You are invited to attend the master's thesis defense of Fanglue Jiao, please see the following information:

Name: Fanglue Jiao
Date: 11/26/2024
Time (EST/EDT): 01:00 pm
Location: IMET MPR
Remote Access: email: mees@umd.edu
Committee Chair: Dr. Feng Chen
Committee Members: Dr. Yantao Li Dr. Elizabeth North

Title: Impact of salinity on morphology, growth, and pigments of Scenedesmus obliquus HTB1 under ambient air and elevated CO 2 (10%) conditions

Abstract: Certain microalgal species tolerate high CO 2 concentrations and proliferate faster with elevated CO 2 than with ambient air. This feature makes them attractive for utilization for carbon sequestration, a tool for mitigating climate change due to increasing atmospheric CO 2 . Scenedesmus species are among these microalgae. Scenedesmus obliquus strain HTB1 is a microalgal strain isolated from the Baltimore Inner Harbor (brackish water) and has shown a faster growth with 10% CO 2 compared to air. However, we do not know how HTB1 grows in different salinity and if the salt response is affected by elevated CO 2 . Two experiments were set up to address these questions. The first experiment tested the impact of salinity gradient (0, 17.5, 20, 22.5, 25, 27.5, and 30 ppt) on HTB1 under ambient air. With increasing salinity, HTB1 cells became smaller, and the cultures changed color from green to brown, yellowish brown, and pale. The pigment analysis shows that HTB1 reduced several pigments (i.e. zeaxanthin, lutein, chlorophyll b) in response to salt stress. However, HTB1 produced higher concentration of canthaxanthin under the salt stress. The growth of HTB1 decreased with increasing salinity and was inhibited when the salinity was greater than 22.5ppt. In the second experiment, we compared the impact of salinity (0, 10, and 20 ppt) on HTB1 under air and 10% CO 2 , respectively. HTB1 cultures showed little color change with increasing salinity under 10% CO 2 . In contrast, the change of culture color from dark green to brown was observed with increasing salinity when HTB1 was grown with air. Interestingly, the growth of HTB1 was less inhibited with salt under 10% CO 2 than air, suggesting that elevated CO 2 mitigates the salt stress of HTB1. Both lutein and canthaxanthin increased with increasing salinity when HTB1 was grown with 10% CO 2 . Our results indicate that increased salinity affects the growth of Scenedesmus obliquus HTB1 more with air than 10% CO 2 . This study provides insight into the impact of salt stress on algal morphology, growth, and pigment composition.