| The resource status of macrozoobenthos and characteristics of ecological environment in the mainstream, main tributaries and affiliated reservoir of the Ili River and Irtish River in Xinjiang(China) have been investigated from 2012 to 2014. We studied the characteristics of community structure in the two rivers, including the species composition, dominant species, density, biomass and the spatiotemporal pattern. Based on the data of zoobenthos community structure, we built the B-IBI assessment criteria to evaluate the health of the two rivers. Furthemore, we used the technique of DNA barcoding to classify species in Xinjiang through comparing the phylogeny relationship of macrozoobenthos between Xinjiang and other areas. The main results were shown as follows:A total of 94 species of macrozoobenthos were recorded in the Ili River, among which Insecta(75 species), Oligochaeta(3 species), Mollusca(9 species) and others(7 species), accounting for 79.8%, 3.2%, 9.6% and 7.4% of the total species number, respectively. In the Irtysh River, a total of 117 species of macrozoobenthos were recorded, among which Insecta(106 species), Oligochaeta(3 species), Mollusca(6 species) and others(2 species), accounting for 89.8%, 2.5%, 5.1% and 1.6% of the total species number, respectively. Insecta distributed throughout the river basin of the two rivers, Mollusca distributed mainly at Nileke in the Ili River and Tuohongtai reservoir, 635 in the Irtysh River. Mayfly larva and Chironomidae larva were the dominant taxa in these two rivers. Predator and gatherer were the dominant functional feeding groups(FFG), which accounts for a large proportion of the macrozoobenthos species, followed by the scraper. In particular, the shredder was the lowest FFG in the two rivers. The distribution of Insecta was correlated negatively with p H in the Ili River(p<0.01). And the biomass of macrozoobenthos was correlated positively with water velocity(p<0.01). In contrast, the distribution of aquatic insect was correlated positively with water transparency in the Irtysh River(p<0.05). Oligochaeta was correlated positively with the salinity, conductivity and TDS(total dissolved solid), but correlated negatively with the resistance(p<0.05). There was no significant relationbetween the distribution of Mollusca and environmental 12 factors. The density of macrozoobenthos was correlated positively with water transparency. The biomass was correlated positively with the salinity, conductivity and TDS(total dissolved solid), and had negative relation with the resistance.The species number of macrozoobenthos exhibited temporal and spatial patterns. Seasonal trend was shown: normal season > wet season > dry season. In particular, the sampling site Yanchi had the lowest species number(6 species) in the Irtysh River, followed by sampling site 185(14 species). For the tributaries, the upstream reach in Bu‘erjin River had the highest species number. In the Ili River, Sanxiang had the lowest species number(16 species) and Kashi River(47 species) showed the highest species number in the three tributaries, followed by Gongnaisi River(37 species) and Tekesi River(32 species).The annual-averaged density and biomass of zoobenthos in the Ili River and Irtysh River was 299.43 ind./m2, 4.59 g/m2 and 518.55 ind. /m2, 4.94 g/m2, respectively. Insecta contributed the most to the density and biomass of zoobenthos in these two rivers. In the Ili River, the average density and biomass was 242.81 ind./m2 and 2.54 g/m2, which accounted for 81.09% and 55.34% of total average density and biomass, respectively. And the values were 380.28 ind./m2 and 4.33 g/m2, 73.33% and 87.65%, respectively in the Irtysh River. The density of zoobenthos was the highest in wet season and the lowest in dry season for the two rivers. In contrast, the biomass of macrobenthos was higher in normal season than that in wet season. Among three tributaries, Gongnasi River had the highest density of macrozoobenthos and Kashi River had the highest biomass, and Tekesi River exhibited the lowest density and biomss in the Ili River. In the Irtysh River, the density of macrozoobenthos in the mainstream was more than those at the tributaries, and the upstream region in Kelan River had the highest density(487.57 ind./m2) of macrozoobenthos. But the biomass in tributaries was more than those at the mainstream, and Kayierte River exhibited the highest biomass(15.52 g/m2).Three and Five key metrics were detected and entered into the final B-IBI system for Ili River and Irtysh River, respectively. The assessment criteria of B-IBI in the Ili River was as follows: B-IBI>1.31 represents excellent, 1.01<B-IBI≤1.31 represents good, 0.68<B-IBI≤1.01 represents fair, 0.34<B-IBI≤0.68 represents poor, B-IBI≤0.34 represents very poor. In the Irtysh River, the criteria was B-IBI>2.04 represents excellent, 1.02<B-IBI≤1.53 represents good, 0.51<B-IBI≤1.02 represents fair, 0.51<B-IBI≤1.02 represents poor, B-IBI≤0.51 represents very poor. Based on the assessment criteria presented, 3 reaches of Ili River were excellent or good, 2 were fair and 3 were very poor, and the ecological status varied seasonally. In the Irtysh River, 6 reaches were excellent or good, 3 were fair and 1 was very poor. Overall, Kashi River and Gongnaisi River in Ili River basin belonged to better state except partial reaches of this river, but the mainstream was poor.A total of 131 sequences were determined from the collected specimens and were composed of 27 in the Ephemeroptera, 40 in the Plecoptera, 24 in the Trichoptera, 10 in the Hemiptera and 31 in the Diptera. The sequence length of the order were 662 bp for Ephemeroptera, 628 bp for Plecoptera, 661 bp for Trichoptera, 602 bp for Hemiptera and 667 bp for Diptera, respectively. Cluster analysis showed that the sequences of the same macrozoobenthos order were from BOLD and our sequenced were divided into the same groups, suggesting that the technique of DNA barcoding classified the species of macrozoobenthos effectively accompanied with morphological and molecular approaches. |
PDF Full Text Request