OA21377A - Artificial reef. - Google Patents

Abstract

The invention relates to an artificial reef (1) comprising: a base plate (2) having an upper surface (2a) and a lower surface; a central pole (3) having an upper extremity (3a) and a lower extremity (3b), the central pole (3) being connected perpendicularly to the upper surface (2a) of the base plate (2) by its lower extremity (3b); a peripheral structure fixed to the upper surface (2a) of the base plate (2) and disposed around the central pole (3), said peripheral structure being formed of a plurality of interconnected units (4) having different orientations. The invention also relates to a method for the restoration of coral reefs by using said artificial reef (1).

Description

Artificial reef

Technical field

The présent invention relates to an artificial reef and to a new method and strategy of restoring coral reefs.

Technical backqround

Coral reefs are extremely complex marine ecosystems which serve as food, shelterand protection for a multitude of marine animais and plants, including vital links in the food chain such as crustaceans, sponges, and invertebrates. Coral reefs are thought by many scientists to be the most biologically diverse, species-rich and productive ecosystems on the earth. Coral reefs occupy approximately 0.2 % of the world's océan surfaces and are home to nearly a million marine species, including a quarter of ail fish species. Coral reefs also provide several important benefits to the world's population, such as tourism, private and commercial fishing, mainland and island protection, medicines, and ecological indications.

Unfortunately, many of the earth's coral reefs are in danger of being severely injured or destroyed by human activity. Water pollution, global warming and direct physical contact from boat anchors, divers, etc., are among many of the causes of this détérioration. Moreover, the spread of non-sustainable fishing methods, such as dynamite fishing, hâve caused a rapid décliné in the live coral cover on many of the world's coral reefs.

The effeçt of these activities has led to the significant destruction and réduction of our natural reef Systems. Because natural reefs cannot rebuild themselves fast enough to keep up with their destruction rate, the fragile océan reef System stands in péril.

Since large natural coral structures take hundreds to thousands of years to develop, man has developed different methods to accelerate restoration processes, and assist coral colonies in their recovery following severe disturbance and dégradation. Most of existing methods today are based on the transplantation of individual colonies from a donor site or nursery to the site in need of restoration.

These methods usually demand an important workforce and can be deployed for the restoration of limited seabed surfaces only. They also limit the genetic and local diversity of corals as only spécifie strains are transplanted. Sexual propagations methods are less studied and are not privileged to date.

Artificial reefs hâve been used in coral restoration projects either as substrate for the attachment of transplanted coral colonies, or as an alternative habitat to pre-existing coral reefs, or both. In both cases, the use of artificial reefs has not addressed the main shortcomings of asexual propagation methods 5 mentioned here above.

Document CN 110606715 A relates to a latticed concrète artificial coral reef comprising a coral reef body, wherein a rough surface facilitating coral larvae and calcified algae spore attachment is arranged on the coral reef body. The artificial coral reef further comprises fixing holes and simulated corals arranged 10 on the coral reef body.

Document CN 210808819 U relates to a coral repair type artificial fish reef which comprises a hollow curved main body, a first opening formed on the top end of the main body, and a second opening formed on the bottom end of the main body; the first opening and the second opening extending outwards to be 15 provided with rolling openings, and the rolling openings and the body being integ rally formed.

Document KR 101681578 B1 relates to a tetrapod having a fishing bank function, comprising a tetrapod mounted on a breakwater; and a groove formed outside the tetrapod.

Document KR 20130104609 A relates to a marine algae attachment block comprising a porous structure having multiple embosses and holes. In addition, such block further comprises a rope for cultivation of marine algae wound on the outer surface of the porous structure.

Document WO 2020/107576 A1 relates to a composite-concrete artificial 25 reef for ecological restoration of coral reefs, comprising concrète reef and iron fibers which are distributed overthe surface of the concrète reef.

Document WO 02/068762 A1 relates to an artificial reef module for coral reef remediation which includes a central body having an upper plate, a middle plate, a lower plate, a plurality of primary tines extending from such plates and a 30 plurality of secondary tines extending from the primary tines.

Document WO 2014/007926 A1 relates to an artificial reef molded from a mixture of environmentally friendly homogenized organic and inorganic materials, cernent, and aggregates of sand and gravel.

Document WO 2020/107576 A1 relates to an artificial ecological reef made 35 of a composite concrète material for the ecological restoration of coral reefs. The artificial ecological reef comprises a concrète reef body, wherein iron fibers are at least distributed on a surface of the concrète reef body.

There is thus a need for an artificial reef (and also a restoration method) that makes it possible to efficiently restore coral reefs in damaged marine areas, notably by enabling translocation of colonized artificial reefs on a large scale, while maintaining the taxonomie and genetic diversity of corals and possibly without asexual or sexual transplantation of the corals.

Summarv of the invention

It is a first object of the invention to provide an artificial reef comprising:

- a base plate having an upper surface and a lower surface;

- a central pôle having an upper extremity and a lower extremity, the central pôle being connected perpendicularly to the upper surface of the base plate by its lower extremity;

- a peripheral structure fixed to the upper surface of the base plate and disposed around the central pôle, said peripheral structure being formed of a plurality of interconnected units having different orientations.

According to some embodiments, the peripheral structure is a substantially hemispherical structure.

According to some embodiments, the artificial reef comprises from 10 to 20 units, and preferably 15 units.

