As the depth increases and the light fades in oceanic cold seeps, a variety of chemosynthetic-based benthic communities arise. Previous assessments reported polychaete annelids belonging to the family Siboglinidae as part of the fauna at cold seeps, with the 'Vestimentifera' clade containing specialists that depend on microbial chemosynthetic endosymbionts for nutrition. Little information exists concerning the microbiota of the external portion of the vestimentiferan trunk wall. We employed 16S rDNA-based metabarcoding to describe the external microbiota of the chitin tubes from the vestimentiferan Escarpia collected from a chemosynthetic community in a cold seep area at the southwestern Atlantic Ocean. The most abundant operational taxonomic unit (OTU) belonged to the family Pirellulaceae (phylum Planctomycetes), and the second most abundant OTU belonged to the order Methylococcales (phylum Proteobacteria), composing an average of 21.1 and 15.4% of the total reads on tubes, respectively. These frequencies contrasted with those from the surrounding environment (sediment and water), where they represent no more than 0.1% of the total reads each. Moreover, some taxa with lower abundances were detected only in Escarpia tube walls. These data constitute on the first report of an epibiont microbial community found in close association with external surface of a cold-seep metazoan, Escarpia sp., from a chemosynthetic community in the southwestern Atlantic Ocean.

Drilling activities usually discharge large quantities of fluids and drill cuttings, which are composed of fine particles, such as barite, that can physically affect Lophelia pertusa. An experiment to assess the effects of barite smothering on L. pertusa was conducted with a water recirculation system. The corals were collected in Santos Basin, Brazil. The experiment was conducted in 23 L cone-shaped aquaria, adapted with an individual water recirculation system. Each exposure to suspended barite particles (50 and 100 mg•L -1 ) plus a control group was maintained in triplicate. Three nubbins were accommodated in the aquaria and acclimated for 7 days. The experimental design simulated two cycles of discharge, followed by a recovery cycle of 7 days each, totaling 35 days. Nine polyps per treatment were monitored twice per day regarding their behavior levels. Time-lapse photographs were also taken during the recovery periods. Total polyp survival in the control was 100%, while those in the 50 and 100 mg•L -1 groups were 94.2 and 93.6%, respectively, with no significant difference between treatments. Polyp activity was different between treatments, with both exposed aquaria displaying higher activity than control. This was probably related to the natural cleaning behavior of L. pertusa.

The environmental aspect can be critical in the decision-making process at the onset of offshore E&P projects, especially in sensitive areas. Thus, we developed a methodological framework and a web tool to support the selection of technological and locational alternatives in subsea system installation and decommissioning activities. This framework relies on the assessment of environmental pressures and biological sensitivities. Our model's main assumption is that an activity can cause a number of environmental pressures, which can have different effects on each environmental component (habitats or biological groups). In the end, a potential environmental impact of a technology can be the result of its pressures on the components at a location. The work relied on experts' judgement and it was based on some previously established criteria for the classification of these environmental pressures and components' sensitivities. Scores were set and ranked in these assessments and a formula calculated the potential environmental impact of each activity/technology. A web tool called SCENARIO was developed to incorporate these results in a user-friendly interface, where one can compare scenarios made up with different technological options and different habitats or biological groups. This tool points out the potential environmental impact of each available choice. It also details how each component relates to that impact. Finally, one can acknowledge the environmental performance of its own scenario choices within the range of the best and worst possible alternatives. The tool was tested and proved to be technically sound and capable of contributing effectively to support the decision making process in the environmental aspects of offshore E&P subsea projects. It is also flexible to incorporate any pressure review, new activities and technological updates whenever necessary.