The search for indigenous dune stabilizers: Germination requirements of selected South African species

The coastline of South Africa is characterized by extensive dune fields which are threatened by development, and thus the demand of stabilization of drift sand will increase. The non-invasive alien grass speciesAmmophila arenaria is at present the dominant sand stabilizer. Due to its foreign origin and invasiveness in North America its use was criticized and indigenous sand-binding species would be preferred. The germination requirements of the nativeArctotheca populifolia, Ipomoea pes-caprae. Myrica cordifolia andScaevola plumieri were investigated. The results showed that for all four species the total germination time and germination phase could be shortened and germination success (number of germinated seeds) improved. The different scarification and stratification treatments broke the dormancy ofI. pes-caprae, M. cordifolia andS. plumieri, whereas the seeds ofA. populifolia were not dormant. Seeds ofI. pes-caprae andM. cordifolia had induced an innate dormancy, respectively, whereas the type of dormancy in seeds ofS. plumieri dormancy processes remained unknown.     

Extension of twoCaulerpa species along the Tunisian coast

Two species of the green alga genusCaulerpa are considered as invasive in Tunisia:Caulerpa racemosa andC. taxifolia. C. racemosa is found in a many new localities at the central and southern Tunisian coast, and even in the North of the country in colder water. These new observations lead to the hypothesis of the multiplicity of the origins of the introduction of the species and suggest possible invasive potentialities. The general thallus, and more particularly the number, the shape as well as the arrangement of ramelli on fronds allowed us to identify four morphologically different groups. These groups could be either different systematic entities or polymorphic variations of the same taxon due to different ecological conditions.Caulerpa taxifolia was observed for the first time in Tunisia at the roadstead of Sousse in the beginning of the year 2000. It is recognized as identical to that found in the other Mediterranean localities (GenBank number AJ228960). Up to the end of March 2000, a submarine prospecting campaign revealed an affected area of about 350 ha in front of 2 km of coast. Colonies ofCaulerpa taxifolia disseminating in this area appear in isolated spots. form, In the growing stage, they form surfaces varying between 0.5 to 6 m² and located 20 to 100 m from each other. The total covered surface was estimated to be between 0.5 and 1 ha.     

Rapid shoreline retreat along the Esmeraldas coast, Ecuador: natural and man-induced processes

Along the coast facing the Pacific Ocean in the province of Esmeraldas (Ecuador) one can observe some stretches where a process of rapid erosion is currently in progress. If it is not prevented, it seriously risks compromising the development of any form of utilization. In this paper, which summarizes the observations carried out in three different periods (1989, 1992 and 1999), we express the opinion that this process is the product of two distinct main causes. Along the Atacames bay, which may be considered as the main seaside resort of Quito, the capital of Ecuador, progressive cliff retreat is not only very dangerous for the existing tourist settlements, but also hinders their further development. The shoreline dynamics that seems to be due only to ‘natural’ causes (sea level rising, or the lastEl Niño event) are so active that defence works are not recommended. At Camarones the erosion of the coast is clearly due to the systematic destruction of mangroves by man. Also as a result of the lastEl Niño event, the situation has become alarming and it could rapidly get worse. By means of the present contribution, the Authors intend to attract the attention of the international scientific community upon the processes, not surveyed so far, affecting the ‘weakest’ stretches of the Ecuadorian coast.