Comparison of different anchoring techniques for seagrass (Posidonia oceanica) restoration

Abstract

Seagrass ecosystems face threats from multiple human-derived stressors that are causing the loss of these important habitats worldwide. Active restoration using innovative, cost-effective techniques, particularly with uprooted fragments that avoid damage to donor meadows, offers potential for recovery. However, non-ecological factors such as cost, logistics or supply are rarely considered but are essential for decision-making and implementation. This two-year study evaluates the feasibility and effectiveness of four anchoring techniques for securing uprooted Posidonia oceanica fragments to the substrate, integrating ecological success with feasibility to identify optimal methodologies. Experiments were conducted in two bays in Mallorca characterized by historical P. oceanica presence. Big staples, small staples, bamboo sticks and calcite pegs, were tested to fix fragments with plagiotropic rhizomes. Across sites, small staples and bamboo sticks supported high establishment success (94 %) while having a low carbon footprint, and ease of use. These methods effectively utilized smaller fragments, which are more commonly available, making them practical for large-scale projects. Although larger fragments may develop more new shoots, their limited availability restricts widespread application. As expected, shoot survival declined, a common patter observed early in P. oceanica restoration process, indicating that a two-year period is insufficient to fully assess long-term restoration success. Consistent performance across sites indicates broad applicability of these techniques in Mediterranean shallow, sheltered areas. Non-ecological indicators also highlight the socio-environmental benefits of bamboo sticks and small staples, making them well-suited for sustainable restoration. These findings underscore the need for a balanced, integrated approach that aligns ecological outcomes with efficiency metrics.