Seed Burial Alleviates Wave Energy Constraints on Zostera marina (Eelgrass) Seedling Establishment at Restoration-Releva
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Seed Burial Alleviates Wave Energy Constraints on Zostera marina (Eelgrass) Seedling Establishment at Restoration-Relevant Scales Scott R. Marion 1 & Robert J. Orth 2
&
Mark Fonseca 3 & Amit Malhotra 4
Received: 9 April 2020 / Revised: 26 August 2020 / Accepted: 3 September 2020 # Coastal and Estuarine Research Federation 2020
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. Keywords Eelgrass . Seeds . Hydrodynamics . WEMo
Introduction
Communicated by Melisa C. Wong Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12237-020-00832-y) contains supplementary material, which is available to authorized users. * Robert J. Orth [email protected] 1
Marine Resources Program, Oregon Department of Fish and Wildlife, 2040 SE Marine Science Dr., Newport, OR 97365, USA
2
Virginia Institute of Marine Science, William and Mary, 1375 Greate Rd., Gloucester Point, VA 23062, USA
3
CSA Ocean Sciences Inc., 8502 SW Kansas Avenue, Stuart, FL 34997, USA
4
Geohorizons Consulting, 239 Rutledge Ave, Beaufort, NC 28516, USA
The demographic stages in plants that lead to a successful adult from a seed are influenced by numerous biotic and abiotic factors (Harper 1977). The relative influence of each factor on any particular s
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