title: Effects of light and nutrients on periphyton and the fatty acid composition and somatic growth of invertebrate grazers in subtropical streams.
abstract: Algal polyunsaturated fatty acids (PUFA), essential for somatic growth and reproduction of aquatic animals, are influenced by ambient environmental conditions, including light and nutrients. Few studies have addressed the extent to which changes in algal PUFA can influence stream herbivore PUFA profiles and the implications for stream food webs. We manipulated subtropical stream periphyton by applying two light levels (open and shaded canopy) and two nutrient regimes (ambient and enriched) to investigate the response of PUFA and somatic growth in stream herbivores. After 6 weeks, the relative content of periphyton PUFA (%) changed distinctly and differed among treatments. Periphyton in the control treatment with open canopy showed a decline in eicosapentaenoic acid (EPA) relative to initial conditions, whereas shading increased EPA and total highly unsaturated FA (HUFA), but decreased α-linolenic acid (ALA), linoleic acid and total C18 PUFA. The interaction of open canopy and added nutrients increased periphyton ALA compared with initial conditions, while the combined effects of shading and added nutrients led to greater total HUFA. FA similarity between stream grazers (the mayfly Austrophlebioides and caddisfly Helicopsyche) and periphyton increased with periphyton HUFA content. In addition, the growth of large instars of both grazers also increased in response to increased periphyton HUFA %. Our findings show that environmental changes, associated with riparian canopy and nutrients, can lead to changes in periphyton PUFA composition that in turn affect growth and PUFA composition in stream grazers.
authors.affiliation: Australian Rivers Institute, Griffith University, Nathan, QLD, Australia. fen.guo@griffithuni.edu.au.|State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, People's Republic of China. fen.guo@griffithuni.edu.au.
authors.forename: Fen
authors.initials: F
authors.lastname: Guo
authors.affiliation: WasserCluster Lunz Inter-University Centre for Aquatic Ecosystem Research, Lunz am See, Austria.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Kainz
authors.affiliation: Australian Rivers Institute, Griffith University, Nathan, QLD, Australia.
authors.forename: Fran
authors.initials: F
authors.lastname: Sheldon
authors.affiliation: Australian Rivers Institute, Griffith University, Nathan, QLD, Australia.
authors.forename: Stuart E
authors.initials: SE
authors.lastname: Bunn
mesh_terms: D000818:Animals; D005227:Fatty Acids; D007313:Insecta; D007448:Invertebrates; D008027:Light; D045483:Rivers
chemical_list: D005227:Fatty Acids
keywords: Algae; Food quality; Food webs; Polyunsaturated fatty acids; Riparian canopy