Phosphate, nitrogen and iron enrichment in the polluted Izmir Bay, Aegean Sea

Abstract

Izmir Bay is one of the most polluted estuaries in the Mediterranean Sea. The extent of pollution due to anthropogenic inputs in the Izmir Bay is investigated on the basis of nutrients together with basic oceanographic parameters. Significant phosphate, nitrogen (N) and iron (Fe) enrichment has been found in the water of inner Izmir Bay. The situation of middle Izmir Bay is also similar but not as critical as in inner Izmir Bay, whereas outer Izmir Bay shows ‘typical Mediterranean coastal marine ecosystem’ characteristics. The average atomic ratios of apparent oxygen utilization (AOU) and nutrient fractions (N and phosporous [P]) have been found as AOU:P (49:1), AOU:N (48:1) and N:P (5:1). A comparative evaluation of these ratios leads to the conclusion that they are too low; e.g. such a low AOU:P ratio supports fairly high P enrichment. Principal component analysis (PCA) indicates that 31% of the variation in the data is related to enrichment parameters, i.e. dissolved inorganic phosphate, NH 4 +, reactive Fe, 15% is related to NO 3 −, pH and 13% is related to temperature and total Fe. Additionally, PCA shows that the middle Izmir Bay has an ecological transient character between the inner and outer Izmir Bay.