Method for repairing eel grass sea grass bed in gravel substrate sea area

Abstract

The invention provides a method for restoring an eel grass sea grass bed in a gravel substrate sea area, and belongs to the technical field of marine ecological restoration. The invention provides a method for repairing an eel grass bed in a gravel substrate sea area, which comprises the following steps of: excavating a circular pit body in the gravel substrate sea area to form a single repairing unit, and accumulating a matrix generated by excavating the circular pit body on a near-shore side and an offshore side of the repairing unit to form a plurality of submerged embankments; after the inner wall of each repairing unit is covered with an improved matrix, eelgrass plants are transplanted into the repairing units, and eelgrass seeds are sown into the repairing units. According to the method, through terrain transformation, substrate improvement, plant transplanting and seed sowing, a suitable growth environment is provided for eelgrass, the repairing effect of the eelgrass sea grass bed in the gravel substrate sea area is effectively improved, and the method is suitable for large-scale repairing of the eelgrass sea grass bed in the gravel substrate sea area.

Description

Technical Field

[0001] The invention belongs to the technical field of marine ecological restoration, and particularly relates to a method for restoring eelgrass seagrass beds in gravel bottom sea areas. Background Art

[0002] Seagrasses are large submerged angiosperms, fully adapted to the marine environment. They are the only angiosperms that can complete their developmental stages, including flowering and fruiting, in seawater. Seagrasses play a vital role in marine ecosystems. They not only absorb nutrients, improve water quality, and provide habitats, breeding grounds, and food sources for many animals, but also stabilize sediments, attenuate waves, and protect coasts. Seagrass beds also have a significant carbon sequestration capacity. However, global seagrass beds have been declining in recent years, making their protection and restoration crucial.

[0003] Eelgrass, also known as giant kelp, is the most widespread seagrass species along the temperate Pacific and Atlantic coasts of the Northern Hemisphere and is the dominant seagrass species in my country's temperate waters. A facultative annual species, eelgrass is found in shallow waters from the intertidal to subtidal zones. Its habitat consists of sediments ranging in particle size from mud to gravel, primarily growing in shallow, muddy, and sandy seabeds with gentle currents. Currently, active restoration methods for eelgrass seagrass beds include seed restoration and plant transplantation. However, seed restoration methods suffer from low seed germination rates, high seed loss rates, and low seedling establishment rates. Furthermore, the stable establishment of transplanted plants remains a major challenge for plant transplantation, typically requiring anchoring techniques to ensure effective establishment. However, these methods are not ideal when the restoration site has coarse-grained sediments. Currently, eelgrass seagrass bed restoration efforts are primarily focused on sandy and silt-sand substrates; no methods exist specifically for eelgrass seagrass beds in gravelly substrates. Summary of the Invention

[0004] In view of this, the present invention provides a method for repairing eelgrass seagrass beds in gravel bottom sea areas, which effectively solves the problems faced by the repair of eelgrass seagrass beds in gravel bottom sea areas, such as low seedling establishment rate, difficulty in establishing seedlings and transplanted plants, and contributes to the rapid repair of eelgrass seagrass beds.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for repairing eelgrass seagrass beds in gravel bottom sea areas, comprising the following steps:

[0007] A circular pit is excavated in a gravel bottom sea area to form a single restoration unit, and the matrix generated by the excavation of the circular pit is deposited on the nearshore and offshore sides of the restoration unit to form multiple submerged dikes;

[0008] After the inner wall of each restoration unit is covered with the improved matrix, eelgrass plants are transplanted into the restoration unit, and then eelgrass seeds are sown into the restoration unit.

[0009] Preferably, the depth of the repair unit is 2 to 3 meters; the opening diameter of the repair unit is 10 to 15 meters.

[0010] Preferably, the repair units are distributed in a direction parallel to the shoreline.

[0011] Preferably, the number of submerged dikes stacked on the offshore side of the repair unit is 2 to 3; the number of submerged dikes stacked on the offshore side of the repair unit is 1 to 2, and the height of the submerged dike is 0.8 to 1 meter.

[0012] Preferably, the distribution direction of the submerged dikes is perpendicular to the water flow direction in the repair unit area.

[0013] Preferably, the improved substrate comprises clay and eelgrass seagrass bed in-situ soil;

[0014] The volume ratio of the clay to the in-situ soil of the eelgrass seagrass bed is (9-4):1.

