Assessment of the establishment success of Zostera marina (eelgrass) from seeds in natural waters: Implications for large-scale restoration

We described and evaluated an aquaculture system that can grow Zostera marina (eelgrass) from seeds in natural waters for restoration projects through a two-year field experiment. The system included protective seed bags filled with high-silted sediments, flowerpots, and culture beds. To determine the suitable conditions for seedling establishment, we subjected Z. marina seeds to treatments including different durations of low temperature (4 °C) prior to seed planting, seed planting densities, and numbers of holes on the side of each flowerpot. In the spring following seed distribution, the seedling establishment of Z. marina was significantly promoted within 30 days by low-temperature storage prior to seed planting and seven holes per flowerpot, but the seed planting density showed no effects. The average shoot density of the plants large enough for transplanting was 614 shoots m−2 in the optimal eelgrass transplant season, which was 10 months after planting. New plants from the seeds were fully developed and well maintained 2 years after distribution with the maximum shoot density of 2661 shoots m−2. Results demonstrate that growing Z. marina from seeds is an alternative approach to harvest plants from donor beds. The presented aquaculture system should be considered for future large-scale restoration projects of Z. marina.