Effect of some physicochemical parameters on the zooplankton community of Lake Oubeira - a Ramsar wetland in the extreme east of Algeria-

This study aims to evaluate the variability of physico-chemical parameters and their influence on zooplankton communities in Lake Oubeira. The issue that arises in this context is how does the seasonal variability of physico-chemical parameters structure the spatiotemporal distribution of zooplankton communities in Lake Oubeira?

Two sampling stations were selected: station 1: Demnet Errihane north of the lake; station 2: Oued Messida south of Lake Oubeira. The physico-chemical parameters of the environment are measured in situ using a multiparameter, monthly from January 2021 to January 2022. The zooplankton sampling was carried out using a zooplankton net (mesh size = 50 μm), 50 liters of lake water were filtered per sample to obtain a concentrated volume of 50 to 120 ml, 3 ml of the concentrate were subsequently observed under an optical microscope.

After taxonomic identification and the enumeration of zooplankton individuals, statistical data analysis -software R- revealed that: the temperature reaches its maximum in summer and decreases in winter, while the dissolved oxygen concentration is higher in spring. As for the autumn, it is distinguished by high values of electrical conductivity and pH.

PERMANOVA test revealed a very highly significant effect of seasons on species distribution (P-value < 0.001), while "stations" factor showed no significant effect.

The results of NMDS (Non-Metric Multidimensional Scaling) analysis indicated a marked seasonal structuring of communities. Copepods are predominantly abundant during the warm seasons, while rotifers and cladocerans predominate in colder seasons. Moreover, some species have a broader distribution, being observed over several seasons. At the end of this research work, we can confirm that physico-chemical parameters such as temperature, pH, dissolved oxygen, electrical conductivity strongly structure the zooplankton communities of Lake Oubeira. These results highlight the role of zooplankton as a valuable bioindicator of ecosystem health through its sensitivity to environmental change.