Roles of dispersal and predation in determining seedling recruitment patterns in a foundational marine angiosperm

© Inter-Research 2015. Seed dispersal and seed predation are 2 important processes in the early life history of plants. These mechanisms have been described extensively in terrestrial plants and have resulted in the creation of various models to describe seedling recruitment with increasing distance from the parent plant. However, it is unclear whether theoretical models derived from terrestrial studies apply to marine angiosperms. We performed observational and experimental tests of seed dispersal mechanisms in a marine environment to elucidate patterns of seed dispersal and predation in a foundational marine angiosperm, eelgrass Zostera marina. We also modeled seed dispersal and predation to explore how recruitment varies under different scenarios of predator activity and abundance. We found that seed densities were highest within and adjacent to vegetated areas. Predation pressure was low overall, and there was no significant difference in predation pressure between vegetated and unvegetated areas. Seedling densities were highly correlated with seed densities from the previous year, suggesting that seed predation had a limited impact on population recruitment. These results are consistent with the invariant survival model, which states that seed survivorship has no spatial trend. The theoretical scenarios we generated suggest that a low abundance of highly mobile, generalist predators may explain the patterns observed in our system. Therefore, seedling establishment rates are almost solely attributable and inversely proportional to distance from the parent plant. The results from this study have important implications for the recovery and restoration of these highly threatened coastal ecosystems.