Intraspecific variation in Gracilaria birdiae (Gracilariales, Rhodophyta): growth, and agar yield and quality of color strains under aquaculture

Abstract

Abstract Based on their distinct physiological characteristics, we postulated that different strains of Gracilaria birdiae (Gracilariales, Rhodophyta) would have distinct performances when grown in the sea. Samples from a northeastern Brazil population, including red (RD-CE), greenish-brown (GB-CE), and green (GR-CE) strains, and one red strain (RD-ES) from a southeastern population were cultivated in Ubatuba Bay, southeastern Brazil. We analyzed the survival ability, growth rate, and the agar yield and quality of these strains. The growth rates (GRs) and seawater temperatures were measured for 16 months. The northeastern population strains were in good condition during all the cultivation periods, while the RD-ES strain had a lower GR and died during some time periods. Overall, the GR ranged from 0.4% to 4.4% day-1, depending on the strain and the period of cultivation. The GRs of the RD-CE, GR-CE, and GB-CE strains were similar during all the cultivation periods. The increased GR in all the strains of G. birdiae seemed to be related to a slight rise in the seawater temperature. However, the GRs decreased in all the strains when the temperatures remained high for the protracted periods. In addition to their similar GRs, the RD-CE and GR-CE strains had similar yields and qualities as the polysaccharides. We concluded that these three strains are suitable for testing as the candidates for future commercial cultivation.