Ecological protection system and method for Chinese horseshoe crab near port construction area

Abstract

This invention relates to an ecological protection system and method for horseshoe crabs near port construction areas, belonging to the field of collaborative technology between marine ecological protection and port engineering. The protection system consists of an artificial horseshoe crab channel and a submerged plant composite barrier surrounding it. The artificial horseshoe crab channel is laid perpendicular to the coastline and adopts a three-layer biomimetic structure consisting of a permeable concrete layer, a gravel buffer layer, and a silt mixture layer. It is equipped with flexible baffles, pebble guidance areas, and hiding pits to ensure the safe migration and temporary habitat of horseshoe crabs. The submerged plant composite barrier forms a three-ring protection system from the outside to the inside, with the artificial horseshoe crab channel as the center. By selecting salt-tolerant plant species for mixing and three-dimensional planting, it achieves integrated functions of noise reduction, pollution blocking, water purification, and habitat buffering. It solves the problems of physical disruption of horseshoe crab migration channels and interference from multiple stress factors caused by port construction, effectively improving the survival and reproductive success rate of horseshoe crabs, while taking into account engineering compatibility and ecological sustainability.

Description

Technical Field

[0001] This invention relates to the field of collaborative technology of marine ecological protection and port engineering, specifically to a method for the protection of horseshoe crabs that combines artificial migration channels with a composite barrier of submerged plants, applicable to port construction areas near horseshoe crab intertidal spawning grounds and shallow sea habitats. Background Technology

[0002] The Chinese horseshoe crab (Tachypleus tridentatus) is an ancient marine arthropod, hailed as a "living fossil," and is currently a Class II protected wild animal in China. Its life cycle depends on the migration route between its intertidal spawning grounds and shallow-sea habitats. The connectivity, substrate stability, and water quality of this route are crucial to its reproductive success and survival. However, with the rapid development of the coastal economy and the increasingly frequent construction of large-scale coastal engineering projects such as ports and waterways, these engineering activities pose a serious and complex threat to the Chinese horseshoe crab's critical habitats.

[0003] Port construction projects, especially dredging of main channels, land reclamation, and pile foundation construction, generate a series of overlapping negative ecological impacts: 1) Physical barriers and damage: Construction activities directly cut off or cover the natural migration routes of the Chinese horseshoe crab and destroy the soft sandy bottom required for spawning; 2) Water quality deterioration: High concentrations of suspended sediment and other pollutants are generated, leading to decreased water transmittance and dissolved oxygen, and may cover horseshoe crab eggs and larvae; 3) Noise and disturbance: High-frequency noise from ship navigation and machinery operations, as well as strong water currents, interfere with the orientation and foraging behaviors of the Chinese horseshoe crab. These multiple stressors work together to cause habitat fragmentation, a sharp decline in habitat quality, and a severe challenge to the survival of the species.

[0004] Currently, conservation technologies and research for horseshoe crabs are mostly focused on post-construction remediation or in vitro conservation, which are insufficient to address the continuous and proactive engineering disturbances in port construction areas. Existing technologies mainly include: 1) In terms of artificial breeding and release technology, the patent application CN201811135540.5, "A Scientific Release Method for Chinese Horseshoe Crab Seedlings," and the patent application CN201821334591.6, "An Ecological Simulation Aquaculture Device for Chinese Horseshoe Crab Juveniles," mainly focus on improving the success rate of seedling cultivation and the survival rate of release by optimizing the laboratory or aquaculture pond environment. These technologies aim to supplement the wild population, but do not solve the problem of direct destruction and continuous stress on the habitats of wild adults for survival and reproduction caused by construction activities; 2) In terms of sustainable resource utilization technology, the patent application CN202010449378.5, "A Sustainable Blood Collection Method Based on Artificial Culture of Chinese Horseshoe Crabs," focuses on replacing the consumption of wild resources by establishing cultured populations. Although this helps to reduce the fishing pressure on wild populations, it also does not involve the in-situ restoration and protection of the ecological functions of wild habitats; 3) In terms of disease prevention and aquaculture management research, existing studies have focused more on pathogen control and feed feeding of horseshoe crab eggs and larvae in aquaculture environments. These technologies are applicable to controllable closed or semi-closed environments and cannot be directly applied to solve complex ecological engineering problems such as the disruption of migration channels, compound pollution, and physical disturbance caused by construction in open sea areas.

