Summary:

Since the Polish accession to European Union we are to obliged to carry out the river quality assessment by biological monitoring. The part of the assessment is a macrophyte-based methods used in the evaluation of the ecological status of rivers in respect of biodiversity. Macrophyte Method for River Assessment has been used since 2007 and provide us information about ecological state of rivers.
The assessment was made at small, lowland Cetynia River (35,6 km total length), which is a left bank tributary of Bug River. At the chosen, examinated section of the river (100 m) was described the composition of water plants (ma-crophytes), morphological and abiotic conditions of the River. The paper presents resolute of preliminary assessment of ecological state of Cetynia River and oxygen indicators (BOD, COD-Cr and dissolved oxygen).