Abstract
The large canopy-forming macroalga, Sargassum ilicifolium, provides shelter and food for numerous coral reef species, but it can also be detrimental at high abundances where it outcompetes other benthic organisms for light and space. Here, we investigate the microbial communities associated with S. ilicifolium in Singapore, where it is an abundant and important member of coral reef communities. We collected eight complete S. ilicifolium thalli from eight island locations along an approximate 14 km east-to-west transect. Each thallus was dissected into three separate parts: holdfast, vesicles, and leaves. We then characterized the bacterial communities associated with each part via polymerase chain reaction (PCR) amplification of the 16S rRNA gene V4 region. We then inferred predicted metagenome functions using METAGENassist. Despite the comparatively short distances between sample sites, we show significant differences in microbial community composition, with communities further differentiated by part sampled. Holdfast, vesicles and leaves all harbor distinct microbial communities. Functional predictions reveal some separation between holdfast and leaf communities, with higher representation of sulphur cycling taxa in the holdfast and higher representation of nitrogen cycling taxa in the leaves. This study provides valuable baseline data that can be used to monitor microbial change, and helps lay the foundation upon which we can begin to understand the complexities of reef-associated microbial communities and the roles they play in the functioning and diversity of marine ecosystems.
Highlights
Introduction published maps and institutional affilThe macroalga, Sargassum ilicifolium (Phaeophyceae: Sargassaceae), is a large and abundant canopy-forming brown seaweed found throughout the coral reefs of Singapore.It provides habitat and food for numerous reef-associated species [1,2], and at high abundances it can be a competitor with other benthic organisms for light and space [3]
Sargassum ilicifolium thalli were collected over two days in January 2018 from each of the eight islands (Figure 1)
principal coordinate analysis (PCoA) plots for the combined data across all structures show that microbial communities associated with the holdfast are distinct from leaves and vesicles, while plots by individual structure suggest weak differentiation by island locations generally (Figure 2)
Summary
The macroalga, Sargassum ilicifolium (Phaeophyceae: Sargassaceae), is a large and abundant canopy-forming brown seaweed found throughout the coral reefs of Singapore. It provides habitat and food for numerous reef-associated species [1,2], and at high abundances it can be a competitor with other benthic organisms for light and space [3]. Microbial associations with algae are ubiquitous in marine systems [4,5,6,7,8,9] These associations help improve host fitness and in return the host provides habitat, carbohydrates and other nutrients along with oxygen that can be used by bacteria [10]. This contact can be detrimental to benthic organisms via indirect mechanisms, such as smothering, abrasion, shading [15,16], and direct mechanisms, iations
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