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Abstract
To understand dispersal and assimilation of aquaculture waste subsidies in a naturally
low-productivity environment, we applied a novel, rapid transmethylation technique
to analyse sediment and biota fatty acid composition. This technique was initially
validated at Atlantic salmon farms in Macquarie Harbour, Australia, where sediments
were collected at farm and control locations. Subsequently, sediment, benthic polychaete
and zooplankton were sampled at sites 0, 50, 250, 500 and 1000m distant from multiple
cages. Results demonstrated an acute deposition zone up to 50m from cages and a diffuse
zone extending 500m from cages. Changes in sediment concentration of linoleic acid,
oleic acid and total fatty acids were effective tracers of farm deposition. Bacterial
biomarkers indicated that aquaculture waste stimulates bacterial productivity in sediments,
with elevated biomarker concentrations also detected in benthic polychaetes. Overall,
fatty acid analysis was a sensitive technique to characterize the benthic footprint
of aquaculture influence.