Biogeochemical behavior and distribution of biogenic silica in marine sediments from Izmir Bay, Aegean Sea (Turkey)

• The distributions of biogenic silica were investigated in inner Izmir Bay sediments.
• Diatomeae productivity might have significant importance on the stability of manganese.
• The carbonate content of sediments controls the Mn anomalies from terrestrial sources.
• Maximum values of BSi at inner bay are due to the freshwater source at the deep.

The distribution of BSi (biogenic silica) in surface sediment and pore water from Izmir Bay was investigated using Si-only and Si/Al methods for determining the appropriate methods. Surface sediment samples were collected using a box core from 15 stations in the inner Izmir Bay from March to May 2008. The relationships between biogenic silica, heavy metals and geochemical data were investigated. Si/Al ratios (weight/weight) ranged between 0.88–1.39 for positive BSi values and 1.21–12.409 for negative BSi values.The silica dissolution values showed a rapid increase in Al concentrations during the first 5 h of the experiment when the silica dissolved, followed by constant silica level at all stations. The dissolution curves in all stations have been stable in a maximum DSi (dissolved silica) value after 5 h. The linear curve of Al against the silica dissolution explained the biogenic silica content from intercept. The BSi measurements for this study give more accurate results according to the method of Si/Al. Factor analysis was used to determine the relationships between silica and geochemical data. BSi and Sipore have a strong association with manganese. The diatomeae productivity in the water column has a significant importance on the stability of Mn in the sediment. Carbonate content of sediments controls the Mn anomalies from terrestrial sources in the bay. Maximum values of BSi at inner parts of the bay are due to the freshwater source at the deep.