[0015] Preferably, the thickness of the improved matrix covering the inner wall of the repair unit is 5 to 15 cm.

[0016] Preferably, the inner wall of the repair unit is covered with the improved matrix for 5 to 10 days before the eelgrass plants are transplanted and the eelgrass seeds are sown.

[0017] Preferably, the eelgrass plant transplanting is performed by burying the rhizomes of the eelgrass in the improved substrate and covering the rhizomes with gravel.

[0018] Preferably, the eelgrass seeds are in a state where germination is promoted until the seed coat is broken and the embryo has not yet fully extended.

[0019] Preferably, the period for transplanting eelgrass plants or sowing eelgrass seeds includes the neap tide period.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] The present invention provides a method for repairing eelgrass seagrass beds in gravel-bottom sea areas, comprising the following steps: digging a circular pit in a gravel-bottom sea area to form a single repair unit, and using the matrix generated by digging the circular pit to pile up on the nearshore and offshore sides of the repair unit to form multiple submerged dikes; after the inner wall of each repair unit is covered with the improved matrix, eelgrass plants are transplanted into the repair unit, and eelgrass seeds are sown into the repair unit. The method can effectively slow down the impact of water flow, enhance the sedimentation effect, and stabilize the bottom sediments through terrain transformation, thereby reducing the negative impact of environmental factors on seed retention, germination, seedlings, and plant colonization processes; and through bottom improvement measures, the adaptability of eelgrass to the new environment is improved. Through the above method, a more suitable growth environment is provided for eelgrass, thereby improving the repair effect of eelgrass seagrass beds in gravel-bottom sea areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a cross-section of the restoration unit in the landform transformation;

[0023] Figure 2 This is a bird's-eye view of the terrain transformation, where 1 is the restoration unit and 2 is the offshore submerged breakwater. DETAILED DESCRIPTION

[0024] The present invention provides a method for repairing eelgrass seagrass beds in gravel bottom sea areas, comprising the following steps:

[0025] A circular pit is excavated in a gravel-bottomed sea area to form a single restoration unit, and the matrix produced by excavating the circular pit is piled up on the nearshore and offshore sides of the restoration unit to form multiple submerged dikes; after the inner wall of each restoration unit is covered with the improved matrix, eelgrass plants are transplanted into the restoration unit, and eelgrass seeds are sown into the restoration unit.

[0026] In the present invention, the gravel-bottom sea area refers to a sea area with a predominantly gravel bottom. The gravel preferably includes gravel as specified in the national standard GB / T 12763.8-2007. The method can effectively improve seed retention, seedling establishment, and transplanted plant establishment in the restoration of eelgrass seagrass beds in gravel-bottom seagrass areas, enhance the adaptability of eelgrass to the environment, and promote the restoration of eelgrass seagrass beds in gravel-bottom seagrass areas.

[0027] In the present invention, the depth of the repair unit is preferably 2 to 3 meters, more preferably 2.5 meters; the opening diameter of the repair unit is preferably 10 to 15 meters, more preferably 11 to 13 meters, and most preferably 12 meters. The distance between the opening of the repair unit and the water surface is preferably 1.2 to 1.8 meters, more preferably 1.4 meters. Repair units of this specification help to slow down the water flow while meeting the light requirements for eelgrass growth, which is beneficial to the stability and accumulation of bottom sediments. The repair units are preferably distributed in a direction parallel to the shoreline. Distribution parallel to the shoreline is conducive to maintaining relatively consistent water depth at the location of the repair unit.

[0028] In the present invention, the matrix generated by excavating a circular pit is deposited perpendicular to the direction of water flow on the nearshore and offshore sides of the restoration unit to form multiple submerged dikes. The distribution direction of the submerged dikes is preferably perpendicular to the direction of water flow in the restoration unit area, and more preferably perpendicular to the direction of water flow in the restoration unit area all year round. The number of submerged dikes deposited on the offshore side of the restoration unit is preferably 2 to 3, and the number of submerged dikes deposited on the nearshore side of the restoration unit is preferably 1 to 2. The height of the submerged dikes is preferably 0.8 to 1 meter, and more preferably 1 meter.

