Planter

Abstract

A means for planting seagrass plantlets or subsea or intertidal plants in the seabed, comprising a platform 1 capable of being lowered to the seabed, and having a topside 2 and an underside 3. The top

Description

This disclosure relates to a method and apparatus for planting out plantlets of seagrass or other subsea and intertidal plants in the seabed. Seagrass is a vital plant for conservation purposes. It is currently in significant decline around the world. Globally, seagrass captures carbon up to 35 times faster than tropical rainforests, accounting for 10 to 18% of total ocean carbon storage, despite covering less than 0.1% of the seafloor [source: www.wwf.org.uk]. Natural seagrass meadows (which, of course, are not simply a monoculture) provide a vital habitat for marine life and reduce erosion of the seabed, particularly in coastal and estuarine situations. Seagrass is declining by around 7% a year globally, making it the fastest disappearing habitat on planet Earth [source: Ocean Conservation Trust]. In the United Kingdom alone, 92% of the previous seagrass meadows have been lost in the last century; and globally it is thought that an area of two football pitches is lost every hour. Reasons for the decline include pollution, coastal development and vessel and / or anchor damage. Heretofore, seagrass has been planted out into the seabed by hand, with individual plants needing to be individually planted into the seabed, which is slow, expensive and involves an inevitable element of risk. The present disclosure seeks to overcome these problems. In accordance with a first aspect of this disclosure, there is provided an apparatus for planting out plantlets of seagrass or of other subsea or intertidal plants in the seabed, comprising: a platform capable of being lowered to the seabed, and having a top side and an underside; the topside being open and communicating with a plurality of individual open pockets, each pocket having an openable base and being adapted to receive therewithin a said plantlet, each pocket being defined by at least two members moveable relative to each other between a first condition in which the two members of the pocket define an edge at the base of the pocket on the underside of the platform which edge is adapted to dig into the seabed when the platform is lowered thereonto, and a second condition in which the base of the pocket is open; whereby, when the individual pockets are filled with said plantlets and growing medium, and the platform is thereafter lowered into the sea and onto the seabed, the edges dig into the seabed so that subsequent movement of the two members into the second condition opens the base of each pocket to deposit the said plantlet into a planting hole dug in the seabed by the edge. Preferred arrangements have one or more of the following features: the platform is liftable as a whole or lowerable as a whole with the platform in a substantially horizontal configuration by a crane mounted on a seagoing vessel. Individual plantlets are provided in a growing medium within a hessian bag, the hessian being adapted to reduce the risk of growing medium being dispersed as the platform is lowered into the sea. The side walls of each pocket are pivotable relative to each other by a hydraulic mechanism. The platform is provided with a vibrator adapted to vibrate the platform as a whole either to enhance the digging effect of the edges and / or to firm individual plantlets in their individual holes. The pockets are arranged in a grid format and the platform also includes stabilizing legs adjacent its comers outboard of the grid. The stabilizing legs are adjustable to adjust the depths at which plantlets are planted. The stabilizing legs are provided with selectively replaceable pads of differing area depending on the softness of the seabed. According to a second and alternative aspect of this disclosure, there is provided a method for planting a meadow of seagrass or other subsea or intertidal plants in the seabed, the method comprising the steps of: preparing a plurality of planting packets each comprising a plantlet of seagrass or other subsea or intertidal plant and growing medium therefor; loading individual planting packets into individual pockets arranged in a grid on a platform having a top side and an underside, each pocket having an edge at its lowermost position on the underside of the platform; lowering the platform into the sea and onto the seabed in a substantially horizontal configuration so that the respective said edges dig into the seabed; moving sides of the pockets to form a hole in the seabed and to open the base of the pocket so that each said plantlet and its associated growing medium is deposited into a respective said hole; and lifting the platform as a whole to leave an infant meadow of seagrass or other subsea or intertidal plants on the seafloor. This process causes minimal harm to the seabed. Preferred methods have one or more of the following features: the individual packets are wrapped in hessian to restrict dissolution of the growing medium as the platform is lowered into the sea. Vibration is applied to the platform on the seabed to enhance the digging effect of the respective edges into the seabed. Depending on the specific plant species, growing conditions, location and time of year, the term “plantlet” may include “seeds, sprouted seeds, cuttings, or fully formed miniature plants”. Reference should be made to the accompanying drawings, by way of example only, for further details of seagrass planting methods and apparatus, in which: Fig- 1 is a top plan view of an apparatus in accordance with the present disclosure adapted to be lowered into the sea to rest on the sea bed; Fig. 2 is a perspective view of the apparatus shown in Fig. 1; Fig. 3 is a front elevation view of the apparatus shown in Figs. 1 and 2; Fig. 4 is a side elevation view of the apparatus shown in Figs. 1 to 3; Fig. 5 is a perspective of one pocket of the apparatus of Figs. 1 to 4 shown in the open condition; Fig. 6 is a side elevation view of the pocket as shown in Fig. 5; Fig. 7 is a similar view to Fig. 5 showing the pocket in the closed condition; Fig. 