INTRODUCTION TO THE WORLD'S MARINE SEAWEED CONSUMPTION

The consumption of seaweed as food worldwide is concentrated in China, Japan and Korea, where several species of the natural environment have been collected in a traditional way. There are other Nordic European countries with a tradition of consumption where consumption is increasing or is being maintained and in other countries such as France and Spain their consumption is being promoted quite successfully. In the last 50 years, consumption has increased in a greater proportion than natural production, which is why at present most of the market demand is covered by cultivated algae. The estimated annual volume handled annually for this use is 6,000,000 tons of fresh marine algae.

Seaweed grown for human consumption

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Regarding the consumption of marine algae for industrial uses, the production of food additives such as alginate, agar and carrageenan stands out. It is estimated that approximately 1,000,000 tons of fresh seaweed are destined for this use per year. The production of agar and carrageenan is almost entirely covered with cultivated algae, while for alginate production, extracts of brown algae collected from the natural environment are still used, due to the high cost of their cultivation.

Algae grown to extract hydrocolloids

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Regarding the other uses of seaweed, they have been used traditionally as fertilizer in coastal areas but with the appearance of chemical fertilizers the use of fresh algae has decreased. Recently, transformation methods are being used to convert them into feed additives or to incorporate them as fertilizer, but at the moment they represent a residual part of the use of algae.

THE CULTIVATION OF MARINE SEA WORKS IN THE WORLD

Worldwide, the most cultivated algae in the world are destined for direct human consumption: Porphyra (nori), Laminaria (kombu) and Undiaria (wakame). In volume, Laminaria species stand out, with a production (in dry weight) estimated at a world level of 1,000,000 tons compared to 90,000 tons of Porphyra or 33,000 tons of Undiaria.

The cultivation of algae for the production of agar is concentrated in the species of Gracilaria, although wild algae of this species are also extracted for this use. Spain is among the main producers of agar and, although they are also harvested, most of the algae used are imported from countries such as Chile, Indonesia and China, where intensive cultivation has been developed.

In terms of carrageenan production, warm-water algae species such as Kappaphycus alvarezii and Eucheuma denticulatum are grown in countries such as the Philippines, Indonesia and Tanzania (85%). But Gigartina species are also produced in Chile, Morocco and Mexico (10%) and Chondrus in Canada, Spain and France (5%)

Importance of the crop

• They provide a high nutritional content for fish, crustaceans and molluscs. Also for human consumption it offers us good
• The algae do not need agricultural land or clean water
• The algae offer the biosphere a considerable proportion of ovigens
• They are capable of producing antibiotics, pigments, steroids and other compounds making only use of sunlight, carbon dioxide and seawater.

Crop systems:

• Open system: In which the crop is exposed to the atmosphere

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• Closed system: commonly called photobioreactors in which the crop has little or no contact with the atmosphere.

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The intensive culture can be imitating the life cycle of the algae or taking advantage of the phases of vegetative multiplication of the algae (a piece of an algae can give rise to a complete algae). In addition to this, the crop can be carried out in the medium (outdoor), in a production plant (indoor) or in a mixed culture, in which the seed and preparation of the seed is done in the laboratory, but the culture is in the middle.

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Culture methods

There are some methods of growing macroalgae that are the most used since ancient times. In the majority these are used for the reproduction of red algae or Rhodophytas, which has a great commercial and industrial value.

Rafting algae method

Basket raft

It consists of five or more cylindrical bamboo baskets 1 meter long and 17 cm in diameter, tied together with a line.

Each basket contains a porous cylinder of strongly buffered mud containing 1.5 kg of fertilizer. Above all, they have an opening in the upper side of the basket that facilitates the removal of the fertilizer cylinder. This cylinder must be filled monthly.

A rope is tied on each side of the basket and the juvenile sporophytes adhere by inserting the basal end of the stipe, between the strings of the rope.

As the liquid fertilizer seeps out of the cylinder, the nutrients are absorbed by the sporophytes.

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The Tube Raft of a Line

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It is built by attaching tubes of rubber or extreme bamboo with end. This is, to form algae-cultivation-a single line about 60 m long. Every 6 meters along the raft a porous mud jar of 2.8 lt is suspended. Which contains fertilizer, at a depth of 1.3 meters.

The juvenile sporophytes adhered to the strings, similarly adhere at intervals of about 50 cm.

The distance between the plants on a string varies between 1.7 to 3.0 cm. And the length of these can be from 1 to 3 meters.

These rafts are placed every 3 or 4 meters between them.

The Two Lines Tube Raft

It is a staircase structure composed of 1 m long bamboo tubes. Which, are tied through two strings of 12 to 15 meters of intervals of 1 meter.

The tubes are placed in groups of three, with a porous mud cylinder with fertilizers of 2.8 lt. And suspended from the middle of the tube of each group.

Ropes with juvenile sporophytes adhere to the tubes. In the same way described for the other types of raft. Up to four tube rafts of two lines can be tied every 5 meters.

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Basic culture method in the background

It is used only in shallow areas at low tide. The idea is to allow the use of floating rafts, which is called "stone pouring". And it consists of placing large stones that have 16 kg of weight in the water. What provides an adhesion surface for zoospores produced naturally.

The stones are placed in rows every 2 meters. And separated from each other every 20 centimeters; resulting in densities of 3800 to 4800 stones per hectare.

Where the background is smooth, the stones can be replaced by round baskets made of bamboo or willow branches. Here, the spores can adhere to the baskets before they are placed in the sea, or sporophytes with sori can adhere.

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Finally, there are many advantages that nature offers us. Especially Seaweed and its benefits for man and the planet in general

High concentrations of vitamin B12, Vitamin E and antioxidants that help our body, do not absorb contaminants and are energy plants. Its high content of minerals such as iodine, calcium, magnesium and fibers help the production of natural fertilizers.

In case of constipation, it is useful to use them as natural remedies, just as they are effective when used as part of diet meals and strict diet regimen for diseases such as thyroid.

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I hope you liked this post about aquaculture in the seaweed, soon I will continue to show you more about this wonderful world.
A hug for you.

@francismoure