[0029] In the present invention, by implementing terrain transformation and adopting restoration units and multi-channel submerged dike structures, the impact of water flow can be effectively mitigated, the sedimentation effect can be enhanced, and the bottom sediment can be stabilized, thereby reducing the negative impact of environmental factors on seed retention, germination, seedlings and transplanted plant establishment processes, providing a more suitable growth environment for eelgrass, improving the seedling establishment rate, and promoting the establishment of transplanted plants.

[0030] In the present invention, the thickness of the improved matrix covering the inner wall of the restoration unit is preferably 5 to 15 cm, and can be 7 cm, 8.6 cm, 10 cm, or 13 cm. The improved matrix comprises clay and in-situ soil from the eelgrass seagrass bed; the volume ratio of the clay to the in-situ soil from the eelgrass seagrass bed is preferably (9 to 4):1, more preferably (8 to 5):1, and most preferably 5:1. The clay is preferably clay in accordance with the national standard GB / T 12763.8-2007. The improved matrix is ​​beneficial for increasing the seedling establishment rate and promoting the establishment of transplanted plants. In the present invention, after the inner wall of the restoration unit is covered with the improved matrix, the improved matrix is ​​allowed to settle for 5 to 10 days before transplanting eelgrass plants and sowing seeds. The settling time is preferably 5 to 10 days, more preferably 7 to 10 days, and most preferably 10 days. Transplanting plants and sowing seeds after the improved matrix has settled facilitates the complete settling of the improved matrix and its natural mixing with the substrate, resulting in a matrix that is conducive to eelgrass growth and ensuring that the light transmittance of the seawater meets the light requirements for eelgrass growth.

[0031] In the present invention, the eelgrass seeds are in a state where the germination is accelerated until the seed coat breaks and the embryo has not yet fully extended. The eelgrass seeds in this state are more likely to grow into seedlings.

[0032] In the present invention, through terrain transformation combined with bottom improvement measures, clay and in-situ soil of eelgrass seagrass beds are mixed in a specific proportion to prepare improved soil, which can provide a more suitable growth environment for eelgrass, improve the adaptability of eelgrass to the new environment, increase the seedling establishment rate, and promote the establishment of transplanted plants, thereby improving the restoration effect of eelgrass seagrass beds in gravel bottom sea areas.

[0033] In the present invention, the period for transplanting the eelgrass plants and / or sowing the eelgrass seeds is preferably during the neap tide period. The water flow is slower during the neap tide period, which is conducive to seed retention and plant establishment. The water flow velocity during the neap tide period is preferably 10 cm / s to 20 cm / s, and most preferably 10 cm / s. The water temperature for transplanting the eelgrass plants and / or sowing the eelgrass seeds is preferably 16 to 20°C, more preferably 17 to 19°C, and most preferably 18°C. In the present invention, the eelgrass plant transplantation is to bury the rhizomes of the eelgrass in the improved substrate and cover the rhizomes with gravel, which is conducive to the stable establishment of the transplanted plants.

[0034] The present invention employed the method to conduct restoration work in October. In May of the following year, the seedling establishment rate and stem and branch density of transplanted plants were surveyed. In July of the following year, the stem and branch density of eelgrass was surveyed. In July of the third year, the stem and branch density of eelgrass was surveyed again to evaluate the restoration effectiveness of the method.

[0035] In order to further illustrate the present invention, the solutions provided by the present invention are described in detail below with reference to the accompanying drawings and embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0036] Example 1

[0037] A method for repairing eelgrass seagrass beds in gravel bottom sea areas

[0038] Restoration of eelgrass seagrass beds in the gravel-bottomed waters of Dalian Bay, Liaoning Province. The restoration process is as follows:

[0039] Terrain Renovation: Circular pits were excavated parallel to the shoreline to form individual restoration units. Each unit was 2.5 meters deep, 12 meters in diameter, and 6 meters in diameter at its base. The matrix created by the circular pits was deposited perpendicular to the flow on both the nearshore and offshore sides of the restoration units, forming multiple submerged dikes. Two submerged dikes were deposited offshore, and one on the nearshore side. The dikes were 1 meter high and 2.5 meters thick. The distance between adjacent dikes was 5 meters, with the distance between adjacent dikes and the restoration unit being 6 meters. The opening of the restoration unit was 1.4 meters above the water surface.

[0040] Substrate Improvement: Clay and in-situ eelgrass seagrass soil were mixed in a 5:1 volume ratio to form an improved substrate. The improved substrate was applied to the inner walls of the restoration unit to an average thickness of 8.6 cm. After the improved substrate had completely settled within the unit for 10 days, eelgrass plants were transplanted and seeds were sown.

