Abstract We investigated a Holocene (since ∼10 500 cal yr BP) sediment core from a high-altitude, UV-sensitive tundra lake in northwestern Finnish Lapland to disentangle long-term dynamics in underwater UV exposure, lake-catchment coupling processes, and aquatic community development under changing climate. We analyzed biogeochemical and paleobiological proxies indicative of catchment impact, lake production and water transparency, including inferences of lake-water total organic carbon (TOC), sediment chlorophyll-a and UV-induced cladoceran (Crustacea) melanin (ABSUV), cladoceran communities, and elemental and isotopic fingerprints of sediment organic matter (OM). The results depicted a general climate-mediated ontogeny of early, mid- and late Holocene limnological regimes. The rapid postglacial temperature increase and the regionally early Holocene temperature maximum initiated lacustrine changes with rapid community turnovers, increasing benthic-dominated autochthonous production and high UV exposure due to low input of terrestrial OM (TOC ∼1–2 mg L−1) from the deglaciated catchment. The mid-Holocene regime was characterized by a general stabilization of the catchment and a benthic-dominated aquatic community that became gradually more productive under the warm and dry climate conditions. Superimposed on late Holocene climate cooling and increasing effective moisture, TOC increased to the highest Holocene values (>3 mg L−1), which was associated with abundant aquatic macrophytes and a phytophilous Acroperus harpae dominated cladoceran community around 4500–3000 cal yr BP. Over the past three millennia, TOC declined to low modern values (∼2 mg L−1) and UV-resistant Alonopsis elongata became the dominant taxon indicating a regime of increased underwater UV exposure. ABSUV was consistently higher around ∼1500–1000 cal yr BP after the late Holocene TOC decline, suggesting a photoprotective response to the new UV regime, possibly through a reduction of available UV refugia among aquatic macrophytes. While ABSUV did not show a straightforward relationship with TOC or solar forcing over the Holocene, the cladoceran community shift suggested a clear limno-ecological response to altering TOC and underwater UV regimes.

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亚北极fennoscandia水生生物光学的全新世记录

摘要 我们调查了芬兰拉普兰西北部高海拔、对紫外线敏感的苔原湖的全新世（距今约 10 500 卡年 BP）沉积物芯，以解开水下紫外线照射、湖泊-集水区耦合过程和水生气候变化下的社区发展。我们分析了指示集水区影响、湖泊产量和水透明度的生物地球化学和古生物学指标，包括对湖水总有机碳 (TOC)、沉积物叶绿素-a 和紫外线诱导枝角类动物 (甲壳纲) 黑色素 (ABSUV)、枝角类动物群落、以及沉积物有机质 (OM) 的元素和同位素指纹。结果描述了早期、中期和晚期全新世湖沼学制度的一般气候介导的个体发育。冰后温度的快速升高和区域性早期全新世温度最大值引发了湖相变化，群落快速更新，增加了以底栖生物为主的本土生产和由于陆地 OM（TOC ∼1-2 mg L-1）的低输入而导致的高紫外线暴露。冰川消融的集水区。全新世中期制度的特点是集水区总体稳定，底栖主导的水生群落在温暖干燥的气候条件下逐渐变得更有生产力。叠加在全新世晚期气候变冷和有效水分增加的基础上，TOC 增加到全新世最高值（> 3 mg L-1），这与丰富的水生大型植物和 4500–3000 cal yr BP 左右的植株 Acroperus harpae 主导枝角类群落有关。在过去的三千年里，TOC 下降到较低的现代值（~2 mg L−1），并且抗紫外线的 Alonopsis elongata 成为主要分类群，表明水下紫外线照射增加。在全新世晚期 TOC 下降后，ABSUV 在大约 1500-1000 cal yr BP 持续较高，表明对新紫外线制度的光保护反应，可能是通过减少水生大型植物中可用的紫外线避难所。虽然 ABSUV 与 TOC 或全新世的太阳强迫没有直接关系，但枝角类群落的转变表明对 TOC 和水下紫外线体系的改变有明显的湖沼生态反应。在全新世晚期 TOC 下降后，ABSUV 在大约 1500-1000 cal yr BP 持续较高，表明对新紫外线制度的光保护反应，可能是通过减少水生大型植物中可用的紫外线避难所。虽然 ABSUV 与 TOC 或全新世的太阳强迫没有直接关系，但枝角类群落的转变表明对 TOC 和水下紫外线体系的改变有明显的湖沼生态反应。在全新世晚期 TOC 下降之后，ABSUV 在大约 1500-1000 cal yr BP 持续较高，这表明对新紫外线制度的光保护反应，可能是通过减少水生大型植物中可用的紫外线避难所。虽然 ABSUV 与 TOC 或全新世的太阳强迫没有直接关系，但枝角类群落的转变表明对 TOC 和水下紫外线体系的改变有明显的湖沼生态反应。