As algas tienen importancia ecolochica como productors en os ecosistemas aquaticos. O fitoplancton ye formau por algas unicelulars, destacando as diatomeas, as Chlorophyta unicelulars y as Dinoflagellata. As algas bentonicas tienen importancia en as plataformas continentals y en as costas, destacando as Chlorophyta multicelulars, as Phaeophyta y as Rhodophyta. En auguas continentals destacan como algas planctonicas as Chlorophyta y as Charophyta.