MBBO Ph.D. Dissertation Defense | Pingping Qu

Pingping Qu
Ph.D. Candidate, MBBO Graduate Program (PI: Dr. David Hutchins)

Thermal Acclimation and Adaptation of Key Phytoplankton Groups and Interactions with Other Global Change Variables

Wednesday, May 1, 2019
11 AM
AHF 153 (Torrey Webb Room)

Abstract: Marine phytoplankton play critical roles in global primary productivity, carbon export and biogeochemistry. The relationships between environmental forcing and key phytoplankton groups in marine ecosystems need more attention, especially under global change scenarios. Among many other environmental changes, phytoplankton communities in the euphotic zone are anticipated to be most sensitive to concurrent ocean acidification, warming, more thermal variability and reduced nutrient supplies.

Marine diatoms play critical roles in global primary productivity, carbon export and the food web. Marine diazotrophic cyanobacteria are equally important as a source of new nitrogen through nitrogen fixation. In order to better understand the possible responses of marine diatoms and diazotrophs to a changing ocean environment, my studies focused on the synergistic effects of multiple climate change variables on an important diatom, as well as the responses of two keystone diazotrophs to thermal variability and to long-term selection by warming.

In my first chapter, the physiological responses of the widespread centric diatom Coscinodiscus sp. to interactions between three climate-change variables (elevated CO2, warming, and nitrate availability) were investigated to better understand the interactions of multiple global changes on large, carbon-exporting diatoms. The second one examined how short-term thermal variability affects the growth and physiology of the diazotrophic cyanobacterium Trichodesmium erythraeum GBRTRLI101, as well as the interaction between temperature variation and phosphate availability. The third chapter tested the physiological responses and compared and contrasted acclimation and  adaptation of Trichodesmium erythraeum IMS101 and Crocosphaera WH0005 under long-term experimental selection at different temperatures, exploring possible ecological and biogeochemical implications of ways that these two representative diazotrophic cyanobacteria may cope with future warmer conditions.