According to some embodiments, at least one unit, and more preferably ail the units are plates having an inner surface oriented towards the central pôle, an outer surface oriented away from the central pôle, and a polygonal, preferably hexagonal perimeter.

According to some embodiments, the units are fixed together via respective edges of their polygonal, preferably hexagonal perimeters.

According to some embodiments, the inner and/or outer surface of the units, preferably the outer surface, comprises a ridge surrounding a central recess.

According to some embodiments, the ridge is polygonal-shaped, preferably hexagonal-shaped.

According to some embodiments, the ridge comprises an inner wall oriented towards the recess and an outer wall oriented away from the recess, the inner wall and/or the outer wall being preferably provided with multiple grooves.

According to some embodiments, the peripheral structure comprises openings between the base plate and some of the units, and/or between some of the units.

According to some embodiments, the openings are polygonal-shaped, preferably pentagonal-shaped.

According to some embodiments, the units are interconnected by internai rods extending from each unit to an adjacent unit, and are preferably fixed together by mortar.

According to some embodiments, one or more surfaces of each unit comprises a three-dimensional structuring selected from grooves, projections, dépréssions and protrusions, defining concavities having a dimension from 100 pm to 100 mm.

According to some embodiments, one or more surfaces of each unit comprises pores having a mean diameterfrom 0.1 to 3 mm.

According to some embodiments, the artificial reef comprises at least one additional structure comprising a cavity, located between the central pôle and the peripheral structure.

According to some embodiments, the artificial reef comprises a flexible element having at least one end attached to the central pôle and/or the peripheral structure.

According to some embodiments, the flexible element comprises a network of flexible strands, fixed between two flexible bands extending in a longitudinal direction and secured together, the two flexible bands having at least an edge and said strands having a portion projecting from said at least one edge in a transverse direction.

According to some embodiments, the central pôle comprises a throughhole, proximate to the upper extremity of the central pôle.

The invention also relates to a method for the restoration of coral reefs, the method comprising:

- placing at least one artificial reef, in a first marine area comprising corals, so as to colonize the artificial reef with corals from the first area;

- transporting the at least one colonized artificial reef to a second marine area, so as to promote the colonization of the second area with corals.

According to some embodiments, the artificial reef is as detailed above.

According to some embodiments, the second marine area is initially devoid of corals or comprises damaged corals.

According to some embodiments, the artificial reef is transported over a distance equal to or lower than 50 km.

According to some embodiments, the colonization of the second area is carried out by coral larvae originating from the artificial reef, and/or by coral larvae attracted to the second area by the artificial reef.

The présent invention enables to meet the abovementioned needs. In 5 particular the invention provides an artificial reef (and also a restoration method) that makes it possible to efficiently restore coral reefs in damaged marine areas, notably by enabling translocation of colonized artificial reefs on a large scale, while maintaining the taxonomie and genetic diversity of corals and possibly without asexual or sexual transplantation of the corals.

This is achieved by the artificial reef according to the présent invention.

More particularly, the artificial reef comprises a peripheral structure fixed to the upper surface of the base plate and disposed around the central pôle, said peripheral structure being formed of a plurality of interconnected units having different orientations and élévation from the seabed. This makes it possible to 15 form an artificial reef which has different orientations and provides different conditions (such as température, current exposure, sunlight exposure, sensitivity to siltation, orientation of substrate relative to gravity, élévation from the substrate) for the development of the coral populations depending on the respective orientation and geometry of the various units. This créâtes different environmental 20 conditions on the same artificial reef, which allows the colonization of the reef by different coral species and thus favors a large taxonomie and genetic diversity.

In addition, the spécifie structure of the artificial reef according to the invention favors sexual reproduction of the corals (which involves natural settlement of planulae, growth, survival and future spawning) and thus avoids a 25 transplantation step. Advantageously, the presence of additional structures comprising cavities to shelter high trophic level species such as groupers or snappers limit the development of corallivorous species. Still advantageously, the presence of flexible éléments such as ropes mimicking artificial seagrass allow the presence of herbivorous species to limit the expansion of macroalgae. In other 30 words, this makes it possible to optimize natural colonization of the artificial reef by corals, therefore saving the need for assisted colonization through transplantation for example, and saving significant manpower and resources for large scale applications.

Therefore, the method according to the présent invention makes it possible 35 to restore coral reefs in marine areas which hâve been damaged, for instance by pollution or mechanical disruption, with représentative species, and after the identified pressure has been reduced. This is made possible by placing the artificial reef in a first marine area comprising healthy corals (in other words in an area which has not been substantially damaged), so as to allow healthy corals to colonize the artificial reef, and then by transporting the colonized artificial reef to a second (damaged) marine area, so as to so as to improve the colonization of the second area, thanks to the colonized artificial reef. More particularly, the 5 installation of the colonized artificial reef on the second area has two effects.

Firstly, mature and productive corals émit larvae, which colonize the environment to be restored. Secondly, the larvae are attracted by coral environments (especially noise). This means that the artificial reef can attract larvae présent in the environment and catalyze the attachment of larvae in the second marine area.

Thus, the présent invention allows the translocation of the colonized artificial reef and the restoration of coral reefs and associated ecological functions in damaged areas. In addition, the translocation of the entire artificial reef including the coral colonies and their substrate, minimizes stress and improves the survival rate and reproductive capacity of the coral colonies translocated to the damaged site.

