Zostera marina population genetics in Barnegat Bay, New Jersey, and implications for grass bed restoration

Within Barnegat Bay, New Jersey, Zostera marina populations have declined by 62% over the last 20 years, and restoration efforts have met with mixed success. We have completed a microsatellite-based genetic investigation of eight populations of Z. marina within Barnegat Bay to determine whether the genetic stock origins of the plants used in management projects may affect restoration success. Additionally, we assessed the genetic diversity of Z. marina in Barnegat Bay to better understand its population structure. Clonal diversity ranged from 0.70 to 0.95 for the populations studied. Individually, Barnegat Bay populations are not genetically diverse, and there is also little divergence among populations. The Atlantic populations had mean Hobs values (0.20-0.34) that were far lower than the Hexp values (0.69-0.83). Also, the F_IS values in all of the eastern populations indicate a surfeit of homozygotes over heterozygotes, suggesting a low degree of outcrossing in the Barnegat Bay populations. Six of the ten populations studied (Ham Island, Manahawkin Bay, Shelter Island, Marsh Elder, Harvey Cedar Sedge, and Long Island) show evidence of historical bottlenecks. Mean estimated F_ST values would suggest that most alleles are undergoing moderate genetic differentiation, with values that range from 0.06 to 0.13. Oyster Creek and Sedge Island demonstrate the largest estimated effective population sizes and may be the most appropriate populations for use in future eelgrass restoration projects.