The ocean is a vast ecosystem, the health of which depends on balanced interactions between the chemical composition of the water and the organisms that inhabit it. One major threat to this balance is ocean acidification. Ocean acidification is the result of the rapid increase in atmospheric carbon dioxide (CO₂) in the past 200 years. Carbon dioxide in the atmosphere is absorbed by the ocean, triggering a chemical reaction that lowers the pH of the water, making it acidic. This chemical change in the water may negatively impact vital organisms in this ecosystem. Diatoms, a type of algae, are of particular interest because they form the base of food webs in nutrient-rich coastal systems. These systems support fisheries, which are important to the human food supply. In addition, diatoms play a central role in nutrient and carbon cycling within their ecosystem, and account for 40% of total marine primary production. Despite the importance of diatoms, their response to ocean acidification is not well-understood.

To address this gap in knowledge, Dr. Monica Orellana, a principal scientist at the Institute for Systems Biology and the Polar Science Center at the University of Washington (pictured above on the right), and Dr. Nitin Baliga professor at the Institute for Systems Biology (pictured above on the left), partnered with Dr. Virginia Armbrust, Director of the School of Oceanography at the University of Washington. Together, these researchers and their teams developed experiments to mimic ocean acidification in the laboratory, and observe the DNA transcription response in the model diatom cell, T. pseudonana, to forecast diatoms’ response to projected environmental scenarios for the 21st century.

In a recent article published in Nature Climate Change, the research team reports that the diatom cell responds to increasing CO₂ levels (i.e., increasingly acidic water) by decreasing the products of groups of genes involved in carbon-concentrating mechanisms (CCMs) and photorespiration, which are regulated by the same transcription factor. This response may allow diatoms to save energy when exposed to the increased CO₂ levels predicted for the end of the century. This acclimation process also suggests one may see a shift in the species composition and primary productivity of marine microbial ecosystems at higher CO₂ levels.

As a broader impact of this research, an inquiry-based curriculum module for high school science courses was developed to teach the process of systems science in the context of ocean acidification. This module engages and motivates students to be involved in the learning process and helps develop critical thinking skills necessary to solve a global problem. The students act as interdisciplinary scientists and delegates to investigate how increasing atmospheric carbon is affecting the oceans’ chemistry and biology, as well as integral populations of organisms. The students are trained to think on a systems level to critically assess information, predict effects of high CO₂, and design and conduct collaborative, multivariable experiments to explore the consequences of high CO₂ in seawater. In the concluding activity, the students discuss the system consequences of ocean acidification and they make recommendations for further research, policy-making, and lifestyle changes.