Evaluation of the organic pollution impact on freshwater diatoms in the northern Algerian river “Allala”

Résumé

In order to evaluate the impact of organic pollution on freshwater diatoms, water and periphyton were analyzed in Allala river during April and May 2015. Values of biological oxygen demand (BOD5), ammonium, nitrite and orthophosphate were used to calculate the organic pollution index (OPI). Identifying genera of periphyton diatoms were used to calculate the generic diatomic index (GDI).

Water and periphyton sampling was taken at the upstream and the downstream of the river.

During the two months of the study, the evaluation of the organic pollution index (OPI) indicated that the upstream site 1 located near an agricultural farmland is characterized by a high level of pollution. However the downstream site 2 that receives urban waste discharge is characterized by a much higher level of pollution.

The evaluation of the (GDI) showed that the site 1 is marked by an intermediate pollution while the site 2 is characterized by high pollution. Most prevalent diatoms genera in both sites are Nitzschia, Navicula and Hantzschia which are mostly resistant to pollution.