Invertebrate uptake of lipids in the vicinity of Atlantic salmon (Salmo salar) aquaculture sites in British Columbia

Abstract

Samples of invertebrates, primary producers, seawater and cores were taken surrounding several aquaculture sites in coastal British Columbia, Canada. Analysis of dissolved organic carbon (DOC) showed a significant decrease (P = 0.027) over 1 km and an overall average of 290 ± 40 μM at 1 m depth. At 10 m, the decrease was not significant and DOC averaged 81 ± 3 μM. The essential fatty acid 22:6ω3 (docosahexaenoic acid, DHA) was significantly lower nearer to the farm sites for all mollusc taxa as well as for mussels alone (P < 0.01). However, mussel wet weight as well as the zooplankton fatty acid marker (ZFA; Σ 20:1ω9, 22:1ω11, 22:1ω9) and 20:1ω9 individually, decreased significantly with distance from the farms (P < 0.03). Principal components analysis showed a similar trend with DHA being higher in molluscs further from the farm. Mussels had significantly higher amounts of DHA compared with other molluscs indicating their potential in multi-trophic, co-culturing systems. Bacterial fatty acid markers increased in molluscs with distance from the farms; however, 18:1ω7, which is representative of methane-oxidizing bacteria, remained higher closer to the farm. In addition, DHA proportions in mussels showed a significant breakpoint at 339 m from the farm suggesting co-cultured mussels would benefit from placement further than 339 m from farms where DHA would be optimized.