[0005] In summary, existing conservation technologies have significant limitations: they either focus on artificial population replenishment or sustainable resource utilization, but generally lack a technical solution that can be implemented in situ during engineering construction, providing proactive protection and systematically addressing the core contradiction between "ensuring migratory connectivity" and "isolating multiple stressors." Therefore, developing a technical system that can be coordinated with port engineering construction, is engineering-operable, and protects the Chinese horseshoe crab from both physical channel restoration and ecological buffering perspectives has become a critical technical challenge urgently needing to be solved in the coordinated development of marine ecological protection and coastal engineering. Summary of the Invention

[0006] The purpose of this invention is to at least solve one of the technical problems existing in the prior art. To this end, an ecological protection system and method for horseshoe crabs near port construction areas is proposed. This system ensures migration connectivity through artificial horseshoe crab channels and combines a composite barrier of submerged plants to achieve an integrated protection system of "noise reduction, pollution blocking, purification, and habitat," thereby improving the survival and reproductive success rate of horseshoe crabs in port construction environments.

[0007] The first aspect of this application provides an ecological protection system for horseshoe crabs near a port construction area, characterized in that it includes a composite barrier of artificial horseshoe crab channels and submerged plants; The artificial horseshoe crab channel is laid perpendicular to the coastline, connecting the intertidal spawning grounds and the shallow sea habitat. It has a three-layer biomimetic structure, from bottom to top: a bottom permeable concrete layer, a middle gravel buffer layer, and a surface mud and sand mixed layer. The artificial horseshoe crab channel is equipped with flexible baffles on both sides, guidance areas at both ends, and hidden pits at intervals in the middle of the channel. The submerged plant composite barrier is arranged around the artificial horseshoe crab channel, and includes three ring barriers arranged sequentially from the outside to the inside: the first barrier is composed of a mixture of small water chestnuts and Potamogeton pectinatus, used for noise reduction and primary pollution blocking; the second barrier is composed of three-dimensional planting of Ceratophyllum demersum and Vallisneria natans, used to enhance pollutant interception and water purification; the third barrier is composed of a mixture of Potamogeton pectinatus and Hydrilla verticillata, combined with gravel piles, used for buffering protection and habitat creation.

[0008] The second aspect of this application provides a method for constructing an artificial horseshoe crab channel, which is used to provide a safe migration route for Chinese horseshoe crabs, adapts to the strong current environment of ports, and meets the need for juvenile horseshoe crabs to hide and inhabit. The overall layout of the artificial horseshoe crab channel is as follows: the channel should be laid perpendicular to the coastline to precisely connect the intertidal spawning grounds with the shallow sea habitat. The path should avoid the main channel of the port, areas with strong waves, and areas prone to disturbance during construction. The distance from the boundary of the construction area should be no less than 500 meters to minimize direct interference from construction activities. Two to three channels should be arranged in parallel, with a minimum distance of 3 meters between adjacent channels. This design prevents blockage of a single channel from affecting overall migration efficiency. The width of each channel should be 1.0 to 1.5 meters, suitable for the crawling needs of adult horseshoe crabs. The channel length should range from 50 to 200 meters, adapted to the actual distance between the intertidal zone and the shallow sea habitat. The channel slope should not exceed 1:5 to reduce crawling resistance and thus improve migration efficiency.

[0009] The artificial horseshoe crab canal has a three-layer structure from bottom to top, including a bottom layer, a middle layer, and a surface layer; The bottom layer is made of C30 permeable concrete with a thickness of 15 to 20 centimeters and a porosity of 10%. This layer ensures structural strength and resists erosion flow velocities of no less than 1.5 meters per second, while also providing good permeability to prevent water accumulation in the channel from affecting the horseshoe crab's crawling. To enhance performance, 5% basalt fiber can be added to the concrete to improve its crack resistance and seawater corrosion resistance.

[0010] The middle layer is a crushed stone buffer layer, made of granite crushed stone with a particle size of 5 to 10 mm and a thickness of 8 to 10 cm. This layer buffers the impact of water flow through the gaps between the particles, reducing the scouring pressure on the underlying concrete layer, while also helping to improve the air permeability of the channel surface.

