Geographic Variation for the Composition of Parrotfish in the South China Sea

Based on the key ecological processes of parrotfish in coral reefs, we compiled species presence-absence data across 51 sites in the South China Sea to identify the distribution and composition of parrotfish and explore the relationship between species distribution and environmental factors, and 50 species (the Pacific: 57 species) of parrotfish were record. Nansha islands had the highest abundance with 41 parrotfish species. Nestedness analysis indicated parrotfish community had statistically significant nested patterns in the South China Sea and Nansha islands was the topmost site of nested matrix rank. Scleractinian coral species richness and Log(reef area) both had a significant effect on sites nested matrix rank (P < 0.05), which supports habitat nestedness hypothesis in the South China Sea. Scrapers were the most important functional group composition while the browser had a greater contribution on species nested matrix rank. Linear regression model showed parrotfish species richness increased with increasing longitude, scleractinian coral species richness and reef area. Variations in the parrotfish species richness in longitude was related to distance from the biodiversity hotspot in the Indo-Australian Archipelago. Parrotfish was mainly distributed in the range of 26-29℃, which was almost the same as the optimum temperature for coral growth. Nansha islands should be as biodiversity conservation priority areas, which could provide important reference significance for conservation efforts of parrotfish in degraded coral reefs habitats, especially in the context of increasing natural variability and anthropogenic disturbance.

Spatially Modeling the Synergistic Impacts of Global Warming and Sea-Level Rise on Coral Reefs in the South China Sea

Global warming and sea-level rise (SLR) induced by rising atmospheric CO2 concentrations can cause coral bleaching, death, and submergence of the world’s coral reefs. Adopting the GIS and RS methods, we modeled how these two stressors combine to influence the future growth of the atolls and table reefs of three archipelagoes in the South China Sea (SCS), based on geomorphic and ecological zones. A large-scale survey of the coral communities in Xisha Islands in 2014, Dongsha Islands in 2014–2016 and Nansha Islands in 2007 provided zone-specific process datasets on the range of reef accretion rates. Sea surface temperature and extreme (minimum and maximum) SLR data above 1985–2005 levels by 2100 in the SCS were derived from the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) models forced with the Representative Concentration Pathways (RCPs). Our model projected that: (1) the Xisha Islands and Dongsha Islands may have a better growth status, because the reef flat biotic sparse zone may be recolonized with hard coral and become a biotic dense zone; (2) the southern Nansha Islands reefs have a risk of stopping growing due to their earlier annual bleaching years. The increasing of water depths of these reefs is stronger in the RCP with more emissions. Our approach offers insights into the best-case and worst-case impacts of two global environmental pressures on potential future reef growth under a changing climate.

DNA Barcoding of Fish in Mischief Reef—Fish Diversity of a Reef Fish Community From Nansha Islands

Development of effective conservation and management strategies requires assessments of ecosystem biodiversity status, especially in understudied hotspots of global fish diversity. Coral reefs are important habitats for fishes, with biodiversity hotspots known globally. We present the first data on molecular diversity of fishes of Mischief Reef, the largest atoll in the Nansha Islands. Partial sequences (650 bp) of mitochondrial COI gene (Cytochrome c oxidase subunit I) are used to identify 209 individuals, representing 101 species, referable to 62 genera, 27 families, 8 orders, and 1 class. The most abundant orders are the Perciformes (176 specimens, 84.21%), Tetraodontiformes (13 specimens, 6.22%), and Beryciformes (13 specimens, 6.22%). Mean Kimura 2-Parameter genetic distances within genera, families, and orders are 4.51, 13.90, and 17.63%, respectively. We record Monotaxis heterodon from this region for the first time—a species that may previously have been misidentified as M. grandoculis. In addition, we recognized possible cryptic species of Lethrinus olivaceus based on significantly diverging barcode sequences. Barcode data provide new insights into fish diversity of Mischief Reef, important for developing further researches on this fauna, and for its conservation.

Assessment of Coral Reef Fish Stocks From the Nansha Islands, South China Sea, Using Length-Based Bayesian Biomass Estimation

The South China Sea (SCS) is one of the world’s main centers for coral reef diversity, with more than one-third of all reef fish species being found in this area. Some indications of overfishing have appeared in typical coral reefs of the SCS, as fish diversities have declined and the average body lengths of dominant fish species have decreased. However, only few assessments of coral reef fish stocks have been conducted, due to insufficient available data. In this study, we applied a newly developed length-based Bayesian biomass (LBB) estimation method to assess 10 dominant coral reef fish species from three main reefs (Yongshu Reef, Zhubi Reef, and Meiji Reef) of the Nansha Islands, SCS. Simulations indicated the estimated parameters were not sensitive to sample sizes (more than 100) using the LBB method. Our results showed that the relative biomass levels (B/BMSY) of Cephalopholis spiloparaea, Cephalopholis urodeta, Lutjanus gibbus, Gnathodentex aureolineatus, Pentapodus caninus, and Cheilinus fasciatus were between 0.16 and 0.45, suggesting an overfishing status; the relative biomass levels of Epinephelus merra, and Parupeneus crassilabris were 0.98 and 1.1, respectively, indicating that they were fully exploited; and the relative biomass levels of Lutjanus kasmira and Melichthys vidua were 1.3 and 2.5, respectively, indicating the populations were in good conditions. The estimates of Lc/Lc_opt were less than one for seven stocks, suggesting that the stocks were suffering from growth overfishing. Therefore, we emphasize the need to reduce fishing mortality and increase the mesh size of the coral reef fishery in the Nansha Islands, to achieve a sustainable yield and biomass.