Impacts on microbial communities in sediment by aquaculture farming during one salmon cycle

In recent years, the salmon farming industry has grown significantly worldwide, and in the Faroe Islands, it has become a major industry with an annual production of over 94,000 tonnes, yielding 24% of the GDP. According to environmental regulations, the ocean floor is monitored during every production cycle at all farming sites, involving macrofaunal, sensory, and chemical analyses. However, the impact of farming activity on microorganisms in the Faroe Islands remains unknown. This study aimed to assess the impact of Atlantic salmon farming on benthic microbial communities, giving a better understanding of the effects on the foundation of the benthic food web and to assess if these are more prone to environmental impact than traditional macrofaunal biomonitoring. Sediment cores were sampled along a transect from directly below the salmon cages to a background reference site. The sampling occurred prior to the release of salmon into the cages (‘before stocking’) and immediately before t..., Sample collection and preparation
Sediment samples were collected on the 25th of September 2019 and 15th July 2020 at the fish farming area A-83 in Sørvágar, Faroe Islands (Figure 1). The first sampling effort was conducted after a three-month fallowing period, and the second sampling effort was carried out when the salmon biomass was at its highest.
Starting from the cage station RS20, six stations were sampled along a transect (Figure 1). The first station was collected directly at the periphery of the cage (0 m), and then approximately at 12 m, 40 m, 150 m, 190 m, and 600 m from RS20. The transect into the fjord follows the prevailing current direction, measured approximately 225 m west of the farm (Norði et al., 2023) (Figure 1). The sampling station at 600 meters was designated as a background sample, based on findings from a study indicating that the maximum impact range of organic enrichment from fish farms in Faroese fjords is 200 m (Mortensen et al., 2021). Our background site,..., , # Impacts on microbial communities in sediments by aquaculture farming during one salmon cycle

**DOI:** 10.3389/fmars.2024.1266410

#### Authors:

Bjarta O. Johansen
Environmental Department, SMJ Consulting Engineers, Tórshavn, Faroe Islands.
Faculty of Science and Technology, University of the Faroe Islands, Tórshavn, Faroe Islands.
[[e-mail]](mailto:[e-mail])

Svein-Ole Mikalsen
Faculty of Science and Technology, University of the Faroe Islands, Tórshavn, Faroe Islands.

Eyðfinn Magnussen
Faculty of Science and Technology, University of the Faroe Islands, Tórshavn, Faroe Islands.

Esbern J. Patursson
Department of Sea Farming, Hiddenfjord, Sandavágur, Faroe Islands

Gunnvør Á Norði
Department of Ecology, Firum, Hvalvík, Faroe Islands

Anni Djurhuus
Faculty of Science and Technology, University of the Faroe Islands, Tórshavn, Faroe Islands.
[[e-mail]](mailto:[e-mail])

### Sampling in A83 Sørvágur, before stocking and peak biomass

[https://doi.org/1...