Long-term adjustment of phytoplankton structure to environmental traits at timescales during lifetime development and over generations

Abstract

Long-term ecological research of deep Lake Mondsee covers over more than six decades of phytoplankton observation. According to our study, phytoplankton groups of various phenological traits are suitable to address the impact of two major environmental stressors: nutrient surplus by eutrophication from 1968 to 1998 and warming by climate change. Here, we focus on phytoplankton biovolume, phytoplankton assemblage structure, net changes rates, and phytoplankton biodiversity. Biweekly net change-dependent persistence of phytoplankton assemblages followed a dome-shaped relationship of observations. A short-term persistence of taxonomic traits along weeks is predominant and contributes to the structural stabilization of phytoplankton assemblages. This short-term persistence is interpreted by the benefit of lifetime adjustment of phytoplankton organisms. The long-term development phytoplankton structure is discussed as an alignment of organisms over generations. Single key taxa, as Planktothrix rubescens (De Candolle ex Gomont) Anagnostidis &Komárek 1988, which are omnipotent players in phytoplankton assemblages and occur during different environmental scenarios in the long-term, are most suitable for long-term ecological research. Our findings interpret that phytoplankton taxa are excellent organisms to track the impact of environmental constraints due to their short generation time (1), their lifetime adjustment (2), and the re-occurrence in the long-term over generations (3).