The effect of submarine thermal springs of Doganbey Cape (Seferihisar - Izmir) on foraminifer, ostracod and mollusc assemblages

Abstract

The aim of this study was to figure out the effects of the submarine hot water springs located on the coast of Doganbey Cape (north of Kusadasi Bay) on various micro- and macrofaunal assemblages living around these springs. Young sediment samples were collected from different depths at 15 stations. The benthic foraminifer, ostracod and mollusc faunas were investigated. 35 genera and 61 species of benthic foraminifers, 16 genera and 20 species of ostracods and 14 genera and 15 species of molluscs were identified. Typical Aeegan foraminifer fauna was found to be dominant. Besides, individuals with colored tests or abnormal morphology, as well as alien species, which are frequently observed on the Aegean coasts were also observed in the study area. The foraminifer, ostracod and mollusc species also constituted typical Aegean fauna. It is known that the ecological conditions experienced of the Amphistegina lobifera Larsen individuals in typical Aegean benthic foraminifer assemblage have an effect on the abundance distribution. Ideal conditions for Amphistegina lobifera Larsen was found to be 18.00-32.00 m depth range and 19-20 degrees C temperatures. CTD conductivity values gradually increased near to the hot water spring but a decrease in the number of individuals were observed. Chemical analyzes in sediment samples were performed with X-Ray Fluorescence Analysis Spectrometer (WDXRF). Heavy metal ingredients (Cr, Mn, Co, Ni, Cu, Zn and Pb) of the sediments were evaluated, concentrations were recorded as Cr>Ni>Mn in samples DB1-DB6 and also in DB15; Mn>Cr>Ni in DB8-DB11 and DB13-DB14; Cr>Mn>Ni in DB7 and in DB12. The radioactive elements U and Th were found to be high in DB9, DB10 and DB11. The chemical and radioactive properties of the sediments were observed to affect the tests of benthic foraminifers, where as no such effect was found on ostracod and mollusc tests.