Threatened species of Eustigmatophyceae

Nature 
***.
Background 
These are unicellular organisms found primarily in soil and freshwaters. Only a few species are known. The taxonomy is unclear with different treatments according to author. Some place the class Eustigmatophyceae in the Chrysophyta, others in the Heterokontophyta, and yet others in the Protista (regocognizing its single cell nature).
Type 
(C) Cross-sectoral problems