Investigation of Tajan River Quality with Using Population Structure of Benthic Invertebrates and BMWP Index

Bioassessment of the Tajan River with using of BMWP index and population structure of macro invertebrates has been done every month in six research stations with three times in each station at a distance of about 80 km from September 2011 to August 2012. Sampling Invertebrates was done by surber sampler (with an area of 0.1 square meters and with 60µ mesh net), and macro invertebrates were indentified belonging to 32 genera, 30 families, 12 orders and 5 classes. Population structure of macro invertebrates showed that aquatic insect´s larvae dominated among identified in all stations, and sensitive taxa to pollution (EPT) was dominant in stations 1, 3, 4 and 6 respectively, that have significant increase than other stations (p≤0.05). Based on BMWP Index results, research stations are classified in 3 qualitative categories, good, moderate and poor. This index has maximum value at station1, in spring season and has minimum value at station 5, in summer season. The maximum abundance of macro invertebrates there was at station 3, in winter season that has significant increase than other stations (p≤0.05), also the minimum of this index was observed at station 5, in winter season. Population structure macro invertebrates and abundance, %EPT and BMWP indices indicated that stations 5, 6 and 2 are not in an appropriate condition qualitatively.