海南西岛珊瑚群落变化及其影响因素 *

在2018年的海南三亚西岛珊瑚群落分布和水质环境因子调查中, 共记录到造礁石珊瑚68种, 多孔螅2种。基于珊瑚礁底质类型的非度量多维标度分析, 可将西岛站位划分为区域1(东-南侧)和区域2(西侧)。全岛活珊瑚覆盖率为13.6%, 区域1和区域2分别为4.2%和27.7%, 区域2珊瑚多样性高于区域1。区域1珊瑚礁处在显著退化状态, 而区域2相对健康, 但是优势种类单一。与历史资料对比分析, 东侧站位造礁石珊瑚覆盖率从2011年的近40%降至2018年不足4%, 退化显著, 而西侧站位珊瑚礁无明显退化; 丛生盔形珊瑚(Galaxea fascicularis)逐渐取代分枝状的鹿角珊瑚成为绝对优势种类; 珊瑚礁区浊度、溶解无机氮(dissolved inorganic nitrogen, DIN)和喇叭藻的δ¹⁵N均值分别为2.54NTU、9.63μmol·L^-1和5.09‰, 均处在较高水平。相关性分析表明, 环境因子的空间变化并不能解释珊瑚群落的空间分布。因此, 推测人类活动引起的极端扰动事件可能是导致西岛珊瑚群落空间分布和东侧站位珊瑚近几年显著退化的主要原因, 如三亚河清淤在三亚湾随意倾倒引起的浑浊事件。应加强对三亚湾清淤和西岛人类活动的管控, 减轻颗粒物沉积和营养盐富集的影响, 促进西岛珊瑚礁逐渐恢复。

Coral community change and its influencing factors in Ximaozhou Island of Hainan

In 2018, the coral community distribution and environmental parameters around Ximaozhou Island of Sanya were surveyed. We recorded 68 species of reef building corals and two species of Millepora spp. Based on the nMDS analysis of coral reef benthic substrata, we divided the sites of Ximaozhou Island into zone 1 (the south/east side) and zone 2 (the west side). The mean live coral coverage is 13.6% for the whole island, 4.2% in zone 1 and 27.7% in zone 2. The diversity of coral species in zone 2 is higher than that in zone 1. The reefs in zone 1 are in a significant degradation state, while the reefs in zone 2 are relatively healthy with single dominant coral species. Compared with the historical data, the mean live coral coverage at the east sites decreased from nearly 40% in 2011 to less than 4% in 2018, showing significant degradation, while the coral reefs at the west sites did not show significant change, with branching Acropora spp. shifting to massive Galaxea fasciculis. The mean values of turbidity, dissolved inorganic nitrogen (DIN) and δ¹⁵N of Turbinaria ornata in coral reef of Ximaozhou Island are 2.54 NTU, 9.63 mol·L^-1 and 5.09‰, respectively. Our correlation analysis shows that the environmental factors could not explain the spatial distribution of the coral community. Therefore, we speculate that the extreme disturbance event caused by human activities may be the main cause for the spatial distribution of coral community in Ximaozhou Island and the significant degradation of coral on the east side in recent years, such as the turbidity event caused by random dumping of sediments from the Sanya River into Sanya Bay. It is necessary to strengthen the control of sediment dumping and human activities in Sanya Bay, to reduce the impact of sedimentation and nutrient enrichment, and to promote a gradual recovery of coral reefs in Ximaozhou Island.