Trophic pathways of omega-3 fatty acids in stream food webs

Research on stream ecosystems is strongly influenced by the well-established River Continuum Concept that suggests that headwater streams in temperate forests are strongly dominated by leaves and other terrestrial material. At the same time, these streams are important habitats for freshwater salmonids, such as trout and charr, which are an important source of omega-3 fatty acids for higher consumers, including humans. However, only very little omega-3 fatty acids occur in such terrestrial material of headwater streams. Thus, the high dietary omega-3 fatty acid demand for salmonids and other headwater consumers may be too low. This research project targets this conundrum and will investigate, a) spatial and seasonal variation in stream consumer dependence (including insects and fish) on elemental and molecular composition of basal resources in pre-alpine streams (ecosystem approach), b) under different light conditions, the effect of terrestrial and stream diet sources on food supply and retention of fatty acids in stream invertebrates (experimental approach), and, c) the ability of freshwater fish to synthesize long- chain omega-3 fatty acids using state-of-the-art radioactive methods in fish liver cells (lipid metabolism in stream fish). This research will develop and use methods, including stream experiments and fish liver cells analyses, linked with field investigations and apply stable isotopes and fatty acids as a new combined effort to understand how diet sources are retained in fish. Results will thus shed considerable light on the long-standing question of how insects and fish in streams manage or fail to obtain essential nutrients and high quality forms of energy. Together with an international team of high-profile researchers this project will clearly further stream biofilm research and stream food webs. This research will provide excellent training opportunities for young scientists at the graduate and post-graduate level considerably contribute to a more comprehensive understanding of dietary energy transfer and lipid dynamics in stream organisms along increasing trophic levels.

No additional funding sources recorded.