While many streams and rivers are dominated by terrestrial inputs of organic carbon, algae are important trophic base for stream food webs. However, the nutritional importance of algae for stream invertebrates has only recently been highlighted. Algae are acknowledged as higher quality food compared with terrestrial organic matter for the growth and reproduction of invertebrates. In part, this is because of algal higher polyunsaturated fatty acid (PUFA) content. Current studies on algal PUFA and their effect on invertebrates are mainly from lacustrine systems, and only few studies have explicitly investigated algal PUFA in streams. This thesis aimed to evaluate the role of algal food quality, as assessed by PUFA, in stream food webs by using a range of methods literature review, field investigation, field manipulative study and laboratory feeding experiment. All experiments involved in this thesis were conducted in subtropical streams in South-East Queensland, Australia.