Shift in plankton diversity and structure: Influence of runoff composition in the Nagqu River on the Qinghai-Tibet Plateau

Understanding the response of runoff composition in the Qinghai-Tibet Plateau (QTP) is essential for the ecology and environment. However, precise measurements of runoff composition in the QTP, especially in remote areas with limited climatic records, are a challenge. In rivers and lakes, some plankton is highly sensitive to changes in runoff composition. Here, we demonstrated how plankton indicators could be used as an indicator of runoff composition in the QTP. The stable isotopes of runoff, precipitation, groundwater and snowmelt in 9 sampling sites were studies of the Nagqu River in the QTP. The multi-source mass balance model (IsoSource model) was used to calculate the range of runoff composition at each sampling site. We found that the change of plankton biodiversity was associated to the runoff composition, and groundwater ratio was negatively correlated with biodiversity, while precipitation ratio was positively correlated with biodiversity, but not with snowmelt. Therefore, plankton diversity is expected to be a simple indicator of runoff composition, which can be easily quantified in remote plateau areas.