Interconnectivity vs. isolation of prokaryotic communities in European deep-sea mud volcanoes

Abstract. By exploiting the available data on 16S rRNA gene sequences – spanning over a sampling period of more than 10 yr – retrieved from sediments of the Haakon Mosby mud volcano (HMMV), Gulf of Cadiz (GoC) and eastern Mediterranean (Amsterdam and Kazan mud volcanoes; AMSMV, KZNMV) mud volcanoes/pockmarks, we investigated whether these systems are characterized by high (interconnectivity) or low (isolation) connection degree based on shared bacterial and archaeal phylotypes. We found only two archaeal and two bacterial phylotypes to occur in all three sites and a few more that were found in two of the three sites. Although the number of shared species depends a lot on the analysis depth of each sample, the majority of the common phylotypes were related mostly to cold seep deep-sea habitats, while for some of them their relative abundance was high enough to be considered as key-species for the habitat they were found. As new tools, like next generation sequencing platforms, are more appropriate for revealing greater depth of diversity but also allow sample replication and uniform sampling protocols, and gain wider recognition and usage, future attempts are more realistic now for fully elucidating the degree of specificity in deep-sea mud volcanoes and pockmarks microbial communities.