The great environmental importance of wetlands is linked to the high
biodiversity of flora and fauna they support, so that the
international Ramsar Convention focused on these areas and highlighted the need
to preserve them. The bacterial communities that thrive in these ecosystems
play a key role in regulating the local biogeochemical processes and yet their
distribution, abundance and dynamics are poorly known. This work is aimed to
study the bacterial assemblages over a year long, to contribute to the
understanding of the natural processes occurring in wetlands at variable
salinity. The knowledge of bacterial groups, species or assemblages can provide
a useful bioindicator for conservation and restoration efforts. Macchiatonda
Natural Reserve (Santa Severa, Rome, Italy) is a relic ecosystem, once found
along the entire Tyrrhenian coast. This wetland encompasses three coastal ponds
with different salinity, where both peculiar vegetation and highly diverse
migratory and resident avifauna can be found. This ancient system has been
scarcely investigated and nothing is known about its microbial community. The
molecular metagenomic analyses performed to investigate the
salinity/bacterioplankton relationship, highlighted differences in the
bacterial structure, between ponds and seasons. Analogous trends in SSCP
profiles, Shannon Index, and bacterial composition (16S) were observed in the
two saltier ponds, whereas the entire set of results was different for the less
salty one. The species diversity in the three ponds varied according the
salinity gradient, with the maximum diversity corresponding to a salt
concentration range between 20 and 30. At higher and lower salinity, the
microbial diversity lowers, according to the “Intermediate Disturbance
Hypothesis”.