Résumé:
The study was undertaken on 19 samples taken between 5 and 51 m depth in the West Coast
of Mostaganem. This work aimed to determinate the biodiversity of the fauna living within
the sediment, the type of sediment, and its content in particulate organic matter. The sampling
was carried out from a small boat using a "Van Veen" grab. All the samples from Stidia and
Salamandre presented common species, such those belonging to the Gastropods group
(Turritella communis), those forming part of the Annelids group (Sthenelais boa), and the
group of Crustaceans (Upogebia pusilla). The species identified showed a dominance of
Polychaetes and Bivalves (alive). According to the results of the Shannon and Equability
Index, 15 out of 19 samples indicated that the sampled habitats were out of balance. Three
stations in Stidia and two in Salamandre have a certain balance in terms of biodiversity.
Probably, human activities (industrial and domestic waste, port and development, etc.) have
contributed to the deterioration of the quality of coastal waters and therefore, that of the
sediment. The type of sediment also played a determining role for the quality of the habitat,
especially regarding the ability of oxygen to penetrate the substrate. The study showed that
coarse and medium sand samples contained less than 5% organic matter; probably, this type
of sediment is better oxygenated. The organic matter was more concentrated (5 - <40%) in
sediments composed by fine “muddy like” particles (fine sand and silts); in such a substrate,
the oxygenation was probably insufficient. The sieve analysis showed that the sediment of
Stidia and Salamandre presented a good range. The dominant fractions in all the samples were
0.1 mm (fine sediment) and 0.2 mm (medium sediment); fractions <0.05mm, 0.05, 0.08, 1
and 2 mm were present only in the minority of the samples.
