Freshwater picocyanobacteria: what has changed 22 years after Stockner's "view from the summit"?

More than two decades have passed since the publication of the historical volume edited by John Stockner, as a special issue of the Int. Revue ges. Hydrobiol. 76, dedicated to autotrophic picoplankton (APP) in freshwaters. My intention is to climb the mountain again and map a wider view of what we now know on the ecology and diversity of at least one component of APP: picocyanobacteria. Their taxonomy evolved with the publication of phylogenetic trees of different genes, different ecotypes were recognized in the gradient of underwater light quality and turbidity, their prominent role in the production of different aquatic systems has been better detailed. I will present some examples of short- and long-term field researches (high altitude volcanic athalassohaline lakes, deep ultraoligotrophic andine and mesotrophic subalpine lakes,) and recent laboratory work (microcolony formation in single-cell culture) with the 'presumptuous' aim to indicate which new perspectives on picocyanobacteria research could emerge in the next future.