New device could unravel the microscopic mysteries of plankton

Scientists from Stanford University have created a revolutionary new device which can study individual plankton movements in simulated oceanic conditions. It is hoped it will open up a whole new field of research into these microscopic organisms and the crucial roles they play in global systems.

rotating microscope
The new rotating microscope, worked on by PhD student Deepak Krishnamurthy in a lab at Stanford University

Despite their microscopic size, plankton are one of the most important groups of organisms on the planet. They create over half the oxygen we breathe and help to support marine food webs, fix atmospheric carbon and even influence weather patterns. However, because of the obvious challenges associated with studying these microorganisms in their natural habitat, there is still so much we don’t know about them. Thankfully a new rotating microscope, created by researchers from Stanford University, could be about to revolutionise the way we study these microscopic mysteries. Nicknamed the ‘hydrodynamic treadmill’ or ‘gravity machine’ this new device simulates varying ocean conditions to let researchers track the minute movements of individual plankton, which will help complete our understanding of these vital microorganisms.

Planktonic mysteries

While our overall understanding of the processes plankton perform in our oceans has improved over the last few decades, there are still some large knowledge gaps in terms of how individual organisms operate at microscopic levels. One of the biggest mysteries is how they are able to move about in the water column and control their movements without any appendages that aid in mobility. We know that they are able to do this because every night billions upon billions of plankton migrate to the surface from the depths and back again, in what is known as the vertical diel migration.

copepods
Microscopic zooplankton are capable of moving large distances though the water column, but studying how they are able to do this is extremely challenging

This important biological phenomenon is just one of the many crucial roles plankton perform in marine ecosystems. However, because of the challenges associated with studying individual microorganisms moving across large depth and time scales in a dynamic environment, we remain in the dark over the microscopic details that underpin it. In an ideal world we would be able to tag plankton like whales, sharks or turtles to track their movements and uncover these mysteries. But until we develop electronic tags smaller than plankton this remains impossible. Instead the only other option is to be able to bring the ocean into the lab, which is exactly what this new device aims to do.

The rotating microscope

Created by researchers from the Parakash lab at Stanford University, the rotating microscope is essentially a water wheel that creates an infinite loop of seawater. Plankton are inserted into the continuous cylindrical tube which is then rotated, recreating the natural flow of the water column either upwards or downwards depending on the direction of the spin. The plankton therefore act as if they are moving against the water flow, but actually remain suspended in place. A camera then captures full-resolution colour images of the plankton into a computer for analysis, which allows researchers to track the minute details of their microscopic movements. The device can also recreate depth characteristics in the ocean, such as light intensity, creating what the researchers call a ‘virtual reality environment’ for the single celled organisms.

In a recent press release, the studies senior author and lab leader Dr Manu Parakash explains that “it opens scientific possibilities we had only dreamed of until now”. To see the rotating microscope in action and learn more from Dr Parakash and his team check out the video below.

 

 

Proof of concept

As you can see from the video not only does the rotating microscope work, but the team have also been hard at work using it to study different plankton movements already. They have made observations on the minute details of larvae, including for species such as the bat star, sea cucumber and Pacific sand dollar. As well as the vertical swimming behaviours of single-celled organisms such as dinoflagellates, which could allow scientists to better understand algal blooms. They were also surprised to discover that a diatom, a type of phytoplankton with no swimming appendages whatsoever, can repeatedly change its own density to drop and rise in the water column.

researchs working on rotating microscope
The stanford team working on the rotating microscope, lab leader Dr Manu Parakash (left) and first author Deepak Krishnamurthy (right)

The team’s preliminary results are all included in a new paper released last month in the journal Nature Methods. It is hoped that their technique can rapidly increase the rate at which we learn about plankton and the important natural processes they are involved in. They also believe a similar set-up can be achieved using regular microscopes and hope other researchers follow their lead in studying the microscopic organisms in the same way.

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