Conforming to the cliché you may have of marine biologists, what drew me into this field in the first place goes back to the moment I put on a mask and suddenly saw below the ocean’s surface, some three decades ago. Visible with the naked eye, sharks and octopuses have fascinated me for years. However, I rapidly realized that this diversity was just the tip of the iceberg, below which was hiding what literally fuels life on Earth and what became the focus of my research: marine microorganisms. These small organisms have a huge impact, as they are collectively responsible for as much oxygen production as land plants, fix 30–50 billion metric tons of carbon every year and support entire ecosystems. Without marine microorganisms, atmospheric CO2 concentration would be twice as high, which would make our life challenging.

In my opinion, the 1983 paper by Azam et al. entitled ‘The ecological role of water-column microbes in the sea’ already contained many key elements that would shape the direction of the field over the next 40 years. Interestingly, rather than an article reporting original findings, it summarizes and combines discoveries made in the previous decade, all pointing towards the major role of microorganisms in ecosystem function. Precisely, the paper merges the findings under a unified concept and gives it a name: ‘the microbial loop’. This would have a tremendous impact on the field.