In:
The ISME Journal, Springer Science and Business Media LLC, Vol. 16, No. 1 ( 2022-01), p. 233-246
Abstract:
The role of diazotrophs in coral physiology and reef biogeochemistry remains poorly understood, in part because N 2 fixation rates and diazotrophic community composition have only been jointly analyzed in the tissue of one tropical coral species. We performed field-based 15 N 2 tracer incubations during nutrient-replete conditions to measure diazotroph-derived nitrogen (DDN) assimilation into three species of scleractinian coral ( Pocillopora acuta , Goniopora columna , Platygyra sinensis ). Using multi-marker metabarcoding (16S rRNA, nifH , 18S rRNA), we analyzed DNA- and RNA-based communities in coral tissue and skeleton. Despite low N 2 fixation rates, DDN assimilation supplied up to 6% of the holobiont’s N demand. Active coral-associated diazotrophs were chiefly Cluster I (aerobes or facultative anaerobes), suggesting that oxygen may control coral-associated diazotrophy. Highest N 2 fixation rates were observed in the endolithic community (0.20 µg N cm −2 per day). While the diazotrophic community was similar between the tissue and skeleton, RNA:DNA ratios indicate potential differences in relative diazotrophic activity between these compartments. In Pocillopora , DDN was found in endolithic, host, and symbiont compartments, while diazotrophic nifH sequences were only observed in the endolithic layer, suggesting a possible DDN exchange between the endolithic community and the overlying coral tissue. Our findings demonstrate that coral-associated diazotrophy is significant, even in nutrient-rich waters, and suggest that endolithic microbes are major contributors to coral nitrogen cycling on reefs.
Type of Medium:
Online Resource
ISSN:
1751-7362
,
1751-7370
DOI:
10.1038/s41396-021-01054-1
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2022
detail.hit.zdb_id:
2299378-2
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