ENVIRONMENT

Gdansk is located on the shore of the Gdansk Bay at the mouth of the Vistula River. It forms a tri-city with Sopot and Gnydia. The Vistula flows from the mountains in southern Poland across Poland, and 26 million people live in its catchment area. The river receives municipal and industrial wastewater, 45% of which is discharged untreated into the river, which in turn takes this nutrient-rich load into the Gdansk Bay.

Gdansk Bay is a rather shallow water basin with a sandy bottom. It is separated from the Baltic Proper by the Hel peninsula, which limits the exchange of water.

Vistula River	Gdansk Bay
Lenght 1047 km	Area 291 km²
Flow 1080 m³/s	Mean depth 59 m
	Catchment area 323 000 m²

Research history

The areas of the bay near Gdynia and Hel were studied intensively in 1918-1939. Systematic weather and oceanographic recordings were started by the Marine observation station in Gdynia. This activity was resumed after the Second World War at the mouth of the Vistula, especially during 1958-1965. In 1971-1975 the research was extended to include the entire bay.

Since 1985 pollution in this area has been regularly monitored. The pollution records are kept mainly in the Marine Section of the IMGW Institute in Gdynia. Since the mid-1970s studies of the Bay of Gdansk have been conducted by the Institute of Oceanography at the University of Gdansk.

The ecosystem changes in brief

During the last 30 years there is evidence of an increase of eutrophication due to the massive load of nutrients carried by the Vistula River. Sediment studies have revealed that concentrations of heavy metals have increased in the sediments. Oxygen deficit and hydrogen sulphide are features commonly encountered in the bottom layers. Meanwhile the ecosystem structure of the Gulf of Gdansk has undergone vast changes: the species structure has changed significantly, many species have disappeared and others have become dominant.

The following is a timeline of the most important changes of the ecosystem caused by anthropogenic pollution:

• The end of 1960s - significance increase of nutrient concentrations in water
• The beginning of 1970s - increases in the amounts of suspended solids and considerable deterioration of water transparency
• Mid-1970s - disappearance of Fucus vesiculosus and Furcellaria lumbricalis in the Puck Lagoon (an inner part of the bay)
• Changes in the fish population are observed, e.g. roach, cod, pike, perch and garfish are disappearing. Since 1975 sticklebacks, Gasterosteus aculeatus and Pungitus pungitus, have become more abundant
• Closure of many beaches along the tri-city coast line
• The 1980s - shrinking of underwater grass meadows and fish spawning areas, collapse of coastal fishery
• 1985 up to present - abundance of protozoas. Intensive blooms of brown algae (Ectocarpales) and phytoplankton
• 1993 - area of algal blooms in the bay increased by 7% compared to 1992
• 1994 - the first recorded bloom of toxic bluegreen algae Nodularia spumigena
• 1995 - appearance of a gill neoplasia in the bivalve Macoma baltica
• Gdansk Bay is also suffering from chemical pollution. High concentrations of the following substances are found in the bay: nutrients (N, P), detergents, pesticides, polycyclic aromatic hydrocarbons, aromatic amines, phenols, heavy metals (Hg, Cd, Cr, Se, As, Ni, Pb, Mn, Cu, Fe), and radioactive isotopes.