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Laminaria mariculture in China


C. K. Tseng
Institute of Oceanology
Academia Sinica
Qingdao, China


Laminaria is not a native of Chinese shores though it has been a well-known food commodity on the Chinese market for more than one thousand years. It was first imported to China from Korea and later from Japan in large quantities (Tseng 1958, 1981a,b). In 1927 Laminaria was accidentally introduced to Dalian (Dairen), Liaoning Province, in the North Huanghai Sea. From then until 1952, wild and semi-wild Laminaria growing on natural rocks was harvested commercially with the largest annual output being 40.3 tons of the dry product in 1949 (Tseng, 1981a,b). Mariculture of Laminaria on artificial floating rafts started in 1952 and commercial production increased steadily until 1980 when the peak production of 252,907 tons of the dry product was produced (Tseng, 1981a,b; Zeng [=Tseng], 1984).


1.1 Crop history and nomenclature
1.2 Taxonomy
1.3 Morphology and anatomy

1.1 Crop history and nomenclature

Laminaria has been known in China, first, as kunbu (meaning "large cloth") and, more recently, as haidai (meaning "sea ribbon"). According to Chinese literature, more than one thousand years ago, Chinese herbal doctors found that a seaweed under the name kunbu growing on the East China Sea coast had a curative effect on goiter. This has been shown by Tseng and Chang (1961) to have been Ecklonia kurome. It was later discovered that another seaweed, a Laminaria growing on the eastern Korean coast, also had a similar function, and so a large quantity of the dried seaweed was imported to China from Korea under the same name, kunbu. This name was evidently broadly employed for large brown seaweeds having the property of curing goiter. Later it was found that Laminaria grows in even much larger quantities in Japan, which eventually became the most important exporter of kunbu, called kombu by the Japanese (Tseng and Chang, 1961).

A few hundred years ago the name haidai was introduced to refer to this seaweed which the Chinese imported from Japan and Korea. Nowadays, this Laminaria is popularly known in China as haidai and this name has been adopted as the official commercial name for this seaweed. The name kunbu, used for many hundreds of years for both Ecklonia and Laminaria, is no longer employed for Laminaria, but rather is restricted to Ecklonia, at least, in Fujian Province (Tseng and Chang, 1961).

Thus Laminaria has come to be known in China as haidai and in Japan as kombu. Internationally, "kelp" is a widely used name for Laminaria. The term "kelp" was applied originally a few hundred years ago to the ash of laminariaceous algae used for the extraction of soda and potash. In the early part of the present century, American scientists seeking sources of potash began to call other seaweeds belonging to the Laminaria group, including Macrocystis pyrifera, kelps. Nowadays, Macrocystis is well known as "giant kelp", Nereocystis as "bladder kelp" and Laminaria as "kelps". For the different species of commercial Laminaria, the use of an adjective before the word "kelp" is suggested, for instance, "Japanese kelp" for Laminaria japonica and "sugar kelp" for L. succharina, etc.

1.2 Taxonomy

In and before the early fifties, when large quantities of Laminaria were still imported into China from Japan, the haidai or Japanese kelp on Chinese markets was principally Laminaria japonica mixed with various other species of Laminaria. In the early fifties we analyzed haidai on the markets in different places in China and, besides L. japonica, found a significant admixture of L. angustata. There has been quite a controversy among Japanese phycologists on the taxonomy of the Japanese Laminaria, especially concerning L. japonica and the related species L. ochotensis, L. diabolica and L. fragilis. These are treated as independent species by Miyabe (1957). The group of phycologists headed by Hasegawa (1963) considered them to be merely varieties of the same species under the first name applied, L. japonica, as follows:

L. japonica var. japonica (L. japonica and L. fragilis)
L. japonica var. ochotensis (L. ochotensis)
L. japonica var. diabolica (L. diabolica)

Even L. religiosa may belong to the same species complex. The more we work with the haidai in China, which was transplanted to China from Japan more than half a century ago, the more we come to believe that these "species" are nothing but variants of the same taxon growing under different ecological conditions. It may perhaps be better to treat them as ecological variants. The Chinese haidai now under cultivation is closer to L. japonica var. japonica, but in earlier stages of development it resembles more closely L. japonica var. ochotensis with forms resembling L. japonica var. diabolica also occasionally being found (Tseng and Wu, 1962; Zeng [=Tseng], 1984).

1.3 Morphology and anatomy

The Chinese haidai is a typical laminariaceous seaweed consisting of an elongated simple broad rich-brown, strap-like frond provided with a cylindrical or subcylindrical stipe attached to the substratum by a profusely branched rhizoidal holdfast. The strap-like frond is generally called the "blade". There are two shallow channels in the central parts of the blade forming a central strap portion. This is especially clear-cut in the first year. The concave surface faces outward toward the light and the convex surface inward. The central portion is thicker, and the lateral part thinner, appearing somewhat wavy. When young, this Laminaria has a leafy frond with a strongly cuneate base reminding one of Laminaria ochotensis. When mature, the leafy frond attains a length of 2-6 m, varying from 2 m or less in the Xiamen region in the south to 6 m or more in the Dalian region in the north, and a breadth of 35-50 centimeters. The thallus has a stipe 5-6 cm long and the broad base typical of L. japonica. In its original habitat in Hokkaido, the typical life span of this Laminaria is three years, but in the cultivated forms it is only two years. However under farmed conditions it is actually grown in the sea for only 8 months (Hasegawa, 1963; Miyabe, 1957; Tseng, 1958, 1981a,b).

