roman_romanov's Identifications

Violet-black cells in gelatinous sheaths at the surface of a layer of gelatinous cyanobacteria, growing on a lost sock in the mud of a flooded abandoned limestone quarry. I'm not certain that these photos are all of the same organism - some are dark violet and some are more strongly just black. The violet capsule absorbs so much light that it is difficult to induce autofluorescence in the chlorophyll of the cell inside. The first picture shows the violet layer beside some Trentepohlia. The various pictures demonstrate the colours in contrast to some of the other species present (Hassallia, Trentepohlia). Cells themselves are 3-6 µm and the capsules are 6-12 µm. The surface violet-black layer covers a deep layer of gelatinous cells inside lamellated mucilaginous sheaths, of different generations, that I now think are another species entirely.
Part of a gelatinous community: https://inaturalist.ca/observations/208411876.