( ( This cycle ) ( ( ( ( ( removes ( carbon dioxide ) ) ( from ( the atmosphere ) ) ) and ) ( ( sequesters it ) ( in ( ( the oceans ) ( as ( calcium carbonate ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This) (NN cycle)) (VP (VP (VBZ removes) (NP (NN carbon) (NN dioxide)) (PP (IN from) (NP (DT the) (NN atmosphere)))) (CC and) (VP (VBZ sequesters) (NP (PRP it)) (PP (IN in) (NP (NP (DT the) (NNS oceans)) (PP (IN as) (NP (NN calcium) (NN carbonate))))))) (. .)))
This cycle removes carbon dioxide from the atmosphere and sequesters it in the oceans as calcium carbonate.
(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.