Arsenic speciation and susceptibility to oxidative stress in the fanworm Sabella spallanzanii (Gmelin) (Annelida, Sabellidae) under naturally acidified conditions: An in situ transplant experiment in a Mediterranean CO2 vent system

- Polychaete S. spallanzanii was transplanted at a natural CO2 vent system for 30 days.
- The response induced by low pH/high pCO2 conditions was characterized.
- Significant variations in the pattern of accumulated arsenic compounds occurred.
- Changes in the antioxidant system were indicative of oxidative challenge.
- The species results as potentially vulnerable to near-future OA conditions.

The fanworm Sabella spallanzanii (Gmelin, 1791) (Annelida, Sabellidae) is considered tolerant to several types of stressors but is generally absent from the CO2 vents. A peculiar characteristic of this species is the elevated content of arsenic in the gills, particularly dimethylarsinic acid (DMA), stored as an anti-predatory compound. In this study, modulation of trace metal levels, chemical speciation of arsenic and oxidative stress biomarkers were quantified in S. spallanzanii after a 30 days transplant experiment into naturally acidified conditions in a Mediterranean vent system. No significant bioaccumulation of metals was observed in the thoracic tissues and branchial crowns after the translocation period, whereas variations occurred in the relative abundance of different arsenic compounds with the appearance of inorganic forms.The antioxidant system of translocated polychaetes exhibited a significant decrease of enzymatic activities of both catalase and glutathione peroxidases, and the impairment of the overall capability to neutralize hydroxyl radicals (OH). This highlighted an oxidative challenge primarily on the detoxification pathway of hydrogen peroxide.Overall low pH-elevated pCO2 may have detrimental effects on arsenic metabolism and oxidative status of S. spallanzanii, supporting the hypothesis of species-specific differences in vulnerability to ocean acidification.