[0011] The surface layer is a mixture of mud and sand, with a volume ratio of 7:3, and a thickness of 10 to 15 centimeters. This layer simulates the mudflat substrate where the Chinese horseshoe crab naturally inhabits, improving the comfort of adults crawling and the stability of juvenile attachment. The particle size of the mud and sand used should not exceed 2 millimeters to avoid sharp particles damaging the surface of the Chinese horseshoe crab.

[0012] The auxiliary functional structures of the artificial horseshoe crab passage include flexible baffles, a guide area, and a concealed pit; The flexible baffles, made of polyurethane and 12 to 15 centimeters high, are installed on both sides of the passage and fixed to the base on both sides of the horseshoe crab channel. These flexible baffles prevent horseshoe crabs from being injured during collisions and also prevent external silt from accumulating and entering the passage. The top of the baffles is covered with an ecological protective blanket with a 30% shading rate to reduce direct sunlight and create a suitable low-light environment for the horseshoe crabs' migration.

[0013] The guidance zone is located at both ends of the channel and is composed of pebbles with a particle size of 2 to 3 centimeters and a width of 1 meter. By utilizing the roughness of the pebble surface and the tactile sensitivity of the horseshoe crab, it guides the fish to identify and enter the migration channel, thereby improving the utilization rate of the channel.

[0014] The hiding pits are located in the middle of the passage, with one pit every 20 meters. Each pit is 50 centimeters in diameter and 20 centimeters deep, and is lined with a mixture of humus and small stones in a volume ratio of 3:2. The humus provides a breeding environment for small crustaceans, annelids, and other prey, while the small stones create a hiding space for juvenile horseshoe crabs to temporarily inhabit and avoid predators.

[0015] The third aspect of this application provides a method for constructing a submerged plant composite barrier. The submerged plant composite barrier is constructed with the artificial horseshoe crab channel as the center, forming a three-layer ring protection system, including a first barrier, a second barrier and a third barrier, so as to achieve the functions of noise reduction, blocking pollutants, purifying water quality and creating a habitat. The submerged plant composite barrier is laid out as a three-layered ring structure surrounding the artificial horseshoe crab channel, with a total width of 15 to 20 meters. The minimum distance between the barrier and the edge of the channel is no less than 3 meters to prevent plant roots from encroaching on the channel and affecting the horseshoe crabs' movement. Each layer of the barrier is functionally zoned, forming a gradient protection from the construction area towards the channel.

[0016] The selection and configuration of the submerged plant composite barrier are based on the high salinity environment of 8‰ to 15‰ in the port area and the functional requirements. Submerged plants with strong salt tolerance, excellent purification ability and good impact resistance are selected for configuration.

[0017] The first barrier, located on the outermost side and adjacent to the construction area, serves primarily to reduce noise and provide initial protection against pollutants. Salt-tolerant plant species are selected, with *Potamogeton crispus* requiring a salt tolerance of at least 15‰ and *Potamogeton pectinata* requiring at least 10‰. A mixed planting pattern is employed to enhance community stability, with a total planting density of 120 plants per square meter and a plant ratio of 6:4 for *Potamogeton crispus* and *Potamogeton pectinata*. Plant height is controlled between 30 and 50 centimeters, and the plants are arranged in a staggered pattern. The vibration damping effect of the plant stems and leaves reduces construction noise while simultaneously intercepting large particulate suspended pollutants.

[0018] The second barrier, located between the first and third barriers, forms the core purification layer. Its primary function is to enhance the interception of suspended pollutants and water purification. Plant species with moderate salt tolerance and strong pollutant adsorption capacity are selected, with *Ceratophyllum demersum* having a salt tolerance of at least 6‰ and *Vallisneria natans* having a salt tolerance of at least 8‰. A three-dimensional planting pattern is adopted: the upper layer is planted with *Ceratophyllum demersum* at a density of 80 plants per square meter, with a plant height of 40 to 60 cm; the lower layer is planted with *Vallisneria natans* at a density of 100 plants per square meter, with a plant height of 20 to 30 cm. This three-dimensional structure forms staggered interception layers to improve the removal efficiency of suspended pollutants, while simultaneously increasing dissolved oxygen in the water through plant photosynthesis.

