Substrate influence and temporal changes on periphytic biomass accrual and metabolism in a tropical humic lagoon     

Rafael D. Guariento  Adriano Caliman  Francisco A. Esteves  Reinaldo L. Bozelli  Alex Enrich-Prast  Vinicius F. Farjalla   《Limnologica》2009,39(3):209-218

We performed a field experiment in a tropical humic coastal lagoon to evaluate periphyton biomass accrual and metabolism on three different substrates (1) plastic ribbons, (2) green and (3) senescent leaves of the emergent macrophyte Typha domingensis) over 30 days. The contribution of autotrophic biomass decreased as total biomass increased over the time. Mean periphytic ash free dry weight ranged from 0.8 to 5.6 mg cm⁻², but periphyton chlorophyll a concentrations presented shorter amplitudes, which oscillated from 0.12 to 0.44 μg cm⁻² throughout the experiment. Periphyton metabolism was overall heterotrophic on all substrates, especially on senescent leaves. Our data show that substrate type influenced both biomass accrual and periphyton net productivity and respiration rates throughout periphyton development and highlighted the dominance of heterotrophic metabolism. The periphyton respiration may be subsidized by both water- and substrate-derived allochthonous energy pathways, shedding light on the role of periphytic assemblages to the carbon cycling, as a source of CO₂ to the system.  相似文献   

Effects of fish manipulation on the plankton community in small hypertrophic lakes from the Pampa Plain (Argentina)     

Alejandro Sosnovsky  Rolando Quirs 《Limnologica》2009,39(3):219-229

Trophic cascade hypotheses predict that fish will affect the structure and biomass of pelagic plankton communities. In order to investigate trophic cascade effects from fish down to phytoplankton, whole-lake studies were performed in five hypertrophic (mean total phosphorus (TP) concentrations higher than 1000 mg m⁻³) shallow lakes located in the Pampa Plain. The main climatic characteristic of this region is the alternation between periods of drought and flood, with corresponding changes of lake depth and conductivity of lake water. All lakes were studied from April to December 2000. Samples were taken of their physical and chemical characteristics and biotic communities, focusing on the zooplankton community. Fish were manipulated in four lakes (Capurro, Longinotti, Vedia 1, Vedia 2), while the fifth (Lake Vedia 3) was left undisturbed as a reference system. High abundance of planktivorous minnows (Jenynsia multidentata and Cheirodon interruptus) dominated the fish community in the reference lake. In the manipulated lakes, fish stocks were largely reduced in late autumn (May). During winter, Capurro, Longinotti and Vedia 1 were stocked with a visual planktivore, the pampean silverside (Odontesthes bonariensis, Atherinidae). Fish stocking was 24, 33 and 19 kg ha⁻¹, respectively. In contrast, no fish were stocked in Lake Vedia 2. Following fish removal, large Daphnia appeared in these lakes and grazed intensively on the phytoplankton. In contrast, no Daphnia were found in the reference lake (Vedia 3). The stocking of O. bonariensis in lakes Capurro, Longinotti and Vedia 1 led to a decrease in the percentage of large cladocerans and a rise in the phytoplankton biomass:TP ratio. Moreover, the lakes mentioned were stocked with different quantities of silversides over different periods of time. These differences were reflected temporarily in the plankton dynamics, affecting mainly larger sized zooplankton. Nevertheless, the presence of Daphnia was short lived in the lake where fish had been removed and no O. bonariensis were stocked. Competition for resources and recruitment of remaining fish probably caused a collapse in the zooplankton biomass. Our results support the idea that fish predation on zooplankton and its effect on phytoplankton is very intense in small pampean lakes. Fish removal was short lived, however. This could be because in small pampean lakes fish recolonization is favored, and minnows are highly prolific. Moreover, if manipulation of the trophic structure of lakes is undertaken in the pampean region, high nutrient loading from the watershed, climate and hydrology should also be taken into account.  相似文献   

Biometric analysis of lacustrine and riverine populations of Palemonetes antennarius (H. Milne-Edwards, 1837) (Crustacea, Decapoda, Palaemonidae) from north-western Greece     

Chryssa Anastasiadou  Roman Liasko  Ioannis D. Leonardos   《Limnologica》2009,39(3):244-254

