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“Quantitative science is not just about getting the number, it’s a way of thinking” – Prof. Tom Trull, director of QMS

Prof. Tom Trull in his lab

Professor Tom Trull was part of the first voyage in the Southern Ocean examining the possibility of spreading iron in the ocean to fertilise or promote phytoplankton activity and thus, biological carbon uptake in the ocean. Tom works as a biogeochemist at CSIRO and the University of Tasmania in Hobart. In addition to being the director of the Quantitative Marine Science program, he teaches QMS students in a marine biogeochemistry unit.

What are the main issues in your field that would have an impact on decisions made in a context of global warming?

Chemicals control biology and the biology feedbacks in the carbon cycle. That's why our work is important in understanding the carbon cycle. We measure the amount of carbon transfer from the surface to the deep ocean. The oceans provide the largest part of carbon uptake on earth and, of this, the Southern Ocean is the most important part. Our research is based on some questions: how much carbon is removed by the ocean? Is that going to continue in a context of warming climate? Could we increase the rate of ocean uptake?

Could you explain the iron fertilization research?Tom Trull background

It turns out that biological production in some parts of the ocean is limited by a lack of iron. The Southern Ocean is one of these, and also the largest region of the global ocean with an abundance of other essential nutrients such as nitrate and phosphate. Iron supply to the Southern Ocean is very low, because it is far from land which is the major source of iron, and also because most of the land in Antarctica is ice-covered. We have been involved in trying to assess whether iron fertilization 1) would actually lead to a removal of CO2 from the air, 2) would have sufficient capacity to contribute to offsetting CO2 emissions 3) if the possible damage to the ecosystem would be acceptable as a trade-off for reducing global warming.

I was onboard the very first Southern Ocean iron fertilization experiment called SOIREE (web link)(Southern Ocean Iron Release Experiment) in 1999. It's easily the most exciting research I have been involved in. It was a bit like gardening - stunning to realise that a very tiny amount of iron can have such a huge influence on ocean ecosystems.

What do you think of these solutions to slow global warming?

Other people say: "just by iron fertilization we can solve 15% of the problem." I think of this as only a small fraction whereas other people think it's a bigger fraction than any other technique we have. I personally don't think that the risk is very large but I think that the capacity is very low.

We should not do anything on a large scale because our knowledge is insufficient to say "yes, we know what will happen". That's wrong! We don't know what will happen. We have to continue the experiments, so that our knowledge grows but we are certainly not in a position to do large scale fertilization now. It won't become an option soon.

Will the Southern Ocean ultimately stop absorbing CO2 from the atmosphere?

The reason why atmospheric carbon dioxide levels are low enough for life to exist on the planet is because we do have a biological pump. The biological pump is the process through which plants and phytoplankton absorb the atmospheric CO2, and release oxygen. In the oceans, the biological pump creates a CO2 gradient between the surface and the deep ocean. The CO2 is absorbed at the surface by the phytoplankton and when life dies, it sinks into the deep ocean.

ven prior to any industrial activity, without the biological pump there would be much more carbon in the atmosphere, and our climate would be too hot!

As we stuff more and more CO2 into the deep sea, the gradient is more and more difficult to maintain. And that's how we may reach a situation of no net uptake of CO2 in the Southern Ocean.

We have already seen some evidence for that in ocean models.

What is your interest in leading experiments in the field?

Getting away from my office!

What I like about the research cruises is that all the scientists are together and it's an exciting exchange. There are at least 50 different functional groups of organisms that are important to the carbon cycle in the ocean and for each one, you need somebody who knows those things. It's great that oceanography leads you to work with all these other specialists where everybody is focused on understanding the oveverall system and brings a little piece to it.

The other thing I like is not to work from nine to five, you don't go to work and go home. It's an exciting time!

You supervise a QMS PhD student, Ernesto Molina. He studies phytoplankton production in the Southern Ocean. What is significant about this research?

