A recent study published in Frontiers in Marine Science, the third most-cited journal in marine and freshwater biology, has shed new light on the impact of salmon farming on the seabed.
The research, conducted by a team from the University of the Faroe Islands, examined the effects of a full salmon farming cycle on the benthic microbial communities that form the foundation of marine ecosystems.
The study revealed that microbial community structures in sediments beneath salmon farms undergo considerable changes throughout the farming cycle. These changes were most pronounced near the salmon cages, where microbial diversity was found to decrease significantly as the cycle progressed.
The accumulation of organic matter (OM) from salmon waste and uneaten feed, which intensifies as the salmon grow, was identified as a key factor driving these shifts.
Three months not enough?
One of the critical findings highlighted by the researchers is that the current three-month fallowing period—intended to allow the seabed to recover—may be insufficient.
The study observed that microbial communities had not fully reverted to their pre-farming state even before new salmon were introduced, suggesting that the seabed may still be impacted by previous farming activities.
The research advocates for the inclusion of microbial DNA metabarcoding as a standard component of environmental monitoring protocols in aquaculture. Microbial communities, which respond more rapidly to environmental changes than larger organisms, could serve as more sensitive indicators of the health of aquaculture sites. This approach could offer a more accurate and comprehensive assessment of the environmental impact of salmon farming, according to the paper.
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The study also suggests that relocating farming operations to more exposed locations with stronger currents could help disperse organic waste more effectively, thereby reducing environmental impacts.
