Undisturbed Posidonia oceanica meadows maintain the epiphytic bacterial community in different environments

Abstract

Seagrasses harbour different and rich epiphytic bacterial communities. These microbes may establish intimate and symbiotic relationships with the seagrass plants and change according to host species, environmental conditions, and/or ecophysiological status of their seagrass host. Although Posidonia oceanica is one of the most studied seagrasses in the world, and bacteria associated with seagrasses have been studied for over a decade, P. oceanica’s microbiome remains hitherto little explored. Here, we applied 16S rRNA amplicon sequencing to explore the microbiome associated with the leaves of P. oceanica growing in two geomorphologically different meadows (e.g. depth, substrate, and turbidity) within the Limassol Bay (Cyprus). The morphometric (leaf area, meadow density) and biochemical (pigments, total phenols) descriptors highlighted the healthy conditions of both meadows. The leaf-associated bacterial communities showed similar structure and composition in the two sites; core microbiota members were dominated by bacteria belonging to the Thalassospiraceae, Microtrichaceae, Enterobacteriaceae, Saprospiraceae, and Hyphomonadaceae families. This analogy, even under different geomorphological conditions, suggest that in the absence of disturbances, P. oceanica maintains characteristic-associated bacterial communities. This study provides a baseline for the knowledge of the P. oceanica microbiome and further supports its use as a putative seagrass descriptor.

Accelerated nitrogen cycling on Mediterranean seagrass leaves at volcanic CO2 vents

“…Similarly, Banister et al 76 found that the leaf-associated microbiome of the seagrass Cymodocea nodosa was stable across pH gradients at a comparable Mediterranean CO 2 vent site. The microbial community of P. oceanica was also found to be stable in environments differing in other geomorphologically traits (e.g., depth, substrate, and turbidity) 77 . Conversely, colonization experiments using an inert substrate showed marked differences in coastal microbial biofilms between natural pH and vent-exposed sites 78 .…”