Algal reefs

Abstract

We provide small-scale algal reefs that can be stably installed in diverse environments. [Solution] The algal reef 100 comprises a cylindrical base body 1 having one end open in the axial direction and a top surface 1a at the other end in the axial direction. The base body has a plurality of protrusions 11 on the outer circumferential surface on the side of the one end in the axial direction. The base body also has an annular rat-proof section 2 with a larger outer diameter than the base body on the other end in the axial direction. The base body has a plurality of wall sections 13 that protrude in the axial direction from the periphery of the top surface, and each of the plurality of wall sections has a projection 131 that protrudes radially outward from the base body at an intermediate point in the axial direction, and the rat-proof section is detachably supported by the projections of each of the plurality of wall sections.

Description

Technical Field

[0001] This disclosure relates to algal reefs.

Background Art

[0002] Conventionally, various algal reefs for creating algal beds have been known (see, for example, Patent Document 1).

[0003] In recent years, the environment for creating algal beds has diversified, and along with this, the provision of small-sized algal reefs that can be installed in extremely shallow waters, steep terrains, etc. has been expected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, compared with large-sized algal reefs, small-sized algal reefs are more likely to be toppled or washed away by waves.

[0006] One aspect of this disclosure has been made in view of the above, and an object thereof is to provide a small-sized algal reef that can be stably installed over a long period in various environments.

Means for Solving the Problems

[0007] The algal reef according to one aspect of this disclosure includes a cylindrical base body having one end in the axial direction open and a top surface at the other end in the axial direction. The base body has a plurality of protrusions on the outer peripheral surface on one end side in the axial direction.

Effects of the Invention

[0008] According to this disclosure, it is possible to provide a small-sized algal reef that can be stably installed in various environments.

Brief Description of the Drawings

[0009] [Figure 1] Figure 1 is a perspective view showing an example of the structure of an algal reef according to the embodiment. [Figure 2] Figure 2 is a side view showing an example of the structure of an algal reef according to the embodiment. [Figure 3] Figure 3 is a plan view showing an example of the configuration of a seaweed reef according to the embodiment. [Figure 4] Figure 4 is an enlarged side view illustrating the configuration of the protrusion according to the embodiment. [Figure 5] Figure 5 shows the state in which the algal reef according to the embodiment is installed on the target surface. [Modes for carrying out the invention]

[0010] The embodiments for implementing the algal reef according to this disclosure (hereinafter referred to as "Embodiments") will be described in detail below with reference to the drawings. However, this disclosure is not limited by these embodiments. Furthermore, each embodiment can be combined as appropriate, provided that the processing content is not inconsistent. In the following embodiments, the same parts are denoted by the same reference numerals, and redundant descriptions are omitted.

[0011] Traditionally, various types of algal reefs have been known for creating seaweed beds. Conventional algal reefs have been predominantly large and heavy to ensure stability, requiring the use of large vessels and heavy machinery for installation. In contrast, with the increasing diversification of seaweed bed environments in recent years, there is a growing demand for smaller algal reefs that can be installed in extremely shallow waters and steep terrains.

[0012] However, while small algal reefs are easier to handle than large ones, they are susceptible to being overturned or washed away by waves. This disclosure has been made in view of this, and aims to provide small algal reefs that can be stably installed in diverse environments.

[0013] The configuration of the algal reef 100 according to this embodiment will be described below with reference to Figures 1 to 5. Figure 1 is a perspective view showing an example of the configuration of the algal reef 100 according to this embodiment. Figure 2 is a side view showing an example of the configuration of the algal reef 100 according to this embodiment. Figure 3 is a plan view showing an example of the configuration of the algal reef 100 according to this embodiment. Figure 4 is an enlarged side view for explaining the configuration of the projection 11 according to this embodiment. Figure 5 is a diagram showing the algal reef 100 according to this embodiment installed on the installation target surface S.

[0014] As shown in Figures 1 to 3, the algal reef 100 according to this embodiment comprises a base body 1 and a rat-proof part 2 that is detachable from the base body 1. Below, the configuration of the base body 1 according to this embodiment will be described in detail.

[0015] As shown in Figure 1, the base body 1 is a cylindrical member. One end of the base body 1 in the axial direction (Z-axis direction) (the end on the negative Z-axis side) is open. The other end of the base body 1 in the axial direction (the end on the positive Z-axis side) is located on the top surface 1a. As will be described later, the top surface 1a functions as the main algae-forming surface in the algal reef 100.

