Chlorophyta, Green Algae
Ulva olivascens P. Dang
Chlorophyta, Order: Ulvales; Family: Ulvaceae.
Etymology
The scientific name of the alga, Ulva, is the ancient name originally given to all algae. Since the days of Linnaeus, the name has been dedicated to the algae most dominant in nature. The Ulva olivascens is coloured green, shading towards olive-green, and hence its scientific name, olivascens.
Description
The Ulva olivascens connects to the substrate through a holdfast from which several flattened thalli emanate. Often, holes can be found in the thallus. A microscopic overview reveals a smooth ‘leaf’ edge. The cells are usually scattered,
and only rarely can small sections of organized cells be seen. Usually a single Pyrenoid.
Size
The size of the thallus varies according to environmental conditions, usually attaining a maximal length of 30 cm; however, lengths of up to 50 cm have been found. The width of the thallus at its bottom is about 110-115 microns.
Colour
The green colour of the Ulva olivascens is comparatively light, tending towards olive-green.
Special features
To identify the alga accurately, a microscope is required. In the field, several flattened thalli can be seen emanating from the same holdfast.
Habitat
The Ulva olivascens grows in pools on the abrasion platform and sometimes in the subtidal zone. Sightings of the species at depths of up to 50 m. have been reported abroad.
Biology and reproduction
See entry in chapter on Ulva.
Seasonality and distribution
This species is apparently very common, perhaps the most prevalent in the Eastern Mediterranean. It is widely distributed and is known throughout the Mediterranean and the North Sea.