I didn’t see any Physcomitrium readeri – perhaps I’m just overlooking it. The Riccia is spread over quite a large area at SW709372, which is a different part of the reservoir from where you found it in 2023. I don’t think the water level is low enough to expose the area where it grew then.

Intersting, I've been seeing Riccia crystallina in pavement cracks in Cornwall in recent years. Perhaps I better have a closer look and check that some populations are not R. cavernisa

It's delicious, have just cut it and shared with friends. Flowers from the garden make it colourful.