Restoring Halodule uninervis: evaluating planting methods and biodiversity

Abstract

Seagrass provides a crucial habitat for numerous marine species and serves as a vital food source for endangered species, like dugongs. While extensive research on restoration has been conducted on certain temperate and slow-growing climax seagrass species, limited attention has been given to tropical pioneer species. This study aimed to assess and compare two restoration methods for the pioneer seagrass Halodule uninervis and evaluate their potential for biodiversity recovery after planting. We conducted a field experiment at subtropical Inhaca Island, southern Mozambique, testing the efficiency of two planting methods (plugs and single shoots) and two planting densities (~100 and ~300 shoots/m2). We monitored seagrass shoot density in two sites for 16 months, and benthic macrofauna density for 12 months. Results demonstrated that seagrass could grow in all combinations of planting methods and densities in both sites. Specifically, the single shoot method at the high-density treatment proved the most effective, resulting in approximately 1000 shoots/m2 within a year. Faunal densities, primarily dominated by polychaetes followed by malacostraca, bivalves, and gastropods, indicated rapid colonization of the planted areas, especially in the high-density treatments. Our findings suggest that restoring H. uninervis is feasible using the two tested planting methods. This is particularly significant because H. uninervis is a preferred dugong food source, and its decline due to anthropogenic activities could be reversed through restoration efforts. Nonetheless, conserving existing seagrass should be the primary focus, and restoration approaches should be employed as a valuable tool for managing coastal areas.