Though they may be small, microorganisms are the most abundant form of life in the ocean. Marine microbes are responsible for making of the organic carbon that鈥檚 usable by life. Many marine microbes live near the surface, depending on energy from the sun for photosynthesis.

Yet between the low supply of and high competition for some key nutrients, like nitrogen, in the open ocean, scientists have puzzled over the vast diversity of microbial species found there. Researchers from the 天美影视传媒, in collaboration with researchers from 12 other institutions, show that time of day is key, according to a published Jan. 20 in Nature Ecology & Evolution.

The effort began in 2015, when scientists in the , a program now co-led by UW oceanography professor , looked at microbes in the surface of the North Pacific Subtropical Gyre, the Earth鈥檚 largest stretch of contiguous ocean.

鈥淸We were interested in] understanding how that fluctuation of photosynthesis during the day and the absence thereof at night propagates through the microbial community [in the ocean],鈥� explained co-first author , who did the work as a doctoral student at the UW and is now a postdoctoral researcher at the University of Chicago. 鈥淭hat influences how the ecosystem overall functions, how much carbon is stored, where the carbon moves around, and how organisms might interact with each other.鈥�

By integrating data on the timing of metabolic processes of different microbes in the surface ocean throughout the 24-hour light cycle 鈥� from the transcription of genes for proteins used in metabolism to the synthesis of molecules, like lipids, into the microbes鈥� cells 鈥� the researchers discovered that the coexistence of such diverse microbes may not be dictated by competition, but by the timing of their nitrogen uptake.

With staggered uptake of the essential nutrient nitrogen, 鈥渋nstead of having to compete with the whole field, [microbes] only have to compete with the organisms that share that specific shift with [them]. Perhaps that’s one way that the competition is slightly alleviated and can facilitate all of these diverse microbes being able to live off of the same nutrient source,鈥� said co-first author , a doctoral student at Georgia Tech.

Because of the interdisciplinary team present on the 2015 research cruise, data on almost the entire metabolic process was collected simultaneously from the same water every four hours, giving researchers an unprecedented look at how metabolic activity differs among these microbes throughout the 24-hour cycle.

鈥淐ollecting all these different sample types 鈥� at the same time is really a first way to look at the whole ecosystem all at once from all these different perspectives,鈥� , a co-first author and research scientist at the Gloucester Marine Genomics Institute.

The data revealed that most of the activity occurred at four time points: dusk (6 p.m.), night (2 a.m.), morning (6 a.m.) and afternoon (between 10 a.m. and 2 p.m.). While these times were important for many types of microbes, different groups鈥� activities at each time weren鈥檛 uniform.

鈥淩ealizing that various types of microbes acquire nitrogen at different times of day helps to answer a long-standing question in oceanography: How can there be such an incredible diversity of life, all essentially in the same place at the same time?鈥� said co-author , a UW professor of oceanography. 鈥淏eing able to explain the underlying reasons for this diversity will help oceanographers better predict how these communities may shift as the ocean changes.鈥�

, a UW research scientist in oceanography, is also a co-author. The research was supported by grants from the Simons Foundation, the National Science Foundation, Woods Hole Oceanographic Institution and the U.S. Geological Survey.

A full list of authors is available with the .

For more information, contact Boysen at aboysen@uchicago.edu or Ingalls at aingalls@uw.edu.

This post was adapted from a by Georgia Tech.

An increasingly popular method to deduce historic sea surface temperatures uses sediment-entombed bodies of marine archaea, one of Earth’s most ancient and resilient creatures, as a 150-million-year record of ocean temperatures. While other measures have gaps, this one is increasingly popular because it promises to fill in gaps to provide a near-global record of ocean temperatures going back to the age of the dinosaurs.

But 天美影视传媒 research shows this measure has a major hitch: The single-celled organism’s growth varies based on changes in ocean oxygen levels. Results published in August in the show that oxygen deprivation can alter the temperature calculations by as much as 21 degrees Celsius.

“It turned out that oxygen has a huge, dramatic effect,” said corresponding author , a UW associate professor of oceanography. “It’s a big problem.”

Recent research shows these archaea, which draw energy from mere whiffs of ammonia, make up about 20 percent of microbial life in the oceans. Their bodies are plentiful in the ocean floor.

A method uses fats in the archaea’s cell membrane to measure past ocean temperatures, including during a about 56 million years ago that is one of the best historical analogs for present-day climate change, and a of up to 11 degrees Celsius during a period of low ocean oxygen about 100 million years ago, when other records are scarce.

Climate scientists found they could measure ocean temperature by looking at the change in the index, a temperature proxy named for the 86-carbon lipids in the cell membrane, which often tracks the surrounding water temperature.