[0016] The seaweed reef 100 is fixed to the surface of an object to be installed, such as a wave-dissipating block or a steel pipe pile (hereinafter referred to as the "installation target surface"), at the end of the base body 1 on the negative Z-axis side, that is, the open end. Specifically, as shown in Figure 5, the outer surface of the end of the base body 1 on the negative Z-axis side of the seaweed reef 100 is joined to the installation target surface S by a bonding material 3 such as underwater bond. Note that the axial direction (Z-axis direction) of the base body 1 does not necessarily have to be in the direction of gravity. For example, if the seaweed reef 100 is installed on the surface of a steel pipe pile extending along the direction of gravity, the radial direction (horizontal direction) of the steel pipe pile becomes the axial direction (Z-axis direction) of the base body 1.

[0017] Here, the algal reef 100 of the present disclosure has a plurality of protrusions 11 on the outer peripheral surface at the above-mentioned end of the base body 1. Compared with a structure without the plurality of protrusions 11, the algal reef 100 of the present disclosure has a larger contact area between the base body 1 and the bonding material 3. Therefore, the algal reef 100 of the present disclosure has a higher adhesive strength with the bonding material 3 compared with a structure without the plurality of protrusions 11. Also, in such a configuration, the so-called anchor effect is exerted when the bonding material 3 solidifies while entering the gaps between the plurality of protrusions 11. This also improves the adhesive strength between the algal reef 100 and the bonding material 3.

[0018] Thus, the algal reef 100 of the present disclosure having a plurality of protrusions 11 has a high bonding strength between the base body 1 and the bonding material 3. Therefore, the algal reef 100 of the present disclosure can firmly bond the base body 1 and the installation target surface S with the bonding material 3. Accordingly, even when the mass and size of the algal reef 100 of the present disclosure are small, it is difficult for the algal reef to fall or be washed away by waves.

[0019] Therefore, the algal reef 100 of the present disclosure can be stably installed in various environments (for example, near an algal seedling supply source, extremely shallow waters where suitable light quantity can be ensured, steep terrain where it is difficult for pest organisms to invade, estuarine areas where abundant nutrients exist, etc.).

[0020] Also, since the end on the negative Z-axis side of the base body 1 that abuts against the installation target surface S of the algal reef 100 of the present disclosure is open, compared with a configuration in which the end on the negative Z-axis side of the base body 1 is closed, it is possible to install the algal reef 100 flexibly on a curved or uneven installation target surface S.

[0021] For example, when placing the algal reef 100 on an uneven installation target surface S, by allowing the convex portion on the installation target surface S to enter the inside of the base body 1, the algal reef 100 can be placed on the installation target surface S while avoiding the convex portion. Thus, the algal reef 100 according to the present embodiment can be installed flexibly on the installation target surface S compared with a configuration in which the end on the negative Z-axis side of the base body 1 is closed. In other words, the algal reef 100 according to the present embodiment has a high degree of freedom in installation.

[0022] Furthermore, compared to a configuration in which the base body 1 has a closed end on the negative Z-axis side, the seaweed reef 100 according to this embodiment requires less effort in finding a suitable installation location (for example, a location without protruding parts) for installation. For this reason, the installation work for the seaweed reef 100 according to this embodiment is easier compared to a configuration in which the base body 1 has a closed end on the negative Z-axis side.

[0023] Furthermore, in this embodiment, by making the base body 1 a hollow member, the mass of the algal reef 100 can be reduced compared to the case where the base body 1 is solid.

[0024] As shown in Figures 1 and 2, the multiple protrusions 11 are provided around the entire circumference of the base body 1. This configuration allows for a favorable increase in the bonding strength between the base body 1 and the installation surface S via the bonding material 3. Furthermore, since the stress applied to the joint can be evenly distributed along the outer circumference of the base body 1, the base body 1 can be fixed to the installation surface S with high stability.

[0025] Furthermore, the multiple protrusions 11 do not necessarily need to be provided around the entire circumference of the base body 1. For example, the outer circumference of the base body 1 may alternately consist of a first region where the multiple protrusions 11 are provided and a second region where the protrusions 11 are not provided, along the circumferential direction.

[0026] Here, with reference to Figure 4, the configuration of the multiple protrusions 11 will be described in more detail. As shown in Figure 4, the base body 1 has multiple groups of protrusions P. Each of the multiple groups of protrusions P includes two or more protrusions 11 arranged along the circumferential direction of the base body 1. Specifically, each of the multiple groups of protrusions P includes two or more protrusions 11 arranged in a line at equal intervals along the circumferential direction of the base body 1.

