Differential tolerances among soft-water macrophyte species to acidification

Abstract
Twenty-six macrophyte species were studied for their degree of tolerance to extremely acid conditions. They are characteristic of soft water on sandy soils in The Netherlands. These species were divided into two groups based on their recent distribution by pH and alkalinity. The first group consists of the species that can (at least temporarily) survive under extremely acid conditions (pH < 5); the second group contains species that are limited by a distinct minimum pH of the water (pH 5–6). This sharp distinction between groups on.the basis of pH can be used for reconstruction of the development of acidification in waters using historical data on the macrophytes involved. The two groups of species can be used to discriminate between two types of soft water in The Netherlands. Key words: soft-water macrophytes, ecological groups of macrophytes, autecology, acidification, indicator species.