Spatial and Structural Factors Shape Seagrass-Associated Bacterial Communities in Singapore and Peninsular Malaysia

Abstract

Plant-microbe relationships play critical roles in the functioning and health of terrestrial plants, but little is known about this relationship in marine angiosperms such as seagrasses. Here, we investigated the microbial communities associated with the seagrass Enhalus acoroides throughout Singapore and Peninsular Malaysia. At each sampling location we collected 10 individual and unconnected plants. Each plant was subsequently broken down into leaves, roots, and rhizomes. In addition to living plant parts a sediment sample was taken in close proximity to each. Using high throughput 16S rRNA gene amplicon sequencing we characterised the bacterial communities associated with each plant part and the associated sediment sample. Results indicate geographic structuring of bacterial communities, with a significant pattern of distance decay suggesting dispersal limitation is a contributing factor to the differences we see in bacterial community structure. Bacterial communities can be further differentiated by the function of the collected sample (leaf, root, and rhizome), and we identified a number of microbial indicator species that are associated with each plant part. Further analysis revealed the presence of several microbial taxa that have previously been identified as indicators of “unhealthy” or “stressed” seagrass meadows. This study addresses a current scientific gap related to the characterisation of seagrass microbiomes, and provides a foundation on which future studies can build, particularly those in the Southeast Asian seagrass biodiversity hotspot.

The Mangrove Microbiome of the Malay Peninsula

“…Consistent with other work examining microbial community structure in a variety of host taxa, we show that microbial community structure does exist around the Malay Peninsula [39, 40, 54, 55, 78, 79], and this structure is driven primarily by plant part sampled, location sampled, and host identity. It is likely that these differences are driven by local environmental conditions, with locations closer together tending to have more similar environmental conditions in comparison to those that are more geographical distant.…”

“…Despite this recognised importance, the dynamics, distribution, and community composition of microbes in mangrove ecosystemsremains vague [10, 11, 38]. This paucity is particularly acute in Southeast Asian coastal regions, but see [39, 40] for relevant work examining seagrass ecosystems.…”

Compositional stability of sediment microbial communities during a seagrass meadow decline

“…Depthdependent changes in taxonomic composition have been well described differentiating surface sediment communities dominated by Bacteria, especially Proteobacteria, from deeper communities characterized by Archaea (Orcutt et al, 2011;Chen et al, 2017;Petro et al, 2017). Coastal surface sediments colonized by seagrass are not as well investigated due to studies focusing primarily on rhizosphere communities and only occasionally including sediment communities for comparison (Cúcio et al, 2016;Rabbani et al, 2021). Communities in the rhizosphere are not species-specific and differ from those in the sediment (Cúcio et al, 2016;Ettinger et al, 2017;Zhang et al, 2020).…”

A review of plastic and microplastic pollution towards the Malaysian marine environment

“…Besides hosting a wide range of marine organisms, seagrasses meadows are also bioengineers where they redistribute and dissipate energy from strong ocean waves and storms [94]. Recently, seagrasses are discovered to elevate the effect of climate change by sequestering approximately 10% of atmospheric carbon dioxide into the marine environment [92].…”

“…Seagrasses are submerged halophytes found in enclosed coastal regions that reproduce vegetatively to form seagrass meadows [34]. It has been estimated that the seagrass destruction rate stands at 45% per year throughout SEA due to extensive coastal development and water pollution [92]. Similarly in Malaysia, seagrass was previously reported to be extensive and abundant along its Peninsular coastline but current statistics have shown significant loss [34].…”