Furthermore, the artificial reef of the présent invention is easy and relatively cheap to manufacture and assemble, and easy to move from one marine area to another marine area.

Brief description of the drawings

Figure 1 illustrâtes a perspective view of an artificial reef according to one embodiment of the invention.

Figure 2 illustrâtes a perspective view of a part of the artificial reef according to one embodiment of the invention.

Figure 3 illustrâtes a perspective view of a part of the artificial reef according to one embodiment of the invention. ,

Figure 4A illustrâtes a perspective view of a part of the artificial reef according to one embodiment of the invention.

Figure 4B illustrâtes a bottom view of a part of the artificial reef according 30 to one embodiment of the invention.

Detailed description

The invention will now be described in more detail without limitation in the following description.

Artificial reef

By making reference to figures 1 and 2, the artificial reef 1 according to the présent invention comprises a base plate 2 having an upper surface 2a and a lower surface (not illustrated in the figures) opposite to the upper surface 2a. When the artificial reef 1 is in use, the lower surface 2a of the base plate 2 in contact with the ground, and more particularly with the bottom of the océan (or sea).

The base plate 2 may preferably hâve a substantially circular perimeter (thus the upper and lower surfaces may hâve a substantially circular perimeter). Alternatively, the base plate 2 may hâve a polygonal perimeter.

According to some embodiments, the base plate 2 may hâve a substantially constant thickness between the upper surface 2a and the lower surface.

The base plate 2 may hâve a diameter from 1 to 10 m, and preferably from 1 to 5 m. For a non-circular base plate, the term “diameter” refers to the maximum dimension of the base plate 2 (perpendicular to the thickness of the base plate 2).

According to preferred embodiments, the thickness of the base plate 2 may vary across the upper surface 2a. More particularly, as illustrated in figure 2, the base plate 2 may comprise one or more zones 2b on its upper surface 2a, which hâve a reduced thickness (relative to the rest of the base plate 2) and which may be configured to receive some of the plurality of units 4. For example, as illustrated in figure 2, the base plate 2 comprises peripheral zones 2b wherein the thickness of the base plate 2 is reduced, relative to a central portion of the upper surface 2a.

These reduced thickness zones 2b may be beveled, planar zones. The angle between each reduced thickness zone 2b and the central portion of the upper surface 2a may be from 0 to 90°, preferably from 10 to 80°. Each reduced thickness zone 2b may be delimited from the central portion of the upper surface 2a by a respective inner edge. Said inner edges may collectively form a polygon, preferably a pentagon surrounding the central portion. Preferably, ail reduced inner thickness zones 2b hâve the same shape and dimensions, and the polygon formed by their inner edges is a regular polygon.

On its upper surface 2a, the base plate 2 may comprise one or more orifices 2c (for example from 1 to 15, and preferably from 5 to 15 orifices 2c, and more preferably 10 orifices 2c) for connecting some of the units 4 to the base plate 2 (as will be explained later). In case the base plate 2 comprises reduced thickness zones 2b as mentioned above, the orifices 2c may preferably be located within such zones 2b.

The base plate 2 may also comprise (on its upper surface 2a) one or more furrows 2d for the connection of one or more (preferably two) structures that comprise a cavity, between the base plate 2, the central pôle 3 and the units 4 (as will be explained below). These cavities are useful as they may provide shelter and protection for a multitude of marine animais such as fish.

The lower surface of the base plate 2 is preferably fiat in order to facilitate the stable positioning of the artificial reef 1 at the bottom of the océan.

The base plate 2 may be made from a material chosen from concrète, Steel, wood and combinations thereof.

The artificial reef 1 according to the présent invention further comprises a central pôle 3 having an upper extremity 3a and a lower extremity 3b and a sidewall between 3c the upper extremity 3a and the lower extremity 3b. As illustrated in figure 2, the central pôle 3 is connected perpendicularly to the upper surface 2a of the base plate 2 by its lower extremity 3b and preferably at the center of the upper surface 2a of the base plate 2. For instance, if the central pôle 3 and base plate 2 are made of concrète, the connection may be performed owing to reinforcing struts arranged in the concrète matrix, and extending from the base plate 2 to the central pôle 3. For instance, the base plate 2 may be manufactured first, with reinforcing struts extending from said base plate 2, and then the concrète for the central pôle 3 may be poured onto these strut extensions.

According to some embodiments, the central pôle 3 may hâve a circular cross-section. Alternatively, the central pôle 3 may hâve a cross-section that is not circular, for example polygonal, or rectangular cross-section, notably a square cross-section.

The diameter of the central pôle 3 may be from 100 to 800 mm, and preferably from 150 to 500 mm.

For a non-circular central pôle 3, the term “diameter¹’ refers to the maximum dimension of the cross-section of the central pôle 3.

According to some embodiments, the central pôle may comprise at least one through-hole 3d on its sidewall 3c, proximate to the upper extremity 3a of the central pôle 3 (as illustrated in figure 2). This makes it possible to facilitate the transport of the artificial reef 1 by passing a strap or a rope through the throughhole 3d for lifting the artificial reef 1.

Alternatively or additionally, the central pôle 3 may be provided with other features for lifting the artificial reef 1, such as one or more hooks, rings, and holes.

