Bathing Water Quality: What if you helped science by becoming a “microalgae hunter”?

Badabloom. This summer, the public research institute Ifremer launched a new version of its collaborative science app, Phenomer 2.0. Initially limited to Brittany, it now covers the whole of mainland France. Its goal? Monitoring the “blooms” of microalgae that cause the water to change color. But what are blooms, and why is it important to monitor these marine phenomena? Explanations.

What is a microalgae bloom?

This term refers to the massive proliferation of microscopic algae – also called phytoplankton – in the water, which can color it green, red or brown depending on the pigments present in the algae cells. “These phenomena are often visible to the naked eye and can be spectacular, especially with species that glow at night and in the waves.” Each bloom can contain hundreds of thousands of microalgae, or even millions, describes Stéphane Guesdon, a marine biologist (water quality specialist) at Ifremer (French Research Institute for the Exploitation of the Sea).

High light, abundant nutrients, and temperatures favorable to photosynthesis: these are the ideal conditions to encourage these blooms. Other phenomena must also be taken into account: Climate change, nutrient inputs from the continent of natural or anthropogenic origin [comme les engrais agri­coles, NDLR], Changes in wind patterns can also play a role in increasing the frequency of flowering.“These events mainly occur in spring and summer,” explains Stephane Guesdon. It can last from a few days to two weeks, The specialist says. However, it is difficult to estimate the number of flowers per year.

What are the risks associated with flowers?

If the flowers that color the water harmless However, their decomposition can have consequences for marine ecosystems. “When the bloom deteriorates, the bacteria that break down the algae can consume a large amount of oxygen. This can lead to hypoxia, or a lack of oxygen in the water, which can be deadly to marine wildlife. Refers to the aquatic world.

But this colored water “Does not pose any particular health risk”“, confirms Stéphane Gosdon. The Regional Health Agency (ARS) Recommended However, do not swim during these episodes to avoid the risk of slipping or drowning in these murky waters. She also recommends showering after swimming and keeping children away from the water to avoid ingesting seawater.

Collaborative Science 2.0

To better study this phenomenon, Everemer decided to focus on collaborative science, continuing to develop its Phenomer program. The idea is simple: ask people to provide information about what they observe in nature. This approach has already proven its value: in 2020, the Studying It showed that 60% of the flowers reported by the phenomer could not have been detected otherwise.

Since July, a new version has been presented to the public. If the phenomenon of colored waters on the French coasts can still be reported via a Mobile App Free of charge, it will soon offer to activate the alert system. It will be sent to users when a bloom is suspected near them. The two satellites used by Ifremer, previously focused on Brittany, to monitor the colored waters from the sky, now monitor all the French coasts continuously.

If detected, the site will encourage users to monitor and report the phenomena, Stefan Gosdon specifies. The public can also obtain sampling kits at ports, sports clubs or even port masters. These samples will then be analyzed in the Evermer laboratories to identify the species present and determine the concentration of phytoplankton.

“The results of the analyses will then be shared with participants, creating a valuable information loop between scientists and the general public.” Aquatic biologists rejoice. Thanks to this citizen contribution, researchers can better understand phytoplankton blooms, their causes and their effects. “By actively engaging the audience, the app turns every user into a ‘flower hunter’,” The world laughs.

Through this project, Ifremer also hopes to predict the effects of climate change on the frequency and distribution of these phenomena, in order to better protect marine ecosystems. This involves studying bloom phenomena in depth. “The goal is not only to understand the surface dynamics, but also to detect any associated species groups, including bacteria, viruses and other forms of phytoplankton.”The flower specialist concludes.