Comparative study of morphometric measurements was undertaken on populations of Palaemonetes antennarius from two freshwater habitat zones (lacustrine pelagic and lacustrine littoral) and from the fluvial littoral habitat zone of three estuaries of north-western Greece. Multivariate statistical analyses (principal component analysis and discriminant function analysis) revealed clear morphometric differences between sexes and sampling sites. The observed differences are expressed mainly thought the measurements related to the body heights (carapace height and second pleon height), as a result of sexual dimorphism, High values for the female body heights seem to be correlated to specific fecundity profile and reproductive strategy. On the other hand, morphometrical variables related mainly to body lengths, such as rostral, telson and pleon lengths, were observed to be correlated to the study sites. Characters related to the summing capacity (telson length, telson width and pleon lengths) were generally found to have higher values in the specimens from habitats with high reophilic profile.  相似文献   

Observations on the relations of some physico-chemical features and DVM of Paradiaptomus africanus in Lakes Bishoftu-Guda and Hora-Arsedi, Bishoftu, Ethiopia     

Brook Lemma   《Limnologica》2009,39(3):230-243

Bishoftu-Guda and Hora-Arsedi are two crater lakes found in close proximity with each other in a locality known as Bishoftu, 50 km south of Addis Ababa, capital city of Ethiopia. The main objective of this study was to measure some physico-chemical features and discuss their relations with the dial vertical migration (DVM) behavior of Paradiaptomus africanus, the dominant macrozooplankton in both lakes. By depth measurements of dissolved oxygen and temperature showed that there is persistent stratification in these lakes. Secchi depth was shallow and the water chemistry as shown from conductivity and chemical analysis were comparable between the two lakes. These data were compared with previous reports to bring out the overall limnological scenario of the two lakes. Then, the relations of these data to the DVM of P. africanus in both lakes were discussed. It was found out that DVM of P. africanus occurred in Lakes Bishoftu-Guda and Hora-Arsedi mostly within a range of about 3 m very likely for two reasons, namely avoidance of solar radiation and ultimately vertebrate visual predation. However, the depth of DVM of P. africanus was found to be very shallow probably due to high water turbidity that provided this calanoid sufficient refuge by daylight from both dangers, while at the same time P. africanus remained in warm and oxygen-rich waters. Temperature was not much of a factor affecting DVM as it remained above 19 °C at all depths. As this study was conducted over limited time frames, seasonal studies regarding changes in physico-chemical parameters, plankton, vertebrate predators and human interference were recommended so that the information so gathered could be used in the management of the study lakes.  相似文献   

Predicting the onset of thermal stratification in shallow inland waterbodies   总被引：1，自引：0，他引：1  

Brett F. Branco  Thomas Torgersen 《Aquatic Sciences - Research Across Boundaries》2009,71(1):65-79

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A zone-specific fish-based biotic index as a management tool for the Zeeschelde estuary (Belgium)     

Jan Breine  Paul Quataert  Frans Ollevier  Ericia Van den Bergh 《Marine pollution bulletin》2010,60(7):1099-233

Fish-based indices monitor changes in surface waters and are a valuable aid in communication by summarising complex information about the environment (Harrison and Whitfield, 2004). A zone-specific fish-based multimetric estuarine index of biotic integrity (Z-EBI) was developed based on a 13 year time series of fish surveys from the Zeeschelde estuary (Belgium). Sites were pre-classified using indicators of anthropogenic impact. Metrics showing a monotone response with pressure classes were selected for further analysis. Thresholds for the good ecological potential (GEP) were defined from references. A modified trisection was applied for the other thresholds. The Z-EBI is defined by the average of the metric scores calculated over a one year period and translated into an ecological quality ratio (EQR). The indices integrate structural and functional qualities of the estuarine fish communities. The Z-EBI performances were successfully validated for habitat degradation in the various habitat zones.  相似文献   

Determination of the freshwater budget of tidal flats from measurements near a tidal inlet     

