Effects of short-term and long-term exposure to ocean acidification on carbonic anhydrase activity and morphometric characteristics in the invasive polychaete Branchiomma boholense (Annelida: Sabellidae): A case-study from a CO vent system.

The aim of this study was to test the effects of short- and long-term exposure to high pCO on the invasive polychaete Branchiomma boholense (Grube, 1878), (Sabellidae), through the implementation of a transplant experiment at the CO vents of the Castello Aragonese at the island of Ischia (Italy). Analysis of carbonic anhydrase (CA) activity, protein tissue content and morphometric characteristics were performed on transplanted individuals (short-term exposure) as well as on specimens resident to both normal and low pH/high pCO environments (long-term exposure). Results obtained on transplanted worms showed no significant differences in CA activity between individuals exposed to control and acidified conditions, while a decrease in weight was observed under short-term acclimatization to both control and low pH, although at low pH the decrease was more pronounced (∼20%). As regard individuals living under chronic exposure to high pCO, the morphometric results revealed a significantly lower (70%) wet weight of specimens from the vents with respect to animals living in high pH/low pCO areas. Moreover, individuals living in the Castello vents showed doubled values of enzymatic activity and a significantly higher (50%) protein tissue content compared to specimens native from normal pH/low pCO. The results of this study demonstrated that B. boholense is inclined to maintain a great homeostatic capacity when exposed to low pH, although likely at the energetic expense of other physiological processes such as growth, especially under chronic exposure to high pCO.