Abstract
Sustained growth of world-wide sea farming and the search of optimal growing conditions have driven several countries, including Norway, to establish new finfish sites in more exposed, high current locations. Characterized by a range of gravel, broken rock and/or bedrock, these complex environments and the associated diverse range of epifauna species are not easily monitored via traditional methodologies (e.g. morpho-taxonomic identification and enumeration, and compound analyses of sediment grabs). Consequently, little is known about many of the benthic inhabitants, or how they may respond to fish farming. In this study, we aimed to initiate addressing this knowledge gap by assessing the response of the sponge Weberella bursa (Polymastidea) to salmon aquaculture. Fourteen specimens were translocated along a distance gradient from a salmon farm located along the mid-west coast of Norway. Following 7 months of exposure, their epithelial tissue were analysed for gene expression analysis (mRNA), fatty acid (FA), stable isotope and taxonomic and functional microbiome characterization. Among all datasets, only fatty acid profiles showed significant changes associated with fish farm activities, with higher proportion of terrestrial FAs and long saturated and monounsaturated FAs near the farm. These results suggest that W. bursa sponges may be more resistant to organic enrichment than previously thought. Nonetheless, several putative indicators of non-lethal response could be identified. Specifically, W. bursa specimens located underneath the farm tended to have reduced ribosomal activity while having increased expression of genes controlling cell apoptosis (e.g. caspase-3, cytochrome c oxidase and death domain proteins). Based on predictive functional analysis, specimens near to the farm were also found to be particularly enriched in sulfur and nitrogen cycling bacteria, and in microbial taxa with anti-toxin and xenobiotic biodegradation capability, notably of benzyl benzoate compounds used in sea lice treatments. These results indicate that potentially harmful elements such as sulfite, nitrite and pesticides may be neutralized and degraded by a particularly enriched set of bacteria in W. bursa microbiome. While additional research is needed to validate these putative indicators, our study provides a first glimpse as to how sessile organisms may respond and adapt to environmental changes induced by fin fish farming, and pave the way to the development of novel monitoring tools adapted to mix and hard bottom habitats.
Highlights
In recent years, the sustained growth of world-wide sea farming (FAO 2018) and the pursuit of optimal growing conditions have led countries such as Norway to locate new production sites, traditionally placed in sheltered locations, in more exposed and high current areas (Holmer, 2010; Lader et al, 2017; Lekang et al, 2016)
Based on predictive functional analysis, specimens near to the farm were found to be enriched in sulfur and nitrogen cycling bacteria, and in microbial taxa with anti-toxin and xenobiotic biodegradation capability, notably of benzyl benzoate compounds used in sea lice treatments
While additional research is needed to validate these putative indicators, our study provides a first glimpse as to how sessile organisms may respond and adapt to environmental changes induced by fin fish farming, and pave the way to the development of novel monitoring tools adapted to mix and hard bottom habitats
Summary
The sustained growth of world-wide sea farming (FAO 2018) and the pursuit of optimal growing conditions have led countries such as Norway to locate new production sites, traditionally placed in sheltered locations, in more exposed and high current areas (Holmer, 2010; Lader et al, 2017; Lekang et al, 2016). These more complex environments usually support greater biodiversity than their soft bottom counterpart (Buhl-Mortensen et al, 2012; Dunlop et al, 2020; Sebens, 1991), yet little is known about the effect of fish farming induced organic enrichment on these types of benthic communities (Dunlop et al, 2020; Holmer, 2010; Salvo et al, 2017; Taranger et al, 2015) This information gap is due to the contemporary nature of the situation, and the challenges associated with monitoring hard-bottom habitats with traditional methodologies (e.g. morpho-taxonomic identification and numeration, compound an alyses of sediment grabs, Dunlop et al, 2020). The ability to detect signs of stress in individuals provides a potential early warning mechanism of sub-lethal effects that may prevent the subsequent loss of potentially valuable ecological assemblages
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