Reiner Onken  Rolf Riethmüller 《Continental Shelf Research》2010

The freshwater budget of a tidal flat area is evaluated from long-term hydrographic time series from an observation pole positioned in a tidal channel in the Hörnum Basin (Germany). For each tidal cycle, the freshwater budget is calculated from the total imported and exported water volumes and the corresponding mean densities. The variability of the budget on a tidal scale is characterised by a period of twice the tidal period, exhibiting a minimum when the tidal flats are dry around daylight hours during the foregoing low tide, and a maximum when low tide occurs at night; enhanced evaporation on the flats at daylight hours is identified as the driving process. On the average over one year, while winter observations are missing, the freshwater budget is negative for the years 2002–2005 and positive only for 2006. The interannual mean is negative and amounts to a freshwater loss of about 2 mm day⁻¹, although the large-scale climate in this region is humid. The results demonstrate that the bulk parametrisations for the latent and sensible heat flux between the ocean and the atmosphere must not be applied for the tidelands.  相似文献   

全国盐湖信息共享平台的设计与实现   总被引：2，自引：0，他引：2       下载免费PDF全文

闫立娟  齐文 《盐湖研究》2010,18(1):15-20

盐湖是宝贵的综合性自然资源,有着重要的经济和社会价值。全国盐湖信息共享平台的建设,一方面能够提供盐湖空间信息,为盐湖动态变化研究提供基础数据;另一方面,能通过属性数据库,提供盐湖现状和资源概况,为资源开发提供基础数据。在分析了WebGIS及其相关技术的基础上,介绍了全国盐湖信息共享平台的软硬件运行环境,详述了平台空间数据库和属性数据库的建设,概括了网站的创建过程及平台的主要功能。  相似文献   

Potential for remediation of acidic mining lakes evaluated by hydrogeochemical modelling: Case study Grünewalder Lauch (Plessa 117, Lusatia/Germany)     

Brigitte Nixdorf  Wilfried Uhlmann 《Limnologica》2010,40(2):167-174

About one third of several hundred mining lakes in Eastern Germany are highly acidified, and there is a need to restore them to neutral conditions because they constitute an environmental hazard for water resources and downstream environments. The aim of this study is to evaluate the efficiency of three different acid pit lake water remediation treatments: dilution with alkaline (river) water, limestone treatment and biological neutralization by organic carbon-driven alkalinity generation. The efficiency is evaluated for the acidic mining lake Grünewalder Lauch by adjusting input values into a geochemical model and making future projections. Current approaches, such as flooding with neutral surface water or extensive liming, are not suitable for many lakes because of a limited supply of alkaline water or high lime immobilizing potential of Fe- and Al-rich water in acidic lakes, respectively. Further treatment methods are, therefore, designed to combine water supply and biological measures with the management of water quality by the application of in-lake microbial processes. These processes are focused on the metabolic response of aquatic ecosystems to nutrient enrichment (enhancement of primary production and thereby organic carbon supply) and the microbial decomposition of organic matter and their effects on the gain or loss of alkalinity.The results and comparisons of different neutralization measures will be generalized by the application of hydrogeochemical models for alkalinity production showing

a)

the long term efficiency of the measures, depending on carbon turnover at the sediment/water interface,

b)

the development of bicarbonate buffering capacity as a consequence of biological measures,

c)

the importance of pyrite formation instead of FeS.

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Outburst flood hazard: Case studies from the Tien-Shan Mountains, Kyrgyzstan   总被引：3，自引：0，他引：3  

Bohumír Janský  Miroslav Šobr  Zbyněk Engel 《Limnologica》2010,40(4):358-364

More than 2000 of mountain lakes covering more than 0.1 ha exist in a territory of Kyrgyzstan. Nearly 20% of them are dangerous because of instability of lake dams, frequent overflows and melting of buried ice inside the moraine dams. According to the Kyrgyz lake inventory, 328 lakes are at risk of outburst and 12 lakes are considered as actually dangerous. Since 1952 more than 70 disastrous cases of lake outbursts have occurred. The majority of the endangered lakes belong to one of the three genetic types: morainic-glacier, supraglacial and lake dammed by landslides and debris flows. Petrov, Adygine and Koltor lakes were selected and studied in the Tien-Shan Mountains as case studies of the most frequent genetic types of hazardous lakes. Observations were focused on the morphology of the lake basin and the surrounding relief, outflow pattern and processes controlling the development of lake. For the hazard assessment, evolution of glaciers and lakes was reconstructed using historical reports, aerial photographs and satellite images.  相似文献