Seed Provision Efficacy of Detached Reproductive Shoots in Restoration Projects for Degraded Eelgrass (Zostera marina L.) Meadows

Eelgrass (Zostera marina L.) is a dominant seagrass species in the temperate waters of the northern hemisphere and is experiencing global declines. The use of eelgrass seeds is increasingly being recognized as a viable option for large-scale restoration projects. Eelgrass reproductive shoots are often collected to obtain seeds or to broadcast seeds in restoration projects. Here, a new method to accurately evaluate the seed provision efficacy of detached eelgrass reproductive is proposed. Viable seeds of detached eelgrass reproductive shoots were collected using in situ net cages at Swan Lake, China. The seed yield and quality of detached eelgrass reproductive shoots under five different treatments (with or without rhizomes and roots, vegetative shoots, and sediment) were compared to select the optimal treatment for this method. The results showed that each detached eelgrass reproductive shoot produced approximately 50 viable seeds on average and the potential seed yield overestimated the actual seed yields by around four times. Seed quality evaluated by size and weight was consistent with that of the natural eelgrass meadow in Swan Lake. Comparing the five different treatments, the simplest treatment (a single reproductive shoot) was convenient and robust for this method. The results indicate that this method is worth further extending to other populations to improve the efficiency of seed use and for effectiveness evaluation in restoration projects.