excessive nutrient loading from the surrounding area is definitely degrading the quality of this urban lake ecosystem. Detailed information regarding the pollution status of a waterbody is very important in this regard, noting it ultimately assists in undertaking proper management of a waterbody. The Palmer Algal Index score for Museum Lake was 37, indicating it is highly organic enriched. The results of different algal indices (e.g. Chlorophycean Index; Nygaard Index) indicated a eutrophic condition for Museum Lake, being attributed to its increased organic enrichment. Canonical correspondence analysis between environmental variables and the microalgal bioindicators also highlighted the influence of the physical and chemical parameters on phytoplankton abundance and distribution in Museum Lake.     

广东省典型中小河流水电站浮游植物组成与特征分析

对广东省典型中小河流的引水式和坝式水电站浮游植物的群落结构和种类组成进行了调查,结果表明,坝式电站浮游植物的种类、密度、生物量及多样性要大于引水式电站;电站坝上、坝下河段的浮游植物的物种组成和优势类群差别不大,浮游植物类群未发生明显分化,浮游植物群落内部都能够稳定发展,达到平衡状态。     

Development of an index based on fish,macroinvertebrates, phytoplankton,and physicochemical properties to assess urban aquatic ecosystems in Jinan,China

Because of the rapid growth in urbanization over recent decades, urban aquatic ecosystems have been subjected to unprecedented threats and challenges. In this study, we visited 48 sites, of which 14 were reservoir sites, in water bodies in Jinan, China, on six occasions in May, August, and October of 2014 and 2015. We sampled fish, macroinvertebrates, and phytoplankton assemblages and physicochemical factors at each site. We used the richness and diversity of fish, macroinvertebrates, and phytoplankton to evaluate the condition of the aquatic ecosystems of the river sites. We also evaluated the water quality of the reservoir sites using the physicochemical factors of the State Environmental Protection Administration of China. We classified the results into five levels—excellent, good, moderate, poor, and bad—with the comprehensive evaluation index (CEI). More than 40% of the sampling sites were in either poor or bad condition. Nearly half of the excellent or good sites were in the south of Jinan. The CEI was significantly different between the reference and impaired sites; it was significantly and positively correlated with the qualitative habitat evaluation index and was significantly and negatively correlated with conductivity, total alkalinity, and ammonia nitrogen.     

黄河流域干旱区湖泊冰封期浮游植物群落结构特征及影响因子研究

为研究黄河流域上游干旱地区湖泊冰封期浮游植物群落结构及影响因子,选取干旱区典型湖泊——乌梁素海、奈伦湖为研究对象,于2019年3月冰封期进行采样调查,分析冰封期湖泊营养状态特征与浮游植物物种组成、数量及多样性指数,利用冗余分析(RDA)揭示浮游植物物种与环境因子影响关系,并运用方差分解分析主要环境因子的影响程度。结果表明,冰封期水体浮游植物共6门21属29种,其中硅藻12属16种,占据全部物种的55.2%;不同采样点浮游植物数量、生物量变化范围为3.2×10~4～1.4×10~5cells/L和0.047～0.328 mg/L,主要优势种以尖针杆藻(Synedra acus)、美丽星杆藻(Asterionella formosa)、双头辐节藻(Stauroneis anceps)等硅藻为主;不同浮游植物多样性指数H′范围0.70～1.74,介于中度污染,表明研究湖泊浮游植物多样性相对较差;不同采样点位之间浮游植物群落相似性主要处于Ⅱ、Ⅲ等级,即极不相似和轻度相似,表明各采样点之间浮游植物群落结构具有较为明显的差异。RDA分析结果表明,影响浮游植物物种分布的主要环境因子水温、总氮和硝酸盐;方差分解分析进一步显示,营养因子(总氮和硝酸盐)单独对优势种物种分布解释量达到33.66%,理化因子(水温)单独对优势种物种分布解释量达到13.24%。     

长江源区浮游植物群落特征与水环境因子关系研究

为研究长江源头区域河流浮游植物群落结构与水环境因子的关系,于2017年5,8,9月份和2018年5,7,9月份在长江源区进行调查分析,并对浮游植物及水环境因子进行了Pearson相关性分析和典范排序分析。结果表明,共发现浮游植物6门79种,以硅藻门和蓝藻门为主。各采样点浮游植物平均密度71.66×10⁴ ind./L。典范分析表明,温度、化学需氧量、高锰酸盐指数、氨氮、总氮、溶解氧是影响长江源区河流浮游植物群落结构的主要因子。研究成果有助于了解长江源头地区浮游植物群落特征,为三江源生态保护提供数据支撑。