南海北部砗磲种群数量变化数据集（过去4500年）

在南海北部西沙北礁中自上而下采集了1406个亚化石砗磲，通过纹层计数挑选出了年纹层超过30（即生命周期超过30年）的大龄亚化石砗磲（共计245个样本），对其进行AMS14C定年。根据AMS14C定年结果统计出了每100年里大个体亚化石砗磲数量，发现亚化石砗磲并非均匀的分布在过去4500年，在部分时段砗磲数量出现了急剧下降的现象。综合砗磲生长生存习性、已有古气候资料及人类活动资料进行分析，研究团队发现在近代人类活动加强以前，南海北部砗磲种群数量主要受自然气候的影响，冬季温度是南海北部砗磲存活的限制性因素，当冬季风增强导致南海北部冬季温度降低时，砗磲种群数量减少。同时，砗磲种群存在较强的自我修复机制，随着温度的回升砗磲种群数量也会迅速回升。但是，在最近的一次急剧下降事件后（发生在~1820 CE – ~1900 CE），砗磲种群数量并没有随近100年的升温而恢复。分析表明近现代人类过度捕捞打破了砗磲自然状态下的自我修复机制，导致目前南海北部现代砗磲种群面临灭绝的风险。

1406 subfossil giant clams were collected stratigraphically from top to bottom at North Xisha Reef, northern South China Sea. Growth lamina counting was conducted on all specimens, and 245 long-lived subfossil giant clams with annual growth laminae exceeding 30 (corresponding to a lifespan of over 30 years) were selected for AMS ¹⁴C dating. Using the AMS ¹⁴C dating results, the abundance of large-sized subfossil giant clams was quantified per 100-year time bins. It was found that the distribution of subfossil giant clams across the past 4500 years was non-uniform, with abrupt declines in their abundance during certain periods. Integrating the growth and survival traits of giant clams, existing paleoclimatic datasets and anthropogenic activity records, the research team concluded that prior to the intensification of modern human activities, the population size of giant clams in the northern South China Sea was primarily governed by natural climatic variability. Winter sea temperature acted as the limiting factor for giant clam survival in this region: when an intensified winter monsoon caused a drop in winter sea temperatures, giant clam populations declined. Meanwhile, giant clam populations exhibited a robust self-repair mechanism, whereby population sizes would rebound rapidly as temperatures recovered. However, following the most recent abrupt decline event (~1820 CE – ~1900 CE), giant clam populations failed to recover despite the warming trend over the past century. Further analysis revealed that modern human overfishing has disrupted the natural self-repair mechanism of giant clam populations, placing modern giant clam populations in the northern South China Sea at risk of extinction.

搜集汇总

背景与挑战

背景概述

该数据集基于南海北部西沙群岛过去4500年的亚化石砗磲样本，通过AMS14C定年分析，揭示了砗磲种群数量的长期变化规律。研究发现，在自然状态下，种群数量受冬季温度影响并具有自我修复能力，但近现代人类过度捕捞已破坏这一机制，导致种群面临灭绝风险。