Morphologically, as seen in the field or by the unaided eye, four different stages may be differentiated: (1) the sporeling stage, (2) the young sporophyte stage, (3) the robust sporophyte stage and (4) the mature sporophyte stage (Fig. 1: 12-15).

Figure 1. Life history of Laminaria japonica under cultivation. 1. Zoospore; 2. Embryospore; 3. Germination of embryospore; 4. Gametophyte just formed; 5a. Female gameto-phyte; 5b. Male gametophyte; 6a. Mature oogonium; 6b. Discharging spermatozoid; 7. Egg on empty oogonium; 8. Sperma-tozoid; 9. Fertilization; 10. Zygote; 11. 7-celled spore-ling; 12. Sporeling; 13. Young sporophyte; 14. Robust sporo-phyte, and 15. Mature sporophyte with sporangial sori.

The first stage, the young sporeling stage, includes the time from the germination of the zygotes to sporelings of 5-10 centimeters. The sporelings are at first monostromatic but before reaching about 1 mm in length they become multistromatic, with all cells remaining meristematic, though later differentiating into blade and stipe. Further differentiation results in the formation of a meristematic growth region between the stipe and the blade. This takes place when the sporelings are about 5 or more cm long.

In the present system of cultivation in China, the first or sporeling stage is grown in two totally different environments. The state from the zygote to sporelings of a few mm to 2-3 cm long or even more are reared in a sporeling-culture house (a "glasshouse" or "greenhouse") with the culture solution cooled to about 8-10°C (Fig. 1:11,12). In mid-October when the seawater temperature (in Qingdao) drops to about 20°C, the strings on which the sporelings are growing are taken outdoors and cultivated in the sea under natural conditions (Fig. 1:12).

The differentiation of the basal meristem of the frond marks the beginning of the second stage, the young sporophyte stage, characterized morphologically by the cuneate bases of the strongly bullate fronds, which are rather thin and brittle. They grow very rapidly in length and fresh weight. In November-December the Chinese transplant the young sporophytes with the meristematic region well differentiated to regular cultivation rafts. Within a few months, by early spring in the Qingdao region, they may reach a length of 3 or more meters. The bulla-tions of the blade gradually disappear as growth advances. This stage occurs during the period when the water temperature gradually drops from about 15°C to the winter minimum of 1-2°C in February and rises to about 13°C in mid to late spring, a period of about 5 months (Fig. 1:13).

When the bullations of the blades have entirely disappeared and the blades have become smooth, flat on the surface, and leathery in substance, with the base of the fronds being roundish instead of cuneate in shape, the sporophytes have reached the robust sporophyte stage, the third stage of their growth and development. In this stage growth of the sporophytes in length practically stops; there may even be a decrease in length due to natural shedding of the tips, but growth in thickness and in dry weight continues (Fig. 1:14).

With further growth of the sporophytes in the robust stage, the blades become increasingly thicker, their bases more broadly roundish, their substance more leathery and, in May to June, depending upon the light conditions, sporangial sori in small roundish patches begin to appear in the upper part of the frond. Thus the sporophytes have arrived at the fourth stage, the mature sporophyte or sporulating mature stage. In late June to early July when the seawater temperature reaches 20°C and higher, the formation of sporangial sori stops.

Anatomically the blade is composed of three basic structures, the epidermis, the dermal tissue and the pith. The epidermis constitutes the outermost tissue of small epidermal cells arranged in a palisade, squarish in transverse section and elongated in longitudinal section, and with ellipsoidal chromato-phores concentrating in the outer portion. Inside the epidermis is a layer of dermal tissue which may be differentiated into two sub-tissues, an ectodermis of comparatively smaller cells and an endodermis of larger ones. Both sub-tissues are composed of elongated subcylindrical cells, and those of the former are more regularly arranged. The pith is composed of pith cells and trumpet cells, both remarkably smaller than the cells of the endodermis (Fig. 2: A1-4). Pith cells are ordinary cylindrical cells but trumpet cells are very much elongated, attaching to each other terminally with their apposed end walls a large circular dish, the sieve plate (Fig. 2:B5), bearing numerous punctate holes. Muscilage glands are distributed here and there in the endodermis, stipes and holdfasts (Fig. 2:C).


2.1 The sporophyte generation
2.2 The gametophyte generation

Many reports on the life history (See Fig. 1) of Laminaria have been published. Although in general they are similar, they differ in detail, especially in the relationship with environmental factors such as temperature. In our investigation of Laminaria japonica under commercial cultivation in China, we have noted differences from previously published reports and have found certain characteristics peculiar to the Chinese strain. Evidently Laminaria japonica, transplanted from Hokkaido and northern Honshu to Dalian several times since 1927, has undergone continuous hybridization and adaptation to its new environment in Dalian, and has formed a new strain genetically different in some respects from the Japanese stock.

2.1 The sporophyte generation

As mentioned above, the sporophyte generation may be subdivided into four different morphological stages. In the mature stage, sporangial sori are found in the terminal portions of the fronds. A cross section of a mature frond shows that the sporangia grow outward from the endodermis and are scattered among paraphyses having gelatinous sheaths (Fig. 2:D). Reduction division occurs in the first division of the spore mother cell divisions, and altogether 32 zoospores are produced per sporangium. For the morphology and anatomy of the sporophyte, please refer to Section 1.3.

