Aix Marseille Univ, Univ Avignon, CNRS, IRD, IMBE, Marseille, France.
Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France.
Sci Total Environ. 2019 Jul 15;674:114-127. doi: 10.1016/j.scitotenv.2019.04.117. Epub 2019 Apr 11.
High mountain lakes are a network of sentinels, sensitive to any events occurring within their waterbodies, their surrounding catchment and their airshed. In this paper, we investigate how catchments impact the taxonomic and functional composition of phytoplankton communities in high mountain lakes, and how this impact varies according to the atmospheric nutrient deposition regime. For two years, we sampled the post snow-melt and the late summer phytoplankton, with a set of biotic and abiotic parameters, in six French alpine lakes with differing catchments (size and vegetation cover) and contrasting nitrogen (N) and phosphorus (P) deposition regimes. Whatever the nutrient deposition regime, we found that the lakes with the smallest rocky catchments showed the lowest functional richness of phytoplankton communities. The lakes with larger vegetated catchments were characterized by the coexistence of phytoplankton taxa with more diverse strategies in the acquisition and utilization of nutrient resources. The nutrient deposition regime appeared to interact with catchment characteristics in determining which functional groups ultimately developed in lakes. Photoautotroph taxa dominated the phytoplankton assemblages under high NP deposition regime while mixotroph taxa were even more favored in lakes with large vegetated catchments under low NP deposition regime. Phytoplankton functional changes were likely related to the leaching of terrestrial organic matter from catchments evidenced by analyses of carbon (δC) and nitrogen (δN) stable isotope ratios in seston and zooplankton. Plankton δN values indicated greater water-soil interaction in lakes with larger vegetated catchments, while δC values indicated the effective mineralization of the organic matter in lakes. The role played by catchments should be considered when seeking to determine the vulnerability of high altitude lakes to future changes, as catchments' own properties will vary under changes related to climate and airborne contaminants.
高山湖泊是一个网络的哨兵，对水体、周围集水区和空气流域内发生的任何事件都很敏感。在本文中，我们研究了集水区如何影响高山湖泊浮游植物群落的分类和功能组成，以及这种影响如何因大气养分沉积模式而异。在两年的时间里，我们在六个法国高山湖泊中采集了融雪后和夏末的浮游植物样本，这些湖泊的集水区（大小和植被覆盖）和氮（N）磷（P）沉积模式不同，采集了一系列生物和非生物参数。无论养分沉积模式如何，我们发现集水区岩石面积最小的湖泊表现出最低的浮游植物群落功能丰富度。集水区植被面积较大的湖泊的特征是，在获取和利用养分资源方面具有更多不同策略的浮游植物类群共存。养分沉积模式似乎与集水区特征相互作用，决定了哪些功能群最终在湖泊中发育。在高 NP 沉积模式下，光自养生物类群主导浮游植物组合，而在低 NP 沉积模式下，在植被面积较大的湖泊中，混合营养生物类群甚至更为有利。浮游植物功能变化可能与集水区中陆地有机质的淋溶有关，这一点可以通过对 seston 和浮游动物中碳（δC）和氮（δN）稳定同位素比值的分析得到证明。浮游动物 δN 值表明，集水区植被面积较大的湖泊中，水-土相互作用更强，而 δC 值表明，湖泊中有机质的有效矿化作用。在寻求确定高海拔湖泊对未来变化的脆弱性时，应该考虑集水区的作用，因为集水区自身的特性将因与气候和空气污染物有关的变化而发生变化。
