41 Ecological status of urban ponds in Białystok, Poland Limnol. Rev. (2016) 16, 1: 41-50 DOI 10.2478/limre-2016-0005 Introduction Small water bodies, both natural and those cre- ated due to human activities, are an essential compo- nent of the urban environment. Tey ofer great spatial variety and afect many environmental characteristics. Te constant presence of surface water modifes the microclimate and reduces the amplitude of tempera- ture and humidity (Kajak 1998). Water bodies and the surrounding vegetation are an integral part of the ur- ban ecosystem, and contribute to growth in biodiver- sity. In addition, they afect aesthetic appearance and the development of recreation in a city. Tey can also act as receivers of rainwater and various substances, including toxic ones (Jarosiewicz et al. 2012). Due to their typically small depth, the bottom of such ponds is completely covered with water vegetation. Te Dojlidy Ponds (DP) in Białystok are an ex- ample of waters of limnic character within urban ar- eas. Te construction of artifcial water reservoirs in the vicinity of settlements has always been driven by water retention for economic purposes. Te origins of water retention in Dojlidy date back to the activity of Klemens Branicki in Białystok and neighboring areas (Dobroński 2010). In the interwar period they served as breeding ponds. Based on the existing fsh ponds in Dojlidy, another big investment began in 1933, i.e. construction of a swimming area in Dojlidy. Te bathing beach was opened in May 1936 and its role of recreation and sports was restored in the 60-70’s of the twentieth century (Dobroński 2012). Te Sports Club was created on the largest reservoir (Plażowy). Its current shape and the recreation facilities ofered there are primarily due to a thorough modernization, completed in 2014. During the development of the recreational and sports complex several reclamation treatments were performed, including mowing the submersed macrophytes and cleaning the bottom. Te aim of these studies was to: (i) assess the current hydrochemical and ecological status of the Dojlidy Ponds, and (ii) indicate the anthropogenic threats to the aquatic environment in the southeastern area of Białystok. Ecological status of urban ponds in Białystok, Poland Elżbieta Jekatierynczuk-Rudczyk, Piotr Zieliński, Katarzyna Puczko Department of Environmental Protection, University of Białystok, Ciołkowskiego 1J, 15-245 Białystok, Poland, e-mail: rudczyk@uwb.edu.pl (corresponding author) Abstract: Stawy Dojlidzkie (Te Dojlidy Ponds) are located in the north-eastern part of Poland, near the capital of the Podlasie province, in Białystok. Te Dojlidy Ponds (DP) are a complex of more than 20 reservoirs arranged adjacent to one another in an area of about 140 hectares. Te largest recreation reservoir (Plażowy) is located within the city limits. Its total area is 34 hectares, it has a capacity of 597 040 m 3 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 frst 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. Te average value of TSI was 55 in the water of the tested objects. Te 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. Key words: ecological status of water, trophic status, ESMI