Figure 2. Sections of fronds. A. Transverse section of blade, showing (1) epidermis, (2) ectodermis, (3) endodermis and (4) pith. B. Longitudinal section of blade, showing (5) trumpet cells. C. Three gland cells. D. Transverse section of blade showing (6) paraphyses and (7) sporangia.

2.2 The gametophyte generation

The haploid zoospores are pear-shaped, about 6-8 urn long and 4-6 m m broad with two lateral unequal flagella, the longer one about 18-20 m m long, directed forward and the shorter one 7-8 m m long (Fig. 1:1). Within about 2 hours after liberation from the zoosporangia, most of the zoospores adhere to the substrate. The time needed for the zoospores to adhere depends, however, on the temperature. At 15-20°C, zoospores will adhere in 5-10 minutes, while at 5°C, they may continue swimming actively for 48 hours before adherence. Soon afterwards the zoospores are transformed into embryo-spores which remain naked with only a cytoplasmic membrane (Fig. 1:2). In about 4 hours, the embryospores give rise each to a germination tube 19-33 m m long (Pig. 1:3), and within 2-3 days the entire cell content flows to its apex, which becomes spherical with a cell wall, thus becoming the initial cell of the gametophyte (Fig. 1:4).

The initial cells of the gametophytes are similar to or slightly smaller than the zoospores; otherwise there is practically no difference between the cells of the male and of the female gametophytes. Soon, however, the difference begins to appear. In the case of some gametophytes, cells start to lengthen and divide, and in the case of others there is no such vegetative division. The former become multicellular, eventually with 7 or 8 to as many as 17 or 18 cells in about 6 days. These cells remain similar in size to the initial cells, i.e., 4-8 m m in diameter. These are the male gametophytes (Fig. 1:5b). Those spores that remain unicellular grow to 11-22 m m in diameter and are female gametophytes (Fig. 1:5a). Vegetative growth of both kinds of gametophytes takes place in about 6 days under the culture conditions normally used.

Development of the gametophytes takes place during the following 2-3 days. In the male gametophytes, each of the apical cells forms a small protrusion with a thinner cell wall and becomes a spermatangium (Fig. 1:6b). The single cell of the female gametophyte is directly transformed into an oogonium (Fig. 1:6a). Our experiments showed that, for the liberation of the male and female gametes as well as fertilization, a short period of darkness is necessary (Tseng, Ren and Wu, 1959). The egg will first protrude from the oogonium and sit on the empty oogonial cell wall (Fig. 1:7). Very soon afterwards spermatozoids in the vicinity break through the thin-walled spermatangium and each spermatangium liberates one spermatozoid (Fig. 1:8). Numerous spermatozoids are attracted to any protruded egg (Fig 1:9), and soon swim to and surround it. Eventually one of the spermatozoids succeeds in entering the naked egg, which immediately forms a cell wall over its surface. Fusion of the male and female nuclei results in the formation of the zygote. Thus, under the most favourable conditions, it takes only 10-12 days for the gametophyte generation to pass through three stages of growth and development from the liberation of the zoospores to the formation of zygotes. This includes 2-3 days for the stage of gametophyte formation, 6 days for its vegetative growth stage and 2-3 days for its differentiation stage and the resulting zygotes, the latter starting the diploid sporophyte generation of the life cycle (Fig. 1:10).

In the present system of Japanese kelp cultivation in China, the entire process from the adherence of the liberated zoospores to the sporeling cords to the formation of the zygotes, all takes place in a sporeling- culture house with controlled environment.

Under natural conditions, it will take twice or even three times the time for the completion of the entire process, namely, from zoospore to zygote.


3.1 Floating raft mariculture
3.2 Culture of summer sporelings
3.3 Fertilizing kelps in the open sea
3.4 Southward extension of commercial cultivation
3.5 The tip-cutting practice
3.6 Environmental and pathogenic diseases

3.1 Floating raft mariculture

Development of the kelp production from the maximal pre-1950 annual output of 40.3 tons (dry) in 1949 to 6253.3 tons in 1958 shows (Table 1) an increase of 155 times within a few years. The large increase in production was made possible by the introduction of artificial substrata constructed of floated lines in raft form for the growth of the kelp. Perhaps for historical reasons these floated line systems are referred to as rafts.

Table 1. Comparison between natural substratum (rock) and artificial substratum (palm rope) production of the kelp (Laminaria japonica) in China, 1946-1958 (in tons dry wt.)*


Production on sub- substratum (sub tidal rocks)

Production on artificial substratum (Palm ropes)


Artificial sub-stratum culture as percentage of total production
















22. 3





114. 7



























*Based on data in Zeng (Tseng) 1984, original figures in fresh weight converted to dry weight by a factor of 1/6.

The floating rafts now in use in China evolved from simple square bamboo frameworks with one piece of bamboo about one meter or less in length on each side, tied together with ropes. Inside the framework two ropes were diagonally tied to the frame. The raft was then anchored to the sea bottom by two anchor ropes and was intended originally as a means of preserving seaweeds following harvest.

The first successful raft cultivation experiment used floating rafts made of palm ropes as the artificial substratum for the growth of the kelp, palm rope in the beginning but nowadays synthetic rope. Thus, natural substrata such as rocks are no longer necessary and cultivation can be effected anywhere even in places without rocks but with a mud-sand bottom.

