Relative abundance of nitrogen cycling microbes in coral holobionts reflects environmental nitrate availability
El-Khaled, Yusuf C.
Voolstra, Christian R.
KAUST DepartmentMarine Science Program
Biological and Environmental Sciences and Engineering (BESE) Division
Red Sea Research Center (RSRC)
Permanent link to this recordhttp://hdl.handle.net/10754/669363
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AbstractRecent research suggests that nitrogen (N) cycling microbes are important for coral holobiont functioning. In particular, coral holobionts may acquire bioavailable N via prokaryotic dinitrogen (N2) fixation or remove excess N via denitrification activity. However, our understanding of environmental drivers on these processes in hospite remains limited. Employing the strong seasonality of the central Red Sea, this study assessed the effects of environmental parameters on the proportional abundances of N cycling microbes associated with the hard corals Acropora hemprichii and Stylophora pistillata. Specifically, we quantified changes in the relative ratio between nirS and nifH gene copy numbers, as a proxy for seasonal shifts in denitrification and N2 fixation potential in corals, respectively. In addition, we assessed coral tissue-associated Symbiodiniaceae cell densities and monitored environmental parameters to provide a holobiont and environmental context, respectively. While ratios of nirS to nifH gene copy numbers varied between seasons, they revealed similar seasonal patterns in both coral species, with ratios closely following patterns in environmental nitrate availability. Symbiodiniaceae cell densities aligned with environmental nitrate availability, suggesting that the seasonal shifts in nirS to nifH gene abundance ratios were probably driven by nitrate availability in the coral holobiont. Thereby, our results suggest that N cycling in coral holobionts probably adjusts to environmental conditions by increasing and/or decreasing denitrification and N2 fixation potential according to environmental nitrate availability. Microbial N cycling may, thus, extenuate the effects of changes in environmental nitrate availability on coral holobionts to support the maintenance of the coral–Symbiodiniaceae symbiosis.
CitationTilstra, A., Roth, F., El-Khaled, Y. C., Pogoreutz, C., Rädecker, N., Voolstra, C. R., & Wild, C. (2021). Relative abundance of nitrogen cycling microbes in coral holobionts reflects environmental nitrate availability. Royal Society Open Science, 8(6), 201835. doi:10.1098/rsos.201835
SponsorsWe thank KAUST CMOR staff and boat crews for their support with diving operations. We thank Nauras Daraghmeh for his support with re-analysing environmental parameter data.
Financial support was provided by KAUST baseline funds to C.R. Voolstra and the German Research Foundation (DFG) grant nos. Wi 2677/9-1 and Wi 2677/16-1 to C.W.
PublisherThe Royal Society
JournalRoyal Society Open Science
Except where otherwise noted, this item's license is described as © 2021 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License, which permits unrestricted use, provided the original author and source are credited.