Scientists find viruses affect life and death of huge carbon-eating algae bloom

It is often easy to think of humans as the most vital form of life on the planet, but most scientists would agree that honor goes to microbes. These often invisible single- to a few-celled organisms are the basis of the food chain on land and in the oceans.

Recently researchers have been using satellite data to learn more about the life cycles of different types of these tiny life forms, in particular algae species that grow in massive patches in the open ocean and are known to ingest huge amounts of carbon dioxide from the atmosphere.

“These blooms have a planetary influence absorbing CO2,” said Chris Bowler, a molecular biologist at Ecole Normale Supérieure in Paris. “Some of which is returned to the environment, but some is deposited in the ocean sediment in the same way as today’s petroleum reserves.” The big question is, how much goes where?

Progress in answering this has been slow because distinguishing individual aspects of this life from space and then matching satellite data to actual samples taken from the water is nearly impossible. To imagine the challenge faced by researchers, Bowler said, is simply to take into consideration the scale.

“Comparing a micro sample of the water column to data collected from space is no easy task,” he said. “I don’t think I need to emphasize that it’s harder than it even looks.”

Over the last year a team of researchers from Israel, the United States and Portugal have been working together to tackle the feat, hoping to not only look at the life cycle and the rate blooms deal with carbon, but also how much of it is trapped in ocean sediment by the influence of another vital player in microbial life: viruses.

“Viruses completely change the fate of carbon absorbed in the bloom,” said Assaf Vardi, co-author of the team’s study. “Stressed or dying algal cells produce sugar and lipids that causes them to stick together and become far larger and denser, allowing them to sink more efficiently.”

This means the more of the bloom that meets its demise by viral infection, the more algal cells are likely to deposit on the ocean floor. This, if true, could mean viruses essentially make blooms more efficient at both absorbing carbon from the atmosphere and pumping it into the ocean depths.

A test tube 18.6 miles wide

Publishing its results in Current Biology, the team found that a patch in the north Atlantic Ocean converted 24,000 tons of CO2 and that nearly two-thirds of that had been processed in a week as the bloom rapidly grew then collapsed. Researchers found specific viruses were present in many of the dead algae cells, indicating that the virus may have played an important role in speeding the decline of the bloom while also forcing more algal cells to become sediment.

“Our major question was the efficiency of the carbon turnover to the depth ultimately,” Vardi said. “Otherwise, this carbon is really just being recycled into the environment.”

This scientific drama included 17 researchers, eight institutions, three countries and a 30-kilometer (18.6-mile) stretch of algae. Vardi, a marine microbiologist from the Weizmann Institute of Science in Rehovot, Israel; Yoav Lehahn, an oceanographer; and Ilan Koren, a cloud physicist, all from the same institute, formed an unusual bond in their desire to align not only the scale of the microbial data of ocean blooms, but also to discover how viruses could regulate carbon capturing within them.

While working with a team out of Woods Hole Oceanographic Institution in Massachusetts, Vardi joined Lehahn and Koren and hatched the plan to answer their questions by studying a particularly prolific patch of algae roughly 30 kilometers in radius, almost evenly between Iceland and Greenland.

Reaching out to other labs in Portugal, Maine, South Carolina and New Jersey, the researchers took colored ocean satellite imagery of the region and carefully compared it with samples they collected in the field. When the data were put together, the team was able to produce a picture of the complete life cycle of the bloom in addition to a calculation of the carbon turnover.

“It’s really quite unique the way they were able to capture all elements of the bloom’s life, from exponential rise to bust,” Bowler said. “This isn’t something we are often able to do in the marine microbial world.”

Koren agreed, adding the physical odds were certainly not in their favor.

“From space, you don’t know the cause of bloom decline, because usually biology and physics are not well-coupled,” he said. “In this rare case, we were able to bring them together and say what is being seen from the sky equates to what is taking place in the water.”

Bowler said the research could have big implications for further work, particularly if it holds true for other environments and species of bloom.

“If it pans out, this enhances our possibility to interpret data from satellite imagery without getting our feet wet,” he said.

A path to geoengineering?

It also could help drive future projects already in the works, Bowler added.

“We need to know how much CO2 is taken down and at what rate, so we can direct efforts already being explored,” he said, “such as stimulating algal blooms to offset carbon pollution.”

While Bowler said he remains open to the potential of such bloom projects in light of the progress made, stating that they may be less dangerous than other efforts being discussed, Vardi and Koren were far less supportive of the concept of human-controlled blooms. Both feel their work should remain as a model to better understand how carbon is currently processed in the ocean and how this may change in the future, not as a way to manipulate microbial life.

“You always seem to know how things start but never how they will end,” Vardi said. “We never want people to add viruses to the ocean. They’re more clever and can adapt much more rapidly than us; this is not a road we suggest going down. We simply want to know how to quantify the events already happening.”

Koren added that often any human intervention into natural environments provides problems, especially in an area we know so little about still. “It’s too early to be happy or make decisions based on this, but we’re carefully optimistic our results are a good first step,” he said.

Vardi said the team can’t discuss what it is working on next just yet, but making its findings more applicable across different environments is important.

“We need to find how general our results are in different blooms and environments and the numbers of turnover at a much higher sample size,” Vardi said. “Then we can begin to use these models to predict better how blooms really work and the impact they will have amongst climate changes.”

 

View original article at: Scientists find viruses affect life and death of huge carbon-eating algae bloom

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