[0019] The third barrier, located closest to the artificial horseshoe crab channel area, serves as a buffer and habitat creation mechanism. Plants with moderate growth rates, low invasiveness, and strong resistance to water flow are selected and combined with gravel mounds to create a concealed environment. The main plants are *Potamogeton pectinatus* and a small amount of *Hydrilla verticillata*, with a planting ratio of 9:1 and a total planting density of 90 plants per square meter. The *Potamogeton pectinatus* must have a salt tolerance of at least 10‰. Furthermore, a gravel mound is placed every 10 square meters, with gravel particles ranging from 8 to 12 centimeters in diameter and 0.05 to 0.06 cubic meters in volume. This provides juvenile horseshoe crabs with a composite habitat combining foliage and gravel, while also buffering the direct impact of water flow on the horseshoe crab channel.

[0020] The planting mode of the submerged plant composite barrier adopts the method of seedling cultivation in nutrient pots combined with planting in submerged beds to improve the survival rate and erosion resistance of plants.

[0021] The nutrient pots are made of environmentally friendly and biodegradable materials, such as coconut coir fiber pots, with a diameter of 10 to 15 cm and a height of 12 to 18 cm to avoid long-term residue pollution. The internal substrate of the nutrient pots is a mixture of humus and sea mud in a volume ratio of 1:2, with 5% shell powder added. The shell powder has a particle size of 0.1 to 0.3 mm. The addition of shell powder can improve the stability of the substrate's pH, maintaining it between 7.5 and 8.5, thereby enhancing the plant's salt tolerance and providing calcium for plant growth.

[0022] The submerged bed is made of environmentally friendly non-woven fabric with a 2-centimeter aperture. This design facilitates plant roots to penetrate and take root on the seabed while effectively preventing substrate loss. Each submerged bed measures 2 meters by 3 meters and is secured to the seabed surface using stainless steel anchors 30 to 40 centimeters long. The anchors are spaced 1 meter by 1 meter apart to ensure the submerged bed remains stable even in strong currents with a flow rate not exceeding 1.2 meters per second, preventing it from tipping over or shifting.

