Effects of deep seawater medium on growth and amino acid profile of a sterile Ulva pertusa Kjellman (Ulvaceae, Chlorophyta)

The potential use of deep seawater (DSW) for the cultivation of macroalgae was evaluated by analysis of the growth rate of thalli (by surface area), photosynthetic pigment content, and total free amino acid content of sterile Ulva pertusa cultured in the control medium (one-fifth strength Provasoli’s enriched seawater (PES) medium), surface seawater (SSW) medium and also seawater medium collected from 400 m depth (400-DSW) and 1,200 m depth (1,200-DSW). The growth rate of the sterile U. pertusa grown in 400-DSW and 1,200-DSW was similar to that of thalli cultured in the one-fifth strength PES medium that had previously been shown to be the optimum concentration for the cultivation of Ulva. Photosynthetic pigment content in the control medium, 400-DSW- and 1,200-DSW-cultured thalli was 1.7–2.0 times higher than that of the SSW-cultured thalli. The total free amino acids content of the control medium and SSW-cultivated thalli was 264?±?64 and 120?±?39 mg per 100 g dry weight, whereas the 400-DSW- and 1,200-DSW-cultivated thalli had significantly more amino acids (342?±?69–327?±?64 mg per 100 g dry weight). The results of this study indicate that DSW has a high potential for cultivation of edible macroalgae without any supply of extra nutrient until it grows to harvest size.