The Marine Algae “SEAWEED”
Seaweed is a macroscopic, multicellular, marine algae that lives near the sea bed. The study of seaweed is known as Phycology. According to coloration seaweed can be classified into three classes.
1.Brown algae– Some genus commonly known as kelp. Example- Order – Laminariales , Sargassum ( Order- Fucales ) 2.Green algae– Ulva species. Commonly known as sea lettuce. 3.Red algae – Gelidium Basically green algae are used as food, brown algae are used as fertilizers.
The red algae are used to make gelatin-like product called agar. Seaweed provides food, protection and shelter to other marine creatures. Fish, diatoms, planktons eat its leaves and stems. Seaweed is at the bottom of the food chain. Without seaweed, many of these creatures would die, causing other marine animals to die. Seaweed is highly nutritive human food also. Seaweed is a very good source of edible iodine also. That is why it is very helpful for thyroid and brain health also. There is also a good amount of vitamin B-12, A. And it’s a great source of fiber also. Seaweed is mostly soluble fiber.
Importance of Seaweed:
Protection and shelter: Many smaller marine creatures hide from predators among the seaweed’s leaves. Some live in the seaweed and and wait for their prey to come along. Sea urchin, diatom, smaller fishes find shelter in the seaweed Cleaner: Seaweed removes gases from the marine environment by absorbing them into its leaves. Thus, the animals in the environment also are healthy. Prevents erosion: Areas with seaweed are more stable than areas lacking seaweed.
History of seaweed culture:
Seaweed culture is one of the most common things all over the world. Seaweeds have been harvested throughout the world as a food source as well as an export commodity for production of agar carrageenan products. Seaweed farming began in Japan as early as 1670 in Tokyo Bay. In the 1940s, the Japanese improved this method by placing nets of synthetic material tied to bamboo poles. This effectively doubled the production. The main food species grown by aquaculture in Japan, Korea, China. Seaweed farming has frequently been developed as an alternative to improve economic conditions and to reduce fishing pressure and over exploited fisheries.
Different culture methods of seaweed and some parameters for suitable site selection:
Mainly culture method can be classified into two major classes- 1. Net method and 2.Monoline method. Net method can be classified into two sub classes- Floating bamboo method and mangrove stakes and nets. Monoline method can be classified into two sub classes – Bottom monoline method and floating monoline method. Site selection is most important thing for seaweed culture. Choose a location where there is a good water movement or where there is a rapid water turn over Water current speed should be between 20 to 40 meter/minute. Salinity of the farm area should be from 27 to 35 ppt. The area should have a water temperature range between 25 to 30 degree Celsius . Water depth in the farm should not less 2 feet during the lowest tide and more than 7 feet during high tide. The area should be selected where there other plants are available and communication is easy.
Seed selection and preparation: Careful selection of seedling is must. Healthy strong branches should be selected. Good seedlings are found at center and near the tip of a healthy plant. Clean and sharp knife should be used. Branch should not be cut in slant position. Planting: Before planting the seedling should be cleaned. Dirt, epiphytes, other materials should be removed properly. Prepared seedlings should be planted properly then. Harvesting: Finally harvesting should be done properly. In this case sharp and clean knife should be used properly. Drying: At the end, drying should be done before marketing. Use coconut palm as flooring when drying in the land. Never dry the seaweed directly on the soil to avoid contamination. Drying should be done for 1-2 days for three times a day. Salt materials should be cleaned from the seaweed by meshed screens. Weight has to be measured before marketing.
Present status of seaweed culture in Bangladesh and their utilization:
In Bangladesh, naturally growing seaweeds are in the littoral and sub-littoral zones of St. Martin’ s island. Ten species of seaweeds have so far been recorded from the island. These include three species of green seaweed, two species of brown seaweed, five species of brown seaweeds. In 1987 Bangladesh imported two tons of agar from Japan and South Korea. Approximately 15 metric ton seaweeds were produced in 1989. The total production was consumed in the country. Bangladesh is not importing seaweeds directly but in product from. Such as – agar. The government is preparing plans for seaweed culture. Natural stock would not last long under the present state of harvesting. Seaweed culture can be a great source of earning of the unemployed people.
A.K.M. Afzal Hossain (Pial), Faculty of Fisheries at Bangladesh Agricultural University