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Taxonomic and functional microbial dynamics of Sargassum surface biofilms and their response to the coral reef environment
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Abstract(s)
Sargassum é uma macroalga frondosa com uma distribuição global ampla em recifes temperados
e tropicais. Esta alga providencia habitat e refúgio a diversas espécies marinhas, mas também
afecta outras negativamente. Apesar da sua importância ecológica, muito pouco se sabe sobre a
vida microbiana nas superfícies de Sargassum. Através do estudo das comunidades microbianas
presentes no biofilme da alga Sargassum sp., em paralelo com a água e o sedimento, ao longo
de uma série temporal, pretende-se com este estudo entender as dinâmicas de sucessão
microbianas do biofilme de Sargassum sp. e de que forma a comunidade microbiana se altera
com as alterações ambientais. A amostragem de Sargassum sp., sedimento e água foi feita em
Magnetic Island, na Grande Barreira de Coral na Australia, ao longo de um periodo de 13 meses.
A sequenciação do gene 16S do rRNA de 30 amostras de Sargassum sp., usando a tecnologia
Illumina, permitiu uma análise aprofundada da diversidade taxonomica do biofilme, ao mesmo
tempo que o possível perfil funcional de taxa bacterianos chave, foi aferido usando o programa
FAPROTAX. A implementação de análise estatística multivariada de ordenação, análises de
correlação e estatísticas de abundância diferencial, permitiram investigar a resposta das
comunidades bacterianas a parâmetros ambientais abióticos tais como: temperatura e
nutrientes orgânicos e inorgânicos. Os biofilmes de Sargassum sp. revelaram estar dominados
por bactérias dos Filos Firmicutes (23-45%), Proteobacteria (35-38%) e Bacteroidetes (13-30%)
com diferenças observadas entre o Inverno e o Verão. As comunidades bacterianas da água e do
sedimento mantiveram-se estáveis ao longo de toda a série temporal equanto que as
comunidades associadas com Sargassum sp. revelaram flutuações ao nível da composição
bacteriana. Os parâmetros ambientais explicam: 56% da variação da comunidade bacteriana da
água, 46% da variação das comunidades associadas com o sedimento e 29% da variação do
biofilme de Sargassum sp. Estes resultados sugerem que os mecanismos que medeiam as
alterações na composição da comunidade microbiana de Sargassum sp. podem estar
relacionados com factores bióticos tais como interação bactéria-bactéria ou interacção entre o
hospedeiro e as bactérias associadas (endo e epifíticas), ou ainda interações com outros
macroorganismos e seus microbiomas. Este estudo destaca a importância de examinar simultaneamente factores bióticos e ambientais, como forças condutoras de alteração dos
microbiomas associados a espécies estruturantes dos recifes de coral.
The canopy-forming macroalgae Sargassum is widely distributed throughout temperate and tropical reefs globally, playing an important role in habitat/refugia provision for diverse marine species, but also affecting others negatively. Despite its ecological importance, little is known about the microbes living on the alga’s surface. This study aimed to understand microbial successional dynamics within the Sargassum sp. biofilm and determine how environmental variations affect the microbial community, by investigating the microbial communities of Sargassum sp. biofilms, seawater and sediment in tandem over a time series. Sargassum sp., sediment and seawater samples were collected over a 13-month period from Magnetic Island on the Great Barrier Reef. Illumina 16S rRNA gene sequencing of 30 Sargassum sp. samples provided an in-depth analysis of the taxonomic diversity existing on the biofilm while putative functional roles of key bacterial taxa were assigned with FAPROTAX. Unconstrained ordination, correlation analyses and differential abundance statistics were used to investigate the response of bacterial communities to measured environmental parameters such as temperature, organic and inorganic nutrients. Sargassum sp. biofilms were dominated by bacteria belonging to Firmicutes (23-45%), Proteobacteria (35-38%) and Bacteroidetes (13-30%) phyla, with differences in community structure observed between winter and summer. Microbial communities of seawater and sediment were stable throughout the time series, while the communities associated with Sargassum sp. fluctuated in composition. Environmental parameters explained 56% of the variation in microbial community composition for seawater, 46% for sediment-associated communities and 29% for epiphytic Sargassum sp. biofilm communities. These results suggest that the Sargassum microbiome could be primarily mediated by biotic factors such as bacteriabacteria interactions or interactions between the host and its associated bacteria (endophytes and epiphytes) and interactions with other species and their microbiomes. This study highlights the importance of simultaneously examining biotic and environmental drivers to determine factors structuring the microbiome of key reef species.
The canopy-forming macroalgae Sargassum is widely distributed throughout temperate and tropical reefs globally, playing an important role in habitat/refugia provision for diverse marine species, but also affecting others negatively. Despite its ecological importance, little is known about the microbes living on the alga’s surface. This study aimed to understand microbial successional dynamics within the Sargassum sp. biofilm and determine how environmental variations affect the microbial community, by investigating the microbial communities of Sargassum sp. biofilms, seawater and sediment in tandem over a time series. Sargassum sp., sediment and seawater samples were collected over a 13-month period from Magnetic Island on the Great Barrier Reef. Illumina 16S rRNA gene sequencing of 30 Sargassum sp. samples provided an in-depth analysis of the taxonomic diversity existing on the biofilm while putative functional roles of key bacterial taxa were assigned with FAPROTAX. Unconstrained ordination, correlation analyses and differential abundance statistics were used to investigate the response of bacterial communities to measured environmental parameters such as temperature, organic and inorganic nutrients. Sargassum sp. biofilms were dominated by bacteria belonging to Firmicutes (23-45%), Proteobacteria (35-38%) and Bacteroidetes (13-30%) phyla, with differences in community structure observed between winter and summer. Microbial communities of seawater and sediment were stable throughout the time series, while the communities associated with Sargassum sp. fluctuated in composition. Environmental parameters explained 56% of the variation in microbial community composition for seawater, 46% for sediment-associated communities and 29% for epiphytic Sargassum sp. biofilm communities. These results suggest that the Sargassum microbiome could be primarily mediated by biotic factors such as bacteriabacteria interactions or interactions between the host and its associated bacteria (endophytes and epiphytes) and interactions with other species and their microbiomes. This study highlights the importance of simultaneously examining biotic and environmental drivers to determine factors structuring the microbiome of key reef species.
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Keywords
Epibiontes de macroalgas 16S rRNA Recife de coral Holobionte Factores Abióticos Faprotax