Biodiversity of natural versus planted mangrove forests across latitudes in Guangdong China with seven new records and potential new species

Mangrove ecosystems in Guangdong Province, China, are vital for their ecological services and biodiversity, yet comprehensive assessments of their species diversity remain limited. A biodiversity survey conducted during the months of July to August 2024 by random sampling using quadrates to assess biodiversity, species richness, and abundance as well as to evaluate species relationships with reference to the usage of mangroves area and mangrove species in the eight stations Shantou, Huiyang, Zhuhai, Huidong (Planted mangroves at higher latitudes 22-23N of non-pristine areas) Yangjiang, Lianjiang, Leizhou, and Xuwen (natural mangrove forests at lower latitudes 20-21N of pristine areas) of Guangdong's mangrove forests. A total of 87 species (overall diversity) with eight phyla were identified, with Mollusca being the most abundant (41 species, including 28 gastropods), followed by Arthropoda (32 species) and Chordata (4 species). Seven species-Bakawan rotundata, Bakawan puti, Haloa wallisii, Platytrombidium sp., Heterocerus sp., Trichoniscus pygmaeus and SHSY140711-were recorded for the first time in China. Penthalodidae sp., key characters do not fit the diagnosis of any of its genera, represent a potential new genus in the family Penthalodidae. The brief taxonomic description for Haloa wallisii and Bakawan puti is recorded here to avoid misidentification with related species. Spatial analysis revealed Yangjiang with the highest number of specimens (N = 318), while Shantou had the lowest number of specimens (N = 25). A clear difference in biodiversity gradient was observed between natural (high biodiversity) and planted (low biodiversity) mangrove forests at pristine versus non-pristine areas, respectively. A same trend has been observed for latitudinal gradient from lower 20-21N (high biodiversity) to higher 22-23N (low biodiversity). Cluster and beta-diversity analyses highlighted distinct ecological zones, with Yangjiang, Leizhou, Xuwen, and Lianjiang exhibiting high species turnover. Analysis of species collection relative to mangrove plant species revealed that the highest proportion of organisms (30%) were found in association with Avicennia marina, while the lowest (2%) were associated with Bruguiera gymnorhiza. Over 60% of species were free-living, underscoring the ecosystem's ecological integrity, while invasive species accounted for only 1%. This research directly aligns with the Sustainable Development Goal (SDG) 14, "Life below water" (Conserve and sustainably use the oceans, seas, and marine resources for sustainable development) and 15 "Life on land". However, this research is also strongly supportive in achieving other SDGs such as (12. Sustainable consumption and production, 13. Climate action, 17. Partnerships for the goal). These findings emphasize the need for targeted conservation strategies, particularly in high-diversity areas, to mitigate anthropogenic threats and sustain mangrove biodiversity. The results of this study help China's target of protecting 30 percent of the planet's land and oceans by 2030 and provided a critical baseline for future monitoring and management efforts for biodiversity in Guangdong's mangrove ecosystems.