[0027] As shown in Figure 4, the arrangement of two or more protrusions 11 included in one of the multiple groups of protrusions P is shifted in the circumferential direction of the base body 1 compared to the arrangement of two or more protrusions 11 included in other groups of protrusions P adjacent to that group P in the Z-axis direction. In other words, the multiple protrusions 11 are arranged alternately in the axial direction of the base body 1.

[0028] With this configuration, for example, the arrangement density of the multiple protrusions 11 can be made uniform compared to the case where the multiple protrusions 11 are arranged in a straight line in the axial direction of the base body 1. In other words, the spacing between adjacent protrusions 11 can be made uniform for all of the protrusions 11. This reduces the risk of stress concentration on a particular protrusion 11, thereby improving the durability of the base body 1.

[0029] Furthermore, this configuration makes it possible to arrange the multiple protrusions 11 at a higher density. If the multiple protrusions 11 can be arranged at a high density, the anchoring effect acting between the base 1 and the joining material 3 can be enhanced. Therefore, the bonding strength between the base 1 and the installation target surface S via the joining material 3 can be suitably improved.

[0030] Furthermore, the multiple protrusions 11 do not necessarily have to be arranged alternately in the axial direction of the base body 1. The multiple protrusions 11 may be arranged in a straight line in the axial direction.

[0031] Furthermore, as shown in Figure 4, each of the multiple protrusions 11 has a length L1 along the circumferential direction of the base body 1 that is greater than the length L2 along the axial direction of the base body 1. For example, an algal reef in which the outer surface of the base body 1 is joined to the installation surface S by a bonding material 3 is relatively strong against lateral forces, but tends to be weak against axial forces, that is, forces that try to pull the base body 1 away from the bonding material 3.

[0032] In contrast, the seaweed reef 100 having the projection 11 of the above shape is stronger against forces that attempt to pull the base body 1 out of the joining material 3 compared to the seaweed reef 100 having the projection 11 with the same length along the circumferential and axial directions of the base body 1. Therefore, the seaweed reef 100 having the above configuration can be stably fixed to the installation target surface S for a long period of time. Note that the shape of the projection 11 is not limited to the illustrated example. For example, the projection 11 may have the same length L1 along the circumferential direction of the base body 1 and the same length L2 along the axial direction of the base body 1.

[0033] Furthermore, as shown in Figure 4, each of the multiple protrusions 11 is tapered from its base to its tip. This shape makes it easier for the bonding material 3 to fit between the protrusions 11, allowing the bonding material 3 to adhere more closely to the base 1. As a result, the bonding strength between the base 1 and the bonding material 3 can be increased.

[0034] Let's return to the explanation of Figures 1 to 3. As shown in Figure 3, the substrate 1 has a plurality of slit-shaped grooves 12 (an example of the first groove) on its top surface 1a for trapping algal seeds (such as young embryos). Each of the plurality of grooves 12 is arc-shaped. The plurality of grooves 12 are arranged concentrically from the center to the outer periphery of the top surface 1a. The length of the grooves 12 that are farther from the center of the top surface 1a is greater than the length of the grooves 12 that are closer to the center of the top surface 1a. Specifically, the length of the plurality of grooves 12 is greater the further away the groove 12 is from the center of the top surface 1a. The width of the grooves 12 may be about the same as the diameter of the algal seeds. Specifically, the width of the grooves 12 may be, for example, about 3 mm to 5 mm.

[0035] This configuration promotes the attachment of algal seeds to the top surface 1a and reduces the risk of seeds being washed away from the top surface 1a by waves or the like. Therefore, with an algal reef 100 having this configuration, algae can be grown suitably on the top surface 1a. The number and arrangement of the grooves 12 are not limited to the illustrated configuration and may be changed as appropriate.

[0036] As shown in Figures 1 to 3, the base body 1 has a plurality of wall portions 13 that protrude in the axial direction of the base body 1 from the periphery of the top surface 1a. The plurality of wall portions 13 are positioned at equal intervals along the periphery of the top surface 1a, spaced apart from each other.

[0037] With this configuration, the sprouts, stems, and rhizoids of algae attached to the top surface 1a can be protected from predation by creeping predatory organisms such as sea urchins and predatory fish that approach mainly from the sides of the substrate 1. Specifically, by providing the wall portion 13, it is possible to prevent predatory organisms from approaching the top surface 1a from the sides of the substrate 1, and as a result, the intrusion of the mouthparts of predatory organisms into the top surface 1a can be suppressed, thereby reducing the occurrence of the aforementioned predation damage.

