(1) The pattern of zonation on rocky shores at Mikhmoret, on the central Mediterranean coast of Israel, is as follows: (a) The supralittoral fringe--here a distinct zone rather than `fringe'--is darkly coloured by endolithic blue-green algae. It is inhabited by Littorina neritoides, Ligia italica and some terrestrial arthropods. In its lower part Littorina punctata is abundant and dispersed individuals of Chthamalus depressus occur mainly in fissures and crevices. (b) The midlittoral zone is conspicuously divided into three: (i) The upper midlittoral zone is dominated by a dense population of C. stellatus accompanied by some rivulariacean blue-green algae forming small patches. Towards its lower limit, the red alga Gelidiella tenuissima is found in shaded environments as well as the molluscs Monodonta and Patella. (ii) The mid-midlittoral zone is covered by algae which suppress the chthamalid population. These are usually Ulva and Enteromorpha, but on sub-horizontal surfaces Alsidium helminthochorton becomes dominant. The most conspicuous among other inhabitants is Brachiodontes minimus. (iii) In the lower midlittoral zone, barnacles are usually replaced by an organogenetic crust: on the walls of sheltered shallow pools it is composed of Neogoniolithon notarisi, sometimes accompanied by other incrusting colonial forms; on seaward dipping layers of beach rock it is built up by Vermetus triqueter and is covered by Laurencia obtusa and Spyridia filamentosa; sub-horizontal platforms and horizontal ledges are incrusted by two vermetids, Dendropoma petraeum on the accentuated margins and Vermetus triqueter on the surfaces. The dominant algae on platforms are Laurencia papillosa, usually overgrown by the common epiphytic alga Jania rubens, Spyridia filamentosa and Padina pavonia. The lower midlittoral zone has a versatile rich, mobile and sessile `epiphytic' and `endolithic' fauna. Throughout the midlittoral zone Pachygrapsus crabs and mites are conspicuous. (c) The infralittoral fringe constitutes a real fringe of the infralittoral zone and, as such, it is densely populated by infralittoral communities. These might be dominated by algae as Corallina mediterranea accompanied by Anemonia sulcata and Dasychone cingulata, all overgrowing a crust of Neogoniolithon and serpulid worms. Although a few species only such as fully developed Cystoseira abrotanifolia were found exclusively in the infralittoral fringe, there are others, such as Laurencia obtusa and Brachiodontes minimus, which reach their lower limit of distribution in this belt. (2) Though the width of most belts increases with increased exposure and consequently most belt-boundaries are being vertically displaced, the boundary between the mid-midlittoral and the lower midlittoral, i.e. the conspicuous landmark which sharply divides barnacles in quantity from the vermetid crust, is rather stationary; under all degrees of exposure it stays at about mean sea level. (3) The zonation pattern at Mikhmoret resembles that described from other parts of the Mediterranean. It agrees with the universal features of zonation even though the supralittoral fringe of the Mediterranean is inhabited in part by an endemic and uniquely distributed barnacle, Chthamalus depressus. Although Mikhmoret bears some resemblance to south Mediterranean coasts rather than to north-eastern ones, there are several outstanding features of the eastern Mediterranean intertidal zone: (a) The complete absence of Lithophyllum tortuosum in the mid-midlittoral zone, and thus a lack of the organogenetic algal formation `Trottoir de Tenarea'. (b) The well-developed vermetid formation in the lower midlittoral zone. (c) The relative abundance of warm-sea forms such as Littorina punctata and Pachygrapsus transversus, and Indopacific elements such as Caulerpa scalpellformis and Pteria occa. |
