Benthic Fauna Shifts Downstream from Alluvial Gold Mine: A Case Study in a Subpolar Urals River

Background and Objective: Intensive industrial development of the northern territories of Russia has led to increasing impacts on aquatic ecosystems. This study presented the aquatic ecological impacts of suspended solids emitted from an alluvial gold mining site in the Hobe-U river, a small subpolar mountain river in the northern Urals. The objectives of the research were the following: To examine whether the riverine macroinvertebrate community is negatively impacted by suspended solids contamination, to test whether the Index of Trophic Completeness (ITC) and its feeding guilds were appropriate for use in this part of the world. Materials and Methods: The article contained two years of summer macroinvertebrate abundance and biodiversity data from pristine and two impacted locations along the river. The samples were collected with benthic D-frame kick-net with a blade length of 30 cm in 3 replicates at a riffle site. Dominant species were defined by biomass values. For each taxon the functional feeding group was determined. Common descriptive statistics (such as mean and Min-Max diapason, percentages, frequency counts) were calculated in MS Excel 2007 and statistical package STATISTICA 6.1. Results: During the research 31, 14 and 23 taxa of benthic macroinvertebrates were found at pristine, impacted and downstream locations of the Hobe-U river. Water turbidity upstream of the mining polygons did not exceed 5 mg LG 1 . Impacted and the third downstream sites had mean turbidity values 30.15 and 14.4 mg LG 1 , respectively. Of total 12 trophic guilds of Index of Trophic Completeness (ITC) their amount varied within three sampling locations as following: 2007-8, 5, 7; 2008-7, 4, 7. Conclusion: At the site impacted, a decline in biodiversity, species domination, trophic structure of the benthic community were observed. The most unaffected trophic guilds included active predators, scrapers and detritivores, while other guilds had disappeared completely from the benthic community. The ITC bio-assessment approach was able to distinguish between an impacted and reference site and provides ecological insights into sensitive species and the impact on ecosystem.