this is Haematococcus pluvialis. The akinets contain the carotenoid astaxanthin as a "sun screen". Large quantities of the akinets color water etc. red - thus the trivial name "Blutregenalge - Bloodrain Algae" in German.
10x Darkfield
16x Phase Contrast
63x Brightfield
100x DIC
The flagellated form has a clearly visible central nucleus. The chloroplast contains one or more pyrenoids and is surrounded by a glycocalyx. The plasma strands, that reach out to the border of the glycocalyx, are a characteristic of this flagellate.
Bild 6: 63x Phase Contrast
Bild 7: 100x DIC
Best regards
Ecki