Molecular mechanisms underlying responses of the Antarctic coral Malacobelemnon daytoni to ocean acidification

SERVETTO, N.; DE ARANZAMENDI, M.C.; BETTENCOURT, R.; HELD, C.; ABELE, D.; MOVILLA, J.; GONZÁLEZ, G.; BUSTOS, D.M.; SAHADE, R.

MARINE ENVIRONMENTAL RESEARCH

ELSEVIER SCI LTD

Año: 2021 vol. 170

0141-1136

Benthic organisms of the Southern Ocean are particularly vulnerable to ocean acidification (OA), as they inhabitcold waters where calcite-aragonite saturation states are naturally low. OA most strongly affects animals withcalcium carbonate skeletons or shells, such as corals and mollusks. We exposed the abundant cold-water coralMalacobelemnon daytoni from an Antarctic fjord to low pH seawater (LpH) (7.68 ± 0.17) to test its physiologicalresponses to OA, at the level of gene expression (RT-PCR) and enzyme activity. Corals were exposed in short- (3days) and long-term (54 days) experiments to two pCO2 conditions (ambient and elevated pCO2 equaling RCP8.5, IPCC 2019, approximately 372.53 and 956.78 μatm, respectively).Of the eleven genes studied through RT-PCR, six were significantly upregulated compared with control in theshort-term in the LpH condition, including the antioxidant enzyme superoxide dismutase (SOD), Heat ShockProtein 70 (HSP70), Toll-like receptor (TLR), galaxin and ferritin. After long-term exposure to low pH conditions,RT-PCR analysis showed seven genes were upregulated. These include the mannose-binding C-Lectin and HSP90.Also, the expression of TLR and galaxin, among others, continued to be upregulated after long-term exposure toLpH. Expression of carbonic anhydrase (CA), a key enzyme involved in calcification, was also significantlyupregulated after long-term exposure. Our results indicated that, after two months, M. daytoni is not acclimatizedto this experimental LpH condition. Gene expression profiles revealed molecular impacts that were not evident atthe enzyme activity level. Consequently, understanding the molecular mechanisms behind the physiologicalprocesses in the response of a coral to LpH is critical to understanding the ability of polar species to cope withfuture environmental changes. Approaches integrating molecular tools into Antarctic ecological and/or conservationresearch make an essential contribution given the current ongoing OA processes.