Abstract:

Aims: Oyster reefs are widely distributed in the intertidal zones and subtidal zones of subtropical and temperate coastal areas, serving as a crucial component of coastal ecosystems and the surrounding economy. The global oyster reef ecosystem has been severely degraded. Moreover, the amount of research on the ecological functions and economic benefits of oyster reefs in many regions remains inadequate, such as those in Guangdong Province, China. This limits our understanding of the integrity of these coastal ecosystems, directly impacting how coastal ecosystems are assessed and limiting our ability to sustainably manage their health. To fill this gap in literature, this study analyzed the distribution of oyster reefs in Guangdong’s coastal zones, summarized the species diversity of oysters and the main threats to these reefs, and provided recommendations for their protection and restoration.

Methods: Oyster habitats in the coastal zones of Guangdong Province were investigated from July 2022 to March 2023. Historical data for this area were also collected. Additionally, the oyster reefs were classified into three types of reefs based on their vertical development and aggregation area: “reef”, “bed”, and “aggregation”.

Results: “Bed” and “aggregation” reef types were widely distributed throughout Guangdong Province, whereas “reef” were located in Zhuhai, Jiangmen, Yangjiang, and the eastern and southern regions of the Leizhou Peninsula in Zhanjiang. A total of 13 oyster species from 3 genera were recorded, including 6 species from the genus Saccostrea (i.e. S. echinata, S. malabonensis, S. mordax, S. kegaki) and 2 undetermined species; 6 species were from the genus Crassostrea (i.e., C. sikamea, C. angulata, C. hongkongensis, C. ariakensis, C. bilineata and C. dianbaiensis); and 1 species was from the genus Dendostrea (i.e., D. crenulifera). The 7 reef-building oyster species found in the coastal zones of Guangdong Province were C. sikamea, C. angulata, C. hongkongensis, S. echinata, S. malabonensis, S. mordax, and Saccostrea sp.1. The primary constructors of oyster “reefs” were C. sikamea, C. angulata, and C. hongkongensis. Crassostrea hongkongensis was found exclusively in estuarine areas, while C. sikamea and S. echinata were found across all regions. Other reef-building oysters were primarily located outside estuarine areas. Oyster “reef” in the coastal zones of Guangdong Province primarily developed on the natural rocky shorelines. “Bed” and “aggregation” were found only in artificial marine structures and aquaculture facilities. Oyster reefs were widely distributed across the coastal zones of Guangdong Province; however, this ecosystem faces numerous challenges. The primary threats to oyster reefs in Guangdong’s coastal zones included overfishing, habitat alteration, water pollution, aquaculture practices, invasive species, and reef degradation.

Conclusion: To effectively protect and restore oyster reefs, it is recommended to enhance the conservation system in Guangdong Province. This can be done by strengthening basic surveys, operational monitoring, and scientific research, as well as by implementing restoration projects and promoting public education on oyster conservation.

Key words: South China Sea, intertidal zone, oyster reef, distribution characteristics, biodiversity