Phytoplankton community response to nutrients along lake salinity and altitude gradients on the Qinghai-Tibet Plateau

Abstract

Abstract The Qinghai-Tibet Plateau is the highest and largest plateau in the world and is composed of the world’s greatest clustering of plateau lake systems. Given their extreme environmental conditions and simplistic trophic structures, certain phytoplankton species endemic to these lakes are extremely sensitive to changes in nutrients. Understanding the different response of phytoplankton communities to nutrients along different environmental gradients will help us devise appropriate ecological protection measures specific to individual lake conditions. This study investigated characteristics of phytoplankton communities and associated environmental factors in 20 alpine lakes, ranging in altitude from 2500\xa0m to 4500\xa0m. Results showed that salinity was the critical controlling factor in all phytoplankton communities, while also hindering phytoplankton abundance and biomass without changing the dominant species of algae. Results also showed that altitude was an important driving factor for variation in individual phytoplankton size, which was endemically smaller than phytoplankton size in low-altitude lakes. Moreover, the phytoplankton community response to nutrients differed under different salinity gradients. In addition, water nitrogen (N) concentrations can alleviate salinity limitations on dominant phytoplankton species in saline lakes (salinity\xa0>\xa035‰) while aggravating those in saltwater lakes (1‰