Musumeci, Simone Maria Santo (2025) From degraded ecosystems to sustainable aquaculture: a case study on Mediterranean Sea urchins. [Tesi di dottorato]

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Abstract

Sea urchins, particularly Paracentrotus lividus and Arbacia lixula, play a critical role in Mediterranean rocky reef ecosystems. However, their populations face significant challenges due to overexploitation, habitat degradation, and environmental changes. This thesis addresses these issues by integrating the study of the effects of conservation strategies, population monitoring, and sustainable aquaculture practices within a circular economy framework. It focuses on two interconnected goals: 1- monitoring the densities and population structure of P. lividus and A. lixula within the Marine Protected Area (MPA) of Porto Cesareo and outside, as an example of overexploitation requiring specific interventions, 2- developing eco-friendly, nutrient-rich diets for sea urchin aquaculture using by-products from the food industry. Field studies revealed notable declines in sea urchin densities and shifts in population structure, with barren grounds persisting in areas of high grazing pressure. These findings highlight the importance of MPAs in mitigating pressures on sea urchin populations while also emphasizing their limitations in ensuring species recovery. To address overgrazing and promote habitat restoration, targeted removal of sea urchins was implemented, facilitating the recolonization of macroalgal beds, particularly foundation species such as Cystoseira sensu lato, which serve as critical habitats for marine biodiversity. In parallel, aquaculture experiments evaluated the effectiveness of innovative diets derived from anchovy processing by-products and carrot peel waste. Results demonstrated the potential of these diets to sustain sea urchin growth and enhance gonadal development, with variations observed across size classes and diet formulations. The diets not only improved somatic and gonadal growth rates but also enhanced marketable traits, such as gonad coloration and sensory qualities, aligning with consumer preferences. These findings underscore the feasibility of using food industry by-products to develop sustainable feeds, reducing the environmental footprint of aquaculture while supporting the conservation of wild populations. By combining population monitoring and sustainable aquaculture practices, this research contributes to the resilience of Mediterranean coastal ecosystems and offers practical solutions to biodiversity loss and resource sustainability. It provides valuable insights for policymakers, resource managers, and the aquaculture industry, promoting the integration of circular economy principles into marine resource management and supporting the transition toward more sustainable food systems.

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