PS 49-147 - Assessment of abundance, genetic diversity and connectivity of eelgrass Zostera marina populations: integrating insights for their conservation

Background/Question/Methods

Seagrass meadows that provide important ecosystem services have declined globally due to global climate change and anthropogenic activities. Restoration of disturbed seagrass meadows and environments has become a worldwide priority to reverse of recover the degradation, function and services of ecosystem. In particular, recognizing patterns of genetic diversity and population is integral to understanding the mechanisms behind population declines and formulating management plans for the conservation of threatened or endangered species. Jeju Island, located in the southern sea of Korea and the largest island in Korea, is strongly affected by increase of sea surface by climate change and by groundwater, fish farm effluents and wastewater with high nitrogen concentrations. Consequently, seagrass meadows are dramatically decreasing along the coast of Jeju Island. Here, we aimed to provide a comprehensive perspective of current status, genetic diversity and structure of the seagrass Zostera marina population. We investigated spatial distribution, environmental factors, biological characteristics of Z. marina on Jeju Island in Korea. A total 377 vegetative shoots of Z. marina were genotyped at eight microsatellite markers to investigate genetic diversity and structure.

Results/Conclusions

There were 11 fragmented Z. marina meadows in the shallow subtidal zone along the coast of Jeju Island. The estimated total area of seagrass meadows on Jeju Island was 31.1 ha. Shoot height, shoot density and biomass were highly variable among locations, indicating that each population adapted to local environmental conditions. The level of allelic richness (1.93) and expected heterozygosity (0.313) of Jeju population was relatively low compared with that in Korea. We found a significant relationship (R²=0.605) between meadows size and clonal richness and allelic richness. Inbreeding coefficient (F_IS) values was positively correlated with sediment pore water NH₄⁺ concentration. These indicates that genetic diversity of Z. marina populations on Jeju Island are strongly affected by habitat size and nitrogen-enriched water. Strong pairwise genetic differentiation (F_ST=0.379) suggests that restricted gene flow promotes population divergence due to the existence of environmental barrier. These results indicate that Z. marina populations on Jeju Island are at elevated risk of local degradation or extinction under small effective population size and eutrophicated water. Thus, a site-specific effective management plan or action will be needed to ensure that existing seagrass beds are preserved and protected.