[0041] Plant transplantation and seed sowing: Eelgrass plants were transplanted and seed sown during the neap tide in October (flow velocity 12 cm / s, water temperature 17°C, seawater salinity 30‰). Eelgrass plants were transplanted into the restoration unit, and the rhizomes of the eelgrass plants were buried in the improved substrate and covered with gravel. The transplant density was 100 plants / m 2 The eelgrass seeds that had been stimulated to germinate were sown into the restoration unit at a density of 100 seeds / m 2 .

[0042] The survey results are as follows:

[0043] In May of the following year, a diving survey of the restoration area was conducted, and it was found that the eelgrass seeds in the restoration unit (seed sowing) had germinated and seedlings had grown, with a seedling establishment rate of 27.3%. The plants in the restoration unit (plant transplantation) had newly produced branches, and the average stem and branch density had increased by 21%.

[0044] In July of the following year, a survey of the restoration area revealed that the eelgrass was growing well, with an average stem density of 30.3 shoots / m in the restoration unit (seeded). 2 The average stem density of eelgrass in the restoration unit (plant transplantation) reached 89.3 shoots / m 2 .

[0045] In July of the third year, multiple eelgrass patches had formed within the restoration unit, with an average stem density of 114.7 to 168.3 shoots / m 2 .

[0046] Example 2

[0047] A method for repairing eelgrass seagrass beds in gravel bottom sea areas

[0048] The method for restoring an eelgrass seagrass bed in a gravelly seabed area was the same as in Example 1, except that the restoration unit depth was 3 m, the opening diameter was 15 m, and the volume ratio of clay to in-situ eelgrass seagrass bed soil was 9:1.

[0049] The survey results are as follows:

[0050] In May of the following year, a diving survey of the restoration area was conducted, and it was found that the eelgrass seeds in the restoration unit (seed sowing) had germinated and seedlings had grown, with a seedling establishment rate of 20.7%. The plants in the restoration unit (plant transplantation) had newly produced branches, and the average stem and branch density had increased by 12.7%.

[0051] In July of the following year, a survey of the restoration area revealed that the eelgrass was growing well, with an average stem density of 22 shoots / m in the restoration unit (seeded). 2 The average stem density of eelgrass in the restoration unit (plant transplantation) reached 80.3 shoots / m 2 .

[0052] In July of the third year, multiple eelgrass patches were formed within the restoration unit, with an average stem density of 102.3 to 136.7 shoots / m 2 .

[0053] Comparative Example 1

[0054] A method for repairing eelgrass seagrass beds in gravel bottom sea areas

[0055] The method for repairing eelgrass seagrass beds in gravel bottom sea areas is the same as that in Example 1, except that the opening diameter of the repair unit is 20 m.

[0056] The survey results are as follows:

[0057] In May of the following year, a diving survey of the restoration area revealed that the eelgrass seeds in the restoration unit (seed sowing) had germinated and grown seedlings, with a seedling establishment rate of 13.3%. The average stem and branch density of the plants in the restoration unit (plant transplantation) had decreased by 15.7%.

[0058] In July of the following year, a survey of the restoration area revealed that the eelgrass was growing well, with an average stem density of 11.7 shoots / m in the restoration unit (seeded). 2 The average stem density of eelgrass in the restoration unit (plant transplantation) reached 54 shoots / m 2 .

[0059] In the July survey of the third year, the average stem density of eelgrass in the restoration unit was 32.7 shoots / m 2 .

[0060] Comparative Example 2

[0061] A method for repairing eelgrass seagrass beds in gravel bottom sea areas

[0062] The method for repairing eelgrass seagrass beds in gravel bottom sea areas is the same as that in Example 1, except that no submerged dike is piled up.

[0063] The survey results are as follows:

[0064] In May of the following year, a diving survey of the restoration area was conducted, and it was found that the eelgrass seeds in the restoration unit (seed sowing) had germinated and grown seedlings, with a seedling establishment rate of 10.7%. The average stem and branch density of plants in the restoration unit (plant transplantation) had decreased by 31.7%.

[0065] In July of the following year, a survey of the restoration area revealed that the eelgrass was growing well, with an average stem density of 10.3 shoots / m in the restoration unit (seeded). 2 The average stem density of eelgrass in the restoration unit (plant transplantation) was 29.3 shoots / m 2 .

