Eelgrass donor sites: potentially overlooked impacts of restoration in Puget Sound

Abstract

Eelgrass (Zostera marina) is an important habitat in the Salish Sea and restoration efforts are being undertaken around the region to increase eelgrass abundance and resilience. Eelgrass restoration is typically performed by transplanting whole shoots or dispersing viable seeds collected from reproductive shoots to a site. Most of the restoration efforts in the Pacific Northwest utilize whole shoots harvested from donor meadows and transplanted into restoration areas, but little work has been done to look at the impacts of the harvest on the donor stock. In response to the lack of existing data for Puget Sound, Washington Department of Natural Resources and Pacific Northwest National Laboratory’s Marine Sciences Laboratory conducted a controlled harvest experiment in two regions of the Salish Sea at sites associated with ongoing restoration activities. These meadows were harvested under different pressure (i.e., different percentage of plants taken from 0 to 50%) using traditional harvesting techniques. The meadows were then monitored for two years for changes in density. The results indicated that the eelgrass meadows were surprisingly resilient to all levels of harvest under ideal conditions and in small harvest areas. Interpretation and implications of these results will be discussed, as well as potential considerations for choosing potential donor sites for future restoration efforts

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