Oxidative stress in the hydrocoral Millepora alcicornis exposed to CO2-driven seawater acidification
Global impacts are affecting negatively coral reefs’ health worldwide. Ocean acidification associated with the increasing CO2 partial pressure in the atmosphere can potentially induce oxidative stress with consequent cellular damage in corals and hydrocorals. In the present study, parameters related to oxidative status were evaluated in the hydrocoral Millepora alcicornis exposed to three different levels of seawater acidification using a mesocosm system. CO2-driven acidification of seawater was performed until reaching 0.3, 0.6 and 0.9 pH units below the current pH of seawater pumped from the coral reef adjacent to the mesocosm. Therefore, treatments corresponded to control (pH 8.1), mild (pH 7.8), intermediate (pH 7.5) and severe (pH 7.2) seawater acidification. After 0, 16 and 30 d of exposure, hydrocorals were collected and the following parameters were analyzed in the holobiont: antioxidant capacity against peroxyl radicals (ACAP), total glutathione (GSHt) concentration, reduced (GSH) and oxidized (GSSG) glutathione ratio (GSH/GSSG), lipid peroxidation (LPO) and protein carbonyl group (PC) levels. ACAP was increased in hydrocorals after 16 d of exposure to intermediate levels of seawater acidification. GSHt and GSH/GSSG did not change over the experimental period. LPO was increased at any level of seawater acidification, while PC content was increased in hydrocorals exposed to intermediate and severe seawater acidification for 30 d. These findings indicate that the antioxidant defense system of M. alcicornis is capable of coping with acidic conditions for a short period of time (16 d). Additionally, they clearly show that a long-term (30 d) exposure to seawater acidification induces oxidative stress with consequent oxidative damage to lipids and proteins, which could compromise hydrocoral health.
KeywordsAntioxidant capacity Coral reefs Lipid oxidation Mesocosm Ocean acidification Protein oxidation
The International Development Research Centre (IDRC, Ottawa, Canada; Grant No. 104519-003), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES—Programa Ciências do Mar, Brasília, DF, Brazil; Grant No. 84/2010) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq—Instituto Nacional de Ciência e Tecnologia de Toxicologia Aquática, Brasília, DF, Brazil; Grant No. 573949/2008-5) are acknowledged for their financial support. The Coral Vivo Project and its sponsors Petrobras, through the Petrobras Environmental Program, and Arraial d’Ajuda Eco Parque are acknowledged for their support in field research. A. Bianchini (Proc. # 304430/2009-9) and C.B. Castro (Proc. # 303970/2010-3) are research fellows from CNPq. A. Bianchini is supported by the International Canada Research Chair Program (IDRC). D.C. Luz was a graduate fellow from CAPES.
Compliance with ethical standards
Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
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