Comparing Eelgrass ( <scp> <i>Zostera marina</i> </scp> L.) Donor Sites for Recovery From Shoot Collection and Success of Transplants at Different Plot Sizes and Densities

ABSTRACT Seagrass restoration has shown mixed results, even in suitable environments, indicating ongoing needs for improved techniques. This study tracked intertidal eelgrass ( Zostera marina ) dynamics at two donor sites, differing in elevation, and one transplant site over multiple years. Based on 0%, 50%, 80% and 100% removal from 4 m 2 plots, recovery times increased with collection intensity at both donor sites, taking up to 2 years when plots were completely cleared. Collected shoots were transplanted at four plot sizes (0.0625, 0.25, 1, 4 m 2 ) and three densities (25, 64, 125 m −2 ) on tidal flats dominated by bioturbating shrimp ( Neotrypaea californiensis ). Initial establishment was reduced at higher shoot densities; only the smallest plots showed no advantage of low density. Despite initial density differences, all plots converged to ~60 m −2 after 1 year and 110 m −2 after 2 years, except 0.25 m 2 low‐density plots (initially six shoots). For total shoot counts, including those extending outside the original plots, proportional increases were inversely related to plot size and density, but a three‐way statistical interaction appeared in both years. Because low‐elevation shoots showed negative density dependence even in the 0.0625 m 2 plots, whereas high‐elevation shoots did not, the 2‐shoot transplants from low elevation had by far the fastest population growth, reaching an average of roughly 190 shoots after 2 years. Both donor sites proved viable for restoration, though performance differences emerged under specific planting configurations, suggesting that planting strategies may be more important determinants of restoration success than donor characteristics in environments suitable for eelgrass.