Seasonal dynamics of plankton communities coupled with environmental factors in a semi arid area: Sidi Sad reservoir (Center of Tunisia)

摘要

In this?study, we studied the influence of the physical-chemical and biological factors (bacterioplankton and phytoplankton abundances) for zooplankton?dynamics?in a Sidi Saad reservoir in Centre of Tunisia. The samplings were carried out in spring, summer, autumn and winter (2005 to 2006) in the deepest station (surface, 5, 10 and 15 m). In this reservoir, the highest density of zooplankton abundance was recorded in summer (92.2 ind L-1; 0.43 × 103?μg L-1) and autumn (86.9 ind L-1; 0.23 × 103?μg L-1) at a depth of 10 m. The copepods (56% of total zooplankton abundance) and cladocera (42% of total zooplankton abundance) were the most abundant groups. The physico-chemical factors, especially the water temperature (r = 0.53, p = 0.027, n = 16) and dissolved oxygen (r = -0.59, p = 0.03, n = 16), influence directly the zooplankton community. It was suggested that in Sidi Saad reservoir, both the top-down and bottom-up regulations account for the regulation of zooplankton. The phytoplankton was the factor responsible for the structure and seasonal dynamics of the zooplankton community, which are well related to changes in algae diversity and abundance, noting that cyanobacteria have major impacts.?The “top-down” effect ofplanktivorous fish?on the?zooplankton?is a significant factor?affecting the planktoncommunity’s?dynamics?in?this reservoir.