SFS Annual Meeting

6/04/2024  |   15:30 - 15:45   |  Salon 10

IRON UPTAKE LEADS TO DIVERGENT RESPONSES IN NITROGEN FIXING MICROORGANISMS IN THE OLIGOTROPHIC OCEAN

Abiel Kidane (Primary Presenter/Author), , akidane@mpi-bremen.de;

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6/04/2024  |   15:45 - 16:00   |  Salon 10

NITROGEN FIXATION IN SHALLOW LAGOONS: RATES, PALYERS AND IMPORTANCE IN NITROGEN CYCLING

Mindaugas Zilius (Primary Presenter/Author), , mindaugas.zilius@jmtc.ku.lt;

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6/04/2024  |   16:00 - 16:15   |  Salon 10

PHOSPHORUS AND IRON AMENDMENTS AFFECT MULTIPLE NITROGEN CYCLING PROCESSES Nitrogen (N) is a limiting factor in many ecosystems, as a result, microbes have developed methods to acquire and recycle N. However, these processes require investment and thus can be limited by resources like phosphorus (P) and iron (Fe). We performed a stream-side mesocosm experiment, drawing water from a reference stream (East Branch Chagrin River, Kirtland, Ohio) to examine the influence of P and Fe on N cycling processes. 32 flow-through mesocosms were dosed with nutrient combinations of NO3- (250 µg/L), PO43- (30 µg/L), and Fe3+ (100 µg/L) in a fully factorial design. These mesocosms received amendments for 23 days, after which we collected biofilm and sediment to measure N fixation and denitrification rates (acetylene reduction and block, respectively), NH4+ uptake and regeneration (15-N labeled ammonium), and aminopeptidase activity. Preliminary results show that there were no significant differences between treatments for N fixation (ANOVA, p-value=0.232). Meanwhile, the rates of both NH4 regeneration and uptake were highest for mesocosms that received a combination of P and Fe and lowest among N treatments. These higher rates of regeneration in treatments with Fe suggest that Fe is increasing heterotrophic production and the activity of proteins responsible for recycling of NH4. These results suggest that Fe and P may play a role in alleviating N limitation primary through stimulation of internal recycling rather than increased N fixation.

Renn Schipper (Primary Presenter/Author), Kent State University, rschipp1@kent.edu;

Olufemi Akinnifesi (Co-Presenter/Co-Author), Kent State University, oakinnif@kent.edu;

Talia Pope (Co-Presenter/Co-Author), Kent State University, tpope8@kent.edu;

David Costello (Co-Presenter/Co-Author), Kent State University, dcostel3@kent.edu;

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6/04/2024  |   16:15 - 16:30   |  Salon 10

Mathematically modeling stoichiometric drivers of heterotrophic N2 fixation The major source of nitrogen (N) to the biosphere is biological N2 fixation–the microbially-mediated reduction of abundant but inert N2 gas to an assimilable form. While photosynthetic “N2-fixers” (diazotrophs) have been well-characterized, organoheterotrophic diazotrophs remain understudied despite their likely significance in satiating community N demand on local to global scales. Importantly, while fixed N availability is a strong driver of N2 fixation in photoautotrophs, recent work suggests that heterotrophic diazotrophs are less sensitive to ambient fixed N concentrations, particularly in organic-rich environments. Here, we introduce a mathematical model to predict the behavior of free-living heterotrophic diazotrophs across the aquatic continuum, coupling Monod- and Droop-type functions to predict elemental fluxes with a Gibbs Energy Dissipation model to calculate growth yields from first principles. We will present simulations from the model exploring population steady state conditions under variable chemical (N, C, O) environments and/or physiological traits.

Rebecca Everett (Primary Presenter/Author), Haverford College, reverett@haverford.edu;

Corday Selden (Co-Presenter/Co-Author), Rutgers University, crselden@marine.rutgers.edu;

Mohamed Hatha Abdulla (Co-Presenter/Co-Author), Cochin University of Science and Technology, mohamedhatha@gmail.com;

Jabir Thajudeen (Co-Presenter/Co-Author), Cochin University of Science and Technology, jabir.t@cusat.ac.in;

James Powell (Co-Presenter/Co-Author), The University of the Virgin Islands, james.powell@students.uvi.edu;

Edwin Cruz-Rivera (Co-Presenter/Co-Author), Morgan State University, edwin.cruz-rivera@morgan.edu;

Luca Schenone (Co-Presenter/Co-Author), Universidad Nacional del Comahue, lucaschenone@comahue-conicet.gob.ar;

Renn Schipper (Co-Presenter/Co-Author), Kent State University, rschipp1@kent.edu;

Megan Berberich (Co-Presenter/Co-Author), Michigan Technological University, meberer@mtu.edu;

Halvor Halvorson (Co-Presenter/Co-Author), University of Central Arkansas, hhalvorson@uca.edu;

Robinson Fulweiler (Co-Presenter/Co-Author), Boston University, rwf@bu.edu;

Amy Marcarelli (Co-Presenter/Co-Author), Michigan Technological University, ammarcar@mtu.edu;

Thad Scott (Co-Presenter/Co-Author), Baylor University, Thad_Scott@baylor.edu ;

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6/04/2024  |   16:30 - 16:45   |  Salon 10

Understanding Nitrogen Fixation in Phototrophic Diazotrophs: Insights from a Stoichiometric mode

Angela Peace (Primary Presenter/Author), Texas Tech University, a.peace@ttu.edu;

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6/04/2024  |   16:45 - 17:00   |  Salon 10

RAISING THE CURTAIN ON THE ECOLOGY AND BIOGEOCHEMICAL SIGNIFICANCE OF CHEMOTROPHIC NITROGEN FIXATION

James Cotner (Primary Presenter/Author), , cotne002@umn.edu;

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