Population Structure and Genetic Diversity of Oysters from a Natural Reef on Magu Island, Shandong, China

Oyster reefs are receiving increasing attention due to severe survival challenges and their significant ecological service functions. Despite increased restorations worldwide, both natural and restored reefs have often not been monitored to an extent. Reef-building oyster populations are the foundation for the development of oyster reefs. In order to provide basic data for further protection and potential restoration of the oyster reef in the muddy tidal flats of Magu Island, in the middle of Dingzi Bay, the population structure and genetic diversity of the reef-building oysters were assessed through field investigation and molecular experiments. Results showed that the area of the oyster reef was 20,689 square meters and the oysters were Magallana gigas. The distribution of oyster patches revealed a reef building-up stage. The mean densities of the oysters were 3260.80 ind·m−2 and 3097.60 ind·m−2 in spring and autumn, respectively, and the biomasses were 25,209.38 g·m−2 and 30,137.44 g·m−2. The frequent distribution of shell height indicated two primary sizes divided by ages. Population genetic analyses based on partial mitochondrial cox1, cox3, and nad2 showed low nucleotide diversity and moderate haplotype diversity, proposing the population growth stage. Both the results of the population structure and genetic diversity suggested a developing status of the oyster reef on Magu Island.