The method is characterized by four important processes. The first is collecting of the zoospores on rope, which is equivalent to the sowing of the seeds in land crop farming. To do this a Laminaria frond with mature sporangial sori is subjected to partial drying in the air and then placed in a small body of sea water in a container. The liberated zoospores will soon attach themselves to the substratum, the seeding cords, which are placed in the water beforehand. The second process is the setting up of the sporeling floating raft (Figure 3) for the cultivation with the seeding cords hanging beneath the floating ropes in the sea. The third process is sporeling transplantation, which is equivalent to the transplanting of rice seedlings in rice farming. This is a crucial process ensuring appropriate density for the growth of the kelp fronds. In the spore collection process, the zoospores attach to the seeding cords randomly and generally in great density, and if the resulting sporelings are allowed to grow in this manner, the growth would be too dense, and the resulting plants small and thin. Therefore when the sporelings reach 10-15 cm in height, it is necessary to detach them from the seeding cords and twist them onto coarser cultivation ropes, the kelp ropes. The fourth process is the cultivation and tending of the sporelings in normal rafts beneath the floating ropes. The floats were formerly elongated bamboo, but now are mostly glass balls (Tseng, 1958, 1981a, 1981b, 1982).

At first autumn sporelings were used but later summer sporelings/a discussion of this point will follow. The four processes together form the culturing program of a kelp farmer.

The employment of floating raft cultivation technique has been a major key to the success and development of the Chinese kelp industry. When the floating raft method was first introduced/many mariculturists were still in favour of the so-called sea-bottom cultivation on natural rocks and stones. The first time in the history of mariculture that kelp was commercially cultivated and harvested on artificial substrata in the form of floating rafts about 10 tons of dry kelp was harvested. Up to 1955 production on sea-bottom rocks was still leading, being 3,218 tons against 206 tons for the raft culture. In 1956 raft culture production began to lead, being 319.7 tons against 167.7 tons produced by sea bottom growth, and in 1958 raft culture produced 5267.3 tons against 986.2 tons by sea bottom culture (Table 1), thus proving definitely the superiority of raft culture as a mariculture method. Since then cultivation on natural rocks on the sea bottom has been abandoned as a method for commercial seaweed cultivation. Nowadays, the floating line systems for commercial cultivation of kelps and other organisms have become elaborate structures. Many kinds are now in use; almost every locality has its own special type to fit its particular environmental conditions.

I. Hanging Kelp Rope Cultivation Method

Figure 3a. Two basic floated line, or raft, kelp cultivation methods, I and II. - a) Single line hanging kelp rope cultivation method.

Figure 3b. Two basic floated line, or raft, kelp cultivation methods, I and II. - b) A hanging kelp rope with kelps.

1. Wooden peg (anchor) 2. Anchor line
3. Float (glass) 4. Floating line
5. Kelp rope 6. Kelp 7. Weight

II. Horizontal Kelp Rope Cultivation Method

a) Figure 3c. Two basic floated line, or raft, kelp cultivation methods, I and II. - "Double line" floating rafts for the horizontal kelp rope cultivation method.

b) Figure 3d. Two basic floated line, or raft, kelp cultivation methods, I and II. - A pair of horizontally-linked kelp ropes with kelps.

1. Wooden peg (anchor) 2. Anchor line 3. Float (glass)
4. Floating line 5. Connected kelp ropes 6. Kelp
7. Link or knot

There are at present two basic variations in the floating rafts, the hanging rope and the horizontal rope forms I and II, respectively, in Figure 3. The former is characterized by its solitary lines, generally abbreviated as "single-raft" type; the latter is generally referred to as the "double-raft" type though sometimes even three or more rafts are tied together.

The "single-rope" or "hanging kelp rope" cultivation method has a large-diameter, more or less horizontal, line about 60 meters long floated at the surface (Figure 3-Ia) by buoys generally made of glass and anchored terminally by anchoring lines tied to wooden pegs driven into the sea bottom. The line is a large diameter rope. Hanging down from such floating lines are numerous kelp ropes, each about 50 cm long and weighted down by a small piece of stone or some other weighting material. To each kelp rope, in turn, are fastened the kelp. Each kelp rope in the Qingdao region has about thirty kelps twisted in it and is about 2 meters in length (Fig. 3-Ib).

The "double-raft" or "horizontal line" cultivation method has parallel pairs of kelp ropes (Fig. 3-II) instead of the solitary pendent kelp ropes of the "single-raft". The only difference being that the kelp ropes opposite each other in position on the parallel lines are linked or tied to each other, each pair of kelp ropes thus forming one horizontally placed floating kelp rope (Fig. 3-IIb) double the length of one of the solitary hanging kelp ropes. To keep the kelp ropes relatively near the surface, the long floating lines should be kept at least 5 meters apart. In order to economize on such floating lines, one may use three lines to support two rows of horizontally placed double length kelp ropes and in this case (Fig. 3-IIa) the middle line serves the function of two single lines.

The hanging kelp rope method has the advantage of better water movement and better utilization of the sea but has the defect of uneven growth of the kelps, since the uppermost kelps receive more and the lowermost kelps less light. The "double-raft" method has the benefit of more even growth of the kelps which, growing more or less in the same plane, receive similar light intensities. However, it has the defect of being more resistant to water motion and thus decreases it. Generally speaking, the "single-raft" method is better adapted to comparatively clearer water regions, and the "double-raft" method to turbid regions with lower water transparency; such as the Zhejiang coast near the Changjiang estuaries.

