Capacity of deep‐sea corals to obtain nutrition from cold seeps aligned with microbiome reorganization

Abstract

Cold seeps in the deep sea harbor various animals that have adapted to utilize seepage chemicals with the aid of chemosynthetic microbes that serve as primary producers.Corals are among the animals that live near seep habitats and yet, there is a lack of evidence that corals gain benefits and/or incur costs from cold seeps. Here, we focused on Callogorgia delta and Paramuricea sp. type B3 that live near and far from visual signs of currently active seepage at five sites in the deep Gulf of Mexico. We tested whether these corals rely on chemosynthetically-derived food in seep habitats and how the proximity to cold seeps may influence; (i) coral colony traits (i.e., health status, growth rate, regrowth after sampling, and branch loss) and associated epifauna, (ii) associated microbiome, and (iii) host transcriptomes. Stable isotope data showed that many coral colonies utilized chemosynthetically derived food, but the feeding strategy differed by coral species. The microbiome composition of C. delta, unlike Paramuricea sp., varied significantly between seep and non-seep colonies and both coral species were associated with various sulfur-oxidizing bacteria (SUP05). Interestingly, the relative abundances of SUP05 varied among seep and non-seep colonies and were strongly correlated with carbon and nitrogen stable isotope values. In contrast, the proximity to cold seeps did not have a measurable effect on gene expression, colony traits, or associated epifauna in coral species. Our work provides the first evidence that some corals may gain benefits from living near cold seeps with apparently limited costs to the colonies. Cold seeps provide not only hard substrate but also food to coldwater corals. Furthermore, restructuring of the microbiome communities (particularly SUP05) is likely the key adaptive process to aid corals in utilizing seepage-derived carbon. This highlights that those deep-sea corals may upregulate particular microbial symbiont communities to cope with environmental gradients.

Probiotics reshape the coral microbiome in situ without detectable off-target effects in the surrounding environment

“…The seawater bacterial community displayed more variability over while the sediment bacterial community remained stable across sampling times. Coral reefs harbor heterogeneous microbial communities in different niches within the ecosystem [113][114][115][116][117][118] . It is widely known that the surrounding microbiomes are distinct from the coral microbiome and exhibit different bacterial community profiles with differential functionality 50,[119][120][121][122][123][124] .…”

Localization and symbiotic status of probiotics in the coral holobiont

“…Quick response and shifts that are correlated with environmental conditions ( 85 ), microbial succession and indirect effects ( 84 , 86 ), and short-term colonization ( 87 , 88 ) are, in fact, some of the main premises of the effectiveness of using probiotics (i.e., microbiomes are flexible ( 10 , 89 ), as well as a safety advantage ( 90 ). It is important to note that probiotic-treated corals were still affected by palling, at significantly lower rates, and past experiments have also shown a faster recovery rate of probiotic-treated corals impacted by heat stress ( 15 ). Probiotics can be used as customized medicine when they are needed (e.g., during a heatwave) ( 91 ), minimizing mortality and retaining native colonies while other solutions are developed and applied.…”

“…Symbiotic microbial communities support the functioning of most living organisms through different beneficial mechanisms, such as increasing input of nutrients, protection against pathogens, removal of toxic compounds, and support in reproduction and early development ( 13 ). Coral-associated microorganisms, more specifically, can inhibit the proliferation of pathogens ( 14 ), provide nutrients to their host ( 15 , 16 ), remove harmful reactive oxygen species (ROS) ( 17 ) excessive DMSP ( 18 ), or hydrocarbons ( 19 , 20 ), and participate in larvae settlement ( 21 , 22 ).…”