( ( ( Ocean acidification ) ( -LRB- ( OA -RRB- ) ) ) ( ( is ( ( the process ) ( by ( which ( anthropogenically ( ( ( derived ( ( ( atmospheric ( carbon dioxide ) ) ( -LRB- ( CO2 -RRB- ) ) ) ( is ( absorbed ( into ( surface seawater ) ) ) ) ) ) , ) ( lowering ( ( the ( ( pH and ) concentration ) ) ( of ( ( ( carbonate ions ) ( in ( the ( global ocean ) ) ) ) ( -LRB- ( ( ( ( ( Caldeira and ) ( Wickett 2003 ) ) ; ) ( ( Doney et ) ( al. 2009 ) ) ) -RRB- ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Ocean) (NNP acidification)) (PRN (-LRB- -LRB-) (NP (NNP OA)) (-RRB- -RRB-))) (VP (VBZ is) (NP (NP (DT the) (NN process)) (PP (IN by) (SBAR (WHNP (WDT which)) (S (ADVP (RB anthropogenically)) (VP (VBD derived) (SBAR (S (NP (NP (JJ atmospheric) (NN carbon) (NN dioxide)) (PRN (-LRB- -LRB-) (NP (NNP CO2)) (-RRB- -RRB-))) (VP (VBZ is) (VP (VBN absorbed) (PP (IN into) (NP (NN surface) (NN seawater))))))) (, ,) (S (VP (VBG lowering) (NP (NP (DT the) (NN pH) (CC and) (NN concentration)) (PP (IN of) (NP (NP (JJ carbonate) (NNS ions)) (PP (IN in) (NP (DT the) (JJ global) (NN ocean))) (PRN (-LRB- -LRB-) (NP (NP (NNP Caldeira)) (CC and) (NP (NNP Wickett) (CD 2003))) (: ;) (S (NP (NNP Doney) (NNP et)) (VP (VBP al.) (NP (CD 2009)))) (-RRB- -RRB-))))))))))))) (. .)))
Ocean acidification (OA) is the process by which anthropogenically derived atmospheric carbon dioxide (CO2) is absorbed into surface seawater, lowering the pH and concentration of carbonate ions in the global ocean (Caldeira and Wickett 2003 ; Doney et al. 2009 ).
(ROOT (S (NP (NNP Ocean) (NNP acidification)) (VP (VBZ occurs) (SBAR (WHADVP (WRB when)) (S (NP (NP (JJ excess) (NN carbon) (NN dioxide)) (PP (IN in) (NP (DT the) (NN atmosphere)))) (VP (VBZ causes) (S (NP (DT the) (NNS oceans)) (VP (TO to) (VP (VB become) (NP (NNS acidic))))))))) (. .)))
Ocean acidification occurs when excess carbon dioxide in the atmosphere causes the oceans to become acidic.