[0023] In summary, compared with existing technologies, the horseshoe crab ecological protection system and method for adjacent port construction areas described in this invention, through the integrated and synergistic design of "artificial horseshoe crab channels" and "submerged plant composite barriers," achieves comprehensive protection from physical connectivity to ecological buffering, and has the following significant beneficial effects: 1) Fundamentally solves migration obstruction and significantly improves channel safety and efficiency: This invention creatively constructs an artificial migration channel specifically designed for horseshoe crabs. It adopts a three-layer biomimetic structure consisting of a permeable concrete layer, a gravel buffer layer, and a mud-sand mixture layer. This not only simulates the natural substrate and meets the needs of adult crawling and juvenile attachment, but its design with an erosion-resistant flow velocity of no less than 1.5 meters per second also ensures structural durability in the strong water flow environment of ports, resulting in a service life of ≥10 years. The flexible baffles on both sides of the channel, the pebble guidance areas at both ends, and the hidden pit in the middle work together to achieve the functions of protection, guidance, and habitat. It can effectively guide horseshoe crabs to identify and use the channel and provide temporary shelter for juvenile horseshoe crabs, thus systematically solving the problem of physical breakage of the migration path caused by engineering construction, and significantly improving the success rate of adult migration and juvenile survival. 2) Innovative Gradient Protection System for Efficient Isolation of Multiple Construction Stresses: This invention pioneered a triple submerged plant composite barrier centered on an artificial horseshoe crab channel. The system is arranged in a gradient according to function: the outermost first barrier uses *Potamogeton pectinatus* and *Potamogeton pectinatus*, whose dense stems and leaves effectively absorb and reduce construction noise by 30-40 decibels and initially intercept large suspended particles; the middle second barrier uses *Ceratophyllum demersum* and *Vallisneria natans*, forming a dense interception net through three-dimensional planting, enhancing the adsorption and filtration of suspended pollutants, and its photosynthesis can increase dissolved oxygen in the water by more than 30%; the innermost third barrier uses *Potamogeton pectinatus*, *Hydrilla verticillata*, and gravel piles to further buffer water flow, purify water quality, and provide a habitat for organisms; this integrated barrier achieves synergistic reduction of combined stress factors such as noise, suspended matter, and water flow impact, with a total suspended pollutant removal rate of no less than 60%, creating a relatively quiet and clean "ecological buffer zone" for the horseshoe crab; 3) Highly adaptable to harsh environments, ensuring continuous and stable protective performance: All technical parameters of this invention have been optimized and screened for the high-salinity and strong-current environment of the waters near the port; the selected submerged plants have a salt tolerance range of 6‰-15‰, completely covering the typical port salinity. Combined with the planting mode of "seedling in nutrient pots + planting in submerged beds", it ensures a high survival rate of over 85% for plants in high-salinity and dynamic water environments and the ability to resist lodging in water flow with a velocity ≤1.2m / s; the basalt fiber added to the artificial horseshoe crab channel enhances its corrosion resistance, and the submerged bed is fixed with anchor nails to prevent displacement; this high environmental adaptability ensures the long-term stable operation of the entire protection system during construction, and the protective performance does not significantly decrease with environmental fluctuations; 4) Excellent engineering compatibility and economic efficiency for promotion: The construction of this system can be carried out in a staggered manner with the main port project without interference. The materials used are all common engineering materials, the construction process is simple, and the overall cost is controllable. Compared with traditional post-repair or relocation protection methods, this invention is an active in-situ protection solution that can continuously play a protective role while construction is underway. The overall cost can be reduced by 20-30%, making it worthy of large-scale promotion and application in similar coastal engineering projects. 5) Producing lasting and extended ecological benefits: This invention goes beyond the protection of a single species and promotes the restoration of local ecosystems; the submerged plant community not only purifies the water, but the complex habitat it forms also provides breeding space for small crustaceans, annelids and other prey organisms, thereby increasing the food source for horseshoe crabs; this virtuous cycle of "structure creation - environmental improvement - biological aggregation" helps to improve the survival rate of juvenile horseshoe crabs, which is expected to be no less than 60%, and improves the overall biodiversity of nearshore waters, realizing the extension of ecological benefits from "single species protection" to "microhabitat restoration". Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of a horseshoe crab ecological protection system near a port construction area, as shown in an embodiment of the present invention. Figure 2 This is a schematic diagram of the artificial horseshoe crab passage structure shown in an embodiment of the present invention; Figure 3 This is a schematic diagram of the layered structure of a submerged plant as shown in an embodiment of the present invention; Attached diagram captions: 1-Artificial horseshoe crab channel, 11-Bottom permeable concrete layer, 12-Middle gravel buffer layer, 13-Top layer of mud and sand mixture, 14-Flexible baffle, 15-Guiding area, 16-Hidden pit, 2-Submerged plant composite barrier, 21-First barrier, 22-Second barrier, 23-Third barrier, 24-Submerged bed, 25-Nutrient pot, 3-Gravel pile. Detailed Implementation

[0025] The preferred embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. It should be understood that the embodiments shown in the drawings are merely illustrative examples, and the present invention is not limited to this specific form. It can be implemented by various equivalent technical solutions and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0026] Example 1: An ecological protection system for horseshoe crabs near a port construction area, comprising an artificial horseshoe crab channel 1 and a submerged plant composite barrier 2.

[0027] The artificial horseshoe crab channel 1 is laid perpendicular to the coastline, connecting the intertidal spawning grounds and the shallow sea habitat. It has a three-layer biomimetic structure, from bottom to top: a bottom permeable concrete layer 11, a middle gravel buffer layer 12, and a surface mud and sand mixed layer 13. Flexible baffles 14 are provided on both sides of the artificial horseshoe crab channel, and guide areas 15 are provided at both ends. Hidden pits 16 are provided at intervals in the middle of the channel.

[0028] The submerged plant composite barrier 2 is arranged around the artificial horseshoe crab channel, comprising three ring barriers arranged sequentially from the outside to the inside: the first barrier 21 is composed of a mixture of *Potamogeton pectinatus* and *Potamogeton pectinatus*, used for noise reduction and primary pollution blocking; the second barrier 22 is composed of a three-dimensional planting of *Ceratophyllum demersum* and *Vallisneria natans*, used to enhance pollutant interception and water purification; the third barrier 23 is composed of a mixture of *Potamogeton pectinatus* and *Hydrilla verticillata*, combined with a pile of gravel 3, used for buffering, protection, and habitat creation; all three ring barriers are fixed using a "seedling in nutrient pots 24 + planting in a submerged bed 25" method. The specific construction scheme of the submerged plant composite barrier is shown in the table below: Table 1. Construction scheme of submerged plant composite barrier

