( ( ( Introduced species ) ( of ( aquatic organisms ) ) ) ( also ( ( pose ( a threat ) ) . ) ) )
(ROOT (S (NP (NP (JJ Introduced) (NNS species)) (PP (IN of) (NP (JJ aquatic) (NNS organisms)))) (ADVP (RB also)) (VP (VBP pose) (NP (DT a) (NN threat))) (. .)))
Introduced species of aquatic organisms also pose a threat.
(ROOT (S (NP (NNP Overharvesting)) (VP (VBZ is) (NP (DT a) (JJ serious) (NN threat)) (ADVP (RB particularly)) (PP (TO to) (NP (JJ aquatic) (NNS species)))) (. .)))