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In partial fulfillment of the requirements for the degree of
Master of Science in Biology
in the
School of Biological Sciences
Shannon Salter
Will defend her thesis
Wednesday, 27, April , 2022
11 AM
https://bluejeans.com/829324769/1440
Thesis Advisor:
Dr. Joseph Montoya
School of Biological Sciences
Georgia Institute of Technology
Committee Members:
Dr. Jennifer Glass
School of Earth and Atmospheric Sciences
Georgia Institute of Technology
Dr. Mark Hay
School of Biological Sciences
Georgia Institute of Technology
Dr. Natalie Loick-Wilde
Leibniz-Institute for Baltic Sea Research
Abstract:
We investigated the biomass concentration and natural abundance of nitrogen and carbon stable isotopes (δ15N and δ13C) of size-fractionated zooplankton collected on two separate cruises to the Amazon River Plume (ARP) region. Mean animal biomass concentrations ranged between 0.106 to 0.811 g/ m3 during the day and 0.242 to 1.90 g/m3 at night for Cruise EN614. The mean animal biomass on Cruise EN640 ranged from 1.541 to 6.874 g/ m3 during the day and 2.505 to 6.291 g/m3 at night. Sampling stations were classified into habitat types identified by Weber et al. (2019) and Pham et al. (in prep): the young plume core (YPC), old plume core (OPC), outer plume margin (OPM), western plume margin (WPM), and oceanic seawater (OSW). In general, zooplankton δ15N varied markedly and significantly among habitats for both cruises, with generally higher values in the YPC, OPC, WPM, and OSW habitats relative to the OPM habitat. Zooplankton δ15N values reflect the sources of nitrogen supporting biological production, and trophic processing within the food web. Suspended particles collected from these habitats showed lower d15N values than the zooplankton, but we did not find a consistent increase in animal δ15N with size. Vertical migration led to diel shifts in zooplankton d15N at the surface, with generally higher d15N values at night than during the day during both cruises. Zooplankton d13C values varied less than their δ15N, with no significant differences among habitats or with animal size.
