Seed bank patterns in Chesapeake Bay eelgrass (Zostera marina L.):: A bay-wide perspective

The decline of eelgrass (Zostera marina) in Chesapeake Bay in the 1960s. and. 1970s has been studied in the context of changes in water quality and habitat suitability, little effort has focused on the importance of reproductive ecology in understanding current and potential recovery of these populations. The spatial variability of seed-bank characteristics of Z. marina in Chesapeake Bay was explored by a reproductive shoot and seed-bank sampling effort. Seed banks were sampled from 105 beds of submerged aquatic vegetation among 12 zones throughout the lower and middle Chesapeake Bay. Number of viable seeds was highly variable among and within zones, with seeds found in all but one zone and also found in cores not containing any Z. marina shoots. Number of reproductive shoots was also highly variable among and within zones, with differences probably driven by different local environmental conditions. Bay-wide, viable seeds were found in more monospecific Z. marina cores than in mixed species or monospecific Ruppia maritima cores suggesting local biological and environmental control on sexual reproduction. Lower densities of viable seeds in the middle Chesapeake Bay region reflect the lower abundance of Z. marina in these regions and provide context for discussion of historical changes in Z. marina in Chesapeake Bay. While this study focused on a snap shot of the seed bank immediately after establishment, we highlight critical questions for future study that may be important for their conservation and restoration.