The Ochrophyta clade includes mainly algae called "brown algae". Their plastids are surrounded by four membranes, the outermost of which is in continuity with that of the reticulum. They have the same structure as in Haptophyta and Cryptophyta. This structure indicates that they are the result of a true secondary endosymbiosis with a Rhodophyta (Silar 2016). Their colors in brown, greenish, yellowish or golden tones are imparted by photosynthetic pigments which include mainly chlorophyll a, chlorophyll and fucoxanthins. Their reserve polymers are oils such as leucosine or particular polysaccharides such as laminarines or chrysolaminarin. These polysaccharides are small β-1-3 and β-1-6 glucans, comprising from 50 to 60 glucose residues. They are stored in a vacuole on the outside of the plastid.
The Ochrophyta are found in virtually all biotopes: waters marine, freshwater or wetland environments. Some are associated with Eumycota to form lichens. Many species have retained the ability to phagocyte prey and nourish by mixotrophy; others can live by osmotrophy. A few lineages lost secondarily their photosynthetic capacity and thus found an exclusively phagocyte diet. The thalli may be unicellular or multicellular. The lineage of Phaeophyta has even invented a multicellularity complex. Their size can vary from a few microns in unicellular cells, to impressive tens of meters long as Sargassum. The Ochrophyta algae are important primary producers at the base of the chain food. They make up a large part of the phytoplankton and the cover of algae along the coast.
The classification of Ochrophyta was completely upset by the arrival molecular phylogenies that have shown that traditional groupings were artificial and that others, however surprising as the presence in this group exclusively phagotrophic organisms were real. Figure 1 shows only the main lineages because the work of analysis of the different species is far from being finished.


Fig. 1. Phylogeny of Ochrophyta (Silar 2016)