Wetland salinization. Feeder creek at Bottle Bend Lagoon, a wetland near Midura, Australia, where inadequate water management in the past has led to salinization and acid sulfate soils.

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a b s t r a c tThe reduction and the smoothened amplitudes of the chloride concentrations since 2000 have resulted in a gradual positive development of the aquatic fauna in the River Werra. In the salinized section of the river increasing species numbers have been determined along the salinity gradient, which shows maximum chloride concentrations of about 2500 mg/l, maximum potash concentrations at approximately 200 mg/l, and magnesia concentrations peaked at 320 mg/l. As an immediate consequence of the reduction in salt concentration the immigration of various caddis fly species into the lower River Werra was observed. The Number of taxa per sample rose from 5 to more than 30 in the lower Werra region. Changes in speciesrichness could be seen more frequently in river sections where chloride concentrations fluctuated around 1500 mg/l.

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a b s t r a c tThe reduction and equalization of the salt concentrations in the River Werra have resulted in a gradual recovery of the aquatic flora. Spatial high-resolution macrophyte mappings document the spread of the aquatic vascular plants in the middle and lower River Werra. Simultaneously, the plankton blooms have declined. Changes in the composition of the algal communities including diatoms also indicated lower salinity. In addition to the salinity, high nutrient concentrations, waste water discharges and structural degradation are important stressors in the River Werra as shown by e.g. low species richness of vascular plants and the common occurrence of pollution tolerant diatoms. From the existing data it is clear that an encompassing improvement of the ecological conditions in the River Werra can only be achieved by further restoration measures considering all stressors.

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