[0029] Example 2: A first method for constructing an ecosystem for horseshoe crabs near a port construction area: The structural parameters for constructing the artificial horseshoe crab passages are as follows: two parallel passages are set up with a spacing of 3m between them; each passage is 1.0m wide and 100m long with a slope of 1:5; the bottom layer is a 15cm thick C30 permeable concrete layer with a 10% porosity allowance and 5% basalt fiber added; the middle layer is a gravel buffer layer with a particle size of 5-8mm and a thickness of 8cm; the surface layer is a mud-sand mixture with a volume ratio of 7:3 and a thickness of 10cm; the flexible baffle is 12cm high and covered with a 30% shading polypropylene ecological blanket; the guide zone has a 1m wide pebble strip with a particle size of 2-3cm; and hidden pits are laid every 20m, with a diameter of 50cm and a depth of 20cm, filled with humus and small stones in a volume ratio of 3:2.

[0030] In the construction of the submerged plant composite barrier, the three-layer ring structure has a total width of 15m and a distance of 3m from the edge of the horseshoe crab channel. The first barrier (3m wide) is a mixed planting of small water chestnut and Potamogeton pectinatus, with a total density of 120 plants / m², a plant ratio of 6:4, and a plant height of 30-40cm. The second barrier (8m wide) consists of an upper layer of Ceratophyllum demersum with a density of 80 plants / m² and a lower layer of Vallisneria natans with a density of 100 plants / m². The third barrier (4m wide) is a mixed planting of Potamogeton pectinatus and Hydrilla verticillata with a total density of 90 plants / m², a plant ratio of 9:1, with a 0.05m³ gravel pile every 10m². The nutrient pots are 10cm in diameter and 12cm in height, with a substrate of humus soil: marine mud = 1:2, and 5% shell powder added. The submerged bed is 2m × 3m in size and is fixed with stainless steel anchors (30cm in length) at a spacing of 1m × 1m.

[0031] Complete the artificial horseshoe crab channel base treatment, structural laying, and auxiliary structure installation according to the above parameters; cultivate plant seedlings in an indoor nursery pond (water temperature 22℃, salinity 10‰), and transplant them to the sedimentation bed after 40 days of cultivation; complete the sedimentation bed planting during the construction break (March), and fix the sedimentation bed in the order of first layer → second layer → third layer; clean the horseshoe crab channel debris every 7 days, monitor water quality, noise, and horseshoe crab activity every 15 days, and replant degraded plants every 3 months.

[0032] Example 3: A second method for constructing a horseshoe crab ecosystem near a port construction area: The structural parameters for constructing the artificial horseshoe crab passages are as follows: three parallel passages are set up with a spacing of 4m between passages, a single passage width of 1.5m, a length of 150m, and a slope of 1:6; the bottom layer is a 20cm thick C30 permeable concrete layer with a reserved porosity of 10% and 5% basalt fiber added; the middle layer is a 10cm thick gravel buffer layer with a particle size of 8-10mm; the surface layer is a 15cm thick mud-sand mixture layer (volume ratio 7:3); the flexible baffle is 15cm high and covered with a 30% shading polypropylene ecological blanket; the guiding area has a 1m wide pebble strip (particle size 2-3cm); and hidden pits are laid every 20m, with a diameter of 50cm and a depth of 20cm, filled with humus and small stones (volume ratio 3:2).

[0033] In the construction of the submerged plant composite barrier, the three-layer ring structure has a total width of 20m and a distance of 4m from the edge of the horseshoe crab channel. The first barrier (width 5m) is a mixed planting of small water chestnut and Potamogeton pectinatus, with a total density of 120 plants / m², a plant ratio of 6:4, and a plant height of 40-50cm. The second barrier (width 8m) consists of an upper layer of Ceratophyllum demersum with a density of 80 plants / m² and a lower layer of Vallisneria natans with a density of 100 plants / m². The third barrier (width 7m) is a mixed planting of Potamogeton pectinatus and Hydrilla verticillata, with a total density of 90 plants / m², a plant ratio of 9:1, and a 0.06m³ gravel pile is placed every 10m². The nutrient pots are 15cm in diameter and 18cm in height, with a substrate of humus soil: marine mud = 1:2, and 5% shell powder added. The submerged bed is 2m×3m in size and is fixed with stainless steel anchors (40cm in length) at a spacing of 1m×1m.