Ernesto has been working on a lovely paper that is using an ecosystem model to try to extend the results from the first Southern Ocean iron fertilization experimentation. Using a model, he applied the knowledge we learnt from the SOIREE iron fertilisation to other places in the Southern Ocean and other times of the year. What we learnt, interestingly, is that the intensity of the response depends very strongly on the time of the year. It's not just through light availability, it's actually through the seasonal cycle of zooplankton, if it has developed a large population or not. In summer, there is not much phytoplankton biomass buildup, uptake because the phytoplankton is eaten by the zooplankton, but there can still be significant carbon uptake. In contrast, in spring there is a strong phytoplankton biomass "bloom" because few zooplankton have survived the winter to feed on it.

What is the importance of quantitative science in marine research?

You can't do good research without quantitative science because you really don't know the answers before you do the calculation.

I also think that mathematics is a language. You take an idea, transform it into an expression, manipulate the expression and come out with a new idea. Sometimes you are surprised by the new idea but the formalism of the mathematics can lead you to new ideas and new conclusions. It's not just about getting the number, it's a way of thinking !

You are supervising five PhD students. Why be a supervisor?

I get paid for that!

I love teaching one on one. I don't enjoy teaching in a classroom as much but I love the thing you learn when you work with somebody and think about problems together. Students usually ask the big questions and sometimes we can only answer a small question but sometimes being asked the big questions makes you thinking about new ways to formulate the small questions.

I think I have had 13 PhD students now. And they have all been enjoyable. They have all finished, it is above the average!

Four of the five are on their last year now so I am eager for new students. I don't tend to do the same thing over and over again. Currently I am interested in looking at oxygen cycle in the sea. It's sort of a complement to carbon. Plants release oxygen so by looking at the oxygen cycle we will discover new things about the processes that control the transfer of carbon into the deep sea.

You are the director of QMS. Why did you choose to lead this program?

Because I was asked to lead it!

What I hope to achieve in the job is first of all to increase the number of students who know about the program particularly in mainland Australia because there are many talented students who don't realise how good the program is.

And, it's unusual for a PhD program in Australia in that there are courses. I want to create more links between the courses. I would like that the physical oceanography course feeds directly into the carbon cycle course, and this feeds directly into the ecosystem course, and that this feeds directly into the fisheries course.

I want our courses to become less about exposure of ideas but more about presentation of tools for the students to be aware of the best practices in the fields.  Partly because we have so many great science agencies in Hobart now, that exposure comes to us every day through seminars, workshops, etc.

What advantages would you spell out to a potential QMS student?

One of the key things is that the QMS program has a steering committee that evaluates each PhD project. The committee looks at it and asks if it is achievable, if the data are available and if the resources are present. It also helps to know if the supervisors are capable of doing this and if it will be a high profile project if it is successful. When you are a young student and you are looking at opportunities, it might sound great and then a year later you found out that it's not really the way you should do the science.

The second advantage is that you are required to have two supervisors: one at CSIRO and one at the UTAS. And along with that comes the right to use the resources of both the university and the CSIRO. You have the guarantee of two persons interested in your work, two sources of resources, two communities and that is really stimulating compare to a standard PhD at university.

The QMS program is financially a good situation for students, and there are awards available for travel.

Finally, the director is there to help you and ensure that you have a very strong and rich experience as a student.

There are more resources in the QMS program than there are in most universities.

You studied in the United States and worked as a scientist in France before coming to Tasmania. Why did you chose to settle in Tasmania, and what are the advantages of being a scientist here compared to other labs in the world?

It's beautiful here! It is a long way from the rest of the world but there is a large concentration of scientists.

I am particularly amazed by how open to new ideas the Australian and particularly the Tasmanian community is. If you said: "I would like to try this, I think it is a good idea" people will listen and say ok. In other countries, particularly in America, people would say: "you haven't done that before". Nobody has ever said to me here, "you can't do it because you haven't done it before." So, I have been able to do new things and that has been very simulating.

Hobart brings together the CSIRO with the UTas, the AAD (Australian Antarctic Division) with the BOM (Bureau of Meteorology). We have top scientists from several agencies working together and that is also exciting.

Anaïs van Ditzhuyzen