Depth-Dependent Pigment Fluctuations in the Agarophyte Gracilaria corticata at Intertidal Waters

Red macroalgae from the genus Gracilaria (agarophytes) are of ecological and pharmaceutical importance particularly for agar production. In this study, the red, agarophyte alga Gracilaria corticata was investigated for fluctuations of main and accessory pigments and total carotenoids at two depths during its growing season. The alga was sampled from coastal waters in Brice coast, Chabahar, southern Iran, from December to March in shallow (2–3 m) and higher (5–6 m) depths. The accessory pigments (phycoerythrin, phycocyanin and alophycocyanin), chlorophyll a, and total carotenoids were extracted three times using appropriate solvents and estimated through spectroscopy (mg g −1 dry weight). All pigments of G. corticata increased with depth showing significant differences between the two depths (p < 0.05). Phycoerythrin and phycocyanin were utmost at a depth of 5–6 m in December and January. The highest allophycocyanin and chlorophyll a contents were found at a depth of 5–6 m in February, and total carotenoids were of greatest values at depths of 2–3 m and 5–6 m in March and February, respectively (p < 0.05). The pigment ratios (phycobilin/chlorophyll and total carotenoids/chlorophyll a) at the two depths displayed marked monthly variations (p < 0.05). The greatest phycobilin/chlorophyll a (0.4 ± 0.2418) was found in December (5–6 m) and the ratio of carotenoids/chlorophyll a (0.31 ± 0.0058) was highest in March (2–3 m). The remarkable increases in major and accessory pigments with depth could indicate maximum biomass and production of G. corticata , especially in the months of February and March, which is important for field harvesting operations.