Experimental tank cultivation of Porphyra in Israel

Outdoor tank cultivation of several Porphyra (nori) species was carried out from late November 2002 through early May 2003 using 40 L (with a surface of 0.25 m²), 600 L (1 m²), and 24,000 L (30 m²) fiberglass or PVC tanks provided with continuous aeration and seawater flow. Sexual and asexual spores produced from cultured conchocelis and frozen thalli in the laboratory, respectively, were subsequently grown to produce young fronds (ca. 5-10 cm) in an average time of 8 weeks. Growth in outdoor tanks and ponds was possible for a period of up to 20 weeks (i.e. growth season), with yields above 100 g FW m^-2d^-1occurring during 12-14 weeks from late December through late March, when seawater temperatures were below 20°C. These yields correlated with the species and depended on the type of tanks in which the algae were cultivated, with the highest yields observed for Porphyra sp. and Porphyra yezoensis when fertilized twice a week with NH ₄ Cl and NaH₂ PO₄in 40 L tanks. Calculations of productivity for an entire growth season based on ≥100 g FW m ^-2d^-1yields exceed the average productivities using seeded nets in open sea, for all Porphyra species tested (0.96-4.06 kg DW m ^-2 season^-1vs. 0.7-1.0 kg DW m^-2of net season^-1). Therefore, tank cultivation of Porphyra can offer an additional source of nori biomass to international markets. Land-based tank cultivation also offers an environmentally friendly practice that allows for the manipulation of growth conditions to enrich seaweeds with specific, valuable chemicals such as protein and minerals.