Evaluation of the state of conservation of shallow lakes in the province of Leon (Northwest Spain) using botanical criteria

The floristic richness of the aquatic and hygrophytic vegetation of 27 permanent and temporary small lakes located in the León province was analyzed.The evaluation of these wetlands was carried out specifying their significance at a European, national and regional level.The main factors related to species richness were size of the water body and alterations due to pollution and shore degradation.Samplings in 1981 and 1994 were compared.Highly significant differences in genera and species richness were found between years in all lakes.The richness of hygrophytic flora was much larger in the latter sampling.This was related to large interannual variations in mean water levels.Botanical criteria for assessing shallow lake ecological importance use indices based on the abundance of hydrophytes and on floristic richness of sites.We conclude that four of the 27 lakes and wetlands studied here are of European interest, while 10 are of national significance.