[0038] Furthermore, in this configuration, by arranging multiple wall sections 13 spaced apart from each other along the periphery of the top surface 1a, the risk of water exchange near the top surface 1a being obstructed by the wall sections 13 can be reduced. This reduces the risk of silt accumulating on the top surface 1a.

[0039] The separation distance (shortest distance) between two adjacent wall portions 13 along the periphery of the top surface 1a should be smaller than the shell diameter of sea urchins, which are the main predatory organisms. Specifically, such separation distance (shortest distance) may be, for example, 10 mm or less. With such a configuration, sea urchins can be effectively prevented from approaching the top surface 1a from the side of the base 1, thereby effectively reducing algal damage.

[0040] As shown in Figure 2, each of the wall portions 13 has a through hole 131 and a projection 132 that protrudes radially outward from the base 1 from an intermediate portion in the Z-axis direction (the axis direction of the base 1). The through hole 131 and the projection 132 function as mounting parts for attaching the rat-proof portion 2, which will be described later, to the base 1. This point will be described in detail later.

[0041] As shown in Figures 1 and 3, the base body 1 has a columnar portion 14 that protrudes in the axial direction from the center of the top surface 1a. The columnar portion 14 is formed in a cylindrical shape. However, the columnar portion 14 is not limited to a cylindrical shape; for example, it may be formed in a rectangular prism shape. With this configuration, algae seedlings can be fixed to the columnar portion 14 using cable ties or the like, making it easy to cultivate algae. Furthermore, as in this embodiment, by providing the columnar portion 14 in the center of the top surface 1a surrounded by a wall portion 13, the risk of algae seedlings fixed to the columnar portion 14 being damaged by grazing from the side of the base body 1 can be reduced.

[0042] Furthermore, by providing a wall portion 13 around the periphery of the top surface 1a and a columnar portion 14 in the center of the top surface 1a, it is possible to effectively prevent predatory organisms from approaching the top surface 1a from above the base 1. As a result, the sprouts, stems, and rhizoids of algae attached to the top surface 1a can be more effectively protected from predatory damage.

[0043] As shown in Figures 1 and 3, the columnar portion 14 has a plurality (in this case, three) grooves 141 (an example of a second groove) on its side surface that extend along the axial direction of the columnar portion 14. With this configuration, the stems of the algae seedlings can be positioned along the grooves 141, thereby reducing the risk of damage to the stems of the algae seedlings when fixing them to the columnar portion 14. Note that the columnar portion 14 only needs to have at least one groove 141. Furthermore, the columnar portion 14 does not necessarily need to have grooves 141.

[0044] As shown in Figures 1 and 3, the columnar portion 14 has a plurality (in this case, three) of protrusions 142 that project radially outward from the outer circumferential surface at its tip. With this configuration, when algae seedlings are fixed to the columnar portion 14 with cable ties or the like, the risk of such cable ties being pulled out by waves or by predatory organisms can be reduced. Note that the columnar portion 14 does not necessarily need to have protrusions 142.

[0045] As shown in Figure 3, the substrate 1 has multiple (in this case, three) through-holes 15 (an example of the first through-hole) on its top surface 1a. With this configuration, water exchange near the top surface 1a is promoted, thereby reducing the accumulation of floating sediment on the top surface 1a. This promotes the attachment and germination of algal seeds on the top surface 1a. Furthermore, with this configuration, the rhizoids of the algae can become entangled in the through-holes 15, thereby reducing the risk of the algae being washed away from the algal reef 100. Note that the number and arrangement of the through-holes 15 are not limited to the example shown and may be changed as appropriate.

[0046] As shown in Figures 1 and 3, the base body 1 also has through holes in the columnar portion 14. Specifically, the columnar portion 14 has through holes 143 that penetrate the base body 1 in the axial direction. This configuration allows for better water exchange near the top surface 1a, thereby more effectively reducing the accumulation of floating sediment on the top surface 1a.

[0047] As shown in Figures 1 and 2, the base body 1 has multiple (in this case, six) through holes 16 (an example of a second through hole) on its side. Note that in Figures 1 and 2, for the sake of clarity, some of the through holes 16 are omitted from the illustration. With this configuration, ropes or the like can be inserted through the side of the base body 1, making it possible, for example, to install the seaweed reef 100 in a longline manner using longline ropes. Note that the base body 1 does not necessarily need to have through holes 16.

