Baltic Proper, Gdansk Basin, Bornholm Basin, Arkona Sea, Gotland Basin, Landsort Deep, Faro Deep during the period 1981 - 1992 (data set limits: 54 49 - 59 23N; 15 05 - 22 11E). Baltic Proper, Gdansk Basin and Gotland Basin during the period 1993 - 1999 (data set limits: 54 54 - 57 23N; 18 24 - 20 25E). Baltic Proper since 2000 (data set limits: 55 31 - 56 05N; 19 14 - 20 39E).

Alkalinity, acidity and pH of the water column

CTD; discrete water samplers; spectrophotometers

The purpose of the research is to determine the amounts of hydrogen sulphide in the deep waters of the Baltic Sea, to evaluate its changes and influence to water quality and biodiversity. Systematic research of the Baltic Sea was carried out by Lithuanian research vessels 'OKEANOGRAFAS', 'VEJAS' and 'VETRA'. Since 1981 the research of the Baltic Sea has been carried out according to the Lithuanian and Helsinki Commission (HELCOM) monitoring programme. Since 1981 hydrochemical investigations have been carried out in a wide net of stations in national and international waters (including Baltic Proper, Gdansk Basin, Bornholm Basin, Arkona Sea, Gotland Basin, Landsort Deep and Faro Deep), later the net of stations became more narrow and since 2000 research in the Baltic Sea has been defined more exactly and has been carried out only in the exclusive economic zone of Lithuania. Samples are taken from bottom water layers. The data are fully quality controlled. Systematic certification of laboratories, participation in an international intercalibrations, internal control, introduced managing system for researches' quality, use of high quality reagents determine quality of data. Data of hydrogen sulphide is stored in archive and saved on hard disk.

Department of Marine Research of the Environmental Protection Agency
Taikos Av. 26
Klaipeda

LT-91149
Lithuania