Irina Shilova, Second Genome

Moss Landing Marine Labs Seminar Series - October 25th, 2018

Hosted by the Chemical Oceanography Lab

MLML Seminar Room, 4pm

(or Watch it Live here!)

Open to the public

Irina Shilova is a Microbial Ecologist and Bioinformatician with advanced education in Molecular Biology and Microbiology and extensive experience in the field, lab and meta‘omics data analysis. She has developed and implemented novel molecular tools and informatics approaches to study responses of microbial communities to environmental stimuli. Irina is dedicated to mentoring and science outreach and passionate about the microbial world and striving towards constant improvement and learning.

Differential effects of nitrate, ammonium and urea as N sources for microbial communities in the North Pacific Ocean

Nitrogen has long been known to limit phytoplankton growth and productivity in large regions of the oceans. Likewise, the form and supply of N are important controls on microbial community composition, activity and ultimately ecosystem function. However, the effect of different chemical nitrogen species on complex natural phytoplankton communities in the open ocean is not well-known. We investigated the effect of nitrate, ammonium, and urea on microbial and phytoplankton community composition (cell abundances and 16S rRNA gene profiling) and functioning (photosynthetic activity, carbon fixation rates) in the transitional zone of California Current system and oligotrophic waters of the North Pacific Ocean. All nitrogen substrates tested significantly stimulated phytoplankton growth and productivity. Urea resulted in the greatest (>300%) increases in chlorophyll a and productivity at two experimental stations, largely due to increased abundances of Prochlorococcus. Two abundant clades of Prochlorococcus, High Light I and II, demonstrated similar responses to urea, suggesting this substrate is likely an important N source for natural Prochlorococcus populations. The timing and magnitude of response to nutrient amendments varied with geographic location due to the differences in phytoplankton community composition and nutrient status among and within these communities. Finally, both the oligotyping approach applied for 16S rRNA gene sequences and the gene-targeted transcription (microarray) approach showed that sub-populations of Prochlorococcus and Synechococcus had different responses to nitrogen sources. Our results provide support for the hypothesis that changes in nitrogen supply would likely favor specific populations of phytoplankton in different oceanic regions and thus, affect both biogeochemical cycles and ecological processes.