Abstract
Turfs are widespread assemblages (consisting of microbes and algae) that inhabit reef systems. They are the most abundant benthic component in the Abrolhos reef system (Brazil), representing greater than half the coverage of the entire benthic community. Their presence is associated with a reduction in three-dimensional coral reef complexity and decreases the habitats available for reef biodiversity. Despite their importance, the taxonomic and functional diversity of turfs remain unclear. We performed a metagenomics and pigments profile characterization of turfs from the Abrolhos reefs. Turf microbiome primarily encompassed Proteobacteria (mean 40.57% ± s.d. 10.36, N = 1.548,192), Cyanobacteria (mean 35.04% ± s.d. 15.5, N = 1.337,196), and Bacteroidetes (mean 11.12% ± s.d. 4.25, N = 424,185). Oxygenic and anoxygenic phototrophs, chemolithotrophs, and aerobic anoxygenic phototrophic (AANP) bacteria showed a conserved functional trait of the turf microbiomes. Genes associated with oxygenic photosynthesis, AANP, sulfur cycle (S oxidation, and DMSP consumption), and nitrogen metabolism (N2 fixation, ammonia assimilation, dissimilatory nitrate and nitrite ammonification) were found in the turf microbiomes. Principal component analyses of the most abundant taxa and functions showed that turf microbiomes differ from the other major Abrolhos benthic microbiomes (i.e., corals and rhodoliths) and seawater. Taken together, these features suggest that turfs have a homogeneous functional core across the Abrolhos Bank, which holds diverse microbial guilds when comparing with other benthic organisms.
Highlights
Turfs represent one of the most abundant benthic functional groups in the Atlantic, Caribbean, and Pacific reefs; there have been a limited number of studies characterizing the microbial composition of turfs [1,2,3,4,5,6,7]
Bacteria that are pathogenic to corals in the turf can kill the corals, which serve as substrates for turf spreading [16]
Microscopic analyses revealed that the turf assemblages were composed of filamentous, non-heterocystous cyanobacteria in a network with embedded seaweeds
Summary
Turfs represent one of the most abundant benthic functional groups in the Atlantic, Caribbean, and Pacific reefs; there have been a limited number of studies characterizing the microbial composition of turfs [1,2,3,4,5,6,7]. A marked turf spread has been observed over the last decade, potentially reflecting a phase shift process [11]. In this process, a decrease in the abundance of herbivorous fish leads to an increase in turf cover [12], [13]. Previous studies have not addressed the functional metagenomic diversity of turfs. It is currently unclear whether turfs have a specific stable microbiome or several types of turf microbiomes co-existing in the same reef system
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