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Award Detail

Doing Business As Name:University of California-Santa Barbara
  • Mark A Brzezinski
  • (805) 893-8605
Award Date:06/27/2013
Estimated Total Award Amount: $ 484,536
Funds Obligated to Date: $ 484,536
  • FY 2013=$484,536
Start Date:09/01/2013
End Date:08/31/2018
Transaction Type:Grant
Awarding Agency Code:4900
Funding Agency Code:4900
CFDA Number:47.050
Primary Program Source:040100 NSF RESEARCH & RELATED ACTIVIT
Award Title or Description:Collaborative Research: Linking physiological and molecular aspects of diatom silicification in field populations
Federal Award ID Number:1334387
DUNS ID:094878394
Parent DUNS ID:071549000

Awardee Location

Street:Office of Research
City:Santa Barbara
County:Santa Barbara
Awardee Cong. District:24

Primary Place of Performance

Organization Name:Marine Science Institute
Street:MC 6150, UC Santa Barbara
City:Santa Barbara
County:Santa Barbara
Cong. District:24

Abstract at Time of Award

Diatoms, unicellular, eukaryotic photoautotrophs, are among the most ecologically successful and functionally diverse organisms in the ocean. In addition to contributing one-fifth of total global primary productivity, diatoms are also the largest group of silicifying organisms in the ocean. Thus, diatoms form a critical link between the carbon and silicon (Si) cycles. The goal of this project is to understand the molecular regulation of silicification processes in natural diatom populations to better understand the processes controlling diatom productivity in the sea. Through culture studies and two research cruises, this research will couple classical measurements of silicon uptake and silica production with molecular and biochemical analyses of Silicification-Related Gene (SiRG) and protein expression. The proposed cruise track off the West Coast of the US will target gradients in Si and iron (Fe) concentrations with the following goals: 1) Characterize the expression pattern of SiRGs, 2) Correlate SiRG expression patterns to Si concentrations, silicon uptake kinetics, and silica production rates, 3) Develop a method to normalize uptake kinetics and silica production to SiRG expression levels as a more accurate measure of diatom activity and growth, 4) Characterize the diel periodicity of silica production and SiRG expression. Intellectual Merit: It is estimated that diatoms process 240 Teramoles of biogenic silica each year and that each molecule of silicon is cycled through a diatom 39 times before being exported to the deep ocean. Decades of oceanographic and field research have provided detailed insight into the dynamics of silicon uptake and silica production in natural populations, but a molecular understanding of the factors that influence silicification processes is required for further understanding the regulation of silicon and carbon fluxes in the ocean. Characterizing the genetic potential for silicification will provide new information on the factors that regulate the distribution of diatoms and influence in situ rates of silicon uptake and silica production. This research is expected to provide significant information about the molecular regulation of silicification in natural populations and the physiological basis of Si limitation in the sea. Broader Impacts: This project blends concepts in physiology, molecular biology, and biochemistry with marine ecology and oceanography, providing an opportunity for researchers with diverse interests to interact. This project provides an opportunity for a female researcher to get first-time PI experience and, at the same time, provides excellent hands-on, cross-disciplinary training for undergraduate and graduate students. In addition, underserved and underrepresented undergraduate students will be involved in both lab and field-based research. Research activities will also interface with established outreach programs at both Rutgers and UC Santa Barbara to develop novel methods for translating scientific themes and data sets generated from field work into innovative teaching materials aimed at K-12 educators, K-12 students, and undergraduates. Senior personnel will also work to develop educational units to be distributed online and in professional development workshops.

Project Outcomes Report


This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

The vast majority of photosynthesis in the oceans is conducted by microscopic organisms called phytoplankton.  The phytoplankton contain thousands of individual species.  Within the phytoplankton a group known as the diatoms stands out for literally living in a house of glass that they construct using dissolved silicon in seawater. These opal shells are exquisitely detailed and the beauty of diatoms has been appreciated since the first microscopes were invented. The need for diatoms to build these structures extends beyond mere curiosity.  Unlike other phytoplankton diatoms absolutely must have adequate silicon or their growth ceases.  The importance of this constraint becomes more obvious when placed in context of the amount of photosynthesis done by diatoms. Twenty percent of photosynthesis on planet Earth is done by diatoms and that includes comparison with photosynthesis on land and sea. For every fifth breadth of oxygen to breath you can thank a diatom.

This project sought to understand how the availability of the silicon dissolved in seawater controls the distribution and abundance of diatoms. For decades scientists have been making measurements of how fast diatoms take up silicon from seawater and how those rates relate to factors such as the diatom species present, their biomass, the amount of silicon available and other environmental variables. At the same time the relatively new science of molecular biology has advanced to where molecular methods are being applied to environmental problems. Molecular methods revealed the identity of organisms through DNA sequencing and how gene expression varies with changes in the environment. Biogeochemistry and molecular biology each have their strengths and weaknesses. Biogeochemistry can precisely quantify how fast processes occur in nature but those methods cannot always reveal the underlying biological mechanisms.  Molecular techniques can identify what biochemical pathways are activate but struggle to quantify what patterns of gene expression mean for the rate of physiological processes. In this project we sought to combine biochemistry and molecular biology to play to their complementary strengths to better understand how silicon metabolism controls the abundance, distribution and activity of diatoms in the sea. One challenge for the project is that the biochemical pathways associated with silica biomineralization in diatoms, or any other organisms, is unknown. Thus our project also sought to discover additional biomolecules that are part of the silicification pathway.

We conducted our work during three oceanographic expeditions.  On the first we related measures of silica production rates and Si limitation to the gene expression profile of diatoms. By examining changes in gene expression across gradients in Si stress we identified sets of genes that showed a strong response, two order of magnitude change in expression, with severe Si stress. Examination of these genes will reveal a new set of genes that are candidates for being key to diatom silicificiation. On the second expedition we studied interactions between diatom silicification and the trace nutrient iron.  The reason is prior findings that diatoms that have low iron dramatically increase their demand for silicon relative to nitrogen. This physiological response has implications for diatoms running out of silicon earlier than when iron is plentiful and can drive changes in diatom productivity which feeds back into marine food-web structure. What we discovered for iron-stressed diatoms off California was that despite silicon transporters being upregulated the silicon content of diatoms was unaltered by low iron. Nitrogen use was compromised as indicated by reduced uptake of nitrate and the downregulation of the nitrate assimilation pathway. So this was a case where the increased Si uptake implied by the molecular expression data was not manifest opening a new avenue for exploring the relationship between transporter expression and silicon use. Finally, on our third expedition we examined how diatoms adjust to abundant silicon by shutting off silicon transporters relying on diffusion to acquire silicon and we are examining interactions between light availability and silicon metabolism.

Beyond our discoveries this project is training a new graduate student who will use the data that we collected for their Ph.D. dissertation. The student has a unique opportunity to be cross-trained in both biogeochemistry and molecular biology making them one of the new generation of marine scientists that view the ocean from a multidisciplinary perspective allowing ever more sophisticated insights into how phytoplankton, and in our case diatoms, contribute to processes that sustain the ocean ecosystem to the benefit of humankind.


Last Modified: 11/20/2018
Modified by: Mark A Brzezinski

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