Table_3_The depositional history of the Knysna estuary since European colonization in the context of sea level and human impacts.XLSX

IntroductionEstuaries are highly vulnerable systems and increasingly exposed to a number of environmental, climatic and human-induced stressors. The Knysna estuary and lagoon complex, on the south coast of South Africa, is regarded as environmentally and economically important, yet faces regional impacts resulting from ongoing urbanisation and land use change as well as the significant global threats of rising sea levels and changing climate. Although the estuary has been reasonably well studied in terms of modern ecological processes, little is known of how the system has responded to changes in the longer term, not least the impact of European colonization and subsequent population growth and economic development.
MethodsIn order to address this shortcoming, a series of shallow (<1 m) cores was extracted from a range of representative habitats and marine influences in the estuary and three of these (namely KNY-19A, KNY-19B, KNY-19G) selected for detailed analysis, including organic matter content, magnetic susceptibility, selected elemental analysis and particle size.
Results and DiscussionNotwithstanding the challenges of dating estuarine sediments due to the possibility of erosion and resuspension, combined modelling of 210Pb and 14C ages is successfully deployed to develop an age-depth relationship for each core, providing a chronological framework for late Holocene environmental changes. Sedimentary characteristics of the three cores, taken in contrasting estuarine conditions, yield insights as to how different parts of the estuary responded to changes in sea level and anthropogenic activities in and around the Knysna basin, as well as in the wider catchment.

引言
河口是高度脆弱的生态系统，且日益受到多种环境、气候及人为胁迫因子的干扰。位于南非南海岸的克尼斯纳（Knysna）河口与泻湖复合体，被视为兼具重要生态与经济价值的区域，却面临着多重区域影响：既来自持续的城市化进程与土地利用变化，也受到海平面上升、气候变化这类全球性重大威胁的冲击。尽管目前学界已针对该河口的现代生态过程开展了较为充分的研究，但对于该系统在更长时间尺度上的环境响应机制却鲜有研究，其中尤以欧洲殖民活动及其后续的人口增长与经济发展所带来的影响为甚。
研究方法
为弥补这一研究短板，研究团队从该河口内多个典型生境及受海洋影响的区域采集了一系列浅沉积物岩芯（岩芯深度小于1米），并选取其中3个岩芯（编号分别为KNY-19A、KNY-19B、KNY-19G）开展详细分析，分析指标包括有机质含量、磁化率、目标元素分析以及粒度组成。
结果与讨论
尽管河口沉积物定年面临着侵蚀与再悬浮带来的诸多挑战，但研究团队通过结合210Pb与14C测年结果开展综合建模，成功为每根岩芯建立了年代-深度关系，为全新世晚期的环境变化研究提供了可靠的年代学框架。三根岩芯分别采自河口内不同的典型环境条件下，其沉积特征揭示了该河口不同区域对克尼斯纳流域及更广汇水区内的海平面变化与人类活动的响应模式。