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Add To Calendar 07/10/2021 10:20:0007/10/2021 10:40:00Europe/LisbonAquaculture Europe 2021THE GILL MICROBIOTA COMPOSITION IN SEA FARMED ATLANTIC SALMON Salmo salar: LOCATION MATTERSSidney-HotelThe European Aquaculture Societywebmaster@aquaeas.orgfalseDD/MM/YYYYaaVZHLXMfzTRLzDrHmAi181982

THE GILL MICROBIOTA COMPOSITION IN SEA FARMED ATLANTIC SALMON Salmo salar: LOCATION MATTERS

Costelloe, E.1 , Douglas, A.1 , Lorgan-Richie , M.1 , Valdenegro, V.2 , Bickerdike, R.3 , Noguera, P.4 , Król, E.1 and Martin, S.A.M.1

1Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK

2 BioMar AS, Pb 1282 Sluppen, N-7462 Trondheim, Norway

3 Scottish Sea Farms, Laurel House, Laurelhill Business Park, Stirling, FK7 9JQ, UK

4  Health and Welfare, Marine Scotland Science, Aberdeen, UK

 Email: e.costelloe.18@abdn.ac.uk

 



Introduction

 There is a growing interest in  the gill health of economically important species such as Atlantic salmon ( Salmo salar) as this  organ  is central to  many  physiological functions  and overall fish performance. As a mucosal surface , gills  can be colonised by pathogens and  act as a site of pathogen entry . Numerous pathogens and environmental factors contribute to  the gill inflammation, but the underlying response mechanisms to  the disease are poorly understood. The terms “c omplex g ill disorder” (CGD) and “p roliferative g ill disease” (PGD) reflect the complexity and multifactorial aetiology of gill inflammation. Microbiota  associated  with the  gill  mucosal surface that  remain in homeostasis  are  believed to be  an essential part of  the gill  immunity and health. Over the last decade, the  interaction between microbiota and mucosal immunity has become an active  field of research, aiming to improve understanding of gill health. The main objective of this study is to further our understanding of gill health in Sea farmed Atlantic salmon.

Materials and methods

 We sampled Atlantic salmon from three different marine production sites in Scotland (A on Isle of Mull and B and C in Shetland) and examined the gills at three different levels of organization: gross morphology with the use of PGD scores (macroscopic examination), histopathology (microscopic examination) and microbial community composition (samples and other parameters fully described in Król et al. 2020) . Gill mucus swabs were taken from 75 fish in total  and used to extract DNA.  Gill microbiota composition  was  evaluated by sequencing the V3/V4 variable region of the bacterial 16S using an Illumina MiSeq platform, followed by analysis of a mplicon sequence variants (ASVs)  with a DADA2 pipeline 

 . Functionality was inferred using Piphillin (Iwai et al. 2016).

Results

 Fish from  the three  different sites  (A, B and C) had significantly different gill microbiota composition (p < 0.001, Fig. 1) . The dominant gill microbial phyla  were Actinobacteria , Bacteroidetes , Firmicutes and Proteobacteria, which is  consistent  with other  salmonid studies (Brown et al., 2019) .  Site C, which  had lower  gill histopathology scores than sites A and B (Król et al. 2020) ,  was characterised by significantly higher alpha diversity indices. All three sites were clearly separated by beta diversity . Despite the differences, all fish had a core gill microbiota  that was shared between the  sites.   The functional analysis of the gill microbiota composition revealed  the  differences associated with  the  metabolic pathways.

Discussion and conclusions

The d iversity of the gill  microbiota composition  was  predominantly associated with the origin of fish (sites A, B and C) , suggesting the importance of spatial  and temporal drivers in shaping gill microbiota and gill health .  Gill microbiota diversity was the highest in the fish with the lowest histopathology scores (site C), although the causality of this observation remains unknown. Oppositely ,  fish with the decreased gill microbiota diversity had higher  gill  histopathology scores (sites A and B). The relationship between gill microbiota composition and gill histopathology  as well as their impacts on gill health require further studies.

References:

BROWN, R.M. , WIENS., G.D., and SALINAS., I. 2019. Analysis of the gut and gill microbiome of resistant and susceptible lines of rainbow trout. Fish and Shellfish Immunology 86(3), 497-506.

 CALLAHAN, B.J., MCMURDIE, P.J., ROSEN, M.J., HAN, A.W., JOHNSON, A.J.A. and HOLMES, S.P., 2016. DADA2: High-resolution sample inference from Illumina amplicon data.  Nature Methods, 13(7), pp. 581-583.

 IWAI, S., WEINMAIER, T., SCHMIDT, B.L., ALBERTSON, D.G., POLOSO, N.J., DABBAGH, K. and DESANTIS, T.Z., 2016. Piphillin : Improved Prediction of Metagenomic Content by Direct Inference from Human Microbiomes.  PLOS ONE, 11(11), pp. e0166104.

KRÓL, E., NOGUERA, P., SHAW, S., COSTELLOE, E., GAJARDO., K., VALDENEGRO, V., BICKERDIKE, R., DOUGLAS, A. ,  and MARTIN, SAM., 2020. Integration of transcriptome, gross morphology and histopathology in the gill of sea farmed Atlantic Salmon (Salmo salar ): Lessons from multi-site sampling. Frontiers in Genetics, 11, 610.