Reproduction dynamics of eelgrass (Zostera marina L.) populations in Ise–Mikawa Bay, central Honshu, Japan

Suitable methods for the conservation and reconstruction of eelgrass populations are needed because of decreasing eelgrass populations. For this, it is important to understand the reproduction mechanism of eelgrass populations at a molecular level as well as at a macro level. In the present study, we analyzed the dynamic changes in eelgrass populations in Ise–Mikawa Bay by monitoring their distribution from 1993 to 2005 and by genetic analysis using microsatellite polymorphism. The distribution of eelgrass populations in the eastern part of Ise Bay showed a periodic shift with a cycle of 4 years, that is, eelgrass populations appeared on the bar trough, gradually moved to the inshore side of the habitat every year, and disappeared in the fourth year. Microsatellite analysis revealed that the eelgrass populations in Ise–Mikawa Bay have high genetic diversity. The eelgrass populations in Ise Bay and those in Mikawa Bay showed genetic differentiation and genetic connectivity. The importance of upstream parent populations, seed transportation among local populations and genetic diversity were discussed for the sustainability of eelgrass populations.