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Aquaculture Environment Interactions

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AEI 11:161-179 (2019)  -  DOI:

Resilience of dynamic coastal benthic ecosystems in response to large-scale finfish farming

Nigel Keeley1,*, Thomas Valdemarsen2,3, Skye Woodcock1, Marianne Holmer2, Vivian Husa1, Raymond Bannister1

1Institute of Marine Research, 9007 Tromsø, Norway
2University of Southern Denmark, 5230 Odense, Denmark
3Danish Environmental Protection Agency, 2100 Copenhagen, Denmark
*Corresponding author:

ABSTRACT: Global expansion of salmon aquaculture is contingent upon finding new, large-capacity farming locations that are, increasingly, situated in dispersive environments with atypical ecological characteristics. The capacity of such sites to assimilate organic waste and the type and spatial extent of effects remain poorly understood. This study couples intensive spatial and temporal measurements of waste outputs with measurements of benthic ecological diversity and sediment biogeochemistry at a shallow dispersive site on the central west coast of Norway. Despite minimal visual changes to the seabed, pronounced biological effects were evident out to 600-1000 m away from the farm. Greatly enhanced faunal and microbial activity was tightly coupled with strong sediment respiratory responses in the form of oxygen uptake and ammonia efflux. The benthic response was highly dynamic, with rapid and prolific colonization by opportunistic fauna, followed by substantive recovery during the subsequent 7 mo fallowing period. The fate and pathways of farm waste through the environment was compartmentalized by converting measured parameters into equivalent carbon fluxes. During early production, approximately 30-40% of the waste was accounted for by the measured benthic processes, attributed to faunal respiratory activity and the physical properties including sediment type. Later in the production cycle, a sediment burial event was observed down-current from the farm. The remaining 60-70% of organic waste was assumed to be either assimilated in the water column, consumed by large, unquantified benthic fauna, or exported and dispersed. Shallow, dispersive sites therefore appear relatively resilient to acute near-field enrichment, but are also more likely to result in accumulative, far-field effects.

KEY WORDS: Assimilation capacity · Respiration · Atlantic salmon · Salmo salar · Organic waste · Norway

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Cite this article as: Keeley N, Valdemarsen T, Woodcock S, Holmer M, Husa V, Bannister R (2019) Resilience of dynamic coastal benthic ecosystems in response to large-scale finfish farming. Aquacult Environ Interact 11:161-179.

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