Temporal and spatial variation of limnological variables and biomass of different macrophyte species in a Neotropical reservoir (São Paulo - Brazil)

Aim: This study reports an investigation of limnological characteristics and aquatic macrophyte occurrence in a neotropical reservoir in order to assess the spatio-temporal variation of water and sediment variables and their influence on plant distribution. Methods: Macrophytes, water and sediment samples were collected from a Brazilian reservoir in different seasons from four main arms of the reservoir. In total sixteen water-sediment variables were analyzed including N:P ratio and Trophic State Index. The plants were collected using a quadrat sampling procedure and the dry weight per sample was measured. MANOVA was performed to evaluate spatial and temporal variation of environmental variables as well as seasonal biomass differences. To assess the relationship among environmental variables and macrophytes an ordination analysis (using Canonical Correspondence Analysis: CCA) was carried out. Results: The spatial and temporal variation of limnological variables generated a heterogeneous system which supports the presence of different species of macrophyte. pH, dissolved oxygen and sediment composition were important predictors of Polygonum lapathifolium occurrence while nutrients were associated with Eichhornia crassipes and Pistia stratiotes. Inorganic substances were related to biomass variation of Eichhornia azurea and Myriophyllum aquaticum. Conclusions: The spatial variation of the environmental variables has caused heterogeneity in the reservoir and it may support the occurrence of different species of macrophyte. Limnological variables highlighted in CCA are important to predict the species occurrence and their control in the study area

Thermal response of Sanabria lake to global change (NW Spain)

Are large water bodies able to act as sensors of global change? As accumulators of water and heat, some of their thermal characteristics might be altered by long term (decadal) hydrometeorological changes and thus may be used as indicators of the effects of global change on fluvial ecosystems. This work focuses on the effect of global change (climate change plus water quantity and land use changes) in the internal organization of Sanabria Lake, specifically in its thermal annual cycle. The existence of temporal trends in the thermal behaviour of the lake was investigated based on the water temperature profiles are available since 1986. Data analyses include the non-parametric Mann-Kendall trend test and the Sen slope estimate to evaluate long term and seasonal patterns of hydrometeorological and in-lake thermal variables. The main results surprisingly point to a net lake cooling that could be explained by a stronger thermocline and a weaker vertical transfer of heat to the hypolimnion during the stratification period. These results contribute to understand and quantify the effects of global change on Iberian freshwater bodies.Peer ReviewedPostprint (published version

Water quality assessment, trophic classification and water resources management

Quantification of water quality (WQ) is an integral part of scientifically based water resources management. The main objective of this study was comparative analysis of two approaches applied for quantitative assessment of WQ: the trophic level index (TLI) and the Delphi method (DM). We analyzed the following features of these conceptually different approaches: A. similarity of estimates of lake WQ; B. sensitivity to indicating disturbances in the aquatic ecosystem structure and functioning; C. capacity to reflect the impact of major management measures on the quality of water resources. We compared the DM and TLI based on results from a series of lakes covering varying productivity levels, mixing regimes and climatic zones. We assumed that the conservation of aquatic ecosystem in some predefined, “reference”, state is a major objective of sustainable water resources management in the study lakes. The comparison between the two approaches was quantified as a relationship between the DM ranks and respective TLI values. We show that being a classification system, the TLI does not account for specific characteristics of aquatic ecosystems and the array of different potential uses of the water resource. It indirectly assumes that oligotrophication is identical to WQ improvement, and reduction of economic activity within the lake catchment area is the most effective way to improve WQ. WQ assessed with the TLI is more suitable for needs of natural water resources management if eutrophication is a major threat. The DM allows accounting for several water resource uses and therefore it may serve as a more robust and comprehensive tool for WQ quantification and thus for sustainable water resources management

Limnological research in Nigeria: some perspectives

A brief review on limnological research in Nigeria is given: the status of the research in the country and perspectives for future development are illustrate

Determination of water quality in lakes by biological indices

Some problems of evaluation of water quality by biological indices which can be applied in the practice of ecological monitoring on water bodies are considered in this report. Taking into account, that ecological monitoring is the most urgent for large lakes, situated in civilised (urbanised) and (or) agrarian landscapes the corresponding problems will be considered mainly in conformity with large deep lakes of temperate latitudes. The aim is a general evaluation of some of the methods from the point of view of their possible application for monitoring on large water bodies

A chemical survey of standing waters in south-east England, with reference to acidification and eutrophication

This study looks at the distribution and magnitude of acidification and eutrophication in south-east England where there are no natural lakes but a large number of shallow artificial ponds. The study area is defined as the region lying within a 100 km radius of central London but excluding the area within the M25 motorway. Water samples were taken from 120 sites between mid-January and the end of February 1990, with a subsequent monthly survey of a subset of 31 of these waters. Twelve chemical variables were measured in the laboratory using standard techniques. PH values for the full dataset ranged from 3.2 to 8.4, although the majority of sites had pH values in the range 7.0 to 8.5; only five sites had a pH of less than 6.0. The five low pH sites expectedly had low alkalinities and are the only sites with values below 0.1 meq per litre. Concentrations of calcium, sodium, potassium, magnesium, chloride, sulphate and nitrate had normal distributions. The majority of sites had total phosphorus concentrations in the range 25 to 200 mu g per litre, although 10 sites had concentrations above 400 mu g per litre. The low number of acid sites suggests that surface water acidity is not a widespread regional problem in south-east England. However the survey shows that a large number of standing waters in the region have high total phosphorus and nitrate concentrations, and 89% may be considered moderately to considerably eutrophic

Development of an Operational Northern Aquatic Ecosystem Model: Completion Report

OWRR Contract No. 14-31-0001-5217 Grant No. C-6169The work upon which this completion report is based was supported by funds provided by the U. S. Department of the Interior, Office of Water Research and Technology as authorized under the Water Resources Research Act of 1964, Public Law 88-379, as amended