Fossil Diatoms Reveal Natural and Anthropogenic History of Jackson Lake (Wyoming, USA)
Fossil Diatoms Reveal Natural and Anthropogenic History of Jackson Lake (Wyoming, USA)
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DOI：
10.3389/esss.2023.10065
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发表时间：
2023-02
期刊：
影响因子：
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通讯作者：
John Dilworth;J. Stone;K. Yeager;J. Thigpen;M. McGlue
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作者：
John Dilworth;J. Stone;K. Yeager;J. Thigpen;M. McGlue
杰克逊湖为怀俄明州和爱达荷州(美国西部)的上游蛇河流域提供有价值的文化和供应生态系统服务。20世纪初建造的杰克逊湖大坝使湖面上升了∼12米，产生了支持农业和牧场以及与大提顿国家公园相关的旅游业的重要水资源。排水口工程极大地改变了杰克逊湖的表面积、形态以及与流入的蛇河的关系，但对湖中营养动态和藻类的影响尚不清楚。在这里，我们报告了用古湖沼学方法对杰克逊湖进行的回溯性环境评估的结果。古生态(硅藻)和地球化学数据集是在一个测年良好的沉积岩芯上开发的，并与该区域现有的水文气候数据进行了比较，以评估湖泊变化的模式。核心跨越了小冰河时代的结束，并延伸到了今天(∼1654-2019年CE)。在安装大坝之前，硅藻群落的特点是浮游生物的相对丰度很高，在营养物质可获得性较低的情况下茁壮成长，很可能是由于季节性冰盖延长和可能只有一次短暂的深对流混合造成的。随着大坝的修建，硅藻群落转向了浮游物种，这些物种倾向于营养更丰富的水域。沉积物中氮和磷元素的丰度支持了∼1916CE之后杰克逊湖在建造大坝后处于更富营养状态的解释。这些数据与与大坝建设相关的营养负荷增加是一致的，大坝淹没了三角洲湿地和近岸植被，可能还增加了水中停留的时间。这项研究的结果突出了藻类组成和生产力对人类对天然湖泊排水口工程中营养状态变化的敏感性，并对水资源管理具有意义。
Jackson Lake supplies valuable cultural and provisioning ecosystem services to the Upper Snake River watershed in Wyoming and Idaho (western USA). Construction of Jackson Lake Dam in the early 20th century raised lake level by ∼12 m, generating an important water resource supporting agriculture and ranching, as well as tourism associated with Grand Teton National Park. Outlet engineering drastically altered Jackson Lake’s surface area, morphology, and relationship with the inflowing Snake River, yet the consequences for nutrient dynamics and algae in the lake are unknown. Here, we report the results of a retrospective environmental assessment completed for Jackson Lake using a paleolimnological approach. Paleoecological (diatoms) and geochemical datasets were developed on a well-dated sediment core and compared with available hydroclimate data from the region, to assess patterns of limnological change. The core spans the termination of the Little Ice Age and extends to the present day (∼1654–2019 CE). Diatom assemblages prior to dam installation are characterized by high relative abundances of plankton that thrive under low nutrient availability, most likely resulting from prolonged seasonal ice cover and perhaps a single, short episode of deep convective mixing. Following dam construction, diatom assemblages shifted to planktic species that favor more nutrient-rich waters. Elemental abundances of sedimentary nitrogen and phosphorous support the interpretation that dam installation resulted in a more mesotrophic state in Jackson Lake after ∼1916 CE. The data are consistent with enhanced nutrient loading associated with dam emplacement, which inundated deltaic wetlands and nearshore vegetation, and perhaps increased water residence times. The results of the study highlight the sensitivity of algal composition and productivity to changes in nutrient status that accompany outlet engineering of natural lakes by humans and have implications for water resource management.