Maria Vernet conducts fieldwork near Antarctica. Photo: Maria Stenzel

A Scientist's Life: Maria Vernet

Phytoplankton ecologist studies key members of ocean food webs

Maria Vernet is an emeritus researcher in the Integrative Oceanography Division at Scripps Institution of Oceanography at the University of California San Diego. She earned a master’s degree in biological oceanography from the University of Washington in 1981 and a PhD in biological oceanography from the University of Washington in 1983. She began her association with Scripps in 1986 as a postdoctoral fellow and became a researcher in 1991. A phytoplankton ecologist, she considers long-term changes in marine ecosystems with a special emphasis on life in polar regions.

explorations now: What do you do for a living?

Maria Vernet: As a phytoplankton ecologist, I try to understand which phytoplankton species live in the ocean, what do they do, how important they are, and who eats them. In this way, I can understand the factors that control their distribution and abundance, and how they contribute to the carbon that circulates through the food chain—and eventually ends up in animals that we are interested in, like fishes or marine mammals.

With this information, I can understand how phytoplankton have been able to survive in a harsh environment such as the high latitudes like Arctic and Antarctic, where there is 24-hour light in the summer and then 24 hours of darkness in the winter.

en: What are some of the main questions in your field?

MV: One important question is trying to understand how the melt water that comes from the melting of ice on the continents both in Antarctica and Greenland affects the phytoplankton. Because the melt water has a lighter density than ocean water, it usually accumulates at the well-illuminated surface of the ocean in the mixed layer, where the phytoplankton live. We want to know how much melt water there is, where is it distributed, and what is the response of the ecosystem to that melt water. For example, one of the effects is that if you have less dense water at the surface than before, then the difference in density between the surface and the deep water is greater, making it more difficult for nutrients from deep water to be mixed into surface water to support the growth of phytoplankton so the phytoplankton could become nutrient-limited.

The other question I'm pursuing is the importance of Antarctica and the high latitudes in the carbon cycle of the planet. We want to know how much CO2 is taken up from the atmosphere and enters the ocean, and how long it stays in the ocean. Phytoplankton are involved in both of those processes: through photosynthesis they take up dissolved CO2 and make organic carbon, but then part of that is respired and released back into the water. We are interested in knowing how phytoplankton carbon that is taken from CO2 in the atmosphere is transferred to deeper waters—where it can be isolated from the atmosphere. To understand this process requires field measurements from oceanographic ships.

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en: Why are you interested in phytoplankton ecology in the Arctic and the Antarctic?

MV: As a researcher, I'm interested in Antarctica and the Arctic for several reasons. The polar regions are not as well studied as other areas on the planet. In a certain way, it's the last frontier—you feel like an adventurer. It is very pristine so it’s an area in which we can fairly consistently work in areas that aren’t influenced by humans or by our activity on the planet. And that makes [ecological research] easier in a certain way. You’re not looking at the change at the same time that you're trying to understand basic questions about the system. The other thing interesting scientists who work in high latitudes is the remoteness of these areas. They’re like a movie or a novel, where most people don't have any direct experience with them.

However, from the point of view of how these areas influence the environment, they are very important. They influence the atmosphere, they influence the ocean, and they influence the biology.

Finally, scientifically, from the point of view of the ocean it is a very important area because this is where the deep water is formed that forces the circulation of the ocean. There is a deep-water formation from the Arctic, but Antarctica is also important so both of [these areas] really make the ocean water move. As a phytoplankton ecologist, I'm also interested in the high latitudes because this is an area in which phytoplankton are a key component of the system. Phytoplankton can bloom, which means they reach very high abundances. Some phytoplankton like diatoms can be very abundant and also very beautiful to observe under the microscope.

en: What tools do you use for your research?

MV: It depends on the question. For fieldwork, it's usually oceanographic ships from which we deploy instruments over the side. We also collect water at different depths and then bring that water back into the lab, and run experiments or direct measurements. We have several methods to interpret the data collected from these measurements, including statistical and visual methods. Using the analyzed data, we want to synthesize what we've learned over several trips or for several research groups contributing to the same project; for this we often use mathematical models.

There are also questions that come out of those field projects that often need to be tested in the lab. For that we use cultures of species isolated from these environments that we keep in culture chambers in the lab, where we can perform controlled experiments. For example, we can control the exact temperature, exact salinity, exact light conditions. In those controlled experiments then we can come up with estimations that are very difficult to obtain in the field, where conditions are always changing.

en: Why did you come to Scripps?

MV: The reason I work at Scripps is because it's an institution that has a global focus. The oceans of the world are all connected, without physical and political barriers that are present on land so by having a worldwide perspective you go to that area in the ocean where you can best answer your research question. Even though I am in California, I am not limited to working locally, for example in the California Current. Even though I live in a semitropical environment, my work is carried out in freezing temperatures in Antarctica and in the Arctic.

Another reason Scripps is a great place to work is because it is large enough to have all the specialties that I need to develop a research program. For example, right now I'm interested in developing a new instrument to measure cultures in a more efficient way in the lab so I went to the engineering department at UC San Diego to try to interest someone in helping me develop such an instrument.

Finally, I think Scripps is a great place to work because of the people who work here. It's a research environment that really helps you push yourself. Everyone is doing something interesting, and it's fun to learn, even if it’s in areas that you will never do anything.

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