The floating raft method of kelp mariculture is one of the important reasons for the success of the kelp cultivation industry in China. The superiority of the method lies in the fact that it maintains the cultivated kelp at the water level selected as best suited for the growth of the kelp at each specific stage of growth and development. For instance in the Huanghai Sea coastal region; seawater is not as clear as in the original "home" of the Laminaria in Hokkaido and northern Honshu; therefore a series of experiments was carried on to determine which water level would be most suitable for the growth of this Japanese kelp. In the Qingdao region it was found that the kelp grows best two to three meters below the sea surface. When branchlets of the Kuroshio current approach this area and the sea water becomes much clearer in late spring, the kelp ropes are lowered half a meter to one meter to avoid the too strong light. On the East China coast, the sea water is very turbid and the water transparency very low; and the kelp has to be kept practically at the water surface to obtain optimal growth.

3.2 Culture of summer sporelings

There are two seasons for the production of sporangial sori, early summer and mid autumn. For the first few years up to 1956, the kelp spores were collected on sporeling cords in the autumn (mid-October in Qingdao) when the water temperature got down to about 26 degrees Centigrade. The kelp fronds therefore over-summered between July and October, since summer water temperature in the Huanghai Sea got to about 27°C which is intolerable for the Japanese kelp. For oversummering the kelp, fronds had to be moved to deeper waters, i.e., 10 or more meters below the surface. During the summer, typhoons occasionally come to Qingdao, and when they do, most of the submerged rafts with the kelps are destroyed. Loss may amount to about 90 percent. Besides, summer is the time that animals and plants, especially the barnacles, grow luxuriantly and before spores could be collected in autumn the barnacles had to be scraped away mechanically. Moreover, autumn is the season when Ectocarpus, Enteromorpha and other wild seaweeds shed their spores, and as soon as the seedling cords with collected spores were lowered in the sea, the spores of wild seaweeds would attach to them, germinate and grow readily and eventually cover the seedling cords entirely. The collected spores of the kelp generally need about 20 days to develop to seedlings of a few cells and since they had no light, they were unable to grow until about two months later when the wild weeds became mature, set off spores and died. Thus there would be a delay of about two months. The seedlings would not be large enough until late January to early February, which is the coldest season in the year. Then the seawater temperature is about 1°C and transplantation is very difficult work.

In working with summer sporelings, the difficulty is the high water temperature of those months, but by providing seawater artificially cooled down to 8-10°C, the collected spores would have a healthy environment in which to germinate and grow without the interference of wild weeds. Experiments proved the superiority of this method, with an increase of production by 30-50 percent. Labor conditions were greatly improved by transplanting the sporelings in late November or early December, when the seawater temperature was about 10°C (Tseng, Sun and Wu, 1956: Tseng, 1981b, Zeng, 1984). In the initial stage of the development of summer sporeling culturing, fluorescent lamps were used for lighting and the room was cooled to 8-10°C (Tseng, Sun and Wu, 1955a). In later improved systems a glass house ("greenhouse") was employed with natural light and fertilized sea water similarly cooled to 8-10° Centigrade.

The summer sporeling culture glass house is a standard glass house. Other than the water being cooled, if there is anything special it is perhaps in the construction of a series of shallow concrete tanks within it. In one case the paired tanks are about 12 m long, 2.4 m broad and 20-30 cm in depth, with one 20-30 cm higher than the other so that sea water can flow from one tank to the other under gravity.

In the Chinese method of kelp cultivation, collection of the zoospores on the sporeling cords should be effected at a temperature below 20°C., and the sporeling cords should be cultured in fertilized seawater cooled down to 8-10° Centigrade.

Sporeling cords are intertwined into a sort of framework for collecting the spores. After spore collection the frames with their collected spores are placed in a tank in the glass house with running cooled water enriched with nitrogen and phosphate fertilizers. The frames and the tanks differ from place to place but the principle is the same. In one case the sporeling frames are made of repeatedly intertwined palm cords. The sporeling frames are about 1.2 m long and 50 cm broad, so that two rows each with 30 frames can be placed in one tank. In each of the tanks there are four supporting ropes strung under water and parallel to the long axis of the tank. These are for supporting the submerged sporeling frames. In one to two months the sporeling cords on the frames will be crowded with sporelings one or more mm high. (See Section 5, below, for more detail.) When the temperature of the sea water drops to about 20°C these sporeling cords on the frames will be loosened and hung in sea water, and in one to two months the sporelings will grow to be 10-15 cm long. They are then ready for transplantation to the commercial rafts in the field.

3.3 Fertilizing kelps in the open sea

It has been experimentally proved that the inability of the vast Huanghai Sea region to support growth of Laminaria is due to the low nitrogen fertilizer content of the sea water. Water analysis of the so-called outer region of the Huanghai Sea showed that nitrate-nitrogen is only about 2-3 mg/cubic meter. It was also proved that Laminaria kelp needs a rather high gradient for effecting absorption of the nitrogen salts, generally over 20 mg m-3 in terms of nitrate-nitrogen. Experiments further proved that if the sea in this region is not fertilized with nitrogen fertilizers, it will not be able to support commercial production of the kelp. In 1956, small-scale experimental fertilization was conducted on kelp farms. In that year 2350 tons of fresh kelp were produced (Tseng, Sun and Wu, 1955b). In the following two years a large scale program of fertilizing kelp farms in the open sea was carried out, and in 1958, 31,604 tons of fresh kelp were produced, achieving a major increase of production of 1245% within two years. The increase was primarily due to fertilizing, making it possible for kelp mariculture activities to be extended to various coastal districts not previously engaged in kelp cultivation.

Since 1956, kelp farm fertilizer application methods have undergone three stages of development. In the first stage a non-glazed clay-bottle method of fertilizing was the sole method employed. The principle of this method is to utilize the minute porosity of non-glazed clay bottles to disperse and concurrently limit the outward diffusion of the fertilizer solution placed inside each bottle. This assured that the kelps in the vicinity received the necessary fertilizer and at the same time it minimized the loss of the fertilizer due to water currents. In the late fifties and early sixties, an extention of this method of fertilizer application made it possible to cultivate kelp commercially along the vast coast of the Huanghai Sea.

The second stage of the development of a fertilization method for kelp farms took place in the early sixties by simplifying the original clay-bottle method. The same principle of fertilizing by diffusion through porous bottles was employed, but measures to increase the efficiency and lower the cost of operation were taken. In the original method the clay bottles employed were rather heavy and clumsy, their cost was quite high, and much labor was involved in hanging the bottles and in changing their fertilizer solutions. Therefore various improvements were made, for instance, employing plastic bags with a few very minute holes punched in them. Methods for minimizing fertilizer loss and increasing fertilizing efficiency, such as intermittent fertilization, soaking juvenile sporophytes in fertilizer solution and refraining from fertilizing the mature sporophytes, have been suggested and partially applied.

A third stage of development also occurred in the sixties. With the further advancement of the cultivation techniques, the cost of kelp production continued to drop, and the profit obtained from kelp cultivation increased, so that kelp farming became an attractive means of improving the livelihoods of many coastal farmers and fishermen. More kelp farms were organized, and kelp farms became larger; some farms grew from a few acres to tens or even hundreds of acres. In places where fertilization was necessary, it became more and more difficult to apply the methods based on the diffusion of fertilizer through porous materials. By the early sixties, sufficient knowledge had been obtained to indicate that kelps, especially nitrogen-starved kelps, are able to absorb nitrogen fertilizer very quickly in large quantities and satisfy their needs for several days to come. Therefore fertilization by spraying has been popularly employed. This is done by providing a kelp farm with a motor boat equipped with a tank for holding fertilizer solution and a spray gun for applying it. Spraying sessions rotate from one part of the farm to another. It has become evident, because of the large area of the kelp farms, that the loss of the fertilizer due to currents is very small.

3.4 Southward extension of commercial cultivation

China's coastal regions of the East China Sea, south of the Changjiang (Yangtze) River are very fertile. According to our investigation in 1956, the nitrate-nitrogen content of the sea-water in the Zhoushan region of Zhejiang Province was 88-227 mg m-3 and that in the Xiapu region of the Fujian, Province 88-123 mg/cubic meter. These are respectively 11 times and 6 times more than for a fertile region in the Qingdao region. Cultivation of Laminaria in these two provinces, if otherwise possible, would not need the application of fertilizer, thus decreasing greatly the cost of production and broadening the area of cultivation. The turbidity of the sea water in these regions will not be a serious problem for the commercial cultivation of the kelp, since with the floating raft method, the elevation of the plantings and, thus, the light, may be regulated at will. The difficulty lies undoubtedly in the relatively long period of high sea water temperatures there. Therefore an experiment was conducted on the growth of the Laminaria in relation to water temperature. The results of the experiment showed that, although the optimal temperature for the Laminaria growth was 5-10°C, growth was still good enough at 13°C; even at as high as 20°C, a Laminaria frond of 1-2 m was still able to effect some growth. An investigation of the sea water temperature characteristics of Zhejiang and Fujian Province led us to believe the Japanese kelp would grow to commercial standards in these provinces south of the Changjiang River (Tseng, Wu and Ren, 1962).

On the basis of the above experiment and investigations, an experiment was conducted in 1956 on the cultivation of Laminaria at Gouji Island, Zhejiang Province. The results of the experiment fully confirmed our postulation that this Japanese kelp could be cultivated satisfactorily in the region south of the Changjiang River, and thus the groundwork was laid for a large-scale southward extension of its cultivation industry. At present, this extension accounts for about one third of China's total kelp production.

3.5 The tip-cutting practice

Natural shedding of the distal part of the blade is a common phenomenon with Laminaria in late spring. This loss amounts to as much as 25% of the total harvest. Moreover, nutrient matter is transported from the upper parts downward. The accumulation of the nutrient matter is greatest in the basal part of the frond and less near the apex. Experiments employing P32 as a tracer showed that phosporus moves from the apex to the basal part of the frond through the trumpet tissues, then to the stipe and finally to the holdfast. There is no indication whatsoever of a movement of phosphorus in the reverse direction.

On the basis of the downward movement of nutrient matter in the Laminaria fronds, and the phenomenon of natural shedding of the distal parts of the fronds, "tip-cutting methods" have been proposed to increase production. By this method, cutting off and removing the distal part of the frond take place between late April and early May. The cut parts, gathered and dried, have amounted to 12 to 15% of the production and in some cases about 6.75 tons per hectare in northern Shandong. This is in dry weight. Tip-cutting also helps to promote the quality and quantity of the crop because of the improvement of both light penetration and water flow. Besides, for the same reasons it helps also to minimize the occurrence of diseases and improve the environment.

3.6 Environmental and pathogenic diseases

Among the more important diseases in Laminaria cultivation, three are caused by adverse environments. They are the green rot disease, the white rot disease and the blister disease. In addition there are two diseases caused by pathogenic organisms, namely, the malformation disease of summer sporelings and the swollen stipe/twisted frond disease.

The green rot disease is characterized by the apical part of the frond turning greenish and becoming soft. The symptoms gradually spread to the lower part, resulting in the loss of the entire plant. This is due to insufficient light, and it generally occurs on the lowest part of a hanging cultivation rope. To stop the spread of the disease, the light conditions must be improved, for instance, by bringing the kelp ropes up to shallower levels or by inverting the kelp rope so that the lower kelps will receive more light.

The white rot disease is characterized by the kelp fronds turning from brown to yellowish and finally to white; the disease spreads from the tip to the lower part of the frond. Eventually the whole frond decays and drops from the cord. This usually happens in April or May and occurs in places where the transparency of sea water suddenly increases and the nitrogen fertilizer content in the sea water is insufficient to meet the demands of the kelp. In this case, more nitrogen fertilizer has to be applied and the kelp ropes lowered to reduce the light.

The blister disease is characterized by the presence of blisters on different parts of the frond, and decay spots resulting from disruption of the blisters. This is due to the influence of large quantities of fresh water following heavy rainfall. It generally occurs in shallow bays. To stop further spread of this disease; the kelp ropes should be lowered below the fresh water which floats at the surface.

The malformation disease of the summer sporelings is characterized by abnormal cell division of the zygote and in the early stages of the sporeling. The resulting malformed sporelings consequently die and drop off the nursery cords. It has been shown that the presence of hydrogen sulphide resulting from the growth of sulphate-reducing bacteria, such as Micrococcus, causes such abnormal cell division of the zygote and malformation of the sporelings. It has also been shown that mature sporophytes used for production of zoospores for commercial purposes harbour numerous kinds of bacteria, including sulphate-reducing bacteria. It is therefore believed that during the processes of spore collecting, the nursery will be contaminated with these bacteria which, if they multiply and grow in the nursery tanks, cause the disease. Sulphate-reducing bacteria are also found in quantities in old iron pipe systems. Preventive measures have therefore been taken by separating the sporeling culture system from the mature sporophytes employed in spore collecting, and by sterilizing the sporeling culture water system with bleaching powder before the seeding season.

The other disease caused by pathogenic organisms is the swollen stipe and twisted frond disease, usually abbreviated as "frond twist disease". It has a combination of three characteristic symptoms, namely, coarsened and hollowed stipes, twisted fronds and withered or shortened rhizoidal holdfasts. This is a very characteristic disease. It was prevalent in the Dalian region in 1973, causing serious damage to the kelp industry. It became less serious during the following two years. The disease has not recurred during the last ten years. The contagious and biotic nature of this disease has been experimentally proved, and the latent period found to be quite long, 60-70 days. Electron microscope examination revealed the presence of numerous polymorphic mycoplasm-like organisms, mostly coccoid and some ovoid, dumbbell and amoeboid in shape. Experiments also showed that tetracycline antibiotics were effective in controlling the disease. Measures were also taken to increase the disease-resisting ability of the kelps by improving the cultivation techniques.


Genetic studies of the natural stock of Laminaria japonica, the Japanese kelp now under cultivation in China, showed its hybrid nature. This conclusion was derived from the following experimental evidence: (1) Under the same environmental conditions gametophytes can have somewhat different morphologies and growth rates; (2) different female gametophytes react differently under x-ray treatment; (3) different gametophytes react differently to the temperature parameter, and (4) partheno-sporophytes have different morphologies and growth rates. It has also been proved that frond length, frond thickness, stipe length and even iodine content of the kelp under cultivation are all quantitative characteristics controlled by both environmental factors and poly-genes.

The above evidence forms the basis for selection work. Since the Japanese kelp is a hybrid, it can be subjected to selection and x-ray treatment during breeding to develop more desirable strains. It has also been pointed out that the harmful effect of continual inbreeding is relative and conditional; in some inbred lines there are harmful effects, while in others no harmful effects are found. It is these latter which eventually form strains with useful characteristics. Therefore the Chinese genetists have employed methods of continual inbreeding and selection in developing new strains. In the inbreeding process, single fronds of the kelps are used to produce the zoospores instead of several fronds as in the commercial production of the summer sporelings. In this way, the gametophytes and the resulting sporophytes all come from one single kelp frond (Pang, 1983).

In the sixties, three strains of kelp were selected, one with broad fronds, one with long fronds and one with thick fronds. In the seventies, two strains with both high production and high iodine content were selected. The selection of the high iodine content characteristic was effected by the so-called half-frond method. In 1970 the Chinese phycologists conducted large scale selection work in the nine cultivation regions of the five coastal provinces. They selected many mature fronds, cutting half of the frond for iodine analysis and found 19 plants with high production and high iodine content. The other half of each of these plants was left to mature further and zoospores were collected from them. Breeding was carried out by repeated inbreeding and selection and then offspring of a single frond were treated by x-radiation. After a few years of cultivation and examination of genetic characteristics, two new strains with high production and high iodine content were successfully produced. These answered better the demands of the industry and are now under cultivation in large areas where they have won the approval of the kelp farmers. Recently a hybrid between these two strains has been successfully bred; it shows even higher production rates and higher iodine content (Fang, 1983).

Recent studies show that kelp parthenosporophytes can complete their own life-cycles without the help of any male gametophyte. It is therefore suggested that the monoecious sporophyte of Laminaria are really dioecious in nature. It is also suggested that there might be a sex chromosome in the gametophytic cells. No high percentage of natural doubling of chromosome number from haploid to diploid has been observed in any higher plant. The success in monocloning the haploid phases, i.e., the gametophytes, makes Laminaria desirable for further biological genetic investigations (Fang, 1983).


Harvesting takes place when the fronds are mature (Figure 1:15). Selecting the optimal time of year and frond condition are very important subjects.

The time for harvesting the crop is important to kelp farmers, since harvesting too early will affect the quantity and quality of the product and, if the harvest takes place too late, there is a chance that a significant part of the crop may be swept away by a typhoon. Since the Chinese haidai is sold on the market on the basis of dry weight, and since the wet weight to dry weight ratio changes from month to month, and the quality of the product is higher with a lower wet-to-dry ratio, the criterion for selecting harvest time should take into consideration the highest per-unit area production rate plus the lowest wet-to-dry ratio.

Table 2, which follows, shows the results of an experiment conducted on the quantity and quality of the production on kelp rope at different dates. From the table it is readily seen that mid to late June is the best time for harvesting. The harvest on June 11 was the highest while that on June 29 was slightly lower in production but the quality was better. On July 14 production was still lower, but the quality was still better. It is there- fore recommended harvesting begin in mid June and continue until late June or early July in North China.

Table 2. Production quality and quantity per kelp cord at different dates.

Harvest time month/day

Production in wet wt. kg.

Production in dry wt. kg.

Wet Weight Dry weight Ratio

























In harvesting the crop, the kelp ropes are detached from the floating ropes, and collected in small boats, many of which are towed in a long line by a motor boat. In Dalian, when the boats reach the wharf, the harvested kelp is taken up onto the wharf along a wire-rope between two posts, one at the wharf and the other in the sea. The motor boat is also employed in seed-scallop or other work. Actually, therefore, the boats and glass house serve kelp sporeling production only about 50% of the time.

Kelp farms vary greatly in size, but are generally large enough for fertilizer application by spraying in north China. The shore facilities are simple, consisting of a warehouse, working space for transplanting sporelings, space for preparing the floating rafts, an area offshore for their anchorage and, of course, offices for farm management. Each kelp farm in North China uses a fertilizing boat with a fertilizer spraying gun. For tending the kelps, small manually operated boats are provided.

Generally two kinds of workers are employed, skilled and unskilled. The kelp farmers are skilled laborers with experience in tending kelps. Generally about 2 farmers operate one hectare of kelp farm. They are busy for most of the year, since before the cultivation season they have to do a great deal of preparatory work in setting up the floating rafts, including preparation of the various kinds of lines and ropes together with production of a large quantity of floats and anchoring materials, including cement and wooden-peg anchors. Besides the skilled workers employed on a permanent basis, there are temporary unskilled workers for such work as inserting sporelings into the twisted kelp ropes.

After the kelp farms have purchased the necessary number of kelp sporeling culture cords, the latter have to be put in the sea where the water temperature has already dropped to about 20° Centigrade. In a month or so the sporelings of a few millimeters in length will have grown to juveniles of 10-15 or more centimeters long. These juvenile sporophytes have to be brought to the transplanting room and placed in tanks filled with seawater. Since they grow on the cords so thickly that they would crowd each other, resulting in slow and poor growth, they have to be thinned. The best way in our experience is to remove them from the original sporeling cord and insert them in the twists of the kelp ropes in a systematic and orderly fashion generally with about 30 juveniles to each rope. This type of work is important but can be effected by non-skilled workers after a very short period of training. Temporary workers are also employed for drying the harvested kelp.

Production of the kelp per unit area differs from place to place. In the Qingdao region there are in general about 30 kelp plants per kelp rope and these, when dried, weigh about 3 kg,i.e., on the average, about 100 gm for each dry kelp plant. As to the production per hectare (10,000 m²), there are about 12,000 kelp plants per mow (1/15 of a hectare) or 180,000 kelp plants per hectare so that production amounts to 18 tons of dry kelp per hectare in the north. South of the Changjiang estuaries the per unit production of the kelp is lower because of the shorter growth season; per hectare production may be about 13-15 tons. In the south the seawater is very fertile, and no fertilizer application is involved. Thus, production costs are lowered and kelp cultivation is still a profitable industry.


Most of the Laminaria japonica produced in China is used for food. According to an official analysis made in the early fifties of the imports of Japanese kelp by the Chinese Ministry of Health, haidai on the market has the following composition per 100 grams: 0.75 mg carotene; 0.69 mg vitamin B1; 0.36 mg vitamin B2; 1.6 mg nicotinic acid; 8.2 gm crude protein; 57 gm carbohydrate; 9.8 gm crude fiber, and 12.9 gm inorganic salts, including 2.25 gm calcium and 0.15 gm iron, yielding 262 kilo-calories. Our analysis of the samples of the kelp produced in China from different periods of the year showed that 100 gm of the dry kelp contained 17.1-32.0 gm alginic acid, 8.46-28.48 gm mannitol, 5.97-18.99 gm crude protein, and 19.35-45.29 gm ash, including 0.13-0.69 gm iodine and 4.35-12.65 gm potassium. Chemical analysis of the kelp shows that it may be regarded as a "health food", especially desirable in the winter season in the north when green vegetables are comparatively scarce.

Beside its role as a "health" vegetable, in China haidai is also important as raw material to be processed for its algin, mannitol and iodine content in a special program for the comprehensive utilization of Laminaria. The uses of the algin, mannitol and iodine are well known and beyond the scope of the present paper. Recently the kelp produced in China has also been employed in the processing of synthetic feed used in mariculture. Formerly the kelp was sold on the market only in the crude dried form, but recently small packages of shredded and seasoned forms with different flavours have appeared on the market and are very well accepted by the people.


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