Nutrient limitation status of Arctic lakes affects the responses of Cyclotella sensu lato diatom species to light: implications for distribution patterns

摘要

Changing environmental conditions in the Arctic have caused widespread but disparate changes in the relative abundances of diatoms in the Cyclotella sensu lato group since 1850 across Arctic lakes. To better understand the mechanisms behind these species changes, we investigated how the nutrient limitation status of a lake alters the responses of three common Cyclotella sensu lato taxa to light. To assess this, we collected source water with the natural phytoplankton assemblages from lakes in southwest Greenland with different nutrient limitation status (phosphorus (P)-limited or nitrogen & phosphorus (N&P) co-limited). The responses of Lindavia bodanica, Lindavia radiosa, and Discostella stelligera to light levels (low, moderate, or high) and nutrients (limited or replete) were tested using a factorial design. The vertical distributions of these taxa across 20 lakes of varying nutrient limitation status and water transparency were also assessed. We found that light affected Cyclotella growth rates, cell densities, and distribution patterns differently depending on lake nutrient limitation status. L. bodanica fared best at low light under P-limitation, and at high light under N&P co-limitation, while the pattern was generally opposite for D. stelligera. For L. radiosa, regardless of nutrient limitation status, moderate-to-high light was important, with this species absent from lakes with lower light conditions. This study reveals that environmental change affects these species via complex interactions between nutrient and light availability, and helps to clarify some of the complex distribution patterns of planktonic diatom taxa found in lakes of many areas around the Arctic as well as at lower latitudes.