Monostroma (Figure 7.9) and Enteromorpha (Figure 7.10) are the two green macroalgae genera cultivated in Japan, and known as aonori or green laver.
Enteromorpha prolifera and Enteromorpha intestinalis are found in bays and river mouths around Japan, and are also found in many other parts of the world, including Europe, North America, and Hawaii. Fronds usually flat, narrow, and bright green in color can be seen waving gently with water movement. They can be attached to firm substrate in clear, shallow waters, and also occur as epiphyte on cultured red seaweeds such as Kappaphycus, Eucheuma, Gracilaria, Gelidiella, and others.
Ulva sp. is known as sea lettuce, as fronds may be convoluted and have an appearance rather like lettuce. It can be collected from the wild and added to Monostroma and Enteromorpha as part of aonori. It has a higher protein content than the other two, but much lower vitamin content, except for niacin, which is double that of Enteromorpha. Bright green in color, it has a double or multiple cell layer. Slender at the holdfast and growing wider toward the apex, it reproduces seasonally, usually during tropical dry season or temperate spring. It is naturally found in shallow sea water usually less than 1 m in depth, where it grows on rocks, coral, mollusk shells, or other hard substrate, but also as an epiphyte on other sea macroalgae. It was used as flavoring with other seaweed by Kashaya Pomo natives of northern California.
Caulerpa lentillifera (Figure 7.11) and Caulerpa racemosa are the two edible green algae used in fresh salads and known as sea grapes or green caviar. As the common name suggests, their appearance looks like bunches of green grapes. These algae often produce “runners” under the substrate, which can produce several vertical branches that extend above the substrate. They naturally grow on sandy or muddy bottom in shallow protected waters.
Caulerpa lentillifera has been very successfully cultivated in enclosures similar to prawn ponds in the central Philippines, where about 400 ha of ponds are under cultivation, producing 12–15 tons of fresh macroalgae per hectare per year. Water temperature can range between 25 and 30°C. Pond depth should be about 0.5 m and areas of about 0.5 ha are usual. Also some strains of C. racemosa give good yields under pond cultivation conditions.
Planting is done by hand; about 100 g lots are pushed into the soft bottom at 0.5–1 m intervals. Harvesting can commence about 2 months after the first planting; fronds are pulled out of the muddy bottom, but about 25% of the plants are left as seed for the next harvest. Depending on growth rates, harvesting can then be done every 2 weeks. The harvested plants are washed thoroughly in seawater to remove all sand and mud, then sorted and placed in 100–200 g packages; these will stay fresh for 7 days if chilled and kept moist.
Table 7.5 summarizes edible algae and the corresponding food item.
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