Interspecific variability of the red algae: Hypnea musciformis, Gracilaria multipartita and Gelidium sesquipedale (Rhodophyceae) of the Moroccan atlantic coastTotal analysis of the growth of three red algae species; Hypnea musciformis, Gracilaria multipartita and Gelidium sesquipedale were undertaken with an aim of determining interspecific variability within the same natural environment. The studied site is the beach of Mehdia located at the north of the Moroccan Atlantic coast. The results show specific differences in the growth rates of the three studied species. Gracilaria multipartita presents a significant development of the growth parameters like the size, the weight and the total ramification, especially for the aestival period compared to Gelidium sesquipedale and Hypnea musciformis. The active growth periods of Gracilaria multipartita are characterized by slightly important temperatures and light intensities and by high percentages of nitrates and phosphates. On the other hand, the growth of Hypnea musciformis shows fluctuations due to the variations of the environmental factors. The growth of Gelidium sesquipedale is slow and seems more under the influence of intrinsic factors than environmental factors.

Growth and reproductuive capacity of Hypnea musciformis (Rhodophyceae, Gigartinale) on the Moroccan Atlantic coast Carrageenan producing seaweeds represent an important biomass along the Atlantic coast of Morocco and are exported as raw material without any local transformation, while agar industry is well developed in the country. The aim of the present work is the valorisation of the more abundant seaweeds and their local transformation. Hypnea musciformis is one of the species studied in the laboratory and a potential applicant for exploitation. The first step before exploitation is to gather information about the biology and growth of this species in natural environment or under controlled conditions in the laboratory. The seasonal growth and reproductive ability of this species have been studied during 2 years on two different locations of Moroccan Atlantic coast. The species was fertile almost all along the year and tetrasporophyte phase predominated. H. musciformis has 2 periods of active growth: the first one at the beginning of summer and the second one, less active, in autumn. The biological cycle is under the influence of different environmental factors as light, temperature, salinity position of the thallus on the seashore and acclimatization response of the seaweed to different habitats.