This is a stage of the alga Halosphaera sp. - a very complicated organism. To be honest: I have the feeling that I will never understand its life cycle. It has also a period with flagellates, sometimes it changes the colour in yellow ecc...
2 pictures
Thank you Charles. You are right.
This alga is really difficult. Therefore I publish here again two pictures from last year from other stages of the same genus Halosphaera. One can see the differences!
These are beautiful images, Franz. The first of the last two images I think shows a double wall with pores. That would make it Pachysphaera, which is more related to Pterosperma than to Halosphaera.
I am very happy about your help. Pachysphaera (syn. Tasmanites) seems to me very probable because it is a member of the same family like Halosphaera - the Prasinophyceae.
oh yes, definitely closely related. And you've got quite a good collection of images from this family together of thingies we rarely come across (Northsea).
BTW, the old class Prasinophyceae will probably fall apart soon, it's polyphyletic. These organisms will however be retained together within the Halosphaeraceae.