Abstract

Bottlenecks for successful seedling establishment can be both biotic and abiotic, and understanding the contribution of these processes is important in restoration efforts in order to optimize use of limited seed supplies. Here we describe the results of 2 years of experiments assessing mechanisms for burial of Zostera marina (eelgrass) seeds in restoration-scale plots, and evaluating the resulting initial seedling success (establishment of seedlings 5 months after planting) relative to the achieved burial depths. The experiments were conducted at 6 sites in the lower Chesapeake Bay with a range of potential wave exposures, and the wave climate was assessed using WEMo, a hydrodynamic wave model. For linear experimental plots (7–50 m long) planted in 2009 and 2010 and evaluated in April 2010 and 2011, seed planting significantly increased initial seedling success relative to broadcast seeds. Sediment disturbance experiments conducted in both years showed disruption of surface sediments typically extended to a depth of 3 cm, with substantial variation among sites, suggesting seeds buried shallower than 3 cm could experience high losses from being washed out. Relative Wave Exposure values calculated by a wave forecasting software (WEMo) using wind data for the two experimental periods were not consistently correlated with seedling performance for either broadcast or planted seeds, likely as a result of difficulty in down-scaling the model with spatially coarse data. However, in many cases, high seedling success was seen at sites with low maximum wave heights. Overall, the results illustrate the important role that burial depth may play in eelgrass seedling establishment and show promise for increasing the initial success of seed-based restoration efforts.

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