'I’ve always been interested in how the physics of the ocean impacts what lives there.'

PhD student, Russell Arnott is researching phytoplankton in turbulent environments. He tells us about his work and the importance of understanding our oceans.

'We don’t really know how many different species of phytoplankton there are but it could be anywhere between 30,000 and two million. They come in all sorts of weird and wonderful shapes and sizes and greatly impact our lakes, coastal areas and oceans.'

It’s Russell’s first day back on campus after a two-month research trip to the Antarctic and also one of the UK’s hottest days in February on record. It seems appropriate to be discussing his research and the effect global warming is having on plankton and our oceans.

A growing threat to oceans

'My research looks at how the shape of plankton help them become dominant in different turbulent environments. When phytoplankton grow rapidly in number, they can form harmful algal blooms that reduce oxygen levels in the water and kill fish. Around 200 species can produce biotoxins that can cause stomach upsets and respiratory irritation. But if these plankton are ingested by other animals, the toxins can bioaccumulate and work their way up the foodchain. Eating just one contaminated mussel or oyster could lead to paralysis or in extreme situations, death.

'Around the world, harmful algal blooms are occurring more often and more severely. We think this is due to changes in temperature and weather patterns caused by global warming. We saw it in Florida last summer where they experienced a big issue with fish kills and infected bathing waters. Having a better understanding of how the phytoplankton interact with their environment will help us find ways to mitigate this growing problem.

'It can also help us tackle plankton problems closer to home. In my research group, we’re working closely with water companies in the area. They have an issue with algal blooms in their reservoirs causing discoloration and making the drinking water taste funny. There’s a chemical inside plankton called geosmin that gets released when the cell breaks up. It’s harmless but it gives off a musty, mouldy smell, like the smell that we associate with the seaside. Humans are really sensitive to it; we can detect around one nanogram of geosmin per litre of water. Water companies are investing a lot of time and money into finding ways to get rid of this chemical from their drinking water supplies, which is where our research comes in.'

The importance of turbulence

a close up of a student holding a 3d printed phytoplankton
Using 3D printer technology can help to demonstrate the diversity of phytoplankton.

Russell's interest in plankton and the impact of turbulence grew out of his master's degree in oceanography.

'I was studying a swimming and boating lake in Amsterdam for my master’s thesis. Every summer, they had an issue with harmful algal blooms so we started looking at ways we could get rid of the problem plankton. And it turned out that making the water more turbulent made the environment less conducive for the plankton to live in. I thought “Woah, this is incredible! Just by mixing the water slightly, we can completely change what lives there.”

'When you take plankton samples, you usually measure the temperature, salinity and the depth from which you took it. All of these play a crucial role in determining what lives there. I’m of the opinion that turbulence is just as important as any of these factors. But turbulence is a tricky thing to model. On one end of the spectrum you have physicists who love to model turbulence and produce really complex mathematical research. And on the other end of the spectrum you have biologists who have an understanding of its importance, but don’t know how to bridge that gap between the two disciplines.

'I started off studying oceanography at Southampton University. As I went on it dawned on me that everything was compartmentalised. If you were a marine physicist you only cared about the physics of the ocean. And if you were a marine biologist you only cared about the species that lived there. I felt that to really get an understanding of how the ocean works, you needed to be more interdisciplinary. I was interested in how the physics of the ocean impacted on what lived there.'

Accurately analysing plankton

As part of Russell's research, he travelled to Northern Sweden to analyse plankton in a range of turbulent conditions.

'I visited the University of Umeå to use their facilities at Umeå Marine Sciences Centre (UMF). It’s this small centre in the middle of nowhere but it has some of the best mesocosm facilities in the whole of Europe.

'The mesocosms I used are basically big tanks that hold two tonnes of water each. You can fill them up with whatever plankton or sea water you want, then you can change the temperature and other factors and record what these changes in conditions do to the plankton. I filled the mesocosms up with a natural population of plankton from offshore in the Baltic Sea. Then I used convection to generate different turbulent mixing conditions.

'The second part of the experiment was to see how the plankton responded to the manipulated conditions. We took samples and measured the temperature, the salinity and analysed them under a microscope. But then I discovered this cool machine at Plymouth Marine Lab, called a FlowCAM. It’s like a camera, microscope and laser all in one. You pour your sample in and every time the laser is cut by a particle it takes a photograph. In ten minutes it can photograph around 6000 different plankton. Before, it would take an hour and a half to analyse around 300 under a microscope. Even better, I’ve now got a record of all of the plankton because they’ve been photographed. This means I can digitally analyse those images for size, shape, aspect ratio, transparency and more. It gives us a really accurate idea of not only the species of plankton but also their form. And now that I have all this data, it’s just a case of going through it all and seeing if I’ve got a story to tell.'

Bringing research to the next generation

Russell’s fascination with ocean environments developed in early childhood when he was growing up in Dubai.

'When I was eleven, my mum gave me a magazine article about how the blue whale wasn’t going to survive until the year 2000. And I remember being so angry that I felt I needed to do something about it. I coerced two of my friends to do a sponsored bike ride. We cycled 30 miles in the middle of the summer in Dubai. It was 48 degrees and 100% humidity; it was mad. But we raised 600 dirhams, which was about £120 and at the time it was the biggest amount of money I’d ever seen. I remember sending it off to the WWF and thinking "don’t worry; the whales are saved!"'

The importance of raising awareness about our oceans stuck with Russell into his adult life. Before beginning his PhD, Russell was a teacher and then a marine science communicator, which involved him going into schools to give talks on the sea.

'Public engagement is vital and I’m still surprised that it’s not more engrained across everything. I get frustrated that we live on an island yet there’s nothing in formal education about the oceans or how valuable they are or what they do for us. It’s so important to raise environmental awareness and the need to protect our natural waters. But also, it’s important for the economy; there’s a large sector there and we just don’t have enough skilled people to fill the jobs.

'For me, this is kind of why I’m doing a PhD. I want the clout behind my name to go out there and talk to people about our oceans. It feels good to be associated with an academic institution and to be working with actual research that I can bring into discussions. Being able to communicate research to all sorts of audiences also helps you as a scientist. You've got to be able to show people why your research is important and relevant to them.'

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