[0048] Next, the configuration of the rat-proof section 2 according to this embodiment will be described in detail. As shown in Figures 1 to 3, the algal reef 100 according to this embodiment is provided with an annular rat-proof section 2 having an outer diameter larger than that of the base body 1 at the end of the base body 1 on the positive Z-axis side. Specifically, the rat-proof section 2 may be a plate-shaped annular member having an inner diameter about the same as the diameter of the base body 1 and an outer diameter larger than that of the base body 1.

[0049] The algal reef 100 equipped with the rat-proof section 2 effectively prevents predatory organisms from approaching the top surface 1a from the side of the substrate 1. In particular, it effectively reduces the risk of predatory organisms such as sea urchins invading the top surface 1a by crawling along the side of the substrate 1. As a result, the sprouts, stems, and rhizoids of algae attached to the top surface 1a can be more effectively protected from predation. Furthermore, when the algal reef 100 is equipped with the rat-proof section 2, algae can be formed not only on the top surface 1a but also on the surface of the rat-proof section 2, thereby enabling the efficient creation of an algal bed.

[0050] The radial thickness of the rat-proof section 2 should be greater than the length of the tube feet of sea urchins, which are the main predatory organisms. Specifically, the radial thickness of the rat-proof section 2 may be, for example, 20 mm or more. With such a configuration, the penetration of sea urchin tube feet into the top surface 1a can be effectively suppressed, thereby effectively reducing algal damage.

[0051] The rat-proof portion 2 may be detachable from the wall portion 13 located on the periphery of the base body 1. Specifically, as shown in Figure 2, the rat-proof portion 2 is detachably supported by a protrusion 132 on the wall portion 13. Also, as shown in Figure 1, the rat-proof portion 2 has a projection-shaped engaging portion 21 that protrudes radially inward from the inner circumference. The engaging portion 21 engages with a through hole 131 in the wall portion 13. Specifically, the engaging portion 21 is inserted into the through hole 131 in the wall portion 13. This makes it difficult for the rat-proof portion 2 to fall off the base body 1.

[0052] As described above, the rat-proof section 2 of the algal reef 100 according to this embodiment is detachable from the base 1. Therefore, the algal reef 100 according to this embodiment can be used, for example, by removing the rat-proof section 2 when installing the algal reef 100 in a location with little risk of herbivory. By removing the rat-proof section 2 in this way, the algal reef 100 can be made even lighter. Also, when installing the algal reef 100 in a location with a high risk of herbivory, the rat-proof section 2 can be attached to the reef to suitably protect the sprouts, stems, and rhizoids of algae attached to the top surface 1a from herbivory.

[0053] As shown in Figures 1 and 3, the rat-proof section 2 has a plurality of slit-shaped grooves 22 (an example of a third groove) on the surface facing the positive Z-axis for trapping algal seeds. Each of the plurality of grooves 22 is arc-shaped. The plurality of grooves 22 are arranged concentrically from the inner circumference to the outer circumference of the rat-proof section 2. The width of the grooves 22 may be about the same as the diameter of the algal seeds. Specifically, the width of the grooves 22 may be about 3 mm to 5 mm.

[0054] This configuration promotes the attachment of algal seeds to the surface of the rat-proof section 2 and reduces the risk of seeds being washed away from the surface of the rat-proof section 2 by waves or the like. As a result, algae can grow suitably on the surface of the rat-proof section 2. Note that the number and arrangement of the grooves 12 are not limited to the illustrated configuration and may be changed as appropriate.

[0055] Furthermore, the seaweed reef 100 does not necessarily need to be equipped with the rat-proof section 2. In other words, the seaweed reef 100 may consist only of the base body 1.

[0056] In this embodiment, the seaweed reef 100 may have a maximum axial dimension H (see Figure 2) of 80 mm or less, and a maximum radial dimension W (see Figure 2) of 130 mm or less. The maximum radial dimension W referred to here corresponds to the outer diameter of the rat-proof portion 2 if the seaweed reef 100 is equipped with the rat-proof portion 2, and corresponds to the maximum radial dimension of the base body 1 if the seaweed reef 100 is not equipped with the rat-proof portion 2.

[0057] Because the seaweed reef 100 having such a configuration is small in size, it can be easily carried by, for example, a single diver. Therefore, the seaweed reef 100 having such a configuration can be easily installed in a variety of environments.

