Impact of Climate Change Variables on Nutrient Cycling by Marine Microorganisms in the Southern California Bight and Ross Sea, Antarctica

• Main Author: Spackeen, Jenna Lee
• Format: Text
• Language: English
• Published: W&M ScholarWorks 2017
• Subjects: Biogeochemistry; Oceanography; Ross Sea; Antarc*; Antarctica
• Online Access: https://scholarworks.wm.edu/etd/1516639564; https://doi.org/10.21220/V5JB15; https://scholarworks.wm.edu/context/etd/article/1190/viewcontent/Spackeen_vims_0261D_10022.pdf

Ocean environments are being impacted by climate warming, elevated carbon dioxide (CO2) levels, and shifting nutrient sources and sinks. It is essential to quantify the sensitivity of microorganisms to these effects of global change because they form the base of the marine food web and are an integral component of nutrient cycling on the planet. their role in photosynthesis, nutrient uptake, and transfer of organic matter into higher trophic levels or to the deep ocean via the biological pump render microorganisms key in ecosystem structure and function and in regulating the global climate. The goal of this dissertation research was to determine how changing environmental conditions impact microbial communities and the rates at which they take up nutrients. Research for this dissertation took place in the Southern California Bight and in the Ross Sea, Antarctica, where fully factorial designs were used to investigate the response of microorganisms to multiple global change parameters. Nutrient uptake rates were measured using 13C and 15N stable isotopes for carbon and nitrogen substrates and 33P radioisotopes for phosphorus substrates. In the Southern California Bight, a microbial assemblage was collected and incubated in an ‘ecostat’ continuous culture system, where elevated temperature, CO2, and the dominant nitrogen substrate (nitrate or urea) in the diluent were manipulated. During this experiment uptake rates of dissolved inorganic carbon (DIC), nitrate (NO3-), and urea were determined for two microbial size classes (0.7-5.0 μm and >5.0 μm). Urea uptake rates were greater than NO3-, and uptake rates of urea and DIC for both size fractions increased at elevated temperature, while uptake rates of NO3- by smaller microorganisms increased when CO2 levels were high. In the Ross Sea, the impact of elevated temperature, CO2, and iron addition on DIC and NO3- uptake rates by two size classes (0.7-5.0 μm and >5.0 μm) of a late-season microbial community were investigated using a semi-continuous and continuous ...