The Ability of Aquatic Macrophytes to Assess Fish Farm Pollution in Two Salmon Rivers

The wastewater from freshwater fish farming is responsible for important water quality modifications in receiving ecosystems. These point source pollution cause local problems for the management of the freshwater environment, especially in salmon rivers. The aim of this paper is to study the relationship between plant communities and environmental factors in two rivers basins on which seven fish farms are located and to assess the relative part of water pollution compared to other environmental factors involved in water plant distribution. The disturbance due to fish farming wastewater increased both richness and diversity of aquatic plant communities and modified the distribution of 11 aquatic macrophytes. Nevertheless, the main factors involved in the aquatic plant distribution in the whole data set were not the location upstream or downstream from one point source pollution but the belonging to one river system and the habitat physical features. Relevant prediction of macrophytic communities is a useful tool for bioindication purposes but several groups of variables that manifest themselves at different spatial levels must be considered.