In the frigid waters surrounding Antarctica, an unusual seasonal cycle occurs. During winter, from March to October, the sun barely rises. As seawater freezes it rejects salts, creating pockets of extra-salty brine where microbes live in winter. In summer, the sea ice melts under constant daylight, producing warmer, fresher water at the surface.

This remote ecosystem is home to much of the Southern Ocean鈥檚 photosynthetic life. A new 天美影视传媒 study provides the first measurements of how sea-ice algae and other single-celled life adjust to these seasonal rhythms, offering clues to what might happen as this environment shifts under climate change.

The , published Sept. 15 in the International Society for Microbial Ecology鈥檚 ISME Journal, contains some of the first measurements of how sea-ice microbes respond to changing conditions.

鈥淲e know very little about how sea-ice microbes respond to changes in salinity and temperature,鈥� said lead author , a UW postdoctoral researcher who did the work while pursuing her doctorate in oceanography at the UW. 鈥淎nd until now we knew almost nothing about the molecules they produce and use in chemical reactions to stay alive, which are important for supporting higher organisms in the ecosystem as well as for climate impacts, like carbon storage and cloud formation.鈥�

The polar oceans play an important role in global ocean currents and in supporting marine ecosystems. Microbes form the base of the food web, supporting larger life forms.

鈥淧olar oceans make up a significant portion of the world鈥檚 oceans, and these are very productive waters,鈥� said senior author , a UW assistant professor of oceanography. 鈥淭hese waters support big swarms of krill, the whales that come to feed on those krill, and either polar bears or penguins. And the start of that whole ecosystem are these single-celled microscopic algae. We just know so little about them.鈥�

The tiny organisms are also important for the climate, since they quietly perform photosynthesis and soak up carbon from the atmosphere. Polar algae are especially good at producing sulfur-containing molecules that give beaches their distinctive smell and, when lofted into the air in sea spray, promote formation of clouds that can reduce penetration of solar rays.

Antarctic sea ice, though long stable, is at an this year.

In other oceans, satellite instruments can capture dramatic seasonal phytoplankton blooms from space 鈥� but that isn鈥檛 possible for microbes hidden under sea ice. And Antarctic waters are particularly challenging to visit, leaving researchers with almost no measurements in winter.

In late 2018, Dawson and co-author traveled to , a U.S. research station on the West Antarctic Peninsula. They used a small boat to sample seawater and sea ice at the same nearby sites every three days.

Back on shore, the two graduate students performed 10-day experiments in tanks to see which microbes grew as temperature and salinity were adjusted to mimic sea-ice formation and melt. They also shipped samples back to Seattle for more complex measurements of the samples鈥� genetics and metabolites, the small organic molecules produced by the cell.

Results revealed how single-celled algae deal with their fluctuating environments. As temperatures drop, the cells produce cryoprotectants, similar to antifreeze, to prevent their cellular fluid from crystallizing. Many of the most common cryoprotectant molecules were the same across different microbial lifeforms.

As salinity changes, to avoid either bursting in freshening waters or becoming desiccated like raisins in salty conditions, the cells change the concentration of salt-like organic molecules. Many such molecules serve a dual role as cryoprotectants, to balance conditions inside and outside the cell to maintain water balance.

The results show that under short-term temperature and salinity changes, community structure in each sample remained stable while adjusting the production of protective molecules. Different microbe species showed consistent responses to changing conditions. This should simplify modeling future responses to climate change, Young said.

Results also hint that the production of omega-3 fatty acids may decline in lower-salinity environments. This would be bad news for consumers of krill oil supplements, and for the marine ecosystem that relies on those algae-derived nutrients. Future research now underway by the UW group aims to confirm that result 鈥� especially with the prospect of increasing freshwater input from melting sea ice and glaciers.

鈥淲e鈥檙e interested in how these sea-ice algae contend with changes in temperature, salinity and light under normal conditions,鈥� Dawson said. 鈥淏ut then we also have climate change, which is completely remodeling the landscape in terms of when sea ice is forming, how much sea ice forms, how long it stays before it melts, as well as the quantity of freshwater input from glaciers. So we’re both trying to capture what’s happening now, and also asking how that can inform what might happen in the future.鈥�

The study was funded by the National Science Foundation, the Simons Foundation, and the Alfred P. Sloan Foundation. Other co-authors are Anitra Ingalls, Jody Deming, Joshua Sacks and Laura Carlson at the UW; Natalia Erazo, Elizabeth Connors and Jeff Bowman at Scripps Institution of Oceanography; and Veronica Mierzejewski at Arizona State University.

For more information, contact Dawson at hmdawson@uw.edu or Young at youngjn@uw.edu.

Two faculty members at the 天美影视传媒 have been awarded early-career fellowships from the Alfred P. Sloan Foundation. The new Sloan Fellows, announced Feb. 16, are聽, an assistant professor in the Department of Chemistry and , an assistant professor in the School of Oceanography.

Open to scholars in eight scientific and technical fields 鈥� chemistry, computer science, economics, mathematics, molecular biology, neuroscience, ocean sciences and physics 鈥� the fellowships honor those early-career researchers whose achievements mark them among the next generation of scientific leaders.

The 128 Sloan Fellows for 2021 were selected in coordination with the research community. Candidates are nominated by their peers, and fellows are selected by independent panels of senior scholars based on each candidate鈥檚 research accomplishments, creativity and potential to become a leader in their field. Each fellow will receive $75,000 to apply toward research endeavors.

This year鈥檚 fellows come from 58 institutions across the United States and Canada, spanning fields from evolutionary biology to data science.

Theberge is an assistant professor of chemistry. Her research probes the chemical signals that cells use to communicate with one another. The organization of our bodies, with different types of cells taking on discrete functions, depends on this biochemical language.

鈥淲e鈥檙e alive because our cells can exchange chemical messages in appropriate ways,鈥� said Theberge, who is also an adjunct assistant professor of urology at the UW. 鈥淎ll cells 鈥� human cells, microbes 鈥� utilize chemical signals to deliver information and influence the properties of other cells.鈥�

Young聽is an assistant professor in the School of Oceanography. She studies microbial oceanography, with a focus on the role of marine algae in the carbon cycle. In particular, her research explores polar ecosystems and other extreme environments, and the biochemistry of photosynthesis. Her聽research聽combines field聽work,聽algal culture manipulations聽and biochemical and molecular analyses to uncover the evolution and adaptations of biological carbon fixation in the oceans.

鈥淗alf of all photosynthesis happens in the oceans, across an amazingly diverse collection of organisms,鈥� Young said. 鈥淢y group鈥檚 research focuses on understanding the underlying physiological and molecular adaptations of marine photosynthesis. Understanding how marine algae have and will adapt to a changing climate聽reveals insights into how life on Earth evolved and will respond in the future.鈥�

For more information, contact Theberge at聽abt1@uw.edu and Young at youngjn@uw.edu.