ABSTRACT

As essential parts of the unique ecosystem of Tibetan Plateau (TP), the sizes and associated physical properties of alpine lakes have long been investigated. However, little is known about one of the most critical biogeochemical properties, i.e. the Chlorophyll-a (Chl-a) concentrations. Here, for the first time, we presented a comprehensive investigation of the temporal–spatial variations in Chl-a in 82 lakes (>50 km²) across the entire TP region, based on MODIS observations in the period of 2003–2017. The results showed that the 82 lakes exhibited an average long-term mean Chl-a of 3.3 ± 4.3 mg m⁻³, with high Chl-a lakes concentrated in the eastern and southern inner TP basin and northeastern parts of the TP. An interannual trend analysis revealed that lakes exhibiting (significantly) decreasing Chl-a trends and (significantly) increasing Chl-a trends were comparable in numbers but differed in distribution patterns. A correlation analysis indicated that at least 70% of the interannual variability in Chl-a values of lakes was significantly correlated with one of the four environmental factors (wind speed, ice cover duration, lake water surface temperature and surface runoff) and lake size. In addition, glacier meltwater tended to reduce lake Chl-a while salinity levels showed minor influences.

摘要

作为青藏高原（TP）独特生态系统的重要组成部分，长期以来人们一直在研究高山湖泊的大小和相关的物理特性。然而，人们对最关键的生物地球化学性质之一，即叶绿素a（Chl a）的浓度知之甚少。在此，我们首次基于MODIS在2003-2017年期间的观测结果，对整个TP地区82个湖泊（> 50 km ²）中Chl-a的时空变化进行了全面调查。结果表明，这82个湖泊的长期平均Chl-a平均为3.3±4.3 mg m ^-3。，高Chl-a湖泊集中在TP内部的南部和东部盆地和TP的东北部分。年度趋势分析表明，表现出（显着）下降的Chl-a趋势和（显着）上升的Chl-a趋势的湖泊在数量上具有可比性，但是在分布方式上却有所不同。相关分析表明，湖泊Chl-a值的年际变化中至少有70％与四个环境因素（风速，冰盖持续时间，湖泊水面温度和地表径流）和湖泊大小之一显着相关。此外，冰川融水倾向于减少Chl-a湖，而盐度水平显示出较小的影响。