title: Consumption of aquaculture waste affects the fatty acid metabolism of a benthic invertebrate.
abstract: Trophic subsidies can drive widespread ecological change, thus knowledge of how keystone species respond to subsidies is important. Aquaculture of large carnivorous fish generates substantial waste as faeces and lost feed, providing a food source to mobile benthic invertebrates. We used a controlled feeding study combined with a field survey to better understand the interaction between salmon aquaculture and the sea urchin, Echinus acutus, a dominant mobile invertebrate in Norwegian fjords. We tested if diets affected urchin fatty acid composition by feeding them one of three diet treatments ("aquafeed", "composite" and "natural") for 10weeks. To test if proximity to fish farms altered E. acutus fatty acid composition, populations were sampled at 10 locations in Hardangerfjord and Masfjord (Western Norway) from directly adjacent and up to 12km from farms. Fatty acids were measured in gonads and eggs in the diet experiment and in gonads and gut contents from wild animals. Urchins directly assimilated aquaculture waste at farm sites, as evidenced by elevated linoleic acid (LA), oleic acid (OA) and ∑LA, OA in their tissues. The diet experiment highlighted the biosynthetic and selective dietary sparing capacity of E. acutus in both gonads and eggs, with evidence for the elongation and desaturation of eicosapentaenoic acid (EPA) and arachidonic acid (ARA) from C18fatty acid precursors. Elevated biosynthesis of non-methylene interrupted (NMI) fatty acids, in particular 20:3Δ7,11,14 and 20:2 Δ5,11, were also linked to a high C18fatty acid, low ≥C20long-chain polyunsaturated fatty acid (LC-PUFA) diet. Fatty acid composition of gonads of wild urchins indicated a highly variable diet. The study indicates that the generalist feeding ecology of E. acutus, coupled with extensive biosynthetic capacity, enables it to exploit aquaculture waste as an energy-rich trophic subsidy.
authors.affiliation: Sustainable Aquaculture Laboratory, Temperate and Tropical, School of BioSciences, University of Melbourne, Parkville, VIC 3010, Australia; Oceans and Atmosphere, Commonwealth Scientific and Industrial Research Organization, Castray Esplanade, Hobart, TAS, 7000, Australia. Electronic address: camille.white@utas.edu.au.
authors.forename: Camille A
authors.initials: CA
authors.lastname: White
authors.affiliation: Institute of Marine Research, P.O. Box 1870, 5817 Bergen, Norway.
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Bannister
authors.affiliation: National Marine Science Centre, Southern Cross University, Coffs Harbour, NSW 2450, Australia.
authors.forename: Symon A
authors.initials: SA
authors.lastname: Dworjanyn
authors.affiliation: Institute of Marine Research, P.O. Box 1870, 5817 Bergen, Norway.
authors.forename: Vivian
authors.initials: V
authors.lastname: Husa
authors.affiliation: Oceans and Atmosphere, Commonwealth Scientific and Industrial Research Organization, Castray Esplanade, Hobart, TAS, 7000, Australia.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Nichols
authors.affiliation: Institute of Marine Research, P.O. Box 1870, 5817 Bergen, Norway.
authors.forename: Tina
authors.initials: T
authors.lastname: Kutti
authors.affiliation: Sustainable Aquaculture Laboratory, Temperate and Tropical, School of BioSciences, University of Melbourne, Parkville, VIC 3010, Australia.
authors.forename: Tim
authors.initials: T
authors.lastname: Dempster
mesh_terms: D000821:Animal Feed; D000818:Animals; D017756:Aquaculture; D016718:Arachidonic Acid / Q000378:metabolism; D015118:Eicosapentaenoic Acid / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D009664:Norway; D012474:Salmon; D012617:Sea Urchins / Q000378:metabolism*
chemical_list: D005227:Fatty Acids; D016718:Arachidonic Acid; D015118:Eicosapentaenoic Acid
keywords: Aquaculture waste; Dietary tracer; Echinus acutus; Fatty acid; Linoleic acid; Trophic subsidy