The central pôle 3 may hâve a length from 0.5 to 5 m, and preferably from 1 to 2,5 m.

The central pôle 3 may be made from a material chosen from concrète, Steel, wood and combinations thereof.

The artificial reef 1 also comprises a peripheral structure made of a plurality of units 4 (as illustrated in figures 1 and 3) which are interconnected to each other and disposed around the central pôle 3. The penpheral structure is fixed to the upper surface 2a of the base plate 2. This peripheral structure is preferably a substantially hemispherical structure. Each interconnected unit 4 has a different orientation on the peripheral structure. Thus, the peripheral structure allows to multiply the different orientations of the artificial reef 1 so as to create multiple areas (on the reef) having different environmental conditions depending on their orientation.

The artificial reef 1 may comprise from 10 to 20 units 4, and preferably 15 units4. For example, the artificial reef may comprise from 10to 12 units 4; or from 12 to 14 units 4; orfrom 14 to 16 units 4; orfrom 16 to 18 units 4; orfrom 18 to 20 units 4.

As illustrated in figure 3, a unit 4 is preferably a plate having a polygonal perimeter, more preferably a regular polygonal perimeter such as a square perimeter, a pentagonal perimeter or a hexagonal perimeter. More preferably a unit 4 may hâve a regular hexagonal perimeter.

According to some embodiments, the units 4 may hâve different shapes,

According to other preferred embodiments, ail units 4 hâve the same shape, and preferably ail units 4 may hâve a regular hexagonal perimeter.

As illustrated in figure 1 and figure 3, a unit 4 may be a plate having an inner surface (not illustrated in the figures) oriented towards the central pôle 3 (interior of the artificial reef 1) and an outer surface 4a oriented away from the central pôle 3 (exterior of the artificial reef 1). According to preferred embodiments, ail units 4 are plates having an inner surface (not illustrated in the figures) oriented towards the central pôle 3 and an outer surface 4a oriented away from the central pôle 3.

As illustrated in figure 1, the units 4 may comprise a first level of units 4 (such as from 4 to 7, and more preferably 5) fixed to the base plate 2; and then one or more levels of units 4 placed above the first level of units 4. Preferably, they comprise a second level of units 4 (such as from 4 to 7, and more preferably 5) placed above and fixed to the first level of units 4; and then a third level of units 4 (such as from 4 to 7, and more preferably 5) placed above and fixed to the second level of units 4. In the illustrated embodiment, the units 4 consist of these three levels.

The units 4 may be connected to each other (as well as to the base plate 2 when necessary) via respective edges on their perimeters. The connection may include internai rods extending from each unit 4 to an adjacent unit 4 or to the base plate 2.

In fact, the edge of each unit 4 may comprise one or more orifices 4c (such as 1 to 3 orifices, and preferably 2).

These orifices 4c may be aligned with corresponding orifices 4c in adjacent units 4 or with orifices 2c on the upper surface 2a of the base plate 2.

In order to assemble the artificial reef, internai rods may be inserted in these orifices (between adjacent units 4 or between a unit 4 and the base plate 2), and a hardening composition may be injected in the orifices 2c, 4c.

The rods may be in a material chosen from stainless steel, glass fibers, or a polymer.

The hardening composition may be a mortar composition, a resin or a Chemical binder.

Each unit 4 may hâve a maximum thickness between its inner surface and its outer surface 4a from 30 to 100 cm.

Each unit 4 may hâve a minimum thickness between its inner surface and its outer surface 4a from 5 to 15 cm.

Each unit 4 may hâve a diameter from 25 to 200 cm. For a non-circular unit, the term “diameter” refers to the maximum dimension of the unit 4 (perpendicular to the thickness of the unit).

Each of the inner surface and outer surface 4a may be substantially planar or not. Preferably, at least the outer surface 4a is substantially not planar.

As illustrated in figure 3, according to some embodiments, the upper surface 4a of at least one unit, and preferably of ail units 4, may comprise a central recess 4d which is surrounded by a ridge 4b. The central recess 4d may be a substantially planar surface.

Alternatively or additionally, such central recess 4d surrounded by a ridge 4b may be présent on the inner surface of the unit 4.

The ridge 4b may hâve a circular contour or may comprise segments arranged along a polygonal contour, such as a square contour, a pentagonal contour or a hexagonal contour. According to preferred embodiments (and as illustrated in figure 3), the shape of the contour of the ridge 4b is the same as the shape of the perimeter of the unit 4. For example, for a hexagonal perimeter, a ridge 4b made of segments arranged as a hexagon is preferred.

Therefore, the shape of the perimeter of the central recess 4d is preferably the same as the shape of the perimeter of the unit 4.

The central recess 4d may comprise at least one orifice, preferably from 1 to 5 orifices, and more preferably from 1 to 4 orifices. Such orifices make it possible to fix complementary material such as monitoring equipment, habitat complexification modules, and coral transplants.

According to some embodiments, the ridge 4b may comprise an inner wall 4f oriented towards the central recess 4d and an outer wall 4e oriented away from the central recess 4d. The inner wall 4f and outer wall 4e may be joined at a top of the ridge 4b. This embodiment is illustrated in figure 3.

The angle between the inner wall 4f and the central recess 4d may be from

15°to90°.

The angle between the inner wall 4f and the outer wall 4e may be from 0° to 150°.

The ridge 4b may hâve a height from the inner recess 4d to the top from 5 10 to 150 cm.

