INVESTIGATIONS INTO THE ADAPTIVE POTENTIAL OF SOUTHERN OCEAN PHYTOPLANKTON

• Main Author: Bishop, Ian W.
• Format: Text
• Language: unknown
• Published: DigitalCommons@URI 2023
• Subjects: Antarc*; Antarctic; Southern Ocean
• Online Access: https://digitalcommons.uri.edu/oa_diss/1554; https://digitalcommons.uri.edu/context/oa_diss/article/2587/viewcontent/Bishop_uri_0186A_13185.pdf

Southern Ocean (SO) phytoplankton are foundational to Antarctic marine food webs and global carbon and silica cycling. As polar ocean environments continue to rapidly evolve, it is important to assess the extent to which these communities can successfully respond. Adaptation to novel conditions will be particularly important here, as shifts in biogeography to track temperature preferences are unlikely where communities already inhabit the coldest surface waters in the Southern Hemisphere. This work employs high throughput physiological and genomic methods to better understand how three important attributes, thermal trait diversity, standing genetic diversity, and repetitive genomic elements, assessed at a multiple taxonomic scales (community, population and individual genomes), all help shape the adaptive potential of Southern Ocean phytoplankton. Physiological trait variability is crucial to successful and efficient adaptation to novel environmental conditions. As the SO warms, the degree to which traits related to temperature preference and tolerance vary inter- and intra-specifically will be particularly important. Given how poorly characterized traits such as optimal temperature for growth (Topt), maximum temperature for growth (Tmax) and maximum growth rate (μmax) are for cold-adapted phytoplankton (especially from SO), we applied a high throughput phenotyping method to determine growth rates for 43 SO diatom strains representing seven diverse lineages across eight ecologically relevant temperatures. We found these traits to meaningfully vary both among and within species, and that when applied to estimating species-specific thermal fundamental niches, intraspecific differences in observed Tmax values led to large differences (almost 2-fold greater for some taxa) in tolerable geographic range. Ultimately, standing genetic variation underpins the thermal trait variation observed in Chapter 2. Marine phytoplankton, especially diatoms, are well-documented as being genetically diverse and have exhibited a range ...