Spatial and temporal variation of physico-chemical parameters of water and its impact on algal distribution in the Oualidia lagoon (Atlantic coast of Morocco)

The Oualidia lagoon is a restricted lagoon exposed to various sources of pollution, that have a negative impact on the quality of its water. Since 2015, a high increase of algal biomass was clearly observed. Therefore, this study was carried out in order to highlight the relationship between the trophic quality of the water and the appearance of algae. The study of spatiotemporal variation of physicochemical parameters (Temperature, pH, Salinity, Dissolved oxygen, Nitrate (NO3) and Orthophosphate (PO4)) and the spatial distribution of algae was conducted between March 2019 and February 2020. The results showed a significant spatial and seasonal variation (p < 0.01) of the studied physicochemical parameters with the presence of upstream-downstream gradients for most of the parameters. 39 species of algae were identified in all the lagoon and during the whole study cycle. The distribution of algae was highly affected by the concentration of nutrients along the lagoon and also by the variation of physical factors such as stream, the downstream is rich in algal species, while the upstream has a limited biodiversity (around 6 species) with a high abundance of species. (c) 2022 Elsevier B.V. All rights reserved.