Phytoplankton assemblage shifts with dissolved organic matter properties: a functional perspective for sentinel lakes

1. Climate change is altering both dissolved organic matter (DOM) properties and phytoplankton dynamics in lakes. High-altitude lakes are good sentinels of global change. However, their value as sentinels depends on how well we understand their functioning. This study analyzed physical, chemical, and biological data during three pre-defined periods running from complete ice-cover right to the end of the ice-free season, in a high-altitude oligotrophic lake. A functional approach was used to assess how relationships between DOM and the planktonic community vary over time.
2. Phytoplankton functional change was found to occur with shifts in dissolved organic matter. During the ice-influenced period, from February to the end of the thaw, the phytoplankton community was dominated by small autotrophs and mixotrophic flagellates and DOM from sediment and terrestrial origin dominated the DOM pool of the lake. Phytoplankton diversity and richness increased during the post-snowmelt overturn peri...