The biomass and growth of G. birdiae were significantly affected by the abiotic parameters inherent to the depth variation. The lowest biomass increase was obtained at the surface, increasing by 25.3% during the cultivation period. In this depth the lowest biomass recorded in each rope was 150 g (1st week) and the highest 222 g (5th week), with a mean value of 173.9 ± 14.6 g.