Consumption of aquaculture waste affects the fatty acid metabolism of a benthic invertebrate

• Published in: The Science of the total environment Vol. 586; pp. 1170 - 1181
• Main Authors: White, Camille A., Bannister, Raymond J., Dworjanyn, Symon A., Husa, Vivian, Nichols, Peter D., Kutti, Tina, Dempster, Tim
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15-05-2017
• Subjects: Animal Feed; Animals; Aquaculture; Aquaculture waste; Arachidonic Acid - metabolism; Dietary tracer; Echinus acutus; Eicosapentaenoic Acid - metabolism; Fatty acid; Fatty Acids - metabolism; Linoleic acid; Norway; Salmon; Sea Urchins - metabolism; Trophic subsidy; Trophic subsidy; Echinus acutus; Fatty acid; Dietary tracer; Aquaculture waste; Linoleic acid
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2017.02.109

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 C18 fatty 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 C18 fatty acid, low ≥C20 long-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.
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•The sea urchin Echinus acutus is commonly associated with finfish aquaculture.•Fatty acid biomarkers demonstrate E. acutus will consume aquaculture waste.•Capacity for dietary sparing and biosynthesis of long-chain fatty acids is shown.•Assimilation of aquaculture waste has been shown to affect fatty acid metabolism.•E. acutus can exploit aquaculture waste as an energy-rich subsidy.