Quantitative ökologische Analyse eines Rifflagunenareals bei Aqaba (Golf von Aqaba, Rotes Meer)

Abstract

Following previous investigations on a fringing reef in the Red Sea near Aqaba (Mergner & Schuhmacher, 1974; Mergner & Svoboda, 1977) this paper presents a quantitative analysis of the faunal and floral stock in one of the selected test areas (5×5 m) located in the reef lagoon studied. During the observation period 237 macrobenthic species of 192 genera were found. Species numbers were 22 (algae), 18 (cnidarians), 22 (crustaceans), 113 (molluscs), 27 (echinoderms), 14 (fishes) and 21 (smaller animal taxa including foraminiferans, sponges, turbellarians, polychetes and ascidians). These numbers, though derived from a small and relatively monotonous reef area, exceed by far all data known from comparable reef zones. The ecological conditions as well as habitat preferences, times of occurrence, seasonal abundances, species diversities and dominances of the inhabitants observed in the test area are discussed. Comparisons of the population data of October, 1975 and March, 1976 indicate the influence of the succession, abundance and disappearance of the phytal on the environmental conditions of the mobile fauna, for example molluscs, echinoderms and fishes. The increase of some of its species, especially of juvenile individuals, is remarkable. Within the same period juvenile colonies of some xeniids and the stony coralStylophora pistillata undergo similar seasonal fluctuations; colonies eliminated by grazers or other, unknown circumstances, are replaced by new settlers. Altogether, the faunal and algal stock of this lagoon area can be interpreted as a climax community; its impressive density is apparently the result of a high number of various microhabitats. Each of these ecological niches provides manyfold living spaces for specific communities with different adaptive strategies. The highest number of species plus the highest diversity indices rank mostly among the mobile groups.