Evaluation of ecological and biochemical indices of macrobenthic community in the Sari-Su River (Qarnaveh)

Document Type : Original Article

Authors

1 Department of Fisheries, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.

2 Department of Fisheries, Faculty of Agriculture Sciences and Natural Resources, Gonbad Kavous University, Gonbad Kavous, Iran.

Abstract

Macrobenthic communities typically change in response to alternation of the abiotic conditions and human interferences. The aim of this research was to study the macrobenthic community structure dynamics and a biological evaluation of water quality in Sari-Su River. For this purpose, samples were collected seasonally from four stations (Fountains, Agriculture, Rural and Urban) from 2016 to 2017. Samples were collected using Sorber sampler. A total of 1061 species belonging to eight order and eighteen families, including Ephemeroptera (46%), Diptera (40%), Oligocheta (7%), Odonata (4%) and Trichoptera (3%) were identified. The abundance and diversity of macrobenthos showed a significant spatial and temporal differences. The stations 1 (42%) and 2 (36%) have the highest densities of macrobenthic, station 4 in urban area (6%) has less. Multi-dimensional Scaling (MDS) and clustering analysis showed that, due to the frequency of Ephemeroptera and Diptera orders at stations 2, 3 and 4 of all seasons, the groups are separated in 4 separate sections. Also, the results indicate that the highest Shannon-Weaver (1.66) and Margalof (1.64) were in stations 2 and 3 and in all seasons. One-way analysis of variance showed that water temperature, pH and ammonia were significant difference between seasons. The Hillsenhof index was found to be the highest and lowest in spring (6.75) in autumn (6.25), respectively. There was significant correlations between the different index of biological and some water parameters. Garbage evacuation, agricultural drainage, animal waste are the main causes of the water quality decrease in the studied stations. According to water quality indicators of Sari-Su River, the upstream area are without pollution (Oligosaprobic) and down land area has the highest pollution (Polysaprobic).

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