There isn't a lot of literature on the ecological importance with G. pacifica. Photosynthesis is occuring, so it does fix carbon from the environment and produce oxygen like other algae.
Some other algae species do grow epiphytically on G. pacifica but none are exclusive. In turn, G. pacifica also grows epiphytically on other plants.
One person described eating G. pacifica as a delightful experience and "the most delicious alga he has eaten yet". --Anonymous