Ecological Status of Urban Ponds in Białystok, Poland

Stawy Dojlidzkie (The Dojlidy Ponds) are located in the north-eastern part of Poland, near the capital of the Podlasie province, in Białystok. The Dojlidy Ponds (DP) are a complex of more than 20 reservoirs arranged adjacent to one another in an area of about 140 hectares. The largest recreation reservoir (Plażowy) is located within the city limits. Its total area is 34 hectares, it has a capacity of 597,040 m³ and a maximum depth of approximately 2.5 m. DP are supplied by a tributary of the Dojlidy Górne and the River Biała, the principal river of Bialystok. Water tests of a limnic and lenitic character in the upper part of River Biała catchment in Bialystok were conducted from March to October 2014. Referring the obtained results to the actual norms, it can be concluded that most of the parameters analyzed in DP can be assigned to the first class of surface waters. Exceptions were the iron ions, orthophosphates (SRP), total phosphorus (TP), Kjeldahl nitrogen, and also water color and DOC. According to the evaluation of trophic status, the water of DP is eutrophic. The average value of TSI was 55 in the water of the tested objects. The obtained results show that the ecological status of water in the largest pond within the DP complex, in accordance with, the Ecological State Macrophyte Index (ESMI) represent to the good state.