6. Field‐Scale Biotic Applications in Chinese Marine Ranching

Marine ranching was pioneered by China through the establishment of 150 national demonstration zones across various seas by the early 2020s. These zones focus on habitat restoration, stock enhancement, and ecological remediation using biotic organisms such as sea cucumbers, macroalgae, and seagrasses [157]. By integrating artificial habitats into the marine ranching system, ecological carrying capacity is enhanced through the provision of structured environments that support stock enhancement of target species, including the red snail and sea cucumber. Consequently, total yields and stock abundance increase, while negative impacts on ecosystem structure and function were mitigated. Artificial habitats contribute to biodiversity conservation and ecosystem resilience, supporting sustainable marine resource management by facilitating the restoration of depleted fisheries [158].

6.1. Sediment Bioremediation in Sea Cucumber Beds (Bohai Bay and Yellow Sea)

6.1.1. Ecological Role of Sea Cucumber in Sediment Bioremediation

Sea cucumbers play a critical ecological role in marine ranching through their deposit feeding activities, which enhance sediment bioremediation and nutrient cycling. By ingesting organic‐rich sediments, sea cucumbers, particularly Apostichopus japonicus, promote organic matter mineralization and nitrogen cycling. Through deposit feeding, they increase bacterial abundance and shift microbial communities from producers to decomposers, thereby improving benthic health. Integrated with artificial reefs or integrated multi‐trophic aquaculture (IMTA) systems, sea cucumbers reduce organic buildup and pollution, maintaining a healthier marine ecosystem [159].

6.1.2. Case Study: Bohai Bay

In the Luanhe River estuary, sea cucumber aquaculture farms utilizing stone and artificial reef deployments have created habitats that provide nursery grounds for black rockfish (Sebastes schlegelii) since approximately 2013. In addition to enhancing habitat complexity, these farms contribute to sediment turnover and nutrient cycling. In the Bohai Bay region, coastal aquaculture methods, including artificial reef deployment and algal colonization promotion, are used to improve environmental conditions prior to seeding, thereby supporting diverse marine species and strengthening ecosystem resilience [160]. Deposit‐feeding sea cucumbers, such as Australostichopus mollis, facilitate bacterial abundance while suppressing microphytobenthos, thereby increasing mineralization and nutrient cycling in coastal sediments. Their bioturbation activities increase the efflux of inorganic nitrogen, which enhances algal productivity while simultaneously reducing the organic matter content. By mitigating the adverse effects of organic and inorganic pollutants, this shift in microbial balance and nutrient dynamics demonstrates the potential role of sea cucumbers in bioremediation efforts, particularly in organically enriched environments such as Bohai Bay [161].

6.1.3. Case Study: Yellow Sea and Shandong Province

In Shandong Province, on the Yellow Sea coast, the Fuhan Marine Ranch has expanded significantly since 2013 through the release of sea cucumbers, shellfish, and algae onto eco‐reefs, which account for ~25% of the ranch’s structures. This system produces tens of thousands of kilograms of sea cucumbers annually while promoting algal growth and bioremediation [162]. Studies have demonstrated that sea cucumber activity in the Yellow Sea enhances benthic biomass and improves sediment conditions through bioturbation and deposit feeding. These activities contribute to sediment turnover, nutrient cycling, and organic matter reduction, all of which enhance benthic habitats and support overall ecosystem health [163, 164].

Holothuria whitmaei, a sea cucumber commonly known as the black teatfish, enhances nutrient recycling by bioturbating sediments, which supports benthic microalgal communities and enhances nutrient cycling. Despite only 2% to 14% of sediments being bioturbated by H. whitmaei each year, their activity significantly increases physical contact with coral reef sediments, which facilitates nutrient release. Sea cucumbers play a crucial ecological role, especially in light of the documented links between their activity and the health of marine ecosystems [165].

