Diversity and Composition of Microbial Communities in an Eelgrass (<i>Zostera marina</i>) Bed in Tokyo Bay, Japan

Abstract

Zostera marina (eelgrass) is a widespread seagrass species that forms diverse and productive habitats along coast lines throughout much of the northern hemisphere. The present study investigated the microbial consortia of Z. marina growing at Futtsu clam-digging beach, Chiba prefecture, Japan. The following environmental samples were collected: sediment, seawater, plant leaves, and the root-rhizome. Sediment and seawater samples were obtained from three sampling points: inside, outside, and at the marginal point of the eelgrass bed. The microbial composition of each sample was analyzed using 16S ribosomal gene amplicon sequencing. Microbial communities on the dead (withered) leaf surface markedly differed from those in sediment, but were similar to those in seawater. Eelgrass leaves and surrounding seawater were dominated by the bacterial taxa Rhodobacterales (Alphaproteobacteria), whereas Rhodobacterales were a minor group in eelgrass sediment. Additionally, we speculated that the order Sphingomonadales (Alphaproteobacteria) acts as a major degrader during the decomposition process and constantly degrades eelgrass leaves, which then spread into the surrounding seawater. Withered eelgrass leaves did not accumulate on the surface sediment because they were transported out of the eelgrass bed by wind and residual currents unique to the central part of Tokyo Bay.

Microbial communities on eelgrass (Zostera marina) thriving in Tokyo Bay and the possible source of leaf-attached microbes

“…These plant bodies were then gently washed with on-site water to remove sediment particles from the eelgrass surface. To remove loosely associated microbes and plankton, the eelgrass surface was rinsed with filtered and autoclaved seawater (Weidner et al, 1996;Burke et al, 2009;Iqbal et al, 2021). Then, the eelgrass bodies were cut into two parts: aboveground components (trunk and leaves) and belowground components (the root-rhizome) and placed into a sterile plastic bag.…”

“…Another study identified epiphytic microbial communities on three seagrass species from the East African coast (Uku et al, 2007). Recently, some culture-independent surveys of seagrass epiphytic microbes have been published (Mejia et al, 2016;Ettinger et al, 2017;Fahimipour et al, 2017;Crump et al, 2018;Hurtado-McCormick et al, 2019, 2020Ugarelli et al, 2019;Vogel et al, 2020;Iqbal et al, 2021;Rabbani et al, 2021). Most community analyses revealed that microbial communities varied in microbial composition with seagrass tissues: leaves and the root-rhizome (Mejia et al, 2016;Ettinger et al, 2017;Fahimipour et al, 2017;Crump et al, 2018;Ugarelli et al, 2019;Iqbal et al, 2021).…”

“…Recently, some culture-independent surveys of seagrass epiphytic microbes have been published (Mejia et al, 2016;Ettinger et al, 2017;Fahimipour et al, 2017;Crump et al, 2018;Hurtado-McCormick et al, 2019, 2020Ugarelli et al, 2019;Vogel et al, 2020;Iqbal et al, 2021;Rabbani et al, 2021). Most community analyses revealed that microbial communities varied in microbial composition with seagrass tissues: leaves and the root-rhizome (Mejia et al, 2016;Ettinger et al, 2017;Fahimipour et al, 2017;Crump et al, 2018;Ugarelli et al, 2019;Iqbal et al, 2021). Seagrass microbes have also been shown to differ between the root-rhizome and surrounding sediment (Cúcio et al, 2016;Fahimipour et al, 2017;Ettinger et al, 2017).…”

“…Aquatic bacteria are generally separated into two lifestyles: particle-associated (PA) and freeliving (FL). In the marine environment, suspended particles are densely colonized by marine bacteria that can adhere easily to available surfaces (Iqbal et al, 2021). These particles may play a role in transferring adherent bacteria to the surface of other objects.…”

“…These particles may play a role in transferring adherent bacteria to the surface of other objects. It is presumed that bacteria move back and forth between plant bodies and the surrounding water through the process of particle formation, adhesion, and collapse (Iqbal et al, 2021).…”