Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 773, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.scitotenv.2021.145146
Keywords
Aquaculture; Organic matter flux; Depositional footprint; Biochemical tracer; Fatty acid; Stable isotope
Categories
Funding
- Sustainable Seas National Science Challenge [Ecosystem Connectivity], New Zealand
- University of Otago Doctoral Scholarship, New Zealand
- Todd Foundation Award for Excellence, New Zealand
- Claude McCarthy Fellowship, New Zealand
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This study investigated the impact of salmon farms on soft sediment communities, revealing the biochemical and biomass characteristics of organic matter subsidies and farm activities for soft sediment organisms. The results showed that basal organic matter assimilation and trophic levels of soft sediment communities varied with distance from the farms.
Local differences in trophic structure and composition of organic matter subsidies can influence the capacity of soft sediment communities to assimilate recycled organic matter from processes such as salmon farm enrichment. The present study combines biochemical analysis with biomass density information on soft sediment taxa collected within the depositional footprint of salmon farms and at reference sites in the Marlborough Sounds, New Zealand. Distinct biochemical signatures confirmed that the flux of organic matter from salmon farms was an important subsidy for soft sediment communities. Isotopic modelling demonstrated that the proportion of biomass supported by farm-derived organic matter did not change in a consistent pattern along the 300m gradient from each farm site, whereas the average trophic level of communities decreased with increasing proximity to farms. High variability in both the total biomass and the distribution of biomass across trophic levels occurred among sites downstream of farms and among individual farms. Consequently, estimates of basal organic matter assimilation per unit area by communities differed by several orders of magnitude among sites. Total organic matter assimilation tended to decrease with increasing proximity to farms due to a shift towards a more detrital based community. Differences in basal organic matter assimilation among farms did not appear to be directly related to local flow regime, but instead was closely linked to differences in the soft sediment community composition likely influenced by an array of anthropogenic and environmental factors. The results presented here highlight the importance of considering local variability in basal organic matter source pools, and the potential for synergistic and cumulative effects to drive changes in food web trophodynamics when assessing the impacts of aquaculture on soft sediment communities. (C) 2021 Elsevier B.V. All rights reserved.
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