At least one of the inner wall 4f and the outer wall 4e of the ridge 4b may be provided with multiple grooves 4g.

According to preferred embodiments, both the inner wall 4f and the outer wall 4e of the ridge 4b are providèd with multiple grooves 4g. Such grooves make 15 it possible to modify the surface of the unit 4, and thus the surface of the artificial reef 1 and allow fixation of different coral species. The grooves 4g may for example extend along the inner wall 4f and/or outer wall 4e perpendicularly to the contour (such as the polygonal contour) of the ridge 4b. They may substantially extend from the central recess 4d to the top of the ridge 4b, and from the top of the ridge 4b to the perimeter of the unit 4. When the ridge 4b comprises multiple segments, as described above, it may comprise for example from 3 to 10, preferably 5 grooves (as illustrated) per segment and per inner and/or outer wall 4f, 4e. Each groove 4g may hâve a length from 5 to 150 cm. Each groove 4g may hâve a width from 1 to 10 cm.

In addition, such grooves 4g make it possible to limit coral prédation by coral eating species such as parrot fish. In other words, the dimensions and design of these grooves 4g mechanically limit the capacity of these species’ beaks to attain young coral recruits.

More generally, the units 4 of the artificial reef 1 may comprise on their 30 outer surface 4a and (alternatively or additionally) on their inner surface, a threedimensional structuring - of which the grooves 4g described above are one example.

Such structuring may be selected from grooves, projections, dépréssions and protrusions. This structuring allows to create a versatile surface and thus a 35 versatile environment on each unit4. In addition, the three-dimensional structuring may define concavities which may hâve a dimension from 100 pm to 100 mm. By “dimension of the concavitÿ’ is meant in the context of the présent invention the distance from one end of the concavitÿ to the other, in the direction of the concavity. For example, in case the three-dimensional structuring comprises a groove, the dimension of the concavity is the width of the groove. In case the three-dimensional structuring comprises a dépréssion (having for example a circulât, polygonal or ellipsoidal perimeter), the dimension of the concavity is the 5 outer diameter (maximum dimension) of the dépréssion. In case the threedimensional structuring comprises convex features, such as projections or protrusions, concavities may be defined between adjacent convex features.

Each unit 4 may be made from a material chosen from concrète (such as Portland concrète, porous concrète (in other words concrète material built from 10 spécifie formulations and processes so that it présents micrometric to millimetric holes on its surface), and 3D concrète (in other words concrète produced through an additive manufacturing process, preferably with a grooved surface), polymers such as polyvinyl chloride (PVC), vinyl ester polymers, bio sourced polymers (chitosan-sourced material, polylactic acid linen fibers), and ceramics foam.

According to some embodiments, the units 4 may be made from different materials.

According to other embodiments, ail units 4 are made from the same material.

Each unit 4 may hâve a surface (inner and/or outer surface) which 20 comprises pores having a mean diameter from 0.5 to 3 mm, and preferably from 0.6 to 1 mm. The presence of such pores makes it possible to offer shelter to the larvae from different predators and thus allow their development. This porosity is in addition to the three-dimensional structuring described above. The porosity may be adjusted by using granular materials of different sizes and/or by using porosity25 inducing manufacturing techniques, for example by applying vibrations during manufacturing.

Altematively, the surface (inner and/or outer surface) of each unit 4 may be smooth, in other words may be substantially devoid of pores.

According to some embodiments, the surface of each unit 4 may hâve 30 different sizes of pores (or no pores at ail) relative to the other units 4.

Altematively, the surface of ail units 4 may hâve the same size of pores (or no pores at ail).

Each unit 4 according to the présent invention may be integrally formed or in other words formed in a single piece.

Altematively, each unit 4 according to the présent invention may be formed from the assembly of at least two parts. In this case, a first part may comprise the outer surface 4a of the unit 4 and a second part may comprise the inner surface of the unit 4. This présents an advantage as it allows to use two different materials (a first material for the outer surface 4a and a second material for the inner surface), and thus create different environments (surfaces) at the exterior and the interior of the artificial reef 1 for the fixation and development of different coral species.

As described above, when connected to each other to form the peripheral structure, the outer surface 4a of each unit 4 is located at the exterior of the peripheral structure (external side of the artificial reef 1) while the inner surface of each unit 1 is located at the interior of the peripheral structure (internai side of the artificial reef 1).

In this configuration, the outer surface 4a of each unit 4 has a different orientation from the outer surface 4a of the other units 4. In other words, each unit 4 is arranged differently in relation to the cardinal points relative to the other units 4. This différence in orientation makes it possible to create different environments on the same artificial reef 1. More particularly, some parts of the artificial reef 1 may hâve a different exposure to light, silting, gravity or to water currents. As a resuit, the artificial reef 1 of the présent invention allows a diversity of species to grow, each species having its own optimal conditions for development and survival. Thus, it makes it possible to maintain a large taxonomie and genetic diversity.

Furthermore, as illustrated in figure 1, the peripheral structure may comprise one or more openings 5. Such openings 5 may be présent between the base plate 2 and some of the units 4 (for example between the base plate 2 and the units 4 belonging to the first and second level described above). Additionally or alternatively, such openings 5 may be présent between some of the units 4 (for example between the first part of the units 4 which are fixed to the upper surface 2a of the base plate 2 and the second part of the units 4). These openings 5 make it possible for the larvae to colonize the interior of the artificial reef 1 (especially when the inner surface of the units 4 présents a three-dimensional structuring as detailed above).

