During the holidays, go bloom hunting with Ifremer

The goal of this hunt is scientific. The Marine Research Institute needs your help to raise the alarm if a body of water is invaded by microalgae.

These “blooms” that the Institute for Marine Research (Ifremer) is offering you to hunt for this summer using your mobile phone are an exceptional proliferation of microalgae. We speak of efflorescence in French. As part of a participatory science program, Ifremer is asking you to raise the alarm if a body of water or a river has changed color in certain places, that it has become abnormally green, brown, red or yellow.

This happens more easily in the summer with the light and heat. In this case, Ifremer asks to take a photo via a free application called “phenomer” and send it to the research teams.

These sudden multiplications of microalgae are natural phenomena, but some can be harmful to the environment, or pose health problems for aquaculture or leisure activities because out of the 5,000 known species of microalgae, about twenty produce toxins. Their presence can lead, for example, to a ban on the consumption of shellfish in the area concerned. As they decompose, these algae can also asphyxiate other marine species, and unbalance ecosystems. Hence the importance of spotting them quickly.

The general public is involved because these phenomena are often very ephemeral. They can occur in areas far from Ifremer’s observation stations. This operation has already existed for several years and it appears that 60% of sudden appearances of microalgae would never have been detected without these observations by individuals.

It is important for scientists to better understand these blooms, which are likely to multiply with global warming. These blooms are also linked to the amount of nutrients in the water, particularly when there are urban or agricultural discharges of phosphate and nitrate, which is why it is important to monitor them.

Recently, this monitoring of water color changes has also been done from space thanks to satellite observation. From the beginning of 2025, in the event of “blooms” spotted from space, an alert will be issued on the phenomer application. It will invite volunteer citizens to go and take a sample on site if they are nearby.