Can aquaculture impact the surrounding biodiversity? A metabarcoding assessment

Abstract

World’s population growth and rise in food consumption per capita have led to increased food demand and overexploitation of natural resources in recent decades. Such increase has threatened the global feeding schemes to maintain a balance between food supply and demand. Although “The Blue Revolution” promised to fill such gap and simultaneously alleviate the overexploitation of the oceans, deterioration of biota in the surrounding marine environment from aquaculture pollution has been reported. To investigate the effects of this pollution in the biodiversity of benthic communities, I applied a metabarcoding surveillance method before and after the establishment of a salmon aquaculture facility at Dyrøya Island, Norway. Twelve monitoring stations were established and divided into three transects, each containing four stations at increasing distance from the cages. To distinguish the patterns of impact, I estimated alpha and beta diversity for each station using two metabarcoding markers (COI and 18S). Analysis showed a significant increase of alpha biodiversity after the establishment of the aquaculture where such increase occurred only in the North transect (aligned with the main current) at all distances from the cages. Alpha diversity analysis suggested that the spread of impact was heterogeneous throughout the transects and homogeneous throughout the sampled distances. Significant differences in community composition and beta diversity (only for COI marker) after the establishment of the aquaculture were observed. The spread of such change occurred homogeneously among all the monitoring stations, transects and distances from the cages. These findings support the hypothesis that the establishment of the aquaculture activities, alone, did not lead to these changes in beta diversity, which could rather be a result of seasonal variability. This study stresses the need for high sequencing depth, broad study area, and a combination of traditional surveys with metabarcoding approaches when conducting molecular biodiversity assessments.