How much carbon can the ocean absorb and what happens with the warmth of the earth? Sonya Dyhrman, a microbial oceanographer and professor at the Lamont-Doherty Earth Observatory, tried to answer these questions. (Lamont is part of the Columbia Climate School.)
Dyhrman studies marine microorganisms, which is the basis for the dynamics of highly complex marine ecosystems. “This very complex interactive network is really at the heart of the ocean,” she said. “It is crucial to answer the question of how much carbon the ocean can hold.” Dyhrman talked to the State of the Earth about how she conducted her research. Understand the chemical “language” of microorganisms; and why it is important to teach young people about marine science.
What do you learn and why is it important?
I study marine microorganisms, mainly photosynthetic marine microorganisms, which is the basis of the marine food network and is very important, not only for marine ecosystem dynamics, but also for the circulation of carbon and other greenhouse gases. They play a key role in food chains and biogeochemistry.
The first question I encountered was, what will happen to the ocean in the future? We don’t understand the rules that allow us to predict who or what in the ocean, and that they do well to infer the future with the accuracy we want.
There is a surprisingly complex interactive network that occurs on invisible microscale scales. The entire network is composed of thousands of chemicals and microorganisms, all of which have slightly different metabolic characteristics. Some are photosynthesis. Some are predatory. Some people live with each other. This interactive network is indeed the core of the ocean. Just like this heartbeat is based on the basis of every fish, whales, seabirds, seals and creatures you care about. The network is crucial when answering questions when we think about how much carbon the ocean can accommodate and its ability to buffer changes we see in atmospheric carbon.
How do you conduct your research?
Chemistry and ecosystem biology both start with the heartbeat of chemicals and microorganisms interactions, but tracking these interactions is really challenging when you can’t directly observe microbes. One of the exciting things that have happened in my career is the advancement of technology. My work focuses on sequencing and genomics, which emerge from things like the human genome project. These [genomic] Tools allow us to map different areas of the ocean and tell us the species there and what their metabolic capacity is.
What we have to do is double. We have isolates [a culture of microorganisms isolated for study] and the microorganisms we obtain from seawater in different environments. We brought them back to the lab and experimented with them under controlled conditions to understand how they work and how they respond to environmental changes. We also conducted direct field observations and experimented on board to find out what microorganisms are there, their abilities and how they change under different conditions. The tool we use is called the metagenome, because we have studied many different species at once. We take all the microorganisms, extract their DNA, sequence them, and then use a supercomputer to view it.
“This interactive network is really at the heart of the ocean. It’s like this heartbeat based on every fish, whale, seabird, seal and creature you care about.”
How do you use these DNA sequences?
We can see which DNA matches different organisms, so we can say who is there. I can also see that DNA encodes different functions, so we can see what organisms can do. We use tools called Metatransscriptoms and metaproteomics. When a gene in the genome is turned on or transcribed into RNA, RNA can produce a protein that can basically perform the role of the cell. [With these tools] We can map out which genes are turned on and which genes are turned off under different conditions of different components of different populations.
It’s almost magical that we can do this. Early in my career, we would bring microbes into the culture and try our best to try to see a gene, not a whole genome or a protein. Now we can view 10,000 from a sample!
What did some of your findings reveal?
We have developed a model with photosynthetic nitrogen-fixed cyanobacteria [a blue-algae that uses sunlight to make nitrogen]it plays a cornerstone role in the low-resource environment in which it lives. We believe that predicting its activity is only a matter of its interaction with chemical networks, but we understand that the activity of the organism also depends on the activity of the organism growing around it and around it. Basically, these creatures are talking to each other in a chemical language. Understanding this is a key “ahha” moment for me.
We also conducted a large collaborative study to understand some of the work being done at the Aloha station, about 200 miles from Hawaii. The sun appears every day, and photosynthetic organisms fix new pulses of carbon dioxide in the ocean and then reverberate throughout the community. To understand what happens to each other during the day, all of these microorganisms interact with the environment, we have scientists from two ships sampling for weeks during the day and night cycles in the area.
In a paper in this work, we are able to show how organisms move that carbon when there are confined resources (such as nitrogen). We can see that during the day, different groups of nitrogen are segmented using nitrogen at different times. The initial carbon fixation is indeed related to sunlight. We can see that carbon metabolism plays a role in different organisms, and then we see them then take turns using nitrogen. It’s really exciting to be able to put these carbon and nitrogen dynamics together in a day and help us understand how the system works.
How would you connect the very specific research you did with the larger goal of understanding marine dynamics?
Several of my projects are part of a larger collaborative study, where we have chemists everyone measuring chemicals in that network – people like me are watching who is there and what they are doing, and then they also consider how this interaction might affect modelers of the carbon cycle, and how we project it to different environments or futures.
From the research you have done so far, do you have a feeling about the future destiny of the ocean?
As the ocean warms and becomes more acidic, it changes other resources. Here, trying to understand the future is indeed challenging because we are still working on the rules of the present. My colleagues modeled the changes in temperature that will change community dynamics and which organisms exist across latitudes. It may also change how the network operates by changing available resources. Microorganisms will be fine, but they may not be the same species and can do the same things as us. We are trying to understand what sensitivity and rules are, so we can start asking questions about the sensitivity of these rules to potential changes. The more we understand the basic rules, the better we will be, considering the sustainable future and how fisheries, biology, chemistry, etc.
Marine microbial networks play a crucial role in how the oceans work, which literally makes our planet habitable – cyanobacteria in the ocean produce oxygen that oxygenates our atmosphere. So what happens to microorganisms in the ocean is important to what happens to our planet.
Do you think enough people understand the importance of the ocean?
I think it’s crucial to share that information in our education system, and I think it needs to start when I was young. We do not teach marine science in core STEM courses or in our country’s state science standards. By not making it part of the course, we missed an opportunity to share information about the important role the oceans and their microbes play in the way our planet works. I’m keen on trying to find ways to extend this approach.
