Natural volcanic CO2 seeps reveal future trajectories for host–microbial associations in corals and sponges

Abstract

Atmospheric carbon dioxide (CO2) levels are rapidly rising causing an increase in the partial pressure of CO2 (pCO2) in the ocean and a reduction in pH known as ocean acidification (OA). Natural volcanic seeps in Papua New Guinea expel 99% pure CO2 and thereby offer a unique opportunity to explore the effects of OA in situ. The corals Acropora millepora and Porites cylindrica were less abundant and hosted significantly different microbial communities at the CO2 seep than at nearby control sites <500 m away. A primary driver of microbial differences in A. millepora was a 50% reduction of symbiotic Endozoicomonas. This loss of symbiotic taxa from corals at the CO2 seep highlights a potential hurdle for corals to overcome if they are to adapt to and survive OA. In contrast, the two sponges Coelocarteria singaporensis and Cinachyra sp. were ∼40-fold more abundant at the seep and hosted a significantly higher relative abundance of Synechococcus than sponges at control sites. The increase in photosynthetic microbes at the seep potentially provides these species with a nutritional benefit and enhanced scope for growth under future climate scenarios (thus, flexibility in symbiosis may lead to a larger niche breadth). The microbial community in the apparently pCO2-sensitive sponge species S. massa was not significantly different between sites. These data show that responses to elevated pCO2 are species-specific and that the stability and flexibility of microbial partnerships may have an important role in shaping and contributing to the fitness and success of some hosts.

Allelochemicals Produced by Brown Macroalgae of the Lobophora Genus Are Active against Coral Larvae and Associated Bacteria, Supporting Pathogenic Shifts to Vibrio Dominance

“…has been shown to decline significantly. For example, when exposed to high-partial (pCO 2 ) pCO 2 / low-pH conditions found in naturally occurring CO 2 seeps in Papua New Guinea, the coral Acropora millepora demonstrated a 50% reduction in Endozoicomonas-related bacteria in comparison to ambient control sites (55). Furthermore, microbial communities associated with apical lesions on colonies of Belizean P. astreoides were found to be more diverse and harbored a significantly lower relative abundance of OTUs related to Endozoicomonas spp.…”

Responses of Coral-Associated Bacterial Communities to Local and Global Stressors

“…Not only might the observed decrease in these potentially symbiotic taxa during stress events threaten coral resistance to stress, it also may influence coral resilience after the stress is alleviated if Endozoicomonas does not return to its original abundance and function. In a study of volcanic CO 2 seeps where the seawater has naturally reduced pH, researchers found that Acropora millepora and Porites cylindrica contained significantly different microbial communities compared to the same coral species at a control site (>500 m away); for A. millepora this was mainly due to a 50% decrease of this proposed mutualist Endozoicomonas (Morrow et al, 2015). These coral species were also less abundant at the volcanic seeps, potentially due to this loss of symbiont in their microbiomes.…”

Marine Animal Microbiomes: Toward Understanding Host–Microbiome Interactions in a Changing Ocean

“…The gammaproteobacterium Endozoicomonas is emerging as a central member of the coral's microbiome, with flexibility in its lifestyle ( Figure 3D) (Neave et al, 2016(Neave et al, , 2017. Ocean disturbances including elevated temperature and ocean acidification have been shown to disrupt the coral's associated bacteria (Thurber et al, 2009;Meron et al, 2011), including relationships with Endozoicomonas (Morrow et al, 2015). However, some members of this microbiome appear to be stable across large environmental gradients (Hernandez-Agreda et al, 2016).…”