Abstract
To construct robust biogeochemical models for application to marine-based aquaculture settings, careful selection of appropriate model parameters is necessary. This study used an experimental approach to establish biomarkers of farm and marine-derived organic matter, and to derive isotopic turnover rates, and trophic discrimination factors specific to aquaculture associated food webs.
A shift towards a farm-derived resource base resulted in consumer tissues more depleted in the carbon-13 isotope (indicated by more negative δ13C values) and a higher proportion of oleic acid, linoleic acid, and alpha-linoleic acid in the fatty acid profile of consumers over time. Measured trophic discrimination factors between dietary sources and consumer tissues demonstrated high variability among species and tissue types, ranging from −0.25‰ to 0.82‰ for Δ13C and from −0.77‰ to 6.8‰ for Δ15N. Stable isotope half-lives were also diverse among species and tissue types, ranging from <7 days to 462 days.
Results demonstrated that construction of robust models for tracing assimilation of farm-derived organic matter through marine food webs requires the use of taxa and tissue specific parameters. Turnover rates have applications for understanding assimilative capacity of communities and for managing populations within the ecological footprint of farms.
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•Depleted 13C and terrestrially sourced fatty acids are biomarkers of farm-derived waste.•Trophic discrimination factors and tissue turnover rates were highly variable among consumers.•Dietary fatty acid composition was better conserved in high trophic level consumers.•Variability in parameters emphasise the importance of using taxa specific values in mixing models.•Results will aid in constructing food web models to trace assimilation of finfish-derived organics.