Abstract
This multidisciplinary study presents the major characteristics of a set of submarine rock outcrops
in the Northern Adriatic Sea: the rock occurrence, embedded down to about 1 m from the seafloor
in the bottom sediments; numerous gas accumulations in the proximity of the outcrops (e.g.,
bubbling gas from the sediment–water interface); small-scale mud volcanoes; and microbial mats
around the seepage site. Geochemical analysis revealed that these features are related to the seepage
of CH4-rich fluids, which causes the precipitation of methane-derived calcium carbonate as a
cement (δ13C = -49.80‰ V-PDB). 14C data gave radiocarbon ages of about 21,700 ± 2,265
years bp for two cement samples. From the biological point of view, a total of 112 macroalgal
taxa were recorded. The different number of taxa recorded at the San Pietro and Bardelli sampling
sites has been related to the different distance from the coast and to water depth. Some species that
characterize these outcrops are acknowledged as important bioconstructors distinctive of the
Mediterranean area.
