Geographic Variability of Fish Carcass-Associated Microbial Communities

Animal carcasses are common in natural environments and, owing to their high energy and nutrient content, support distinct microbial communities. However, little is known about how carcass-associated microbial communities vary among geographically distinct regions. To address this knowledge gap, we deployed sardine carcasses on surface sediments at seven tidal flats distributed along the Japanese archipelago and compared microbial communities in sediments with and without carcasses. We focused on the taxonomic composition of bacterial assemblages and their potential predators, ciliophorans. Both bacterial and ciliophoran communities associated with carcasses differed markedly among sites. However, the overall effect of carcass addition on community composition was superimposed on strong geographic and environmental patterns. These results suggest that carcass-associated microbial communities are shaped primarily by local species pools and environmental conditions rather than by a common carcass-driven effect across geographically distinct sites.