Background and Objective: Surveying of Balekhloo River’ s water is necessary because it is one of the main branches of Gharasoo River in Ardabil and supplying water for Yamchi dam Due to the presence of contaminant sources such as wastewater, residential areas, and industrial, agricultural and mineral water, river morphology. Today evaluation of water quality based on macro invertebrates variety has completed chemical methods of pollution recognizes. Method: In this study water quality examination of Balekhloo River in Ardebil, macro invertebrates were sampled in 5 stations along the river in 2 times of year (low water season and high water season). For results’ simulation measuring of some physico chemical parametres were perfomed. Macro invertebrates were identified and evaluated with Shannon winner variety index, Margalef biotic index and Pielou similarity index. Findings: In this study, ten orders of invertebrates in 23 categories were identified and counted and result simulation laboratory measured of physico chemical parameters like DO, Nitrate, PH, Debi and velocity. Discussion and Conclusion: Results showed that there are similarities between physical, chemical and biological indexes and Margalef biotic index was known more suitable bio assessment index to determine water quality in Balekhloo River. Finally, by comparison of physical, chemical and bio index parameters of Balekhloo River’ s water quality was classified into three region low, moderate and high pollution.

In order to study the quantity and quality evaluation of benthic invertebrates in shrimp ponds belonging to Persian Prawn Co., in Tiab area (Hormozgan province), sampling of sediments were carried out every other 14 days, from August 18 to October 27, 1998, during the priod of shrimp culture. Sediments were sampled from three different point of 9 ponds by grab (Van Veen 0.02 m2) for identification macrofauna, miofauna, grain size and mesurment of total organic mater. Macrofauna benthics were few and were found only in three ponds. Three groups of miofauna including: Nematoda, Naplius and copepoda were distinguished. Their abundance was increased during main shrimp culturing period and was decreased at the end of it. Silt was the main part of soil in most ponds.

Members of family Pseudocumidae, order Cumacea are among benthic crustacea that constitute a key part of food chain in the Caspian Sea. Study on identification and distribution of these creatures were conducted under the broad project of "Hydrology and Hydrobiology of the Caspian Sea". During this study which was conducted up to l00m depth (depth of 10, 20, 50 and l00m), 9 species of 4 genera were identified. The four most aboundant species were: Stenocuma diastyloides, Schizorhynchus eudorelloides, Stenocuma gracilloides and Schizorhynchus bilamellatus. Density and number of species sampled from different depths with 4 sampling periods were compared.

In order to specify the biological indicators of Zayandeh-rood River, ten sites along the river course from Poleh-Moorkan to Varzaneh in about 210 Km were selected. Three samples from each site were taken in three different seasons (90 samples in total). Sorting and counting of the samples were done in the laboratory and the macroinvertebrates of each sample were identified to the family level using the microscope and the identification keys. The biodiversity of the families of each site was compared and the indicator taxa were specified. The families of Baetidae and Heptagenidae of Ephemeroptera, Hydrpsychidae of Tricoptera and Gammaridae of Crustacea were realized to be the upstream indicators. These indicators were not present in down stream sites, or were present in very low abundance. In contrast, the families of Chironomidae of Diptera, Physidae and Hydrobiidae of Gastropoda and the Oligochaetes were realized to be the indicators of the Poleh-Choom and the other down stream sites.

With regard to the important role of benthos invertebrates in aquatic ecosystems, the purpose of this research was to study about them in Gomishan wetland. The sampling was done by Ekman Grab from the sediments of the wetland bottom within 5 chosen stations for 12 continous months (from Esfand 1377 until Bahman 1378). The specimens were stained by Rose Bengal solvent and then were identified and counted in separate groups of macro-and meio-benthos. Among the macro-benthos, the highest density was observed in Pyrgula caspia species. After that, more density was seen respectively in Abra ovata, Cerastoderma sp., Balanus sp., Nereis diversicolar, Mytilaster lineatus and Dreissena sp. Among the meio-benthos, the highest density was seen in Foraminifera and then respectively in Ostracoda, Nematoda and Bivalve larvae. The indices of diversity and distribution were calculated and are given in this article.