8 is a similar view to Fig. 6 in the condition shown in Fig. 7; Fig. 9 is a see-through view of the pocket as shown in Fig. 7; Fig. 10 is a see-through view of the pocket as shown in Fig. 8; Fig. 11 shows a plurality of planting packets containing seagrass plantlets planted in a plurality of corresponding holes dug by the apparatus shown in Figs. 1 to 4 in dry ground as part of a test; and Fig. 12 is a perspective view of a modified version of the apparatus of Figs. 1 to 4 connected to a crane. Referring first to Figs. 1 to 4, the apparatus comprises an approximately square platform 1 which has a top side 2 and an underside 3. Platform 1 defines an 8 x 8 grid of individual open pockets 4, and has a stabilizing leg 5 adjacent each of the four comers of platform 1 outboard of the grid. The length of each stabilizing leg 5 and the area of its pad 5a is selectable enabling the described apparatus to be adjusted for planting different species of subsea or intertidal plants or for varying softness of the seabed, so that the plantlets are planted out at the optimum depths therefor. The top side 2 is open and allows communication with open mouths 6 of pockets 4. Each individual pocket 4 receives, through its open mouth 6 an individual planting packet 7, which consists of a seagrass plantlet and growing medium wrapped together within a hessian bag 8. A plurality of such planting packets 7 are shown in Fig. 11 as planted in a plurality of corresponding holes 9 dug by the apparatus in a trial on dry ground as explained below. The hessian bags 8 deter growing medium from dispersing when the platform 1 with individual packets 7 filling individual pockets 4 is lowered into the sea, but not so tight as to restrict the growth of the roots of the seagrass plantlet out through the hessian bag 8. The hessian bags also deter fish and other sea animals from eating the plantlets whole before they have had an opportunity to root into the seabed. Referring now to Figs. 5 to 10, each individual pocket 4 is formed from a pair of opposing generally U-shaped members 9 each having a central rectangular wall 10, one rectangular side wall 11 connected to one side edge 12 of its associated central wall 10, and a triangular side wall 13 connected to an opposite side edge 14 of central wall 6. Each U-shaped member 9 is connected to the other by respective pivots 15 through its triangular side wall 13 which overlaps with the rectangular side wall 11 of the other U-shaped member 9, each triangular side wall 13 being located inside and slidable against the rectangular side wall 11 of the other U-shaped member 9. This arrangement enables the two U-shaped members 9 that define a particular pocket 4 to pivot between an open configuration (Figs. 5 and 6) in which a base 16 of the pocket 4 is open and of approximately the same size as the open mouth 6 of the pocket 4, and a closed configuration where the base 16 of the pocket 4 is closed. In this closed condition, lowermost edges 17 of the two central walls 10 furthest from the open mouth 6 of the pocket 4 are brought together. This common edge 17 is adapted to be driven into the soft material of the seabed when the platform is lowered into the sea and onto the seabed as explained below. Each U-shaped member 9 has an arm 18 rigidly joined to it and adapted to be coupled to an hydraulic mechanism 19 for actuating the two U-shaped members 9 of the pocket 4 to pivot relative to each other about their pivots 15, to move the U-shape members 9 between open and closed conditions of the pockets 4 and vice-versa. As best shown in Fig. 10, the inward pivoting of the U-shaped members 9 not only causes the lowermost edges 17 of central walls 10 to be brought together, preventing a planting packet 7 loaded in the pocket 4 from falling through the base of the pocket, but also creates a sharp wedge that is adapted to dig into the soft seabed. Subsequent pivoting of the U-shaped members 9 apart causes the lower edges 17 of central walls 10 to move apart, thus digging a planting hole by pushing away seabed soil adjacent the central walls 10 near the edges 17, while simultaneously opening base 16 to allow the planting packet 7 loaded within the pocket 4 to fall into the planting hole dug in the seabed. The platform 1 connects to an arm 20 of a crane, as shown in Fig. 12, the crane being mounted on a sea-going vessel. The crane operates to lower platform 1 as a whole into the sea and on to the seabed in a generally horizontal configuration. After the planting packets 7 have been released, the crane is arranged to lift the platform 1 from the seabed to leave an infant seagrass meadow. The platform 1 is preferably provided with a vibrator, schematically indicated at 21, adapted to vibrate the platform as a whole to enhance the digging effect of the edges 17 and / or to firm individual seagrass plantlets in their planting packets 7 deposited from each pocket 4 into their respectively formed planting holes in the seabed. As will be readily appreciated, since this effect can be achieved by vibrating the whole platform, the precise location of the vibrator is not particularly important. Best results are achieved with a platform defining a grid of pockets. For planting seagrass, we prefer a separation of around 13 cm between pocket centres, with each pocket having an open mouth of area around 14 cm by 8 cm. This separation 5 allows individual seagrass plantlets to root in the seabed without interference from each other and space for other plant species to grow and wildlife to live between seagrass plants in the mature sea grass meadow to allow for a diverse biological habitat to develop. 10 It will be appreciated that although the illustrated apparatus was designed with the planting specifically of seagrass in mind, it may be used or readily modified for planting out plantlets of other species of subsea or intertidal plants at optimal depths for such plants. 15 It is also to be understood that the expressions “vertical” and “horizontal” are not to be understood as geometrically exact. These terms refer, instead, to generally upright directions adopted by real life objects or by the surfaces of extensive estuarine surfaces.

