( ( ( The reason ) ( the ( coral-reef ( Twilight Zone ) ) ) ) ( ( ( is shallower ) ( than ( ( the ( open-ocean ( Twilight Zone ) ) ) ( ( stems mostly ) ( from ( ( the difference ) ( in ( ( water clarity ) ( between ( the ( two habitats ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN reason)) (NP (DT the) (JJ coral-reef) (NNP Twilight) (NNP Zone))) (VP (VBZ is) (ADJP (JJR shallower)) (SBAR (IN than) (S (NP (DT the) (JJ open-ocean) (NNP Twilight) (NNP Zone)) (VP (VBZ stems) (ADVP (RB mostly)) (PP (IN from) (NP (NP (DT the) (NN difference)) (PP (IN in) (NP (NP (NN water) (NN clarity)) (PP (IN between) (NP (DT the) (CD two) (NNS habitats))))))))))) (. .)))
The reason the coral-reef Twilight Zone is shallower than the open-ocean Twilight Zone stems mostly from the difference in water clarity between the two habitats.
(ROOT (S (NP (NP (NNP Ocean) (NNP ridges)) (VP (VBN formed) (PP (IN by) (NP (NP (JJ marine) (NNS invertebrates)) (VP (VBG living) (PP (IN in) (NP (JJ warm) (JJ shallow) (NNS waters))) (PP (IN within) (NP (NP (DT the) (JJ photic) (NN zone)) (PP (IN of) (NP (DT the) (NN ocean)))))))))) (VP (VBP are) (VP (VBN called) (NP (NN coral) (NNS reefs)))) (. .)))