6.1.4. IMTA Systems

The Sanggou Bay IMTA system integrates sea cucumbers with kelp and abalone, benefiting the environment through the detritivorous feeding of sea cucumbers on sedimented organic matter. This integration reduces organic waste accumulation, improves water quality, and enhances overall system productivity [162]. In summary, field‐scale biotic applications in Chinese marine ranching, particularly the use of sea cucumbers for sediment bioremediation, have demonstrated significant ecological and economic benefits. Through bioturbation, deposit feeding, and nutrient cycling, sea cucumbers improve benthic health, reduce organic pollution, and support the productivity of coastal ecosystems. The integration of artificial reefs, IMTA systems, and stock enhancement strategies has positioned Chinese marine ranching as a global model for sustainable marine resource management and ecosystem restoration.

6.2. Macroalgal Bed (Sargassum/Zostera) and Seagrass Restoration for HAB Mitigation (South China Sea)

6.2.1. Microalgal and Seagrass Bed Ecological Functions, Restoration Techniques, and Artificial Seaweed Reefs (ASRs)

Macroalgal and seagrass beds play a vital role in maintaining water quality and ecosystem health by enhancing water clarity, increasing nutrient uptake, supporting biodiversity, and inhibiting phytoplankton blooms through nutrient competition and allelopathic effects. These habitats also provide critical nursery grounds for marine species, stabilize sediments, and contribute to carbon sequestration (blue carbon) [166]. A variety of techniques are used to integrate microalgal restoration efforts with marine ranching, including planting and transplanting, attaching artificial reefs, and implementing multitrophic systems. ASRs facilitate the establishment of submerged aquatic vegetation beds by fostering ocean macroalgal afforestation, thereby contributing to the overall health and productivity of marine ecosystems. To ensure ASR success, continuous monitoring and refinement are required.

In the South China Sea, pilot projects, approximately nine by the early 2020s, with expansion goals, emphasize the restoration of algae and seagrass beds alongside artificial reefs and stock enhancement. Sargassum and Zostera (or similar) beds are being restored for multiple ecosystem services, including blue carbon storage, wave attenuation, and harmful algal bloom (HAB) control through nutrient extraction and the provision of habitats for algaecidal bacteria.

Seagrass connectivity studies, particularly those examining dietary and ecosystem links with sea cucumbers, highlight the importance of integrated approaches in marine ranching. For instance, sea ranching of Stichopus monotuberculatus has been shown to enhance coral reef ecosystems in Sanya, China. The restoration of sea cucumber beds provides habitat benefits, including reduced eutrophication effects, improved growth performance, and increased survival rates. Additionally, the presence of sea cucumbers may promote seagrass recovery, resulting in clearer waters and a lower risk of HABs [167].

6.2.2. Summary of Field‐Scale Applications and Ecological Significance

Table 1 presents the field‐scale biotic applications and their impacts in Chinese marine ranching from 2018 to 2026.

In summary, field‐scale biotic applications in Chinese marine ranching, particularly the use of sea cucumbers for sediment bioremediation and macroalgal/seagrass restoration for HAB mitigation, have demonstrated significant ecological and economic benefits. Through bioturbation, deposit feeding, nutrient cycling, and habitat provisioning, these biotic approaches improve benthic health, reduce organic pollution, enhance water quality, and support the productivity of coastal ecosystems. The integration of artificial reefs, IMTA systems, and stock enhancement strategies has positioned Chinese marine ranching as a global model for sustainable marine resource management and ecosystem restoration. Table 4 demonstrates the field‐scale biotic applications in Chinese marine ranching from 2018 to 2026 and how they have benefited marine growth in China.

Region | Biotic | Key practice (2018 to 2026) | Benefits | References
Bohai Bay | Sea cucumber (A. japonicus) | Bottom seeding on artificial reefs; IMTA integration | Sediment processing, nutrient cycling, habitats for finfish, and bioremediation of organics | [160]
Yellow Sea | Sea cucumber + macroalgae | Eco‐reefs, bottom culture (e.g., Fuhan, Sanggou Bay) | Increased biomass (>30% in some cases), organic matter decomposition | [168]
South China Sea | Sargassum and Zostera, seagrass | Bed restoration, transplantation, and ranching pilots | HAB mitigation via nutrient uptake, competition, biodiversity and carbon benefits: Marine ranching pilot | [169]