Cystoseira is a genus of brown algae in the order Fucales.

Description

As presently defined, Cystoseira comprises fucoids characterised by antherozoids without stigmata, few antheridial branches, trichothallic hairs in conceptacles, large ovoid oospheres, and eggs that remain attached to the surface of the receptacles through mucilaginous stalks until after fertilization.

Distribution

Cystoseira as presently defined occurs only in the Mediterranean and Northeast Atlantic. Species from the Indian and Pacific oceans are presently included in different genera.

Ecology

Cystoseira are important habitat-forming species in coastal waters of the Mediterranean and Northeast Atlantic. They require good water quality, and can be used as bioindicators for pollution levels.

Species

Cystoseira was recently found to include multiple unrelated lineages. As a result, most species were moved to the genera Stephanocystis, Polycladia, Sirophysalis, Gongolaria and Ericaria. As of January 2024, AlgaeBase lists the following non-fossil species as accepted: Many of these species are poorly studied and require validation.