In September this year, I noticed an orange/green coloured scum layer in a slow-running river (see pictures) close to my hometown (Deinze, Belgium) containing green and orange clusters, as can be seen at the close-range picture of the bloom.
Microscopical analysis revealed a micture of Microcystis-colonies (a bloom-forming cyanobacterium, the green part of the scum layer) and an unknown organism of which I have no clue what it could be. I encountered a similar (mixed) bloom about 10 years ago in a recreative lake in Flanders (see report-snippet in attachment).
It might be some micro-algae, or spores/pollen (but in this season?) infected by an aquatic fungus, or both structures (cells and what looks like hyphae) might concern the same organism (a fungus?). I however doubt it concerns a micro-algae.
Since than, I received more records of such scum layers from the nearby river Scheldt, and I personally saw something quite similar in the river Moldau at Prague three weeks ago. I hope someone familiar with this organism can tell me what it is?
Many thanks!
Jeroen
Kouadri Mohamed El Amine indeed, it seems rust spores and Alnus is a tree growing on the riverbanks of the river where this orange scum layer developed! It seems this rust spore concentration on water is a rare phenomenon. Many thanks for the suggestion and potentially identification!
cheers,
Jeroen
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