The ecology of the fishes in Nyumba ya Mungu reservoir, Tanzania

Twenty species of fish were found in Nyumba ya Mungu reservoir on the River Pangani which, with two exceptions, were indigenous to the river basin. Their distribution is described and some information on their growth, reproduction and feeding habits is presented. The highest densities of fish were found in the littoral and the broad, shallow, upstream region of the lake. The lacustrine environment has favoured the endemic tilapias, Sarotherodon jipe and S. pangani , which graze periphyton, and the introduced species, S. esculentus which feeds on phytoplankton. Males of the endemic forms may grow to a large size, but the introduced species, including Tilapia rendalli , were heavier for a given length. A reduction in tilapia stocks since 1970 is reflected in experimental catches during 1972-74 and was attributed to the combined effects of heavy commercial exploitation and a loss of spawning grounds. In the same period a striking increase in the populations of small carnivores, Rhabdalestes leleupi and Haplochromis gr. bloyeti , was recorded. Kully plantivorous and piscivorous fish are absent but omnivores are represented by Barbus species and Synodontis punctulatus. Tilapias exhibited a high incidence of nematode infection and the available evidence indicates that fish-eating birds are important predators of cichlids in Nyumba ya Mungu.     

Ribosomal Tag Pyrosequencing of DNA and RNA Reveals “Rare” Taxa with High Protein Synthesis Potential in the Sediment of a Hypersaline Lake in Western Australia

Little is known about the potential activity of microbial communities in hypersaline sediment ecosystems. Ribosomal tag libraries of DNA and RNA extracted from the sediment of Lake Strawbridge (Western Australia) revealed bacterial and archaeal operational taxonomic units (OTUs) with high RNA/DNA ratios providing evidence for the presence of ‘rare’ but potentially “active” taxa. Among the ‘rare’ bacterial taxa Halomonas, Salinivibrio and Idiomarina showed the highest protein synthesis potential. Rare but ‘active’ archaeal OTUs were related to the KTK 4A cluster and the Marine-Benthic-Groups B and D. We present the first molecular analysis of the microbial diversity and protein synthesis potential of rare microbial taxa in a hypersaline sediment ecosystem.     

Turbulence increases the risk of microcystin exposure in a eutrophic lake (Lake Taihu) during cyanobacterial bloom periods

Toxic cyanobacterial harmful algal blooms (CyanoHABs) have posed serious water use and public health threats because of the toxins they produce, such as the microcystins (MCs). The direct physical effects of turbulence on MCs, however, have not yet been addressed and is still poorly elucidated. In this study, a 6-day mesocosm experiment was carried out to evaluate the effects of wind wave turbulence on the competition of toxic Microcystis and MCs production in highly eutrophicated and turbulent Lake Taihu, China. Under turbulent conditions, MCs concentrations (both total and extracellular) significantly increased and reached a maximum level 3.4 times higher than in calm water. Specifically, short term (∼3 days) turbulence favored the growth of toxic Microcystis species, allowing for the accumulation of biomass which also triggered the increase in MCs toxicity. Moreover, intense turbulence raises the shear stress and could cause cell mechanical damage or cellular lysis resulting in cell breakage and leakage of intracellular materials including the toxins. The results indicate that short term (∼3 days) turbulence is beneficial for MCs production and release, which increase the potential exposure of aquatic organisms and humans. This study suggests that the importance of water turbulence in the competition of toxic Microcystis and MCs production, and provides new perspectives for control of toxin in CyanoHABs-infested lakes.     

Is coexistence mediated by microhabitat segregation? An in-depth exploration of a fish invasion

Vendace Coregonus albula has invaded the subarctic Pasvik hydrosystem, northern Norway and Russia, after being translocated from its native Finnish range into Lake Inari (Finland), upstream of Pasvik. The development of the invader and the effects on two native lake communities in the upstream and downstream part of the hydrosystem, respectively, have been monitored since 1991. In the upstream lake location, the invader relegated the native whitefish Coregonus lavaretus from the pelagic habitat within a few years. An expected similar development in the downstream location was, however, not observed. Data are presented on the diet and microhabitat use (vertical pelagic zone) for three types of replicated situation: (1) the invader v. the native species, (2) upstream v . downstream lakes and (3) early and late invasion stages, to explore the outcome of the competitive interactions. The use of different microhabitats available within the deeper pelagic zone in the downstream location was observed to have delayed the negative effects on native whitefish, possibly enabling a persistent coexistence between the two species in the pelagic zone of this lake.     

Life-cycle greenhouse gas emissions assessment and extended exergy accounting of a horizontal-flow constructed wetland for municipal wastewater treatment: A case study in Chile

The life-cycle greenhouse gaseous emissions and primary exergy resources consumption associated with a horizontal subsurface flow constructed wetland (HSSF) were investigated. The subject of study was a wetland for municipal wastewater treatment with a 700-person-equivalent capacity. The effects of two types of emergent aquatic macrophytes (Phragmites australis and Schoenoplectus californicus) and seasonality on greenhouse gas (GHG) gas emissions, the environmental remediation cost (ERC) and the specific environmental remediation cost (SERC) were assessed. The results indicate that GHG emissions per capita (12–22 kgCO2eq/p.e/yr) and primary exergy resources consumed (24–27 MJ/m³) for the HSSF are lower than those of a conventional wastewater treatment plant (67.9 kgCO2eq/p.e/yr and 96 MJ/m³). The SERC varied between 176 and 216 MJ/kg biological oxygen demand (BOD₅) removal, which should be further reduced by 20% for an improved BOD₅ removal efficiency above 90%. The low organic matter removal efficiency is associated with a high organic load and low bacterial development. Seasonality has a marked effect on the organic removal efficiency and the SERC, but the macrophyte species does not.     

Reversed trends in the benthic community structure in two confluent streams; one spring-fed,the other lake-fed

The community structure of two confluent streams in southern Sweden was investigated, one stream was spring-fed and the other lake-fed. There was a downstream decrease in the number of species present in the lake outlet stream, no such change being discernible in the spring-fed stream. Taking the sampling site nearest the source of the spring-fed stream as the reference point, there was a downstream increase in dissimilarity and this increase was maintained upstream from the confluence in the lake-fed stream. Apart from generalists, all functional feeding groups showed decreased numbers from the lake outlet to the confluence in the lake-fed stream. In the spring-fed stream, densities of functional groups increased downstream, with the exception of grazers and generalists. There were indications of more predictable changes along the lake-fed stream compared to the spring-fed one, which seemed more influenced by site-specific factors.     

The pH regime sediments underlying acidified waters

The pH of sediments underlying acidified lake waters does not necessarily reflect the acidification of the water. Profiles of sediments in Lake Anna, Virginia showed interstitial pH values between 6.0 and 7.0 within the top 4 cm, even though the sediments are constantly exposed to overlying waters with pH values as low as 3.5. The amount of acidity neutralized by sediment processes is 2 orders of magnitude greater than previously reported observations. The results indicate that caution must be used in drawing conclusions about sediments biogeochemical processes based on the pH of overlying waters. This article originally appeared in an incorrect form in Biogeochemistry, Vol. 2, No. 1., pages 95–99     

青岛胶州湾四种类型湿地AM真菌多样性

对青岛胶州湾4种类型湿地（盐田、滩涂、湖泊和河口）中芦苇Phragmites communis、香蒲Typha orientalis和碱蓬Suaeda glauca 根围土壤中丛枝菌根（arbuscular mycorrhizal,AM）真菌进行孢子分离与鉴定,分析湿地生态系统中植物根围AM真菌群落特征。共分离到AM真菌5属10种,包括斗管囊霉属Funneliformis 2种、无梗囊霉属Acaulospora 3种、近明球囊霉属Claroideoglomus 2种、球囊霉属Glomus 1种、巨孢囊霉属Gigaspora 2种,其中,斗管囊霉属Funneliformis及地斗管囊霉Funneliformis geosporum的分离频度和相对多度最高,分别为湿地中AM真菌优势属和优势种。滩涂和河口湿地中植物AM真菌侵染率显著高于湖泊和盐田湿地植物,AM真菌孢子密度以滩涂湿地最高（572个/20mL）,湖泊湿地最低（220个/20mL）;滩涂湿地的种丰度和Shannon-Wiener指数最高,分别为3.8和1.2。从植物种类来看,AM真菌侵染率总体呈现出香蒲>碱蓬>芦苇,AM真菌孢子密度以香蒲最高,芦苇最低,植物种类对AM真菌种丰度和Shannon-Wiener指数影响不显著（P>0.05）。二因素方差分析和典型RDA相关分析表明,寄主植物种类对AM真菌孢子密度有一定影响,但湿地类型对AM真菌多样性的影响更为显著（P<0.05）,胶州湾湿地土壤因子Ca ²⁺、速效P含量与AM真菌孢子密度、物种丰度和多样性指数显著负相关,而速效K、Na ⁺、pH与其显著正相关。结果表明植物种类主要影响AM真菌孢子密度,AM真菌多样性受植物种类和湿地类型综合影响,滩涂湿地较丰富的AM真菌多样性可能与该湿地较良好的理化性质有关。     

管网雨水补给河道用水的人工湿地水质净化流程研究

中国北方部分地区水资源短缺,河道干涸,但夏季雨水资源潜力丰富。虽径流受到一定污染,但较于生活污水和工业废水,其污染程度更低,成分更简单。雨水通过低运行成本的人工湿地净化系统,可以实现较好的净化效果,满足河道景观需求和生态补水。城市管网雨水承载能力过重的城市边缘区,建设更新过程中进行雨污分流制度,更适于采用人工水质净化的方式将城市雨水管网中的雨水进行就近消纳,减轻城市雨水管网压力,并利用表面负荷率（ALR）来确定并校核人工湿地面积。在综合现在人工水质净化主流程预处理单元、人工湿地单元和消毒存储单元3个环节的基础上,以低运营成本、低管理成本、最优净水量为指向,引入物联网技术智能管控系统,行程具有能控制各级出水水质监测、多级管控、净水生态功能与游览景观功能相结合等多重优点的人工水质净化全流程,达到符合河道水质标准的净化效果。该流程为缓解北方城镇河道缺水现状、解决城市雨洪问题提供新思路。