[0058] Furthermore, the seaweed reef 100 according to this embodiment may have a mass of 100g or less. The mass of the seaweed reef 100 referred to here corresponds to the total mass of the base body 1 and the rat-proof part 2 if the seaweed reef 100 is equipped with the rat-proof part 2, and corresponds to the mass of the base body 1 if the seaweed reef 100 is not equipped with the rat-proof part 2.

[0059] Because the seaweed reef 100 having such a configuration is lightweight, it can be easily carried by, for example, a single diver. Therefore, the seaweed reef 100 having such a configuration can be easily installed in a variety of environments.

[0060] Furthermore, the algal reef 100 according to this embodiment may be made of biodegradable material. That is, each component of the base body 1 and the rat-proof part 2 may be made of biodegradable material. For example, PLA (polylactic acid) can be used as the biodegradable material. An algal reef 100 having such a configuration will decompose and disappear after a predetermined number of years have elapsed since the algae have settled on the installation surface S, thus having less adverse impact on the environment.

[0061] Although the present disclosure has been described in detail above, this disclosure is not limited to the embodiments described above, and various modifications and improvements are possible without departing from the gist of this disclosure.

[0062] The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. Indeed, the embodiments described above can be embodied in a variety of forms. Furthermore, the embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0063] 1 Base 1a Top surface 2. Rat-proof section 3 Bonding material 11 Protrusion 12 grooves (an example of the first groove) 13 Wall 14 Columnar part 15. Through-hole (an example of the first through-hole) 16. Through-hole (an example of a second through-hole) 21 Engaging part 22 grooves (an example of the third groove) 100 seaweed reef 131 Through hole 132 Protrusion 141 Grooves (An example of the second groove) 142 Protrusion 143 Through hole P protrusion group S Installation target surface

Claims

1. The base comprises a cylindrical body having one end open in the axial direction and the other end in the axial direction having a top surface. The substrate is a seaweed reef having a plurality of protrusions on the outer circumferential surface of one end in the axial direction.

2. The algal reef according to claim 1, wherein the plurality of protrusions are provided around the entire circumference of the base body.

3. When two or more of the protrusions arranged in a line at equal intervals along the circumferential direction of the base body are considered a group of protrusions, The substrate has a plurality of groups of protrusions arranged along the axial direction, The algal reef according to claim 2, wherein the arrangement of two or more protrusions included in one of the plurality of groups of protrusions is shifted in the circumferential direction with respect to the arrangement of two or more protrusions included in other groups of protrusions adjacent to the group of protrusions in the axial direction.

4. The algal reef according to claim 1, wherein the length of each of the plurality of protrusions along the circumferential direction of the base is greater than the length along the axial direction of the base.

5. The algal reef according to claim 1, wherein the substrate has a plurality of first grooves on its top surface.

6. The algal reef according to claim 1, wherein the substrate has a plurality of wall portions that protrude in the axial direction from the periphery of the top surface.

7. The algal reef according to claim 6, wherein the base further has a columnar portion that protrudes in the axial direction from the central part of the top surface.

8. The algal reef according to claim 7, wherein the columnar portion has at least one second groove extending along the axial direction of the columnar portion on its side surface.

9. The algal reef according to claim 7, wherein the columnar portion has a plurality of protrusions projecting radially outward from the outer circumferential surface at the tip of the columnar portion.

10. The algal reef according to claim 1, wherein the other end of the base in the axial direction is provided with an annular rat-proof portion having an outer diameter larger than that of the base.

11. The rat-proof portion has a plurality of third grooves on its surface, according to claim 10.

12. The base has a plurality of wall portions that protrude in the axial direction from the periphery of the top surface, Each of the aforementioned plurality of wall portions has a projection that protrudes radially outward from the base body at an intermediate point in the axial direction, The rat-proof portion is detachably supported with respect to the protrusions of each of the plurality of wall portions, as described in claim 10.

13. The algal reef according to claim 1, wherein the substrate has a plurality of first through holes on its top surface.

14. The algal reef according to claim 1, wherein the substrate has a plurality of second through holes on its side surface.

15. The algal reef according to any one of claims 1 to 14, wherein the maximum dimension in the axial direction is 80 mm or less, and the maximum dimension in the radial direction is 130 mm or less.

16. The algal reef according to any one of claims 1 to 14, wherein the mass is 100 g or less.

17. A seaweed reef according to any one of claims 1 to 14, comprising a biodegradable material.

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