[0066] In the July survey of the third year, the average stem density of eelgrass in the restoration unit was 15.7 shoots / m 2 .

[0067] Comparative Example 3

[0068] A method for repairing eelgrass seagrass beds in gravel bottom sea areas

[0069] The method for repairing eelgrass seagrass beds in gravel bottom sea areas is the same as that in Example 1, except that a submerged bank is formed on the nearshore and offshore sides of the repair unit perpendicular to the direction of water flow.

[0070] The survey results are as follows:

[0071] In May of the following year, a diving survey of the restoration area revealed that the eelgrass seeds in the restoration unit (seed sowing) had germinated and grown into seedlings, with a seedling establishment rate of 15.3%. The average stem and branch density of the plants in the restoration unit (plant transplantation) had decreased by 6.7%.

[0072] In July of the following year, a survey of the restoration area revealed that the eelgrass was growing well. The average stem density of the restoration unit (seed sowing) was 14.7 shoots / m. 2 The average stem density of eelgrass in the restoration unit (plant transplantation) was 63.7 shoots / m 2 .

[0073] In the July survey of the third year, the average stem density of eelgrass in the restoration unit was 56.3 shoots / m 2 .

[0074] Comparative Example 4

[0075] A method for repairing eelgrass seagrass beds in gravel bottom sea areas

[0076] The method for repairing eelgrass seagrass beds in gravel bottom sea areas is the same as that in Example 1, except that the volume ratio of clay in the improved matrix to the in-situ soil of the eelgrass seagrass beds is 1:0.

[0077] The survey results are as follows:

[0078] In May of the following year, a diving survey of the restoration area revealed that eelgrass seeds in the restoration unit (seed sowing) had germinated and grown into seedlings, with a seedling establishment rate of 6.7%. The average stem and branch density of plants in the restoration unit (plant transplantation) had decreased by 40.7%.

[0079] In July of the following year, a survey of the restoration area revealed that the eelgrass was growing well. The average stem density of the restoration unit (seeded) was 5.3 shoots / m. 2 The average stem density of eelgrass in the restoration unit (plant transplantation) was 16.7 shoots / m 2 .

[0080] In the July survey of the third year, the average stem density of eelgrass in the restoration unit was 4.3 shoots / m 2 .

[0081] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for restoring eelgrass seagrass beds in gravel-bottomed sea areas, comprising the following steps: A circular pit is excavated in a gravel bottom sea area to form a single restoration unit, and the matrix generated by the excavation of the circular pit is deposited on the nearshore and offshore sides of the restoration unit to form multiple submerged dikes; After the inner wall of each restoration unit is covered with the improved matrix, eelgrass plants are transplanted into the restoration unit, and then eelgrass seeds are sown into the restoration unit.

2. The method according to claim 1, characterized in that The depth of the repair unit is 2 to 3 meters; the opening diameter of the repair unit is 10 to 15 meters.

3. The method according to claim 1, characterized in that The repair units are distributed in a direction parallel to the shoreline.

4. The method according to claim 1, wherein The number of submerged dikes accumulated on the offshore side of the repair unit is 2 to 3; the number of submerged dikes accumulated on the offshore side of the repair unit is 1 to 2, and the height of the submerged dike is 0.8 to 1 meter.

5. The method according to claim 1, wherein The distribution direction of the submerged dike is perpendicular to the water flow direction in the restoration unit area.

6. The method according to claim 1, characterized in that The improved substrate includes clay and in-situ soil from eelgrass seagrass beds; The volume ratio of the clay to the in-situ soil of the eelgrass seagrass bed is (9-4):

1.

7. The method according to claim 1, characterized in that The thickness of the improved matrix covering the inner wall of the repair unit is 5 to 15 cm.

8. The method according to claim 1, characterized in that After the inner wall of the repair unit is covered with the improved matrix for 5 to 10 days, the eelgrass plants are transplanted and the eelgrass seeds are sown.

9. The method according to claim 1, characterized in that The eelgrass seeds are in a state where germination is accelerated until the seed coat is broken and the embryo has not yet fully extended.

10. The method according to any one of claims 1 to 9, characterized in that The period for transplanting eelgrass plants or sowing eelgrass seeds includes the neap tide period.

Images