Deciphering the Mechanisms Behind Climate-Driven Changes in the Relative Abundances of the Diatom Cyclotella
In many lakes across arctic, alpine, boreal and temperate regions of the Northern Hemisphere, paleolimnological records have revealed that the relative abundances of the centric diatom Cyclotella sensu lato taxa have changed over the past century. Cyclotella sensu lato taxa are a key group of diatom...
| Main Author: | |
|---|---|
| Format: | Text |
| Language: | unknown |
| Published: |
DigitalCommons@UMaine
2016
|
| Subjects: | |
| Online Access: | https://digitalcommons.library.umaine.edu/etd/2545 https://digitalcommons.library.umaine.edu/context/etd/article/3602/viewcontent/Malik__Heera_Dissertation.pdf |
| Summary: | In many lakes across arctic, alpine, boreal and temperate regions of the Northern Hemisphere, paleolimnological records have revealed that the relative abundances of the centric diatom Cyclotella sensu lato taxa have changed over the past century. Cyclotella sensu lato taxa are a key group of diatoms that are very sensitive to environmental change and may serve as early indicators of ecosystem effects of global change. Yet patterns of change in Cyclotella species are not synchronous across, or even within, regions, raising the question of mechanisms behind these widespread changes in diatom community structure. Changes in Cyclotella taxa have been attributed to an indirect link with temperature-driven changes in lake thermal stratification, specifically in terms of changes in water column stability that lead to altered light penetration and nutrient availability. In the first chapter, I conducted experiments to test the effects of temperature, light, and nutrients on Lindavia intermedia, Lindavia radiosa, Lindavia comensis, Lindavia ocellata and Discostella stelligera. I found that interactive effects of temperature, light, and nutrients affected all the species except L. radiosa. Responses to these factors varied across taxa. For example, when nutrients were provided, L. radiosa was more abundant under high light conditions, whereas L. ocellata was more abundant under low light conditions. I also determined whether different phytoplankton communities (one dominated by diatoms and the other by a mixed assemblage) altered the response of D. stelligera to abiotic factors. High temperature, light and nutrients only increased cell densities of D. stelligera when this species occurred in the diatom- dominated community. In the second chapter, to further understand the mechanisms behind these species changes, I investigated how the nutrient limitation status of a lake alters the responses of three common Cyclotella sensu lato taxa to light. I found that light affected Cyclotella growth rates, cell densities, and ... |
|---|