[0034] The implementation steps are the same as in Example 1, with a seedling water temperature of 24℃, a salinity of 12‰, a seedling cycle of 45 days, and a transplanting time of 3 months before construction.

[0035] The above describes one or more embodiments of the present invention in a relatively specific and detailed manner, but it should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A horseshoe crab ecological protection system near a port construction area, characterized in that, This includes a composite barrier of artificial horseshoe crab channels and submerged plants; The artificial horseshoe crab channel is laid perpendicular to the coastline, connecting the intertidal spawning grounds and the shallow sea habitat. It has a three-layer biomimetic structure, from bottom to top: a bottom permeable concrete layer, a middle gravel buffer layer, and a surface mud and sand mixed layer. The artificial horseshoe crab channel is equipped with flexible baffles on both sides, guidance areas at both ends, and hidden pits at intervals in the middle of the channel. The submerged plant composite barrier is arranged around the artificial horseshoe crab channel, and includes three ring barriers arranged sequentially from the outside to the inside: the first barrier is composed of a mixture of small water chestnuts and Potamogeton pectinatus, used for noise reduction and primary pollution blocking; the second barrier is composed of three-dimensional planting of Ceratophyllum demersum and Vallisneria natans, used to enhance pollutant interception and water purification; the third barrier is composed of a mixture of Potamogeton pectinatus and Hydrilla verticillata, combined with gravel piles, used for buffering protection and habitat creation.

2. The horseshoe crab ecological protection system in the port construction area according to claim 1, characterized in that, The artificial horseshoe crab channel consists of 2 to 3 parallel channels, with a distance of no less than 3 meters between adjacent channels; each channel is 1.0 to 1.5 meters wide, 50 to 200 meters long, and has a slope of no more than 1:

5.

3. The horseshoe crab ecological protection system in the port construction area according to claim 1, characterized in that, In the three-layer biomimetic structure of the artificial horseshoe crab canal: The bottom permeable concrete layer is C30 permeable concrete with a thickness of 15 to 20 centimeters, a porosity of 10%, and basalt fiber with a proportion of 5%. The intermediate crushed stone buffer layer is paved with granite crushed stone with a particle size of 5 to 10 mm and a thickness of 8 to 10 cm; The volume ratio of mud and sand in the surface mud and sand mixture layer is 7:3, the thickness is 10 to 15 cm, and the particle size of the mud and sand used is no greater than 2 mm.

4. The horseshoe crab ecological protection system in the port construction area according to claim 1, characterized in that, In the auxiliary functional structure of the artificial horseshoe crab passage: The flexible baffle is made of polyurethane and is 12 to 15 centimeters high. It is fixed to the base on both sides of the horseshoe crab channel and the top of the baffle is covered with an ecological protective blanket with a light-blocking rate of 30%. The guiding zone is composed of pebbles with a particle size of 2 to 3 centimeters and a width of 1 meter; The concealed pits are placed every 20 meters, with a diameter of 50 centimeters and a depth of 20 centimeters. The inside is lined with a mixture of humus and small stones in a volume ratio of 3 to 2.

5. The horseshoe crab ecological protection system in the port construction area according to claim 1, characterized in that, The overall layout of the submerged plant composite barrier is a three-layer ring structure surrounding the artificial horseshoe crab channel, with a total width of 15 to 20 meters and a minimum distance of 3 meters from the edge of the horseshoe crab channel.

6. The horseshoe crab ecological protection system in the port construction area according to claim 1 or 5, characterized in that, The plant configuration of each layer of the submerged plant composite barrier is as follows: The first barrier is composed of a mixture of small water chestnut with a salt tolerance of not less than 15‰ and Potamogeton pectinata with a salt tolerance of not less than 10‰. The total planting density is 120 plants per square meter, and the planting ratio of small water chestnut to Potamogeton pectinata is 6 to 4. The second barrier is composed of three-dimensional planting of goldfish algae with a salt tolerance of not less than 6‰ and dwarf valerian with a salt tolerance of not less than 8‰. The planting density of goldfish algae in the upper layer is 80 plants per square meter, and the planting density of dwarf valerian in the lower layer is 100 plants per square meter. The third barrier is composed of a mixture of Potamogeton pectinatus and Hydrilla verticillata, which have a salt tolerance of not less than 10‰. The ratio of the number of plants of the two is 9:1, with a total planting density of 90 plants per square meter. In addition, a pile of gravel is set up for every 10 square meters of area. The gravel has a particle size of 8 to 12 centimeters and a volume of 0.05 to 0.06 cubic meters.

