In order for the software to recognise the creatures correctly, it first had to be trained with thousands and thousands of plankton images. However, before the images from the Aquascope were read into the software for training, a taxonomist determined the exact species of each plankton organism in the photos. The more images of the same species are available to the software, the better it learns to identify that species.
"The camera gives us access to a world that is still very much unknown," says Ewa Merz, a doctoral student at Eawag and first author of a recently published article, which describes the camera in detail. "We can follow and observe the plankton in Lake Greifen live from our office chair," she explains enthusiastically. The camera is currently installed in Lake Greifen at a depth of three metres and delivers images every hour. This enables very high-resolution measurement series, which the researchers can use, for example, to give early warnings of toxic algal blooms.
Since the camera does not directly interfere with the plankton life, it does not affect population dynamics and individual species interactions. Such insights remain hidden with the conventional method because the plankton in the samples usually have to be killed and fixed before they can be analysed under the microscope. Often the fixation destroys the organisms to such an extent that they can no longer be recognised. Such artefacts can falsify the results. "What we discovered with the camera is that the rotifer Paradileptus elephantinus is not as rare in Lake Greifen as we previously thought. We think that the tiny creature would previously disintegrate during chemical fixation. Since the camera has been installed, we see P. elephantinus almost every day,” says Ewa Merz. "Ciliates such as P. elephantinus eat algae and seem to be important in regulating the algae population. The camera now allows us to closely observe the dynamics of these ciliates and other small phytoplankton feeders interacting with the algae. And that is unique," explains Francesco Pomati, head of the Aquascope team.