Graduate student wins presentation award

Joselynn Wallace, a second year Ph.D student in Dr. Bethany Jenkins’ lab, was given  a student presentation award in February at a gathering of the American Society of Limnology and Oceanography.

Her presentation was in the top 3 percent, said Jenkins who noted that the College of the Environment and Life Sciences provided Wallace with travel support to attend the conference in New Orleans.

Joselynn Wallace
Joselynn Wallace

The title of her presentation will be listed in the society’s next newsletter.

Wallace’s research is on diatoms, a type of marine phytoplankton that have a big role in the biogeochemical nutrient cycling and primary production.

Diatoms are the source of 90 percent of photosynthetically fixed carbon in coastal ecosystems and are an important food source for marine life, says Wallace. “Their role at the base of the marine food web is correlated with their growth rates—if they aren’t growing very well they won’t be very good at cycling nutrients or providing fixed carbon from carbon dioxide.”

Diatoms have silicified cells walls, like “glass shells,” she explains, and have an obligate silicon requirement for growth. The “glass shells” are called frustules. The availability of silicon can be a limiting nutrient for diatoms that constrains their ability to grow and utilize inorganic carbon dissolved in the ocean, she added.

Wallace is studying Thalassiosira diatoms, a group that is found throughout the global ocean, from polar to subtropical environments.  Her research has focused on one species in particular, Thalassiosira oceanica.  As the name might suggest, this diatom was isolated from the open ocean.  It has been hypothesized that in large parts of the ocean, diatom growth and carbon fixation are limited by the availability of iron and/or silicon.

In order to validate these hypotheses, she is using global gene expression profiling to characterize the silicon and iron stress responses of Thalassiosira oceanica.  This information will reveal genetic markers of iron or silicon stress that can be used to assess the physiological status of diatoms in the field. Getting a better handle on the environmental variables that constrain diatoms’ ability to grow and fix inorganic carbon will be increasingly important as anthropogenic (from human activity) CO2 emissions increase.