Calcareous spring and spring brook

Calcareous springs, spring brooks and tufa cascades of karstic rivers differ from base-poor springs (C2.1a) and spring brooks due to their hard water, caused by the high calcium content. Consequently, the pH is clearly alkaline, (pH 6.5-8.5), and the specific conductivity high. This habitat occurs in areas of calcareous bedrock and soils. It is a naturally rare and nowadays declined habitat, particularly in most of the lowland areas in Europe. In montane and alpine areas calcareous springs are more common, and have remained intact to a greater extent. Calcareous springs are usually occurring as small patches. Tufa waterfalls and cascades are characteristics of watercourses in karstic areas of Europe, especially in the Dinaric Alps. The tufa-deposition and later the travertine formation are organogenic processes dependent by the organisms (bacteria, algae, mosses and plants) growing on the substrate. The periphyton produces mucopolysaccharides in which crystals of calcium carbonates (CaCO3) are trapped. This phenomenon is pronounced in many karstic areas and is very sensitive to natural or anthropogenic changes in water chemistry. In northern, geologically young springs tufa formations are not well-developed, but calcareous gyttja (organic mud) is common in sediments. Calcareous springs, spring brooks and cascades are species-rich habitats with abundant cover of mosses. Beside species in common with base-poor springs (type C2.1a) there is a number of calcium-demanding mosses and vascular plants. A high dominance of the moss Cratoneuron commutatum is often typical. Threats for this habitat type are the same as in base-poor springs; in lowland areas many calcareous springs have been destroyed by forestry and clearing of agricultural land.

Indicators of good quality:

• Natural hydrology and water chemistry in springs and spring brooks,
• Low anthropogenic influence (drainage, water exploitation, forestry, agriculture, eutrophication etc.) in springs, their surroundings and catchment areas,
• Presence of plants and animals adapted to spring conditions, including threatened species,
• High cover of mosses and specialized vascular plants,
• Absence of invasive alien species.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats