Rope for seaweed cultivation, seaweed cultivation facility and seaweed cultivation method

Abstract

A rope (1A) for seaweed cultivation comprises: a nurturing rope (5) to which seaweed is adhered; a wire (6) attached to the nurturing rope (5); and a magnesium rod (7) that is supported by the nurturing rope (5), is formed from a metal material having a higher ionization tendency than the wire (6), is electrically connected to the wire (6), and supplies electrons to the wire (6) when installed in the sea. The wire (6) may be spirally wound between the strands of the nurturing rope (5). The magnesium rod (7) may be suspended at one end of the nurturing rope (5).

Description

Rope for seaweed cultivation, seaweed cultivation facility, and seaweed cultivation method

[0001] The present invention relates to a rope for seaweed cultivation, a seaweed cultivation facility, and a seaweed cultivation method.

[0002] In recent years, due to environmental changes such as the rise in seawater temperature, the aquaculture production volume of seaweed has been on a decreasing trend, which has become a factor for fishermen to leave. Therefore, the development of aquaculture techniques that can effectively promote the growth of seaweed has been underway. For example, Patent Document 1 discloses an aquaculture method using a rope for seaweed cultivation filled with fertilizer in its internal hollow part.

[0003] Japanese Unexamined Patent Application Publication No. 2010 - 263815

[0004] In the aquaculture method of Patent Document 1, since the rope for seaweed cultivation filled with fertilizer is floated on the sea surface, it is difficult to spread the fertilizer eluted on the sea surface to the entire seaweed in the sea, and there is a problem that the growth of some seaweed is delayed. In addition, there is also a limit to the amount of fertilizer that can be accommodated in the rope. When all the fertilizer elutes from the rope, replacement is required. On the contrary, when the concentration of the fertilizer is high, it may also cause red tides.

[0005] The present invention has been made based on such a background, and an object thereof is to provide a rope for seaweed cultivation, a seaweed cultivation facility, and a seaweed cultivation method capable of continuously promoting the growth of the entire seaweed to be cultivated.

[0006] In order to achieve the above object, the rope for seaweed cultivation according to the present invention includes a cultivation rope to which seaweed is attached, a cathode attached to the cultivation rope, and a sacrificial anode supported by the cultivation rope, formed of a metal material having a higher ionization tendency than the cathode, electrically connected to the cathode, and supplying electrons to the wire when installed in the sea.

[0007] According to the present invention, it is possible to provide a rope for seaweed cultivation, a seaweed cultivation facility, and a seaweed cultivation method capable of continuously promoting the growth of the entire seaweed to be cultivated.

[0008] This is a front view showing the configuration of a seaweed cultivation facility according to an embodiment of the present invention. This is a front view showing the relationship between the cultivation rope and the wire in a seaweed cultivation rope according to an embodiment of the present invention. This is a diagram showing the magnesium rod covered with a protective cover in a seaweed cultivation rope according to an embodiment of the present invention. This is a photograph of the exterior of the prototype machine in the embodiment. This is a photograph of the exterior of kelp cultivated using the prototype machine in the embodiment.

[0009] Hereinafter, a rope for seaweed cultivation, a seaweed cultivation facility, and a seaweed cultivation method according to embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or equivalent parts are denoted by the same reference numerals.

[0010] In the embodiments, "seaweed attachment" is not limited to the attachment of seaweed sporophytes, but also includes the attachment of any of the seaweed's zoospores, gametophytes, or fertilized eggs. The sporophytes include young sporophytes and mature sporophytes. Furthermore, this is not limited to direct attachment of these to the object, but also includes the planting of seedling filaments to which these are attached into the object.

[0011] The seaweed cultivation facility according to this embodiment is a device that promotes the growth of seaweed attached to a cultivation rope by attracting minerals from seawater to the cultivation rope while the cultivation rope, to which seaweed is attached, is placed in the sea. The seaweed can be of any type, but for example, kelp, wakame, mozuku, and nori are preferred, with kelp, especially Makonbu, being preferred. Seedling threads to which seaweed zoospores are attached are preferably planted on the cultivation rope. Seedling threads are, for example, Cremona twisted threads with a diameter of 2 mm, to which seaweed zoospores are attached by being pre-soaked in a liquid containing seaweed zoospores. Cremona twisted threads are twisted threads mainly made from the synthetic fiber vinylon.

[0012] In the seaweed cultivation facility according to this embodiment, an iron wire is wrapped around a cultivation rope, a magnesium rod is connected to the end of the cultivation rope, and the wire and magnesium rod are electrically connected. As a result of diligent research by the inventors, it was found that by applying cathodic protection technology and generating a potential difference between the magnesium rod (sacrificial anode) and the iron wire (cathode) in the sea, seaweed growth is promoted, and a yield of two to three times that of conventional cultivation methods can be achieved.

[0013] The mechanism is explained below. Magnesium and its alloys are metals with a higher ionization tendency than iron wire. Therefore, when a magnesium rod and wire are electrically connected and immersed in seawater, which is the electrolyte, a battery is created with the magnesium rod as the anode and the iron wire as the cathode, and magnesium ions (Mg) are released from the magnesium rod. ２＋ The magnesium gradually dissolves. This creates a potential difference between the magnesium rod and the wire, supplying electrons from the magnesium rod to the wire, and simultaneously causing a corrosion-preventive current to flow from the magnesium rod through the seawater to the wire.

[0014] When electrons are supplied to the wire, minerals in the seawater, such as calcium ions, magnesium ions, and iron ions, are attracted to the wire to combine with the electrons, and these minerals are continuously supplied to the area around the kelp attached to the cultivation rope. At this time, the wire is continuously supplied with electrons from the magnesium rod, so it does not rust due to reduction and functions as a cathode as long as the magnesium rod is present.

[0015] Next, with reference to Figures 1 to 3, the configuration of the seaweed cultivation facility 1 according to the embodiment will be described. As shown in Figure 1, the seaweed cultivation facility 1 comprises a plurality of floats 2 that can be floated on the surface of the sea, a main rope 3 whose ends are connected to each float 2 and which extends along the surface of the sea, a plurality of anchor ropes 4 whose one end is connected to each float and whose other end is fixed to the seabed, a plurality of cultivation ropes 5 which are supported at different positions on the main rope 3 at intervals from each other and suspended toward the seabed by the main rope 3, an iron wire 6 wrapped around each cultivation rope 5, and a magnesium rod 7 which is suspended by the cultivation rope 5 and electrically connected to the wire 6, and which supplies electrons toward the wire 6 while immersed in seawater.

[0016] The cultivation rope 5, wire 6, and magnesium rod 7 of the seaweed cultivation facility 1 constitute the seaweed cultivation rope 1A. Furthermore, the float 2, main rope 3, and anchor rope 4 are examples of mooring means installed in coastal waters to suspend the seaweed cultivation rope 1A in the sea. The components of the seaweed cultivation facility 1 are described below.

[0017] Floats 2 are, for example, buoys used as markers. Floats 2 are provided with a through hole through which the main rope 3 can be inserted, and the main rope 3 is tied to the through hole. The size and number of floats 2 used in the seaweed cultivation facility 1 should be determined considering the weight of the seaweed cultivation facility 1 and the seaweed, as well as the strength of the ocean current. As time passes after the installation of the seaweed cultivation facility 1, various organisms other than seaweed will attach to the seaweed as it grows, so depending on how much the seaweed cultivation facility 1 sinks, additional floats 2 may be added during cultivation.

[0018] The main rope 3 has sufficient strength to prevent it from being cut by external forces from ocean currents or by floating debris, and is, for example, a three-strand rope made of polypropylene. The training ropes 5 are tied to the main rope 3 at intervals along the longitudinal direction of the main rope 3. The interval between adjacent training ropes 5 is, for example, in the range of 1 m to 5 m, and preferably 2 m.

[0019] The anchor rope 4 positions the floats 2 and the main rope 3 so that they are not carried away by ocean currents. The anchor rope 4 is fixed to the seabed by an anchor 4a driven into the seabed. The anchor rope 4 may also be fixed to the seabed by means other than the anchor 4a, for example, by sandbags or blocks.

[0020] The cultivation rope 5 is a rope formed so that seaweed seed filaments are planted on it, and the germinated seaweed can take root against ocean currents. The cultivation rope 5 is twisted, and the seaweed seed filaments are planted between these twists.

[0021] The training rope 5 has sufficient strength to prevent it from being cut by external forces from ocean currents or by floating debris. The training rope 5 may be a rope with the same or equivalent structure as the main rope 3, for example, a three-strand polypropylene rope. The diameter of the training rope 5 may be set considering the required strength, and may be the same as or thinner than the main rope 3. Specifically, the diameter of the training rope 5 may be in the range of 5 mm to 20 mm, preferably in the range of 10 mm to 15 mm, and more preferably in the range of 12 mm. The length of the training rope 5 may be set considering the depth of the seabed and the strength of the ocean currents, for example, in the range of 1 m to 10 m, preferably in the range of 2 m to 6 m, and more preferably in the range of 4 m.

[0022] The training rope 5, the main rope 3, and the magnesium rod 7 are connected using a cross rope 5a. The cross rope 5a is an example of a connecting rope that connects the training rope 5, the main rope 3, and the magnesium rod 7. The cross rope 5a is also called an eight-strand rope and is a rope made by twisting together a total of four sets of two strands, and has the characteristics of being flexible and resistant to twisting. The diameter of the cross rope 5a is set considering strength and ease of tying, and is, for example, in the range of 5 mm to 10 mm, preferably 7 mm.

[0023] The wire 6 is wrapable around the training rope 5 and is made of iron, such as carbon steel or alloy steel. As shown in Figure 2, the wire 6 is wrapped around the twists of the training rope 5, and in this state, the training rope 5 and the wire 6 are tightened together using a cable tie 6a. Because the wire 6 is spirally wrapped around the training rope 5, when the wire 6 becomes the cathode in the sea, it can attract cations from the seawater to the entire training rope 5.

[0024] Returning to Figure 1, the magnesium rod 7 is a rod made of magnesium or a magnesium alloy. The magnesium rod 7 is made of a metal with a higher ionization tendency than the metal material of the wire 6 and is an example of a sacrificial anode that supplies electrons to the electrically connected wire 6. The dimensions of the magnesium rod 7 should be set considering the persistence of the anticorrosion current in the sea, the current density, and the role of the magnesium rod 7 as a weight. The diameter of the magnesium rod 7 is, for example, in the range of 10 mm to 50 mm, and its length is, for example, in the range of 200 mm to 800 mm.

[0025] As shown in Figure 3, the magnesium rod 7 has a circular cross-section and is tapered at both ends. A ring member 7a is welded to one end, through which the cross rope 5a and wire 6 can be inserted. The cross rope 5a is inserted through the ring member 7a and tied to the cultivation rope 5, thereby mechanically connecting the cultivation rope 5 and the magnesium rod 7. The wire 6 is also inserted through the ring member 7a and tied to it, thereby electrically connecting the wire 6 and the magnesium rod 7. This completes the configuration of the seaweed cultivation facility 1.

[0026] Because the seaweed cultivation facility 1 has the above configuration, electrons are supplied from the magnesium rod 7 to the wire 6, and the wire 6, which functions as a cathode, attracts minerals from the seawater around the cultivation rope 5. As a result, the growth of seaweed planted on the cultivation rope 5 is promoted. It takes a long time for the magnesium rod 7 to completely dissolve, and since the minerals in the seawater are inexhaustible, minerals are supplied to the area around the cultivation rope 5 semi-permanently. In addition, since the magnesium rod 7 is connected to the end of the cultivation rope 5, and the cultivation rope 5 is connected to the main rope 3 with the magnesium rod 7 on the lower side, the magnesium rod 7 also functions as a weight, making it less likely for adjacent cultivation ropes 5 to become entangled.

[0027] Next, the manufacturing process of the seaweed cultivation facility 1 according to the embodiment will be explained. First, the worker wraps wire 6 around each cultivation rope 5 and secures it so that it does not come off. Specifically, the worker wraps the wire 6 spirally between the twists of the cultivation rope 5 and secures the cultivation rope 5 and the wire 6 together with a cable tie 6a to prevent them from coming off.

[0028] Next, the worker mechanically connects each training rope 5 to the magnesium rod 7 using the cross rope 5a, and electrically connects the wire 6 to the magnesium rod 7. Specifically, the worker passes the cross rope 5a through the ring member 7a of the magnesium rod 7 and ties the cross rope 5a to one end of the training rope 5. The worker also inserts the wire 6 through the ring member 7a and ties it.

[0029] Next, the worker connects multiple training ropes 5 to the main rope 3 at intervals along the longitudinal direction of the main rope 3. Specifically, the worker ties one end of the cross rope 5a to the other end of the training rope 5, and then ties the other end of the cross rope 5a to the main rope 3.

[0030] Next, the worker attaches floats 2 to both ends of the main rope 3, and attaches an anchor rope 4 to each float 2. Specifically, the worker passes the main rope 3 through the through hole of the float 2 and ties it, and passes the anchor rope 4 through the other through hole of the float 2 and ties it. The above is the procedure for manufacturing the seaweed cultivation facility 1.

[0031] Furthermore, during the manufacturing of the seaweed cultivation facility 1, a cylindrical protective cover 7b is detachably attached to the magnesium rod 7, as shown in Figure 3. The protective cover 7b is attached to prevent the magnesium rod 7 from igniting due to a strong impact, and is removed before the seaweed cultivation facility 1 is installed in the sea.

[0032] Next, the flow of the seaweed cultivation method using the seaweed cultivation facility 1 according to the embodiment will be described. Hereinafter, it will be assumed that seaweed zoospores are attached to the seaweed seed filaments.

[0033] First, the workers attach seaweed seedling threads to each cultivation rope 5 of the seaweed cultivation facility 1 on land. Specifically, the workers use tweezers to insert the seaweed seedling threads between the twists of the cultivation rope 5.

[0034] Next, the workers install the seaweed cultivation facility 1, which is equipped with seaweed seedling threads, in the target coastal area. Specifically, the workers load the seaweed cultivation facility 1 onto a vessel and drop it into the target coastal area. Next, the workers use anchor 4a to secure the anchor rope 4 to the seabed so that the seaweed cultivation facility 1 is not carried away by the ocean currents. This completes the installation of the seaweed cultivation facility 1.

[0035] After the installation of seaweed cultivation facility 1 is complete, cultivation is carried out until the seaweed grows. When the seaweed has grown to a state suitable for harvesting, the workers lift seaweed cultivation facility 1 from the sea and harvest the seaweed attached to each cultivation rope 5. After harvesting the seaweed, seaweed cultivation facility 1 can be used again by planting new seaweed seedling threads. The above is the flow of the seaweed cultivation method.

[0036] As described above, the seaweed cultivation rope 1A according to the embodiment comprises a cultivation rope 5 to which seaweed is attached, a wire 6 attached to the cultivation rope 5, and a magnesium rod 7 supported by the cultivation rope 5, made of a metal material with a higher ionization tendency than the wire 6, electrically connected to the wire 6, and supplying electrons to the wire 6 when placed in the sea. As a result, minerals from the sea are attracted to the wire 6, and the growth of the entire seaweed being cultivated can be sustainably promoted.

[0037] The present invention is not limited to the embodiments described above, and the following modifications are also possible.

[0038] (Modifications) In the above embodiment, magnesium or a magnesium alloy was used as the corrosion-resistant anode and iron was used as the cathode, but the present invention is not limited thereto. As the corrosion-resistant anode, any metal material with a higher ionization tendency than the metal material of the wire 6 may be used. For example, if the wire 6 is made of iron, zinc or an alloy thereof, or aluminum or an alloy thereof may be used. As the cathode, any metal material other than iron may be used, as long as it has a lower ionization tendency than the corrosion-resistant anode.

[0039] In the above embodiment, the wire 6 was wrapped around the cultivation rope 5, but the method of incorporating the wire 6 into the cultivation rope 5 in the present invention is not limited to this. For example, the wire 6 may be incorporated so as to extend in the longitudinal direction of the cultivation rope 5. Alternatively, a cultivation rope 5 with one or more wires 6 already incorporated may be used. Such a cultivation rope 5 can be manufactured, for example, by incorporating the wire 6 when twisting together multiple strands. By using such a cultivation rope 5, the work of wrapping the wire 6 during the manufacture of the seaweed cultivation facility 1 becomes unnecessary.

[0040] In the above embodiment, a wire 6 was used as the cathode, but the present invention is not limited thereto. For example, the cathode may be a ring member that can be attached to the training rope 5, and the magnesium rod 7 and the ring member may be electrically connected with an electric wire.

[0041] In the above embodiment, a cross rope 5a was used to connect the training rope 5 to the main rope 3 and the magnesium rod 7, but the present invention is not limited thereto. Other ropes besides the cross rope 5a may be used to connect the training rope 5 to the main rope 3 and the magnesium rod 7, or each end of the training rope 5 may be directly tied to the main rope 3 and the magnesium rod 7. Furthermore, the cross rope 5a may be omitted to connect the training rope 5 to the magnesium rod 7.

[0042] In the above embodiment, the magnesium rod 7 had a circular cross-section, but the present invention is not limited to this. The magnesium rod 7 may, for example, have a rectangular cross-section or may be a sphere formed of magnesium or a magnesium alloy.

[0043] In the above embodiment, the magnesium rod 7 was attached to the end of the cultivation rope 5, but the present invention is not limited thereto. As long as the magnesium rod 7 can be immersed in the sea, it can be installed at any position with respect to the cultivation rope 5. For example, the magnesium rod 7 may be attached to the middle part of the cultivation rope 5.

[0044] In the above embodiment, the cultivation rope 5 was suspended from one main rope 3, but the present invention is not limited thereto. For example, two main ropes 3 may be arranged in parallel, and a plurality of ropes may be passed between them to form a ladder-like structure, and the cultivation rope 5 may be suspended from the two main ropes 3 or the ropes. It is preferable that the ropes passed between the main ropes 3 have a smaller diameter than the main ropes 3.

[0045] In the above embodiment, the main rope 3 was floated by the float 2 and positioned by the anchor rope 4, but the present invention is not limited thereto. The anchor rope 4 may be omitted, both ends of the main rope 3 may be fixed to the seabed respectively, and the middle part of the main rope 3 may be floated on the sea surface by a plurality of floats 2. Further, the main rope 3 may be positioned by other mooring means, for example, fixed to a boat floated on the sea surface by the anchor rope 4.

[0046] In the above embodiment, the seedling thread with the zoospores of seaweed attached was planted in the cultivation rope 5, but the present invention is not limited thereto. For example, a cultivation rope 5 grown until the young sporophytes or mature sporophytes are established may be used.

[0047] The above embodiments are examples, and the present invention is not limited to these, and various embodiments are possible without departing from the gist of the invention described in the claims. The constituent elements described in the embodiments and modification examples can be freely combined. Also, inventions equivalent to the invention described in the claims are included in the present invention.

[0048] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples.

[0049] (Example) In this example, a prototype was created in accordance with the description of the embodiment above, and it was verified whether it could promote the growth of kelp in the sea. First, the experimenter attached the larval spore bodies of kelp to the cultivation rope, then wrapped a 9 mm diameter iron wire around it and secured it with a cable tie. A 12 mm diameter, 4 m long Dia Super PP rope was used as the cultivation rope.

[0050] Next, as shown in Figure 4, the experimenter connected the training ropes and magnesium rods using a 7 mm diameter cross rope. The magnesium rods are Mag Rods manufactured by Nippon Corrosion Protection Industry Co., Ltd. The dimensions of the Mag Rods are 33 mm in diameter, 510 mm in length, and they weigh 850 g. At the time Figure 4 was taken, protective covers were attached to the Mag Rods. Next, the experimenter attached each training rope to the main rope at 2 m intervals using a 7 mm diameter cross rope.

[0051] In December 2023, a test unit was installed in the sea off the coast of Hokkaido, and demonstration testing commenced. After a certain period, the Normalized Difference Vegetation Index (NDVI) was calculated using satellite data. The NDVI is an index that indicates the distribution and activity of vegetation and is expressed by the following formula: NDVI = (NIR - Red) / (NIR + Red)

[0052] NIR stands for near-infrared light reflectance, and Red stands for red light reflectance. NDVI is a normalized value between -1 and 1, with higher NDVI values ​​indicating denser vegetation. After removing the test apparatus from the sea, the experimenter collected kelp from the cultivation rope and measured its length, width, and weight. As a comparative example, the experimenter also conducted a test using a 1.0 kg lead weight instead of a mag rod and compared the two methods.

[0053] The verification results, as shown in Figure 5, showed that the collected kelp grew much larger when a magnesium rod was used. Specifically, when a magnesium rod was used, the kelp grew to a length of 3.0m to 3.5m and a width of 10cm to 12cm, with an NDVI of 0.84. On the other hand, when a lead weight was used, the kelp grew to a length of 1.1m to 1.5m and a width of 8cm to 10cm, with an NDVI of 0.76. From the above, it was confirmed that generating a protective current in the sea using a magnesium rod promotes the growth of kelp and also increases the density of the vegetation.

[0054] This application is based on Japanese Patent Application No. 2024-195628, filed on 8 November 2024, and includes its specification, claims, drawings, and abstract. The disclosures in the aforementioned Japanese Patent Application are incorporated herein by reference in their entirety.

[0055] The seaweed cultivation rope, seaweed cultivation facility, and seaweed cultivation method of the present invention are useful because they can sustainably promote the growth of the entire seaweed being cultivated.

[0056] 1. Seaweed cultivation facility 1A Seaweed cultivation rope 2. Floats 3. Main rope 4. Anchor rope 5. Cultivation rope 6. Wire 7. Magnesium rod

Claims

1. A rope for cultivating seaweed, comprising: a cultivation rope to which seaweed is attached; a cathode attached to the cultivation rope; and a sacrificial anode supported by the cultivation rope, made of a metallic material with a higher ionization tendency than the cathode, electrically connected to the cathode, and supplying electrons to the cathode when placed in the sea.

2. The rope for seaweed cultivation according to claim 1, wherein the cathode is formed of a wire incorporated into the cultivation rope.

3. The rope for seaweed cultivation according to claim 2, wherein the wire is spirally wound between the twists of the cultivation rope.

4. The rope for seaweed cultivation according to claim 2, wherein the sacrificial anode is suspended from one end of the cultivation rope and the wire is electrically connected to it.

5. The cultivation rope is characterized in that seedling threads to which the zoospores of the seaweed are attached are planted.

6. The rope for seaweed cultivation according to claim 1, wherein the cathode is made of iron, and the sacrificial anode is made of a metallic material selected from the group consisting of magnesium, zinc, aluminum, and alloys thereof.

7. A seaweed cultivation facility comprising: a rope for seaweed cultivation according to any one of claims 1 to 6; and a mooring means installed in a coastal area for mooring the cultivation rope so that it is suspended in the sea.

8. A method for cultivating seaweed, comprising the steps of: attaching seaweed to the cultivation rope of a seaweed cultivation rope according to any one of claims 1 to 6; installing the seaweed cultivation rope with the seaweed attached in the sea with the sacrificial anode facing downwards; and pulling up the seaweed cultivation rope installed in the sea.

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