A Scientist’s Life: Amina Schartup

Amina Schartup is a marine biogeochemist at Scripps Institution of Oceanography at UC San Diego. She received her bachelor’s degree from Universite Paris V, her master’s degree from the Institut de Physique du Globe de Paris-Universite Paris VII, and her PhD in chemical oceanography from the University of Connecticut. She was a postdoctoral researcher at the Harvard T.H. Chan School of Public Health before taking a research associate position at  Harvard John A. Paulson School of Engineering and Applied Sciences. From 2017-2019, she served at the National Science Foundation as an American Association for the Advancement of Science-Science and Technology Policy Fellow. She joined Scripps Institution of Oceanography at UC San Diego in 2019. 

explorations now (en): What do you do for a living?
Amina Schartup (AS): Primarily I study the cycling of mercury, which is a toxic heavy metal, in the marine ecosystem. I am interested in how it's being converted by microbial communities into its most toxic forms, which are methylated organic forms that accumulate in food webs. Our most important research focus is on understanding how environmental change and climate change impact the transformation of mercury into the form that accumulates in fish. What does it mean for human exposure to mercury through fish consumption?

Mercury has been mined and used by humans for thousands of years, but since the Industrial Revolution, our usage has accelerated through a variety of processes because mercury has very interesting physical characteristics that humans exploit. One of those is that it amalgamates gold and silver, which means that it's used in artisanal gold mining to purify the gold. Then it's burned off and emitted into the atmosphere. Mercury has a very long residence time in the atmosphere, which means that it kind of floats around for a while before it deposits, which makes it a global pollutant because even if it's released in one location, it can transport and move around the globe and deposit elsewhere. Another emissions source is coal burning. As humans started producing more power through coal burning, they have emitted really large quantities of mercury into the atmosphere. The quantities are so large, they dwarf the natural cycle of mercury, which exists primarily through emissions from volcanic events. 

We eat fish because it's healthy for us. It has omega 3s, fatty acids such as DHA and EPA, all these are important nutrients for brain development especially. But it also contains contaminants that people have heard of like mercury and POPs, which are persistent organic pollutants. This is the stuff that is purely human-made that we release into the environment, and some of it accumulates in substantial quantities in some animals, so the question is: At which point do we cross over that threshold of where we have so much of the bad stuff in our fish that it's no longer beneficial for a human to consume wild fish because the bad stuff offsets the good stuff that we eat the fish for?

Our goal is to quantify and understand how that balance may shift. I think that for the most part, in most areas, consuming fish is still beneficial because the good stuff outweighs the bad stuff. But when is that going to change? We want to provide for policymakers some tools to say “Here's where we need to stop in terms of emitting all the bad stuff into the environment.”

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

AS: The main question in our field is what happens to mercury once it enters the marine system. We know that emissions of mercury are primarily human-driven. We can control those emissions through policymaking and international agreements, but where we have less control and less understanding is what happens to the mercury that has already reached aquatic ecosystems. We don’t know which microbial communities are involved in the transformation that moves that mercury from its inorganic less-toxic form to a more toxic form, which is called methylated mercury.

Another important aspect is finding out how changes that are occurring on the planet right now such as climate-driven changes impact those transformations. How does seawater temperature impact methylation? How do areas of reduced oxygen levels that are expanding across the global oceans impact methylation? And then how does the food web structure change as we are fishing for different animals and for more of them? The food web structure will impact how the mercury is moving through that food chain. We are trying to understand how that will impact mercury exposure within seafood communities.

A lot of us who are in environmental sciences tend to present people with a lot of problems. We say “well, this doesn't work” or “this situation is going to get worse.” At some point, we also need to think about what kind of solutions we can propose to people. Telling people not to consume fish is not a solution, so what can we propose to reduce exposure to mercury, but still maintain the nutritional benefit that fish can bring to people?

The consensus in the research community is that reducing emissions is our best shot to reducing exposure to mercury. That being said, we already have really high levels of mercury in the seafood that people like to eat. The advice has been to think about what kind of seafood you consume. For apex predator fishes such as shark and swordfish and tuna, we say to consume them in moderation depending on your demographic status or where you are. Eat lower in the trophic food webs, like sardines, mackerel, fishes that are much smaller that live on algae, for example. 