Claims

1. An apparatus for planting out plantlets of seagrass or of other subsea or intertidal plants in the seabed, comprising:a platform capable of being lowered to the seabed, and having a topside and an underside;the topside being open and communicating with a plurality of individual open pockets of the apparatus, each pocket having an openable base and being adapted to receive therewithin a said plantlet, each pocket being defined by at least two members moveable relative to each other between a first condition in which the two members of the pocket define an edge at the base of the pocket on the underside of the platform which edge is adapted to dig into the seabed when the platform is lowered thereonto, and a second condition in which the base of the pocket is open;the individual pockets being adapted to be filled with said plantlets and growing medium, and the platform being adapted thereafter to be lowered into the sea and onto the seabed, with the edges digging into the seabed so that subsequent movement of the two members into the second condition opens the base of each pocket to deposit the said plantlet into a planting hole dug in the seabed by the edge.

2. An apparatus according to Claim 1. wherein the platform is liftable as a whole or lowerable as a whole with the platform in a substantially horizontal configuration by a crane mounted on a seagoing vessel.

3. An apparatus according to Claim 1, wherein individual plantlets are provided in a growing medium within respective hessian bags, the hessian being adapted to reduce the risk of growing medium being dispersed as the platform is lowered into the sea.

4. An apparatus according to Claim 3, wherein the side walls of each pocket are pivotable relative to each other by a hydraulic mechanism.

5. An apparatus according to Claim 3 or Claim 4, wherein the platform is provided with a vibrator adapted to vibrate the platform as a whole either to enhance the digging effect of the edges and / or to firm individual plantlets in their individual holes.

6. An apparatus according to any preceding Claim, wherein the pockets are arranged in a grid format and the platform also includes stabilizing legs adjacent its corners outboard of the grid.

7. An apparatus according to Claim 6. wherein the stabilizing legs are adjustable to adjust the depths at which plantlets are planted.

8. An apparatus according to Claim 6 or Claim 7, wherein the stabilizing legs are provided with selectively replaceable pads of differing area depending on the softness of the seabed.

9. A method for planting a meadow of seagrass or other subsea or intertidal plants in the seabed, the method comprising the steps of:preparing a plurality of planting packets each comprising a plantlet of seagrass or other subsea or intertidal plant and growing medium therefor;loading individual planting packets into individual pockets arranged in a grid on a platform having a top side and an underside, each pocket having an edge at its lowermost position on the underside of the platform;lowering the platform into the sea and onto the seabed in a generally horizontal configuration so that the respective said edges dig into the seabed;moving sides of the pockets to form a hole in the seabed and to open the base of the pocket so that each said plantlet and its associated growing medium is deposited into a respective said hole; andlifting the platform as a whole to leave an infant meadow of seagrass or other subsea or intertidal plants on the seafloor.

10. A method according to Claim 9, wherein the platform is provided with a vibrator adapted to vibrate the platform as a whole either to enhance thedigging effect of the edges and / or to firm individual plantlets in their individual holes.

11. A method according to Claim 9, wherein individual packets are wrapped in 5 hessian to resist dissolution of growing medium as the platform is lowered intothe sea.

12. A method according to Claim 9 or Claim 10, wherein vibration is applied to the platform to enhance the digging effect of respective edges.10

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