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Chlorophyta, Green Algae

Ulva (Enteromorpha) compressa (Linnaeus) C. G. Nees

Chlorophyta, Order: Ulvales; Family: Ulvaceae. Current accepted name: Ulva compressa Linnaeus.


Ulva (Enteromorpha) genus refers to the tubular shape of the thallus, which resembles an intestine. Two layers of reproductive cells are attached to one another, providing the name of the species (compressa), meaning ‘compressed’, ‘flattened’ or ‘pressed together’.


The Ulva (Enteromorpha) compressa connects to the substrate using a disk-like holdfast made of several rhizoids. The algal base, which emerges from the holdfast, is narrower and gradually widens towards the centre of the thallus. The thallus is tubular, more or less cylindrical; sometimes it is

partially flattened, single layered and then forming several strands. The thallus is simple, usually with no branching, and where this occurs it is minimal. An overview usually reveals the thallus cells arranged in rows; however, sometimes, in some areas, they are irregular. The cells are mostly arranged in a rounded rhombus, and the chloroplasts laminate, filling most of the cell seen on the surface. There is usually only one Pyrenoid .


The Ulva (Enteromorpha) compressa’s thallus usually reaches 40 cm in length, and in extreme cases even longer. The thallus’ strands are usually shorter. The thallus width reaches 2 cm and sometimes double that.


The Ulva (Enteromorpha) compressa is coloured yellowish-green to greenish-blue.


Special features

The flattened thallus is characteristic of this alga, as is the cellular arrangement and paucity of branching.


The alga is very common and grows in the upper region of the intertidal zone.

Biology and reproduction

As in Ulva. see entries.

Seasonality and distribution

The Ulva (Enteromorpha) compressa appears year round, usually along with Ulva. The alga is the primary constituent of the supra-tidal zone community, and it is rare to find other species in its neighbourhood. The Enteromorpha’s appearance is cyclical, based on environmental conditions. Under favourable conditions it can occupy the entire habitat,  but not for a lengthy period. Seasonal catastrophes, such as a strong storm that can uproot the plants, or several days of continued low-tide causing exposure and dehydration, harm the colony and enable to develop other species in the habitat.

General distribution is more or less universal, and it is considered one of the most abundant and widespread algae in the world.

Additional species

The Ulva (Enteromorpha) compressa belongs to the group of Ulva (Enteromorpha) intestinalis (Linnaeus) Nees. It has two sub- species:

 Ulva (Enteromorpha) compressa (Linnaeus) C. G. Nees Var.

 compressa Ulva (Enteromorpha) compressa (Linnaeus) C. G. Nees Var. usneoides (Bonnem and J. Agardh) Bliding.

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