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Gracilaria Greville is a genus of seaweed that is economically explored by the cosmetic, pharmaceutical and food industries. One of the biggest problems associated with growing Gracilaria is the discharge of heavy metals into the marine environment. The absorption of heavy metals was investigated with the macroalga Gracilaria tenuistipitata Zhang et Xia, cultivated in a medium containing copper (Cu) and cadmium (Cd). In biological samples, EC50 concentrations of 1 ppm for cadmium and 0.95 ppm for copper were used. These concentrations were based on seaweed growth curves obtained over a period of six days in previous studies. ICP-AES was used to determine the amount of metal that seaweeds absorbed during this period. G. tenuistipitata was able to bioaccumulate both metals, about 17% of copper and 9% of cadmium. Basal natural levels of Cu were found in control seaweeds and in G. tenuistipitata exposed to Cd. In addition, the repertoire of other important chemical elements, as well as their concentrations, was determined for G. tenuistipitata and two other important seaweeds, G. birdiae Plastino & Oliveira and G. domingensis (Kützing) Sonder ex Dickie, collected in natural environments on the Brazilian shore.

This study evaluates the influence of depth and environmental parameters on the development of Gracilaria birdiae Plastino & Oliveira (Gracilariaceae) in an organic shrimp pond. The macroalgae was cultivated on modules placed at three depths (surface, 10 and 20 cm depth). Growth rates were measured weekly based on variation in fresh weight during 35 days. G. birdie showed the greatest productivity (35.7%) at 10 cm, followed by 20 cm (33.4%) and surface (25.3%). Average SGR values were 0.36±0.57% d-1(surface) 0.38±0.96% d-1 (10 cm) and 0.38 ±0.54% d-1(20 cm), over the study period. The biomass variation of G. birdiae showed significant difference among the three depths. The correlations generated by multiple regressions demonstrated that analyzed environmental parameters explain from 62 to 67 % of G. birdiae growth.