Holographic microscopes provide insight into plankton life

Using holograms made with digital microscopes and interpreted using artificial intelligence (AI), researchers can now track plankton life
on an individual level for the first time.
The method is the result of an interdisciplinary research project at the University of
Gothenburg.

Plankton is one of
the most important organisms on Earth.
More than half of the world's oxygen is produced
by phytoplankton in the oceans.
However, knowledge about these life forms is limited, mainly due to their size
.

Erik Selander, a marine biologist at the University of Gothenburg, said: "Until now, I had to study planktonic microbes at the population level, but thanks to this AI-based holographic microscope, I can see how individual planktonic microbes
move, eat, grow and multiply.
"

The only way to study plankton at an individual level

Erik Selander heard physics professor Giovanni Volpe speak at a 2019 conference on a new technique in which holograms of light refracted through particles can be studied
instead of particles.
Using artificial intelligence, holograms can be analyzed at a faster rate, providing more and finer details
.
Subsequently, Zelander and Volpe began an interdisciplinary project
on plankton.

"With large organisms like animals and birds that we see every day, we know exactly who eats whom and where
they go.
The method we have developed is the only one to study microscopic organisms at the individual level," says
Giovanni Volpe.

Artificial intelligence makes this method faster

This method uses LED light to analyze planktonic microorganisms in a holographic microscope, which ensures that organisms are not affected
during the process.
The discovery was published in an article in the journal eLife.

"The planktonic microbial cells we studied were only a few hundredths of a millimeter in size
.
But they are numerous and affect the entire carbon cycle
of the oceans.
In total, single-celled plankton absorbs about three times
as much carbon as humans emit from fossil fuels.
Now we can have a detailed understanding of these processes on an individual level," says
Erik Selander.

With the help of holographic microscopes, methods of recording light-matter interactions with digital cameras have been well studied
in the past.
But thanks to digital technology and the recent AI revolution, this approach has become more useful and analysis easier and faster
.

"By combining holographic microscopy with artificial intelligence, we can now simultaneously monitor large numbers of planktonic microbial cells at the level of a single cell, which was previously a challenge
.
" While the technique is demonstrated on marine microbes, it is methodologically quite universal and can be applied to any microscopic life form
.
By enclosing cells in miniature glass pores, we can track the growth dynamics and swimming behavior of cells throughout their life cycle, from hours to days," says
Harshith Bachimanchi, a PhD student in physics at the University of Gothenburg.

Holographic microscopes also provide a fast, inexpensive way to count, weigh, and determine the size
of cells or other particles in solution.

Microplankton life histories revealed by holographic microscopy and deep learning