Acidified marine systems represent “natural laboratories”, which provide opportunities to investigate the impacts of ocean acidification on different living components, including microbes. Here, we compared the benthic microbial response in four naturally acidified sites within the Southern Tyrrhenian Sea characterized by different acidification sources (i.e., CO₂ emissions at Ischia, mixed gases at Panarea and Basiluzzo and acidified freshwater from karst rocks at Presidiana) and pH values. We investigated prokaryotic abundance, activity and biodiversity, viral abundance and prokaryotic infections, along with the biochemical composition of the sediment organic matter. We found that, despite differences in local environmental dynamics, viral life strategies change in acidified conditions from mainly lytic to temperate lifestyles (e.g., chronic infection), also resulting in a lowered impact on prokaryotic communities, which shift towards (chemo)autotrophic assemblages, with lower organic matter consumption. Taken together, these results suggest that ocean acidification exerts a deep control on microbial benthic assemblages, with important feedbacks on ecosystem functioning.

Ichthyoplankton samples were collected during the November–December 1994 Italian Antarctic Oceanographic Cruise carried out to the western Ross Sea. A midwater trawl (Hamburg Plankton Net) was used to collect samples at 26 stations. Larval and juvenile specimens of 21 species belonging to six families (Artedidraconidae, Bathydraconidae, Channichthyidae, Macrouridae, Nototheniidae and Paralepididae) were caught from surface to 380 m depth. Mean relative abundance of larval fish in the whole area was about 2.7 specimens 1000 m⁻³ of filtered water. Pleuragramma antarcticum were the most abundant as postlarvae and juveniles. Larval and postlarval specimens of Chionodraco myersi were also abundant and widespread. The high number of Trematomus lepidorhinus (570 larvae) found in a single station off Terra Nova Bay (74°48′75“S, 164°36′90”E) was noteworthy. Our data demonstrate that the species diversity of the larval fish community in the western Ross Sea is much as found elsewhere in the Antarctic and show a greater abundance of fish larvae in inshore than in offshore waters.

Heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) can have negative impacts on the marine and freshwater biota. Utilizing microbes, particularly microalgae, which are able to extract metals and hydrocarbons from environmental matrices, the impact of these contaminants in freshwaters, seas, and wastewaters can be reduced. In fact, the contaminants can be passively absorbed and actively accumulated within the organelles of microalgae, reducing their negative impact. River streams, untreated municipal, agricultural, and industrial wastewaters, represent one of the most important issues for the anthropogenic pollution. Microalgae and bacteria can grow in polluted waters containing different metals as cadmium (Cd), lead (Pb), zinc (Zn), chromium (Cr), copper (Cu), and mercury (Hg). They are able to accumulate metal elements within biomass in a dose-dependent manner and are employed in bioremediation thanks to their growth ability in polluted sites. In the following chapter, we analyze the potential of employing microalgae in phycoremediation, their mechanisms of tolerance and resistance to heavy metals, the possibility to use consortia of microorganisms instead of single specie to cope with complex polluted matrices, the possibility to metabolic engineer microalgae to gain their function, and the employment of microalgae in both liquid and solid devices.

Compared to their fossil counterparts, living brachiopods are investigated far less often, due to their occurrence in remote environments such as dark caves or deep environments. Due to the scarcity of studies targeting in situ brachiopods’ populations, large-scale information on their distribution and ecological preferences is still lacking, especially on hardgrounds. The extensive employment of remotely operated vehicles (ROVs), however, has opened up the chance to better explore this taxon’s diversity and ecology in the mesophotic and bathyal zones. The analysis of over 600 h of video footage collected from 624 sites, from 40 m to 1825 m, located along the Ligurian and Tyrrhenian coasts of Italy and the Sicily Channel, allowed for a large-scale investigation. The four identified species, Novocrania anomala, Gryphus vitreus, Megerlia truncata and Terebratulina retusa, emerged as common macrofaunal components of the explored habitats, especially between 150 m and 250 m, with high occurrences in the northern areas, especially on offshore seamounts. All species can form dense aggregations of individuals, with M. truncata showing the densest populations on steep rocky terraces (up to 773 individuals m⁻²). Except for G. vitreus, the only species also recorded on soft bottoms, the others were found exclusively on hardgrounds, with N. anomala showing a peculiar ability to exploit anthropogenic substrates such as terracotta amphorae. No stable species-specific associations were noted, even if numerous species were frequently observed together. Although brachiopods do not show the conspicuous tridimensionality of large filter-feeders, their substrate occupancy and their role in pelagic–benthic processes support their importance in deep-sea Mediterranean ecosystems.