Climate change restricts the habitat of microorganisms

Planktonic foraminifera are small marine organisms that live in the uppermost water layers of all oceans. When they die, their calcareous shells sink to the ocean floor and remain there as microfossils. During their lifetime, foraminifera store environmental information in their calcareous shells, which is why they are also considered climate indicators and witnesses to biodiversity in the past.

For the Nature-study, the researchers from France, Germany, the Netherlands, Japan and Spain analyzed almost 200,000 data sets since 1910. They came to the conclusion that many species migrate to cooler waters in the direction of the poles or adapt their habitat within the water column, for example to cooler water depths instead of near the sea surface. According to the study, the foraminifera population has already been reduced by a quarter in 80 years.

Sonia Chaabane, the study's lead author and researcher at CEREGE and the Max Planck Institute for Chemistry, emphasized the implications of the findings: "Our data show that planktonic foraminifera, which play a crucial role in the ocean’s carbon cycle, are struggling to survive in a rapidly changing climate. These organisms are like sentinels, warning us of the drastic effects that warming and acidification have on marine ecosystems." Complex interactions between climate and ecosystems are likely to be better understood as a whole through bioindicators like foraminifera rather than through individual measurements.