| ABSTRACT | In light of global ocean acidification processes, it is important to study the highly vulnerable chalk littoral caves and the epilithic algae community within. Littoral caves are mentioned in the UNEP-MAP Coastal Area Management Program as important coastal habitats in the heavily exploited littoral zone. The importance of epilithic algae in littoral caves is derived from its place in creating ecological niches and therefore enhancing biodiversity. Epilithic algae allow organisms that would not withstand high wave energy and low light environment, to succeed in littoral caves by settling on the bare cave walls, and produce a complex structural habitat, enabling other organisms to settle on them. Rosh HaNikra cave, carved into a chalk cliff located next the Lebanese- Israel border in the eastern Mediterranean, is the only littoral cave in Israel that is longer than three meters, thus considered a main tourist attraction and a unique geological nature reserve. In the past month, Rosh HaNikra has also become a 15-kilometer wide marine reserve. Where only a few researchers work on algae ecology in the Israeli coastline, and far less studies concentrating on the chalk algal communities, a gap of knowledge exists in the field of littoral algae ecology in Israel. This study is the first algal survey in the coastal cave of Rosh HaNikra, Israel. Results from this study site quantify and qualify the natural light, identify taxonomically the epilithic algae and study the ecological relationship of the red and green epilithic algae with the surrounding environment. We present in this study a taxonomic survey in the littoral cave, including the presence of Rhodophyta, Chlorophyta and Cyanobacteria communities, as well as seasonal and daily light measurements. High occurrence of the pH and desiccation tolerant Hildenbrandia rubra in the upper-medio littoral zone was very interesting, since the first and only report of this specie in Israel, was made at least 50 km from Rosh HaNikra and more than 40 years ago. Our results indicate that the light spectra changes in quantity as well as quality when entering the cave, which has a constructing effect on epilithic algae communities. Nowadays, characterizing the algal community of the cave system of Rosh HaNikra would provide a baseline for any future ecological research in this site as well as evaluate the marine reserve's significance. |