International Journal of Marine Science, 2024, Vol.14, No.4, 275-284 http://www.aquapublisher.com/index.php/ijms 276 demissa) has been shown to clear large volumes of water daily, removing significant amounts of particulate matter and sequestering nitrogen in their tissues and shells, which helps mitigate nutrient over-enrichment in coastal and estuarine ecosystems (Galimany et al., 2017). Similarly, the inshore aquaculture of suspension-feeding cockles (Cerastoderma edule) has demonstrated improvements in water quality by reducing sediment loads and stimulating pelagic microalgal growth, which in turn enhances the growth and meat content of the cockles (Philippart et al., 2020). These filtration activities not only improve water clarity but also contribute to the overall health and resilience of aquatic ecosystems. 2.2 Substrate stabilization and habitat formation In addition to water filtration, shellfish aquaculture contributes to substrate stabilization and the formation of new habitats, which are crucial for coastal habitat restoration. The cultivation of bivalves such as oysters and mussels provides structured habitats that support diverse faunal communities. For example, suspended or elevated mussel and oyster cultures have been associated with increased abundance and species richness of wild, mobile macrofauna, thereby enhancing the ecological value of these aquaculture sites (Theuerkauf et al., 2021). The physical structures created by shellfish farms, such as rafts and cages, offer surfaces for the settlement of various marine organisms, promoting biodiversity and ecosystem complexity. Moreover, shellfish aquaculture can play a role in stabilizing sediments and protecting shorelines. The co-restoration of shellfish and other marine habitats, such as kelp forests, can synergistically stabilize sediments and accelerate ecosystem recovery, providing a more resilient and productive coastal environment (McAfee et al., 2022). This multi-habitat approach to restoration leverages the positive interactions between different species and habitats, enhancing the overall ecological and socio-economic benefits of restoration efforts. Shellfish aquaculture not only improves water quality through filtration but also contributes to substrate stabilization and habitat formation, making it a valuable tool for coastal habitat restoration and the enhancement of ecosystem services. By integrating these ecological functions, shellfish aquaculture can support the recovery and sustainability of coastal ecosystems, providing both environmental and socio-economic benefits. 3 Contributions of Shellfish Aquaculture to Coastal Restoration 3.1 Restoring biodiversity 3.1.1 Habitat creation for marine species Shellfish aquaculture plays a significant role in creating habitats for various marine species. The cultivation of bivalve shellfish, such as mussels and oysters, has been shown to increase the abundance and species richness of wild, mobile macrofauna. This is primarily due to the structured habitats provided by the aquaculture setups, which offer shelter and breeding grounds for fish and invertebrates (Figure 1) (Theuerkauf et al., 2021). Additionally, the presence of these structured habitats can enhance reproduction and recruitment, further supporting biodiversity (Theuerkauf et al., 2021). Shellfish farms provide complex substrate structures that allow fouling organisms to grow, offering breeding grounds, refuges, and resting areas for fish and invertebrates. These structured habitats not only increase species abundance and diversity but also promote the overall health of marine ecosystems. Figure 3 clearly demonstrates the important role of shellfish aquaculture in enhancing and restoring marine habitats, aiding in the understanding of its contributions to biodiversity restoration. 3.1.2 Supporting trophic interactions The introduction of shellfish aquaculture into coastal ecosystems can support trophic interactions by providing food resources for various marine species. Bivalves, for instance, filter feed on plankton, which can help control plankton populations and improve water quality. This, in turn, supports higher trophic levels, including fish and other predators that rely on these resources (Theuerkauf et al., 2021). Moreover, the presence of shellfish can enhance the overall productivity of the ecosystem, creating a more robust and interconnected food web (McAfee et al., 2022).
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