Mediterranean Sea heatwaves jeopardize greater amberjack’s (Seriola dumerili) aquaculture productivity through impacts on the fish microbiota

Abstract

Climate change is dramatically increasing the frequency and severity of marine heatwaves (MHWs) in the Mediterranean basin, strongly affecting marine food production systems. However, how it will shape the ecology of aquaculture systems, and the cascading effects on productivity, is still a major knowledge gap. The present work aims to increase our understanding of future impacts, caused by raising water temperatures, on the interaction between water and fish microbiotas, and consequential effects upon fish growth. Thus, the bacterial communities present in the water tanks, and mucosal tissues (skin, gills and gut), of greater amberjack farmed in recirculatory aquaculture systems (RAS), at three different temperatures (24, 29 and 33 °C), were characterized in a longitudinal study. The greater amberjack (Seriola dumerili) is a teleost species with high potential for EU aquaculture diversification due to its fast growth, excellent flesh quality and global market. We show that higher water temperatures disrupt the greater amberjack’s microbiota. Our results demonstrate the causal mediation exerted by this bacterial community shifts on the reduction of fish growth. The abundance of members of the Pseudoalteromonas is positively correlated with fish performance, whereas members of the Psychrobacter, Chryseomicrobium, Paracoccus and Enterovibrio are suggested as biomarkers for dysbiosis, at higher water temperatures. Hence, opening new evidence-based avenues for the development of targeted microbiota-based biotechnological tools, designed to increase the resilience and adaptation to climate change of the Mediterranean aquaculture industry.

The pathogen Vibrio alginolyticus H1 and its antagonist Pseudoalteromonas piscicida H2 associated with the health status of cuttlefish Sepia pharaonis

“…Meanwhile, Pseudoalteromonas isolates have been generally considered to be involved in predator-like interactions within the microbial loop, and to be used as a defense agent against pathogens in marine fauna [42] . Therefore, the emergence of P. piscicida H2 only in healthy cuttlefish indicated that P. piscicida H2 is healthful for cuttlefish, which is similar to the previous researches that the abundance of members of the Pseudoalteromonas is positively correlated with fish healthy stage [43] . Thus, it could be postulated that the balance of V. alginolyticus H1 and P. piscicida H2 is closely related to the health status of cuttlefish.…”

Influence of host phylogeny and water physicochemistry on microbial assemblages of the fish skin microbiome

“…For saltwater fish, alpha diversity increased with a more basic pH, higher salinity, and dO 2 concentration but decreased at higher temperatures. Studies assessing the effect of physicochemical factors on fish skin microbiomes have similarly shown that exposure to high temperatures results in decreases in alpha diversity over time and differences in beta diversity in saltwater greater amberjack ( Seriola dumerili ) (Sánchez-Cueto et al 2023 ) and in chum salmon ( Oncorhynchus keta ) (Ghosh et al 2022 ). Studies on the flag cichlid ( Mesonauta festivus) and black piranha ( Serrasalmus rhombeus) found no effects of pH on skin microbiomes (Sylvain et al 2019 ), however, in Tambaqui ( Colossoma macropomum ) (data included within this study) exposure to a low pH (pH 4.0) compared to control (pH 6.3) resulted in changes in fish skin beta diversity, but not alpha diversity (Sylvain et al 2016 ).…”

“…There have been far fewer studies, however, examining the microbiota in fish skin (Gomez and Primm 2021 , Wang et al 2023 , Berggren et al 2022 ). Understanding the composition of fish skin microbiomes and the dynamics in response to environmental conditions will help establish their associations with health and disease (Berggren et al 2022 , Debnath et al 2023 ) and in turn, optimize aquaculture practices (Palladino et al 2021 , Sánchez-Cueto et al 2023 ). To date, there has been relatively little exploration of how skin microbiomes are affected by water physicochemical or biological stressors.…”