# Spatial Patterns and Overlap of Sedimentary and Rhizosphere Microbiomes of the Seagrass Zostera capensis

## TL;DR

This study explores the microbial communities in the sediment and roots of a South African seagrass species to understand their roles in ecosystem health and function.

## Contribution

The first characterization of rhizosphere microbiomes of Zostera capensis using 16S rRNA metabarcoding across multiple estuaries.

## Key findings

- Sediment and rhizosphere microbiomes of Zostera capensis share 34 genera but also have distinct core genera.
- Both sediment and rhizosphere microbiomes show significant spatial variability influenced by local and estuary-specific factors.
- The rhizobiome is enriched for nutrient cycling pathways potentially beneficial to Zostera capensis.

## Abstract

Seagrasses are important nature‐based solutions for climate change mitigation and adaptation due to their carbon stocks and ecosystem service co‐benefits. Characterising microbial communities in seagrass sediments and rhizospheres is essential for understanding their roles in biogeochemical cycling, seagrass health, and potential contributions to ecosystem functioning. However, the extent to which seagrass microbiomes are shared at different spatial scales is not well understood. We utilised 16S rRNA metabarcoding to characterise prokaryotic communities in the sediments of the seagrass Zostera capensis at three estuaries spanning the environmental gradient of South Africa. In addition, we characterised the rhizosphere microbiome (rhizobiome) to better understand rhizosphere and sediment community dynamics. Overall, after accounting for community in adjacent seawater, we found that
Z. capensis
sediment and rhizosphere microbiomes largely overlap, sharing 34 genera but also harbour core genera. The sediment microbiome and rhizobiome showed significant spatial variability, suggesting that both local‐scale and broader estuary‐specific factors shape site‐level microbial signatures. Further, predictive functional analysis showed that the rhizobiome was enriched for nutrient cycling pathways potentially beneficial to
Z. capensis
. Our findings support the exploration of sediment and rhizosphere microbial communities for monitoring ecosystem health and assessing impacts from threats such as pollution and climate change.

Sedimentary microbiomes and, for the first time, rhizosphere microbiomes of Zostera capensis, South Africa's most abundant seagrass, were characterised using 16S rRNA metabarcoding across three estuaries. After accounting for seawater‐derived microbes, we found that sediment and rhizosphere communities largely overlapped but also harbor distinct core genera.