Search results for "Man-made lake"

Phytoplankton assemblages in reservoirs: Is it chemical or physical constraints which regulate their structure?

1998

Data on phytoplankton assemblages and the correspondent environmental variables, collected in a limnological investigation carried out on 21 Sicilian reservoirs between 1987 and 1988, were ordered to clarify which physical (light availability, mixing depth), chemical (nutrient availability) and biological (grazing pressure) parameters modulate the structure of the assemblages. In particular, data sets were analyzed using CANOCO 3.1. The results of the analysis have shown that physical factors are more important in selecting species for those environments subject to pronounced water-level fluctuations. The reasons of such strong influence may be understood in the secondary modifications that…

Importance of water-level fluctuation on population dynamics of cladocerans in a hypertrophic reservoir (Lake Arancio, south-west Sicily, Italy)

1997

During a period of three years (1990-1991 and 1993), we studied the population dynamics of planktonic cladocerans in a hypertrophic reservoir. Weekly sampling revealed that the five most common species followed a trend which reflects the peculiar hydrological characteristics of the reservoir and their key position in the pelagic food web. In particular, 1991 was characterized by a strong water inflow which probably interfered with the reproductive activities of the dominant fish population (Rutilus rubilio) and reduced the concentration of inedible planktonic algae allowing the development of small Chlorococcales. This event was associated with higher population densities of Daphnia hyalina…

Phytoplankton dynamics in two reservoirs with different trophic state (Lake Rosamarina and Lake Arancio, Sicily, Italy)

1998

Two man-made Sicilian lakes of differing trophic status were sampled weekly for a year, in order to compare their phytoplankton dynamics and to identify their driving factors. The water bodies store comparable volumes but the eutrophic Lake Arancio may be considered to be a shallow lake whereas the mesotrophic Lake Rosamarina is deep. The dynamics of their principal physical, chemical and biological features were analysed using, among others, Canonical Community Ordination. The results obtained suggest that increased nutrient availability causes an increase of phytoplankton biomass but no community change nor any alteration to the typical assemblages supported. The major influence in the mo…

Phytoplankton assemblages in twenty-one Sicilian reservoirs: relationships between species composition and environmental factors

2000

Data collected in a limnological survey, carried out between 1987 and 1988 on 21 Sicilian reservoirs of varying trophic state, were ordinated using CANOCO 3.1 to generalise the way in which the structure of phytoplankton assemblage is conditioned by both physical and chemical variables. The results showed that in these man-made lakes, characterised by conspicuouswater-level fluctuations, the annual and interannual variability in the abundance and composition of phytoplankton may be strongly influenced by their peculiar hydraulic regimes rather than by nutrient availability. In particular, it was highlighted that, from the early summer, water abstraction often leads to increased circulation …

Climate change and enhancement of water-level fluctuations in Mediterranean reservoirs: a sad fate for water quality?

2010

Studies on Italian reservoirs

1992

The main morphometric and water quality characteristics of the 221 Italian reservoirs covering an area of at least 0.2 km2 is given. Most of the reservoirs are used for drinking water purposes, especially on the islands of Sicily and Sardinia, where the more important cases of eutrophication have been found. These situations are examined in greater detail, with regard to algal population dynamics, the phosphorus budget and the comparison between theoretical and experimental nutrients loads. -from Authors