Ecological Quality Assessment in Izmir Bay Using the Bentix Index

• Alper DOĞAN, Mesut ÖNEN, Zeki ERGEN, Tuncer KATAĞAN, Melih Ertan ÇINAR
• Ege University, Faculty of Fisheries, Department of Hydrobiology 35100 Bornova Izmir, Turkey.
• The Regional Workshop on Marine Sciences & Natural Resources, HIMR, Tishreen Univ., Syria, 25-26 May 2004..

Abstract

Izmir Bay has been exposed to various pollution sources including ballasts from marine transportation and effluents due to increasing human population since the 1960's. These are more evident in the innermost part of the bay. In the recent years, an effective effort to reduce the pollution in the bay has been undertaken by establishing "the Grand Canal Project" which was taken into effect in February 2000. It is planned to gather all kind of wastes coming from the rivers and human activities in a treatment plant established in Cigli 30 km far from the inner bay, and to release them, after processing, to the outer part of the bay where water circulation is more favourable.

The aim of this study was to assess the effects of the pollution on the benthic communities of Izmir bay, by using two ecological indicators namely the BENTIX and Shannon Wiener's Diversity Index (H'). Samples were taken from 15 stations seasonally, by Van-Veen grab between autumn 1995 and summer 1996 and were sieved on the board through 0.5 mm mesh size and fixed in a 5% formalin solution. In the laboratory, the samples were washed in fresh water, sorted under a stereomicroscope and preserved in 70% ethanol. The sorted materials were identified to species level. Based on the quantitative analyses, the BENTIX (={6 X % GI + 2 X (% GII + % GIII) } / 100) (S?mboura & Zenetos,2002) and Shannon Wiener's Diversity (H') (Shannon & Weaver, 1949) indices were used in order to analyze the effects of the pollution on the benthic communities of the bay.

A total of 298 species and 6014 individuals belonging to the major systematic groups, Sipuncula, Nemertini, Turbellaria, Polychaeta, Phoronida, Crustacea, Mollusca, Bryozoa, Echinodermata and Tunicata were determined. Results derived from the calculation of the bentix and community diversity indices have shown an increasing trend from the inner towards the outer bay. This is in agreement with KOCATAS (1978; 1980) who, based on the faunistic and hydrographical aspects, has proposed division of the bay into 3 parts (inner, middle and outer). In addition, sharp seasonal fluctuations, especially in the inner bay, have been also evidenced due to increasing sea water temperatures in the hot seasons which have lead to seasonal azoic condition of the seabed (DOGAN, 1998). Conclusively, implementation of the Bentix proved successful in assessing ecological quality status in Izmir bay. The way forward is applying Bentix with more Mediterranean data sets and cross checking the results with known environmental / faunistic observations.