Selected Nutrients and Iron in Interstitial Waters of the Estuary of Southern Baltic (Gulf of Gdañsk and the Pomeranian Bay) in Relation to Redox Potential

The following parameters were determined in the interstitial waters of the Gulf of Gdańsk and the Pomeranian Bay: nutrients (ammonia and phosphates), sulphates, total iron and iron(II) concentrations. Redox potential (Eh), pH, humidity and organic matter content measured as a loss on ignition were determined in bottom sediments from these regions. Interstitial waters of both regions were found to have reducing character (Eh < 250 mV). Reduction processes were more advanced in the Gulf of Gdańsk, rich in organic matter, as evidenced by lower values of the redox potential, lower Fe(III)/Fe_tot ratio, and incidents of sulphates exhaustion.