Cystoseira barbata

Cystoseira barbata is a large, canopy-forming brown macroalga native to the shallow subtidal zones of the Mediterranean Sea and the Black Sea. It requires rocky substrates to anchor itself using a root-like structure called a holdfast.

This seaweed features highly branched, bushy thalli that can grow up to a meter in length. It is characterized by small, gas-filled bladders along its branches, which help the algae stand upright in the water column to capture sunlight.

It forms dense underwater forests that provide crucial habitat, shelter, and nursery grounds for a wide variety of marine life, including fish and invertebrates. Because it is highly sensitive to pollution, its presence is used as an indicator of high water quality.

While it is not officially listed as a single global endangered species, populations of Cystoseira barbata have severely declined across the Mediterranean and Black Seas. This regression is primarily driven by coastal urbanization, pollution, and the invasion of non-native algae species.