Also, the openings 5 may minimize disruption of water currents by the artificial reef 1.

The number of openings 5 may e.g. range from 5 to 25, preferably from 8 to 15 and is preferably 11.

According to preferred embodiments, notably when such openings 5 are formed between some of the units 4, these openings 5 may hâve a polygonal shape, and preferably a pentagonal shape. They may thus be delimited by respective edges of five adjacent hexagonal units 5).

The central pôle 3 may protrude through one of the openings 5.

As illustrated in figure 1, the peripheral structure may comprise, from bottom to top:

- a number of openings 5 (preferably five) between the base plate 2 and adjacent units 4, each opening 5 being preferably delimited by the base plate 2 and three adjacent units 4 (such as two units 4 belonging to the first level, and one unit 4 belonging to the second level);

- a number of openings 5 (preferably five) between adjacent units 4, each opening 5 being preferably pentagonal-shaped and being delimited by five adjacent units 4 (such as one unit 4 belonging to the first level, two units 4 belonging to the second level and two units 4 belonging to the third level);

- one further opening 5 between adjacent units 4 through which the central pôle 3 protrudes, which is preferably pentagonal-shaped and delimited by five adjacent units 4 (such as five units 4 belonging to the third level).

Preferably, the peripheral structure is not directly fixed to the central pôle 3. Instead, the peripheral structure is fixed to the base plate 2 and the central pôle 3 is also fixed to the base plate 2.

According to some embodiments, the artificial reef 1 may include a variety of features designed to promote interactions with other species, bénéficiai to coral settlement and growth. More specifically, these features aim to promote prédation of corallivorous species and/or prédation of fixed species which could compete with the corals for substrate cover.

Thus, as mentioned above, the artificial reef 1 may comprise one or more additional structures 6 comprising a cavity (figure 4A and 4B) designed to host large specimens of predators for corallivorous species. Such additional structure 6 may be located between the central pôle 3 and the peripheral structure and be connected for example to the base plate 2, for example to one of the furrows 2d located on the upper surface 2a of the base plate 2. The dimensions and the design of the cavities of the additional structures 6 may be adapted to fit with the preferendum of the predators in a variety of environments. Such predator species may include groupera, snappers, etc.

The fixation of the additional structures 6 to the base plate 2 may include rods (as described above) extending between respective orifices in the base plate 2 and in the additional structures 6, and a hardening composition (as described above) may be injected into these orifices.

As illustrated in figures 4A and 4B, the additional structure 6 may comprise a top wall 6a and latéral walls 6b, such as three latéral walls 6b. The latéral walls

6b may be positioned substantially perpendicularly to the base plate 2 (and more specifically substantially perpendicularly to the central portion of the upper surface 2a). The top wall 6a may be positioned substantially parallel to the base plate 2 (and more specifically substantially parallel to the central portion of the upper surface 2a). The above-described fixation of the additional structure 6 to the base plate 2 may be made via at least two of the latéral walls 6b. The above-described orifices 6c may thus extend parallel to the latéral walls 6b, from the bottom end thereof.

A cavity is thus delimited by the base plate 2 on the one hand, and by the top wall 6a and latéral walls 6b of the additional structure 6 on the other hand.

The top wall 6a may partly or preferably fully cover the latéral walls 6b. It may also further extend past the latéral walls 6b, as illustrated. For example, the top wall may comprise a substantially triangular projection. The tip 6d of the triangular projection may be tapered, as illustrated.

As mentioned above, the cavities formed by the additional structures 6 are useful as they may provide shelter and protection for a multitude of marine animais such as fish, preferably fish species which are predators forcorallivorous species. The presence of fish in the artificial coral reef 1 also provides a natural sound environment which is favorable to colonization by coral larvae.

According to other preferred embodiments, the artificial reef 1 may further include a flexible element (or artificial seagrass module) having at least one end attached to the central pôle (3) and/or the peripheral structure.

The flexible element may comprise one or several flexible strands, or filaments. Preferably, the flexible element comprises at least one end opposite the attached end which is free-flowing.

The length of the flexible element, from the attached end to the free-flowing end, may be from 50 to 500 cm.

The flexible element may for example comprise a network of flexible strands, fixed between two flexible bands extending in a longitudinal direction and secured together, the two flexible bands having at least an edge and said strands having a portion projecting from said at least one edge in a transverse direction. Such bands are preferably superimposed to one another. The strands may be made of natural fibers such as hemp fibers, coconut fibers or a mixture of hemp and coconut fibers, or synthetic fibers such as polypropylene fibers.

The above flexible element is described in detail in document FR 3027769. One end of the two flexible bands may be attached to the central pôle (3) and/or the peripheral structure while the opposite end of the two flexible bands (along the longitudinal direction) may be free-flowing.

The flexible element may be attached for example owing to hooks or rings fixed on the central pôle 3 and/or on the peripheral structure, more preferably at the top of the peripheral structure.

The presence of such éléments makes it possible to attract herbivorous 5 species which will naturally graze on different types of algae and therefore makes it possible to limit the coverage of the artificial reef 1 by such algae and therefore limitthe compétition with coral development. Moreover, such éléments may attract any larvae in the water which are proximate to the artificial reef 1 creating positive eues (visual, sounds, vibrations) and lead them to the units 4 of the artificial reef 10 1.

