1-Cystoseira sedioides -This brown alga is an endemic species which habitat is strictly on the north African coast. In Tunisia, it is only present from Tabarka to Bizerte. It lives in shallow waters on rocky sea shores where pollution is absent.
Here, we see a specimen from the Bizertin coast where are fixed young  edible mussels (Mytilus galloprovincialis).

2-Cystoseira spinosa
Cystoseira spinosa is a  sciaphilous Mediterranean endemic  brown alga which habitat is  on rocky shores. To day, it disappeared from a great part of Mediterranean area, but,  it is still present in Tunisia on the  Tunis gulf's coasts.
 
 

3-Cystoseira schiffneri

Cystoseira schiffneri is a  Gabès gulf's endemic  brown alga which habitat is  on rocky shores.  It is  abondant and frequent  on the Kerkena and Jerba islands sea-shores.
All these species can be considerated as  very threatened .
photos  by J. Zaouali