The Ecological Status and Change in High-Latitude Coral Assemblages at the Xuwen Coral Reef, Northern South China Sea: Insight into the Status and Causes in 2020

Simple Summary The Xuwen coral reef, as a potential refuge for corals to adapt to high-temperature migration, is an ideal laboratory to determine the impact of human activities on coral reef ecology in the northern South China Sea (NSCS). Global warming, coastal eutrophication and the decrease in herbivores has influenced coral reef degradation; compared with human activities, global climate change is the stronger influence on coral reef degradation on a large scale. For the Xuwen coral reef, which is in the coastal zone, anthropogenic stressors are more significant to the rapid degradation of its coral reef ecosystems. Under these circumstances, more evidence is required to understand the response of high-latitude reefs under natural and anthropogenic stresses. In this study, we investigated the ecological features of the scleractinian coral assemblage and their correlation with environmental factors on the Xuwen coral reef in 2020. Based on the data acquired by investigation and the implementation of statistical analysis methods, potential environmental conditions favoring coral communities in Xuwen were summarized. These results of the survey are expected to provide a basis for bridging the gap between economic development and sustainable management. Taking the coral communities of the Xuwen coral reef in 2020 as the research object, we analyzed the species composition, diversity, and interspecific Spearman correlation of the scleractinian coral communities, investigated the features and spatial distribution of the scleractinian coral community, and discussed the correlation between the community composition and environmental factors to identify the affecting factors and their sources. These results showed that (1) compared with the survey in 2004, the coverage of corals in 2020 had significantly decreased, while the dominant genera were still Goniopora and Porites. The coral morphology was massive, and the diversity of the coral community (Shannon-Wiener index, H') was 2.87. The distribution of coral was uneven. The competition among some dominant species of coral was intense. (2) The mass coral bleaching event in the NSCS in August 2020 did not cause severe coral death in the short term on the Xuwen coral reef. (3) The growth of the coral community in 2020 might be greatly affected by high suspended solids and nutrient levels, which were related to the current, mariculture, and coastal erosion. (4) Anthropogenic activities such as coastal aquaculture and fishing were the major factors leading to the reduction in coral coverage on Xuwen coral reef in the past 10 years.

Automated summary

This study investigated the ecological features and environmental factors of the Xuwen coral reef in 2020. The results showed a significant decrease in coral coverage compared to 2004, with dominant genera still being Goniopora and Porites. The coral community was characterized by low diversity. The mass coral bleaching event in the NSCS in 2020 did not cause severe coral death in the short term on the Xuwen coral reef. The growth of the coral community was greatly affected by high suspended solids and nutrient levels, related to current, mariculture, and coastal erosion. Anthropogenic activities such as coastal aquaculture and fishing were identified as the major factors leading to the reduction in coral coverage on the Xuwen coral reef in the past 10 years.