Large-Scale Zostera marina (eelgrass) Restoration in Chesapeake Bay, Maryland, USA. Part II: A Comparison of Restoration Methods in the Patuxent and Potomac Rivers

Abstract

In response to systemic losses of submerged aquatic vegetation (SAV) in the Chesapeake Bay (east coast of North America), the U.S. Environmental Protection Agency's (EPA) Chesapeake Bay Program (CBP) and Maryland Department of Natural Resources (MD DNR) have considered SAV restoration a critical component in Bay restoration programs. In 2003, the CBP created the “Strategy to Accelerate the Protection and Restoration of Submerged Aquatic Vegetation in the Chesapeake Bay” in an effort to increase SAV area. As part of this strategy, large-scale eelgrass (Zostera marina) restoration efforts were initiated in the Patuxent and Potomac Rivers in Maryland. From 2004 to 2007, nearly 4 million Z. marina seeds were dispersed over 10 ha on the Patuxent River and almost 9 million seeds over 16 ha on the Potomac River. Z. marina seedling establishment was consistent throughout the project (<4%); however, restored eelgrass survival was highly dependent on restoration site. Restoration locations on the Patuxent River experienced initial Z. marina seedling germination, but no long-term plant survival. Restored Z. marina on the Potomac River has persisted and expanded, both vegetatively and sexually, beyond initial seeding areas. Healthy Z. marina beds now cover approximately five acres of the Potomac River bottom for the first time in decades. The differential success of Z. marina restoration efforts in the two rivers is evidence for the necessity of carefully considering site-specific characteristics when using large-scale seeding methods to achieve successful SAV restoration.