Limnologische Untersuchungen im Rahmen des Thjórsárver-Projektes

Abstract

The Government of Iceland plans the construction of a huge reservoir (150 km 2 ) by damming up the water of the River Thj¢rs . The realization of this hydro-electric project, which is still under duscussion, will result in the destruction of a natural reserve unique in landscape, flora and fauna. The jeopardized area Thj¢rs rver is a boggy semi-tundra, which contains thousnads of water-bodies: rivers and pools of diffeent sizes (Fig. 1). This diversity will be melted up to one uniform basin, that ruins the condition of life for many organisms. One of the most endangered animals is the pink-footed goose (Anser platyrhynchos), for Thj¢rs rver bears the world's largest population of this bird species, whose breeding grounds would be destroyed by the intended inundation. During the season of 1974 a limnological research program was carried out in order to get some hydrobiological data before the expected flooding. However, these information might also be used as arguments against the hydro-electric project. This preliminary report presents the following results: The water-bodies can be classified in 15 types according to their abiotic and biotic characters (Figs. 4 and 11); 5 types of running waters: 1. glacier fed rivers, 2. spring fed rivers, 3. direct run off rivers, 4. drainage rivers, 5. hot springs; 10 types of stagnant waters: 6. lakes, 7. moraine ponds, 8. moraine pools, 9. moss-grown ponds, 10. moss-grown pools, 11. segde-grown ponds, 12. segde-grown pools, 13. vegetationless ponds, 14. vegetationless pools, 15. puddles. These types of water-bodies differ in their physical, chemical, floristic and faunistic characters. Some parameters (e.g. temperature, pH, conductivity) change with the distance from the glacier (Figs. 5 and 6). Rivers show characteristic diurnal oscillations of water-level and temperature (Figs. 8 and 9). Different types of water-bodies are inhabited by different plankton communities, which is reflected by the indices of diversity (Fig. 13). These indices also change between subareas (Fig. 14). The spatial distribution of the animals is determined by abiotic factors (e.g. Fig. 12) as well as by biotic relationships like competition or predation. These relations are demonstrated by affinity coefficients and by a comparison of the major components of the ecological niches (Fig. 15 and 16). The statistical analysis of the data will be continued for all species as soon as their determination by taxonomic specialists is finishes. It is to be expected that a number of soecies new for Central Iceland will be described (Fig. 2) most of which are protozoans. Detailed results will be published later.