Red rain

摘要

When I opened my curtains this morning and looked out onto my roof, I noticed that the rainwater, normally clear, had turned bright red (see photo). Does anyone have any clue as to what could have caused this colouration?rn The most probable explanation is the presence of spores of Trentepohlia, a lichen-forming alga. This alga can be found on tree bark, roofs, damp soil and even lamp posts. The colour would have been caused not by algal growth but by the release of spores.