7. The horseshoe crab ecological protection system in the port construction area according to claim 1, characterized in that, The submerged plant composite barrier is planted using a combination of seedling cultivation in nutrient pots and planting in submerged beds. The nutrient pot is made of environmentally friendly and biodegradable material, and the internal matrix is ​​a mixture of humus and sea mud in a volume ratio of 1:2, with 5% of shell powder with a particle size of 0.1 to 0.3 mm added. The submerged bed is made of environmentally friendly non-woven fabric with a hole diameter of 2 cm. The size of a single submerged bed is 2 meters by 3 meters. It is fixed to the seabed surface by stainless steel anchors with a length of 30 to 40 cm and the anchors are spaced 1 meter by 1 meter apart.

8. A method for constructing an artificial horseshoe crab canal, characterized in that, The method for constructing the artificial horseshoe crab passage according to any one of claims 1-4 comprises the following steps: Base treatment was carried out along the selected path connecting the intertidal spawning grounds and shallow sea habitats; Lay a bottom permeable concrete layer with a concrete strength of C30, a thickness of 15 to 20 centimeters, a porosity of 10%, and add 5% basalt fiber. A middle layer of crushed stone buffer is laid on top of the bottom layer. Granite crushed stone with a particle size of 5 to 10 mm is selected and the thickness is 8 to 10 cm. A surface layer of mud and sand is laid on top of the middle layer, with a volume mixing ratio of 7:3 and a thickness of 10 to 15 cm. The particle size of the mud and sand used is no greater than 2 mm. Flexible baffles with a height of 12 to 15 centimeters are installed on both sides of the passage, and the top of the baffles is covered with an ecological protective blanket with a light-blocking rate of 30%. At both ends of the channel, guide zones consisting of pebbles with a diameter of 2 to 3 centimeters are laid, with a width of 1 meter. In the middle of the passage, a hidden pit is built every 20 meters. The pit is 50 centimeters in diameter and 20 centimeters deep, and is filled with a mixture of humus and small stones in a volume ratio of 3 to 2.

9. A method for constructing a submerged plant composite barrier, characterized in that, The method for constructing a submerged plant composite barrier according to any one of claims 1, 5-7 includes the following steps: Submerged plant species with salt tolerance that meet the requirements were selected, including *Echinochloa crus-galli*, *Potamogeton crispus*, *Ceratophyllum demersum*, *Vallisneria natans*, and *Hydrilla verticillata*. Seedlings are raised in nutrient pots. The substrate in the nutrient pots is a mixture of humus and sea mud in a volume ratio of 1:2, with 5% shell powder added. The cultivated seedlings, along with their nutrient pots, are planted on a sedimentation bed made of environmentally friendly non-woven fabric with a pore size of 2 cm and a size of 2 meters by 3 meters. Centered on the artificial horseshoe crab channel, a three-tiered ring barrier is constructed on the seabed by fixing the seabed in order from the outside to the inside: the outermost layer is the first barrier, which is planted with a mixture of small water chestnuts and Potamogeton pectinatus; the middle layer is the second barrier, which is planted with a three-dimensional mixture of goldfish algae and dwarf Vallisneria natans; the innermost layer is the third barrier, which is planted with a mixture of Potamogeton pectinatus and Hydrilla verticillata, and is complemented by piles of gravel. The slab is secured to the seabed using stainless steel anchors that are 30 to 40 centimeters long, with the anchors spaced 1 meter by 1 meter apart.

10. A method for the ecological protection of horseshoe crabs near a port construction area, characterized in that, The system includes constructing and maintaining the Chinese horseshoe crab ecological protection system as described in any one of claims 1-7. The maintenance measures include: cleaning up debris in the artificial horseshoe crab channel every 7 days, monitoring water quality, noise and Chinese horseshoe crab activity every 15 days, and replanting degraded submerged plants every 3 months.

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