The method seemed to work better in some samples than others, prompting Ingalls and her co-authors to wonder about its physiological basis. The newly published experiments tested that relationship and found an unexpectedly strong response to low oxygen.

“Changing the oxygen gives us as much as 21 degree Celsius shift in the reading,” said first author , a UW doctoral student in civil and environmental engineering. “That’s solid evidence that it’s not just a temperature index.”

This means the TEX-86 measurements are inaccurate in parts of the ocean that may have experienced oxygen changes at the same time 鈥� for example, in low-oxygen zones or during major extinction events. This is exactly when the archaea are a popular index since other life forms, whose shells can provide a chemical signature for their growth temperatures, are absent.

It’s not known exactly why the archaea shift their lipid membranes. They may adapt to a temperature change by making their membrane tighter or less brittle in the new environment, Ingalls said. Low oxygen is another big environmental stressor.

“The envelope that encloses the cell is sort of the gatekeeper, and when stress is encountered of any kind, that membrane needs to adjust,” Ingalls said.

The new study is the first to actually look at how these archaea grow in different temperatures. These archaea are famously hardy 鈥� it’s the same group that lives in Yellowstone hot springs 鈥� but they have stymied attempts to grow them in captivity.

Qin was first author of a that was the first to grow and compare individual strains of the marine Thaumarchaeota archaea under different conditions. He used samples from Puget Sound, a Seattle beach and a tropical-water tank at the Seattle Aquarium to show that related strains occupy a wide range of ecological niches.

In the new paper, he shows that the membrane lipids of different strains can have different temperature dependences. Some of them are a straight line, meaning they would be a good indication of past temperature, but others are not.

He also did experiments in which he changed the oxygen concentration of the air above the culture flasks. Results show that as the oxygen level drops, the TEX-86 measures rise dramatically, with reading spanning 15 to 36 degrees C even though all samples were grown at 26 C.

“This index provides an amazing historical record, but it’s very important how you understand it,” Qin said. “Otherwise it could be misleading.”

Knowing that oxygen affects the membrane structure can help improve interpretation of the TEX-86 record. Researchers can disregard samples from low-oxygen water to improve the accuracy of the technique, which as it is used now has error bars of about 2 degrees C.

“Plus or minus 2 degrees is not very good when you think about the sensitivity of the climate system,” Ingalls said. “This gives us a new way of thinking about the data.”

Next, the UW team hopes to do more experiments to learn how other factors, like nutrient levels and pH, affect these archaea’s metabolisms.

“We think there’s reason to believe that there’s all kinds of things that could affect the membrane lipid composition, not just temperature,” Ingalls said.

The research was funded by the National Science Foundation. Other co-authors are , , and at the UW and at the University of Southern California.

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For more information, contact Ingalls at aingalls@uw.edu or 206-221-6748, Qin at ericqin@uw.edu or 206-543-5454 and Stahl at dastahl@uw.edu or 206-685-8502.

NSF grants: MCB-0604448, MCB-0920741, OCE-1046017, OCE-1029281, OCE-1205232.

“Too often, the most innovative scientists are hampered by funding that binds them to a solid, but conservative research agenda,” said Bruce Alberts, editor-in-chief of Science magazine and a board member of the . The foundation this week $35 million in awards to Armbrust and 15 other scientists to use during the next five years.

“These awards give scientists in marine microbiology the freedom and flexibility to take more risks, forge unusual collaborations and, ultimately, make noteworthy new discoveries,” Alberts said.

Armbrust, who in 2004 received a similar multi-million dollar eight-year award, told , “A lot more freedom comes with this funding. It allows me to take what I refer to as calculated risks in the science and to explore areas that are interesting between disciplines. In my lab I have biologists, oceanographers, mathematicians, computer scientists, engineers 鈥� I’ve been able to bring together a lot of really talented people.”

She and her lab have already developed new instruments. One, for example, counts and identifies microorganisms being collected in a continuous stream while a ship is underway. They also are developing DNA-based technologies.

“We do the equivalent of the human genome project but we do it for entire microbial communities,” she said. Earlier this year, for example, she co-authored a in Science about an advance that allowed researchers to zero in on a single marine microorganism and map its genome even though it made up less than 10 percent of a water sample teeming with millions of other microorganisms.

Armbrust, who joined the UW in 1996, is a professor and director of the School of Oceanography. The marine phytoplankton she studies are single-celled algae and the most abundant photosynthetic organisms in the ocean. Trillions upon trillions of them make up the base of the ocean’s food webs and remove the greenhouse gas carbon dioxide from the atmosphere.

The microbes also generate about half the oxygen humans breathe, leading Armbrust to say, “They are responsible for every other breath you take.”