In addition, such structure may contribute to the development of aquatic fauna or flora by constituting an artificial habitat and shelter for aquatic fauna and flora.

The artificial reef 1 may hâve a weight from 500 kg to 20 tons, and 15 preferably from 1 to 6 tons.

On the one hand, the weight of the artificial reef 1 is sufficient to prevent accidentai movement of the artificial reef 1 due to water currents. On the other hand, this weight allows the transportation of the artificial reef 1 from a first marine area to a second marine area, as explained below.

Method for the restoration of coral reefs

The invention also relates to a method for the restoration of coral reefs carried out with the artificial reef 1 described above.

The method according to the invention comprises a step of placing at least 25 one artificial reef 1 as described above, in a first marine area comprising mature corals. According to some embodiments, the corals may be mature. Additionally or alternatively, the corals may mainly reproduce sexually liberating gametes in the water column. Preferably, the first marine area is a “healthÿ’ area (which has not been substantially damaged) comprising different coral populations. This area 30 acts as a “donor¹' of corals.

It is thus possible to place from 1 to thousands artificial reefs 1 in the first marine area.

The artificial reef(s) 1 may be positioned at a depth in the first marine area from the surface to -100 m depending on the biology of the présent coral species. 35 The artificial reef 1 may be transported in the first marine area by any conventional mode of transport, such as a lifting tool to which the artificial reef 1 may attached and which will lift said artificial reef 1 and immerse it in the first marine area. The artificial reef 1 according to the présent invention may be deployed autonomously, in other words without the assistance of scuba divers generally mobilized to achieve the detachment of the reef from the lifting tool. For example, this is achieved by passing a lifting cable through a hook, ring, or hole présent on the central pôle 3 of the artificial reef 1 (as explained above), such 5 lifting cable being opened remotely which triggers the reef detachment without direct human intervention.

During this step, drifting larvae resulting from a natural sexual reproduction from the different coral populations of the first marine area colonize the artificial reef 1. Various species may colonize the different parts (different areas and/or 10 materials) of the artificial reef 1 depending on their optimal conditions for development.

According to some embodiments and notably according to the biology of the coral species présent in the first area, artificial reef(s) 1 may be placed in the first marine area at a distance of at least 10 m. However, this distance dépends 15 not only on the currents but also on the biology of the coral species.

In addition, the artificial reef(s) 1 may remain in the first marine area for a period of time from 6 months to more than 10 years depending on the reproduction seasons and the biology of the coral species présent in the first area.

After this period of time, the method according to the invention comprises 20 a step of transporting the colonized artificial reef(s) 1 to a second marine area. This second marine area is preferably a “damaged area devoid of corals or comprising a depleted coral population due to some pressure in said area negatively impacting the coral population (e.g. pollution or mechanical disruption pressure), wherein said pressure may hâve been identified and may hâve been 25 significantly reduced. Thus, by “damaged corals” is meant not only corals that are in poor health but also corals in good health but in lower concentrations in the second marine area relative to the concentration of corals in the same area prior to the damage or pressure in the second marine area. After this step, new mature coral colonies from different species become available in the “damaged area.

During the first following season of reproduction (after transportation of the artificial reef 1 in the second marine area), gametes and larvae from the different coral populations that hâve colonized the artificial reef 1 may be released inside the second marine area. Thus, this step allows a rapid natural recolonization of the degraded reefs of the second marine area with coral populations from the artificial reef(s) 1. More particularly, during this step mature and productive corals présent on the artificial reef 1, may émit larvae, which may colonize the second marine area. In addition, during this step, as larvae are attracted by coral environments, the colonized artificial reef 1 may attract larvae présent in the environment and thus catalyze the colonization of the second marine area by such larvae.

The distance between the first marine area and the second marine area may be equal to or lower than 50 km for example from 10 meters (if the pressure 5 is absent) to 50 km.

The artificial reef(s) 1 may be deployed at a depth at the second marine area from the surface to -100 m depending on the biology of the présent coral species and the restoration strategy adopted (for example use of deep supercorals, i.e. corals that can survive both extreme conditions and rapid changes in 10 their environment).

The artificial reef(s) 1 may be transported for example by floating the artificial reef 1 in open water using a lifting balloon, then by towing the artificial reef 1 in open water from the first marine area to the second marine area, and finally by redeploying the artificial reef 1 in the second marine are by progressively 15 lowering the balloon. Alternatively, it is also possible to immerse the artificial reef 1 in a “pool” placed on a transporter barge, the artificial reef 1 preferably being protected from the sun, and transport the artificial reef 1 from the first marine area to the second marine area.

The fact that the colonized artificial reef 1 is transported from a first marine 20 area to a second marine area makes it possible to minimize the time of restoration in the second area as most of mature populations are supposed to be absent or altered after the disruption (or damage). Moreover, the natural migration of larvae from the first marine area to the second marine area may take too long or simply be impossible (depending on local environmental conditions). With the method 25 according to the présent invention, the colonized artificial reef 1 is transported to the second marine area which thus facilitâtes the natural and large scale restoration of the degraded site thanks to the addition of new mature and productive coral populations not only capable of emitting larvae but also of attracting larvae from the environment.

