Succession of benthic community on artificial substratum at Elat (Red Sea)

The development of the benthic community on an artificial substratum in the Gulf of Elat was studied. The artificial substratum exposed for settlement of marine organisms was smooth polyethylene. Every month four test panels were removed and preserved. The animals removed from these panels were sorted and identified, mostly to the specific level. The number of individuals, the wet weight, and the nitrogen content were determined. The community eventually consisted of representatives of ten phyla and about 97 species, as follows: Mollusca, 34 species; Annelida, 23; Bryozoa, 11; Arthropoda, 10; Porifera, 7; Tunicata, 5; Coelenterata. 4; Nemertini, 1 or 2; Nematoda, 1 or 2; and Platyhelminthes, 1. The annelids were the dominant group as measured by the number of specimens, while the crustaceans, molluscs, and bryozoans were the most abundant groups as measured by wet weight and nitrogen content. It was found that 10% of the abundant species made up about 70% of the biomass, 20% made up 90-95%, and 30% made up 99%. Species diversity was calculated by Brillouin's formula, and was found to fluctuate widely from 0.45 to 2.03. The rate evenness ( H H_max) was relatively low (0.09-0.25) for most of the period, which is indicative of a homogenous community. The rate of change in the structure of the communities was found to be relatively high from one month to the next during most of the period, which indicates a high rate of turnover in the various species and their relative abundance. During the year the number of species in the monthly samples increased from 25 to 57.