Different environmental factors play important roles in the growth, reproduction, and distribution of marine macroalgae. We investigated the effects of temperature, salinity, irradiance, and nutrients on the growth of carposporelings and tetrasporophytes of Gracilaria domingensis. Carposporelings grew at temperatures of 25°C and 30°C, but they did not survive at 15°C and 20°C. In contrast, tetrasporophytes grew over a wide range of temperatures (15–30°C) with optimum growth between 20°C and 25°C. Both carposporelings and tetrasporophytes tolerated a wide range of salinity (25–60 and 10–50, respectively), but carposporelings were more sensitive to lower salinities (10–20), while tetrasporophytes were more sensitive to higher salinities (60). The highest growth rates in basal discs of carposporelings occurred when they were grown in 25% strength von Stosch enriched medium (VSES) with an illumination of 150 μmol photons m-2 s-1; erect fronds grew best in 25% and 50% strength VSES with illumination of 100 μmol photons m-2 s-1. The VSES strength did not influence the growth of tetrasporophytes of G. domingensis. Highest growth rates of tetrasporophytes occurred at 100 μmol photons m-2 s-1. These results demonstrate very different physiological responses between carposporelings and tetrasporophytes of G. domingensis and, as such, they offer guidelines for the selection of potential areas for the cultivation of the species.

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