Abstract
Associations between zooplankton community structure and abiotic (temperature, dissolved oxygen, turbidity, nutriments) and biotic factors (chlorophyll a and phytoplankton community) were examined, in Kasseb Reservoir, northern Tunisia. Samples were taken bimonthly from July to December 2002 at 3 sampling stations (deepest station: Station 1, Brik River: Station 2 and M’Zaz Stama River: Station 3). From our results it is evident that zooplankton exhibit seasonally and spatially heterogeneous distribution. The highest density of zooplankton was recorded in September at a depth of 5 m (10.8 × 103 ind·l-1). At Station 1 cyclopoid copepods (65% of total abundance) were the most abundant group followed by Cladocera (21% of total abundance). At Station 2 (93% of total abundance) and Station 3 (98% of total abundance) cyclopoid copepods were numerically dominant throughout the study period. Canonical correspondence analysis (CCA) was used to estimate the influence of abiotic and biotic factors in structuring the zooplankton assemblage. Zooplankton abundance was negatively correlated with turbidity (r= -0.381, P species richness and community structure of zooplankton in Kasseb Reservoir. The presence of zooplankton species considered to be indicators of eutrophic status confirmed the high trophic levels of Kasseb Reservoir.
Highlights
The Kasseb Reservoir is an important feature of Tunisia, and was built to serve a multitude of purposes, such as hydroelectric production, irrigation, and, principally, drinking water supply (30% of the population of Tunis city)
The Kasseb Reservoir is directly connected to Ghdir El Goulla Reservoir
In this system of highly connected reservoirs, Kasseb Reservoir provides the water for the Ghdir El Goulla Reservoir (Sellami et al, 2009)
Summary
The Kasseb Reservoir is an important feature of Tunisia, and was built to serve a multitude of purposes, such as hydroelectric production, irrigation, and, principally, drinking water supply (30% of the population of Tunis city). In freshwater ecosystems the filter-feeding zooplankton play an important role in the production of the clear-water phase (Lair and Ayadi, 1989; Edmondson, 1991; Lampert and Sommer, 1997; Stella et al, 2007). These organisms are important in the structuring and dynamics of aquatic environments, as is their fundamental role in aquatic food chains (Cadjo et al, 2007) and nutrient cycling (Lansac-Tôha et al, 1997; Velho, 2000; Gillooly and Dodson, 2000). The connectivity of ecosystems is expected to influence dispersal rates and induce passive dispersal within meta-communities (Doi et al, 2010)
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