İNŞaat mühendiSLİĞİ anabiLİm dali

Taxonomy, Distribution, Biology and Ecology of Octocorallia Species Present Around the Islands of Marmara Sea
The aim of this thesis was to identify Octocoral species in the Marmara Sea, determine their regional densities and investigate demographic parameters of a representative species of the Marmara Sea. In order to achieve this aim, octocorals were surveyed from the halocline to 40 meters deep by Scuba diving with transect and quadrate techniques. Nine genera, 14 octocoral species belonging to all three orders of the subclassis Octocorallia were identified in this study. Eleven species were found in the Northern Marmara Sea whereas all 14 species were found in the Southern Marmara Sea. Densities of the species were calculated for each station of the study. The diversity and distribution of octocorals in the Marmara Sea were compared to that of the Mediterranean Sea and the differences encountered are discussed. The soft substrates in diving depth limits (20-40 m) where the lower layer seawater of the Marmara Sea is predominant were mainly colonized by sea pens and Veretillum cynomorium was the most common species. Alcyonium palmatum was the most common species in all the Marmara Sea. The mixed and hard substrates of the Northern and Southern Marmara Sea were significantly different in terms of octocoral diversity and abundance. The assemblages consisting of the gorgonians Paramuricea macrospina and Spinimuricea klavereni along with the soft coral Paralcyonium spinulosum as well as those where the gorgonian Eunicella cavolini was dominant were common in the Northern Marmara Sea. Whether P. macrospina and S. klavereni were opportunistic species adapted to the highly turbid environment with low light and high sedimentation conditions of the Marmara Sea was discussed. As for the Southern Marmara Sea, gorgonian assemblages were less common whereas soft corals assemblages (consisting of species such as Alcyonium coralloides, Alcyonium acaule) were more common. The threats such as fisheries and mucilage that can impact corals and gorgonians in the Marmara Sea were argued and protective measures, including the expansion of the present areas closed to fisheries, removal of abandoned fishing nets, prohibition of anchoring and better prosecution of the prohibitions, were presented.
Moreover, the density, size distribution, growth and reproductive features of the species S. klavereni which was found to be common in the Northern Marmara Sea were investigated. In summary, it was found that S. klavereni is a common species on all types of substrates except those formed by fine sand/mud without gravels/pebbles from the depth of the halocline (shallower than the species distribution in the Mediterranean Sea) in the Northern Marmara Sea, that it has a distribution along extensive areas but in low densities (0,35 ± 0,13 colonies.m-2), that it can reach 110 cm high, that the population size distribution is approximately normal (43 ± 20 cm), that it grows fast (4,96 ± 3,01 cm.year-1), that it is a gonochoristic species (female:male sex ratio: 1,64:1) and reproduces year round by broadcast spawning (maximum ovocyte diameter: 538,3 µm; maximum sperm sac diameter: 680,3 µm; mean fecundity: 65 ± 27 ovocyte.polyp-1; mean sperm sac.polyp-1: 38 ± 18) whereas the size at first reproduction was determined as about 20 cm high.