Something that we are actively investigating with collaborators at UCLA is seeing if we can intervene through the gut microbiome and demethylate mercury in vivo, which means that we produce supplements that people can take and demethylate in their gut to reduce methylmercury concentration in the body and eliminate it through an inorganic form that is not as toxic. It's really far from commercial use or even thinking about human applications at this point. We haven't even published work like this, but it's promising. We have some really good results.

I'm also really excited that we have received funding from the National Institutes of Health and the National Science Foundation for the Scripps Center for Oceans and Human Health. Our goal is to look at how the climate-driven changes that we all have heard about – reduction of oxygen in marine systems, increases in seawater temperature, changes in precipitation patterns, for example – are going to impact the ocean phytoplankton communities that are the lungs of our planet. Those communities also accumulate a lot of contaminants such as mercury, but they also accumulate nutrients that they then pass on to higher trophic levels like animals. Our question is how does climate change affect the relative concentrations of those beneficial elements versus those toxic elements that we know we are releasing and accumulating in the seafood? Can we quantify those relative concentrations and project them into the future?

en: What tools do you use in your research? 
AS: We are a somewhat unique lab in the sense that we have yearly field-going campaigns. These are either on foot or by car or we go to sea on ships. We collect samples, we bring them to the lab. We have an analytical facility where we use mass spectrometers to measure those individual atoms of metals that we are interested in. We also use separation techniques where we can separate inorganic forms from carbonated methylated forms of metals. We look at the relative concentration of these organic forms of metals versus inorganic forms of metals, which just means that they have a carbon or hydrogen atom in addition to the metal core.

We need to use clean labs and clean facilities to do our work because mercury is present as a trace element in the ocean. It’s present in extremely low concentration. I sometimes use the analogy where it's like a few drops in 20 Olympic pool-sized bodies of water. Phytoplankton accumulates this 10,000 times, sometimes 100,000 times, and then the concentration continues to increase in the food chain. Because we are studying the transformation of really trace amounts of mercury in the ocean, and mercury is everywhere – in our bodies, in our hair, in our nails, in our skin – we have to work in a clean lab so we don't contaminate our samples, when we try to analyze the levels in seawater.

We also do regional models and global models. Global circulation models such as the MIT-GCM (which stands for MIT, the university, and GCM for global circulation model) allow us to make climate predictions. These are computer models that represent our ocean, how ocean currents are moving and how temperature is changing. We also model phytoplankton growth so we can start testing out in virtual environments and look at what happens in 20 years or 30 years at the global scale.

Right now we are incorporating selenium, for example, which is a micronutrient. It's an important beneficial element. Most animals need some of it, but not a lot of it. We are trying to understand how selenium is going to change in the future in terms of distribution in the oceans. One of the reasons we're interested in it is that it has been described as an antagonist to mercury. It’s possible having a little bit more selenium may counteract the bad impact of mercury. That's why we are interested in how its relative concentration may be changing in food webs. 

en: What got you into your field of science?
AS: I always had this interest in how human activity impacts our quality of life. I was born in Azerbaijan, which is a big oil country. I remember when I was very young there was always a little bit of a sheen of oil on the Caspian Sea and the smell of oil in the air, so I was always curious even then what does it mean for the fish that we collect from the Caspian Sea that I very much like to eat? Then I moved to West Africa where I saw the environment degrading rapidly and I always wondered what that meant for people who are exposed to poor air quality or potentially contaminated food. That’s when I decided that I wanted to become a chemist. My bachelor's degree is actually in chemistry. Then I specialized in geochemistry before focusing on oceanography and looking at the mercury cycle in the global oceans.

en: Why did you want to come to Scripps?
AS: I came to Scripps because I was looking for an institution where I have access to multiple disciplines and experts, as well as a seagoing infrastructure. As a mercury expert, I greatly benefit from being around specialists and experts across all the disciplines that I have to touch upon when I study this and other elements of interest to me. Having access to microbiologists nearby is a huge advantage. I also work with physical oceanographers to think about how things are transported in the oceans. I work with public health experts as well as medical school researchers looking at how humans get exposed to mercury through consumption of seafood. There aren't too many institutions where we have really close proximity to the ocean and seagoing infrastructure.