We have a fantastic (ongoing) collaboration with researchers from the Evolutionary Biology Centrum (EBC; Uppsala), who all seem to have dispersed elsewhere (Sarahi to Stockholm, Stefan to SLU and Vicente to Copenhagen). They are experts in culturing bacteria, and they supplied us with cyanobacteria exo-metabolomes (the mixture of dissolved compounds that this species excretes into the lake water it lives in). We had experiments from 20 and 30 degrees celcius conditions, and one that were grown in natural lake water vs artificial medium.
These guys make a lot of different compounds! After 25 days we determined >1600 chromatographically well resolved molecular formulas in the water, 369 of which were confidently assigned to formulas (see figure below). Considerably less were found when incubated in lake water, and further experiments showed us that this was because the metabolites are highly labile, and consumed by lake heterotrophic bacteria.
This lability explains why autotrophic cyanobateria derived DOM is so difficult to find in lake water - it is tasty food and removed very quickly by other organisms!
This first paper was led by PhD student Claudia Patriarca, and is available open access in Limnology and Oceanography here: