Topic 10: Mariculture of Seaweeds PDF

TOPIC 10: MARICULTURE OF SEAWEEDS BGY4107 BIOLOGY & PROPAGATION OF COMMERCIAL ALGAE  1.0. Introduction 1.1. Need for Mariculture 2.0. Porphyra Cultivation CONTENTS 3.0. Gracilaria Cultivation 4.0. Eucheuma and Kappaphycus Cultivation...

TOPIC 10: MARICULTURE OF SEAWEEDS BGY4107 BIOLOGY & PROPAGATION OF COMMERCIAL ALGAE  1.0. Introduction 1.1. Need for Mariculture 2.0. Porphyra Cultivation CONTENTS 3.0. Gracilaria Cultivation 4.0. Eucheuma and Kappaphycus Cultivation 5.0. Laminaria Cultivation 2.0. Porphyra Cultivation  Porphyra considered the most valuable maricultured seaweed in the world, annual value of more than U.S. $1.8 billion (Yarish et al. 1999). Nearly 1,011,000 metric tons (wet weight) of Porphyra were produced through mariculture.  Six species of Porphyra are usually cultivated; the first three are more common in Asia. Porphyra yezoensis, Porphyra tenera, Porphyra haitensis, Porphyra pseudolinearis, Porphyra dentate, and Porphyra angusta  The plants can grow from 5 to 35 cm in length. Thalli are either one or two cells thick, one or two stellate chloroplasts with a pyrenoid. 2.0. Porphyra Cultivation  The plants can grow from 5 to 35 cm in length. thalli are either one or two cells thick, one or two stellate chloroplasts with a pyrenoid.  Porphyra has an alternation of generation: 1. Gametophytic phase : macroscopic foliose thallus Spermatia + carpogonia cells = zygote After fertilization, carpogonia divides to form carpospores. Carpospore produce filamentous conchocelis phase /sporophyte 2. Sporophytic phase: conchocelis phase (in oyster shells) Conchospores germinates to from the thallus.  Porphyra reproduces by both modes of reproduction, sexual and asexual mode. 2.0. Porphyra Cultivation  Remember : Porphyra needs the multistep farming. Seaweeds with two-step or multistep farming.  The cultivation technique involves four major steps: 1. Culture of conchocelis (Sporophyte stage) 2. Seeding of culture nets with conchospores (‘spores’ diagram) 3. Nursery rearing of sporelings (conchospores) 4. Harvesting.  2.1. Culture of conchocelis In Asia, the culture of conchocelis starts around mid spring (March/April). In nature, the conchocelis phase grows on oyster, clam, and scallop shells. In Japan, artificial substrata, made of transparent vinyl films covered with calcite granules are used. The oyster shells or artificial shells are placed on the bottom of shallow tanks filled with seawater for seeding to take place. Carpospore suspension can be prepared artificially by: 1. Air drying the fertile thalli (gametophye) overnight and the next morning, immersing them in seawater for 4–5 hours. 2. Grinding the fertile blades (gametophye) and separating the suspension of carpospores by filtration. The carpospore suspension is then introduced into the seeding tank, where the spores settle on the substrata (Fig 2b-c). The carpospores germinate and bore into the shells or the artificial substrates under very low light conditions (