Relationships between structure and function in streams contrasting in temperature
Article first published online: 6 MAY 2009
© 2009 Blackwell Publishing Ltd
Special Issue: STRUCTURE-FUNCTION RELATIONSHIPS IN RUNNING WATERS: FROM THEORY TO APPLICATION
Volume 54, Issue 10, pages 2051–2068, October 2009
How to Cite
FRIBERG, N., DYBKJÆR, J. B., OLAFSSON, J. S., GISLASON, G. M., LARSEN, S. E. and LAURIDSEN, T. L. (2009), Relationships between structure and function in streams contrasting in temperature. Freshwater Biology, 54: 2051–2068. doi: 10.1111/j.1365-2427.2009.02234.x
- Issue published online: 9 SEP 2009
- Article first published online: 6 MAY 2009
- (Manuscript accepted 18 March 2009)
- climate change;
- leaf litter;
- stable isotopes
1. We studied 10 first-order Icelandic streams differing in geothermal influence in separate catchments. Summer temperature (August–September) ranged between 6 and 23 °C.
2. Macroinvertebrate evenness and species overlap decreased significantly with temperature whereas taxon richness showed no response. In total, 35 macroinvertebrate species were found with Chironomidae the dominant taxonomic group. Macroinvertebrate density increased significantly with temperature. Dominant species in the warm streams were Lymnaea peregra and Simulium vittatum. Algal biomass, macrophyte cover and richness were unrelated to temperature. Densities of trout (Salmo trutta), the only fish species present, reflected habitat conditions and to a lesser degree temperature.
3. Density of filter-feeders increased significantly with temperature whereas scraper density, the other dominant functional feeding group, was unrelated to temperature. Stable isotope analysis revealed a positive relationship between δ15N and temperature across several trophic levels. No pattern was found with regard to δ13C and temperature.
4. Leaf litter decomposition in both fine and coarse mesh leaf bags were significantly correlated to temperature. In coarse mesh leaf packs breakdown rates were almost doubled compared with fine mesh, ranging between 0.5 and 1.3 g DW 28 days−1. Nutrient diffusion substrates showed that the streams were primarily nitrogen limited across the temperature gradient while a significant additional effect of phosphorous was found with increasing temperature.
5. Structural and functional attributes gave complementary information which all indicated a change with temperature similar to what is found in moderately polluted streams. Our results therefore suggest that lotic ecosystems could be degraded by global warming.