In addition, the transportation of the whole artificial reef 1 and associated adult coral colonies (and not just the coral fragments from one reef to another) makes it possible to reduce the mortality of the corals and improve their reproduction as the stress on corals is minimized during their displacement.

According to some preferred embodiments, the method according to the 35 présent invention is devoid of a transplantation step. In this case, there is no step of artificially (manually or robotically) transplanting and nursering coral fragments onto the artificial reef 1 prior to its deployment in the first area or in the second area.

According to other embodiments, the method according to the présent invention may further comprise an artificial (manual or robot-assisted) transplantation step of corals onto the artificial reef 1 prior to its deployment in the first area or in the second area.

As an alternative to the above method wherein the artificial reef 1 is transported from one area to another area, the artificial reef 1 may also be placed in one marine area and may then remain in place. This marine area may be a healthy area, or a damaged area (preferably in this case in close proximity to a healthy area). The mere placement of the artificial area 1 in said marine area may 10 assist in developing and/or restoring coral reefs in this marine area.

Claims (22)

1. An artificial reef (1) comprising:

- a base plate (2) having an upper surface (2a) and a lower surface;

- a central pôle (3) having an upper extremity (3a) and a lower extremity (3b), the central pôle (3) being connected perpendicularly to the upper surface (2a) of the base plate (2) by its lower extremity (3b);

- a peripheral structure fixed to the upper surface (2a) of the base plate (2) and disposed around the central pôle (3), said peripheral structure being formed of a plurality of interconnected units (4) having different orientations.

2. The artificial (1) reef according to claim 1, wherein the peripheral structure is a substantially hemispherical structure.

3. The artificial reef (1) according to any one of claims 1 or 2, comprising from 10 to 20 units (4), and preferably 15 units (4).

4. The artificial reef (1) according to any one of claims 1 to 3, wherein at least one unit (4), and more preferably ail the units (4) are plates having an inner surface oriented towards the central pôle (3), an outer surface (4a) oriented away from the central pôle (3), and a polygonal, preferably hexagonal perimeter.

5. The artificial reef (1) according to claim 4, wherein the units (4) are fixed together via respective edges of their polygonal, preferably hexagonal perimeters.

6. The artificial reef (1) according to any one of claims 4 or 5, wherein the inner and/or outer surface of the units (4), preferably the outer surface (4a), comprises a ridge (4b) surrounding a central recess (4d).

7. The artificial reef (1) according to claim 6, wherein the ridge (4b) is polygonal-shaped, preferably hexagonal-shaped.

8. The artificial reef (1) according to any one of daims 6 or 7, wherein the ridge (4b) comprises an inner wall (4f) oriented towards the recess (4d) and an outer wall (4e) oriented away from the recess (4d), the inner wall (4f) and/or the outer wall (4e) being preferably

5 provided with multiple grooves (4g).

9. The artificial reef (1) according to any one of daims 1 to 8, wherein the peripheral structure comprises openings (5) between the base plate (2) and some of the units (4), and/or between some of the units 10 (4).

10. The artificial reef (1) according to daim 9, wherein the openings (5) are polygonal-shaped, preferably pentagonal-shaped.

11. The artificial reef (1 ) according to any one of daims 1 to 10, wherein the units (4) are interconnected by internai rods extending from each unit (4) to an adjacent unit (4), and are preferably fixed together by mortar.

12. The artificial reef (1 ) according to any one of daims 1 to 11, wherein one or more surfaces of each unit (4) comprises a three-dimensional structuring selected from grooves, projections, dépréssions and protrusions, defining concavities having a dimension from 100 pm to 100 mm.

13. The artificial reef (1 ) according to any one of daims 1 to 12, wherein one or more surfaces of each unit (4) comprises pores having a mean diameter from 0.1 to 3 mm.

14. The artificial reef (1) according to any one of daims 1 to 13, comprising at least one additional structure (6) comprising a cavity, located between the central pôle (3) and the peripheral structure.

15. The artificial reef (1) according to any one of daims 1 to 14, 35 comprising a flexible element having at least one end attached to the central pôle (3) and/or the peripheral structure.

16. The artificial reef (1) of daim 15, wherein the flexible element comprises a network of flexible strands, fixed between two flexible

bands extending in a longitudinal direction and secured together, the two flexible bands having at least an edge and said strands having a portion projecting from said at least one edge in a transverse direction.

17. The artificial reef (1) according to any one of daims 1 to 16, wherein the central pôle (3) comprises a through-hole (3d), proximate to the upper extremity (3a) of the central pôle (3).

18. A method for the restoration of coral reefs, the method comprising: - placing at least one artificial reef (1), in a first marine area comprising corals, so as to colonize the artificial reef with corals from the first area;

- transporting the at least one colonized artificial reef to a second marine area, so as to promote the colonization of the second area with corals.

19. The method according to claim 18, wherein the artificial reef (1) is according to any one of daims 1 to 17.

20. The method according to claim 18 or 19, wherein the second marine area is initially devoid of corals or comprises damaged corals.

21. The method according to any one of daims 18 to 20, wherein the

25 artificial reef is transported over a distance equal to or lower than 50 km.

22. The method according to any one of daims 18 to 21, wherein the colonization of the second area is carried out by coral larvae

30 originating from the artificial reef (1), and/or by coral larvae attracted to the second area by the artificial reef (1).