[Taxacom] Freshwater algae identification

[Robert Huber]

Dear all,

I would kindly ask you for help in identifying the correct genus or
even better species of these calcifying freshwater algae ?

Some pictures can be found here : http://www.yogile.com/t85ebwks .

The samples have been taken from heavily encrusted stones from the
shoreline of a prealpine lake.

So far I could identify short cylindric cells forming elongated
filaments surrounded by a thick sheath. On some pictures one can see
basal heterocysts, so my first approach was to classify that as
Dichothrix or Schizothrix, maybe Dichothrix calcarea?. However I am
not sure about the false branching I think I see in some pictures, so
it might also be a Tolypothrix species?

It would be very nice if the algae experts here could take a short
look at the pictures, any comment is very welcome..

best regards,
Robert