Microbial communities developing within bulk sediments under fish carcasses on a tidal flat.

Yasutake Kawamoto,Yuji Nagata,Jotaro Urabe,Hiromi Kato,Brenda A Wilson

doi:10.1371/journal.pone.0247220

Abstract

Animal carcasses are often brought into tidal flats where they are at the boundary between terrestrial and marine ecosystems. Since these carcasses act as microhabitats with large amounts of energy and nutrients, they likely develop unique bacterial assemblages in the ambient sediment, which in turn may stimulate colonization of other organisms such as protozoans. However, little is known about the microbial assemblages colonized in sediment around animal carcasses in the tidal zone. Herein we examined the bacterial and ciliophoran assemblages developed in association with fish carcasses by incubating the carcasses in the Higashiyachi tidal flat (Sendai, Japan). We collected sediment samples at 2, 9, and 42 days of incubation and analyzed the bacterial and ciliophoran assemblages by 16S and 18S rRNA gene amplicon sequencing. We observed significant differences in the composition and relative abundance of bacterial and ciliophoran operational taxonomic units (OTUs) between the sediments with and without the carcasses. Our analyses suggest that these unique assemblages were created through the direct effects of the carcass and indirect effects through interactions between bacteria and ciliophorans. These results also suggest that animal carcasses developed a temporally unique microbial food web in the sediments close to the carcasses, although it disappeared for several weeks.

Highlights

Animal carcasses are omnipresent and play functionally important roles for material cycling and sustaining ecosystems [1,2,3,4]
These results suggest that animal carcasses developed a temporally unique microbial food web in the sediments close to the carcasses, it disappeared for several weeks
This study suggested that fish carcasses developed a unique microbial community in the tidal flat sediment

Summary

Introduction

Animal carcasses are omnipresent and play functionally important roles for material cycling and sustaining ecosystems [1,2,3,4]. Several studies have shown that bacterial assemblages developed in the vicinity of carcasses differ significantly from those in the environments without such carcasses [7,8,9]. It is not clear whether the bacterial assemblages developed in the vicinity of carcasses are composed mainly of bacteria inhabiting the surrounding environment or unique bacteria specific to the carcasses. An increase in bacterial abundance associated with a carcass provides diet resources for bacterivores such as Ciliophorans. An increase in bacterial activities results in the consumption of oxygen, creating an anoxic condition in ambient environments.

Methods

Results

Discussion

Conclusion