Mengzhen Xu

Effects of pollution on macroinvertebrates and water quality bio-assessment

Many large rivers in China have an inflow of contaminated water. Water pollution caused by urban sewage and agriculture, and occasionally pollution events from industries have become a significant stress on aquatic ecology. Pollution affects the biodiversity of the aquatic community and the species composition changes from natural species to tolerant species. The species composition of aquatic animals may reflect water pollution level. Extremely non-uniform distributions of functional feeding groups occurred as a result of high nutrient levels. A combination of chemical and biological methods constitutes the best approach for biological monitoring studies that measure water quality. Macroinvertebrates were used as bio-assessment indicator to determine the environmental quality of given water body. In this study, samples of water and macroinvertebrates were taken from several dozen sites in 14 rivers in China with different pollution levels, including the Yangtze, East, Weihe, Songhua, Yongding, and Panlong rivers. Macroinvertebrates were identified to genus or family level. Water samples were classified into different water quality grades according to the concentration of different substances. Five biological indices: taxa richness (S), density (D), total BMWQ score (t-BMWQ), average BMWQ score (a-BMWQ), and the family biotic index (FBI) were used for biological assessment of water quality. Analyzing macroinvertebrates’ occurrence in different water quality levels, taxa-specific indicators, which are defined as the taxa of macroinvertebrates that live in a certain water quality level but do not exist in other water quality levels were proposed for water quality bio-assessment. Leptophlebiidae, Siphlonuridae, Arctopsychidae, Perlidae, and Antocha sp. are the taxa-specific indicators for very good or good water quality; Chironomidae, Lymnaeidae, Tubifex sp., Limnodrilus sp., Limnoperna lacustris, Corbicula sp., Macrobrachium sp., Planorbidae, Glossiphoniidae, and Branchiura sp. are the taxa-specific indicators for very poor water quality; and Psychomyiidae and Hydroptilidae are the taxa-specific indicators for moderate water quality.

Eco-hydraulics and eco-sedimentation studies in China

This paper reviews the state-of-the-art eco-hydraulic and eco-sedimentation studies in China, particularly focusing on the impact of hydropeaking, habitat suitability modelling, bio-invasion control strategies, sediment transport effects on river ecology, and ecological restoration. Field investigations found that macro-invertebrate species number reduced nearly to zero in a short reach downstream of a dam due to hydropeaking, resulting from a hydropower station. Habitat suitability modelling for the Chinese sturgeon indicated that the habitat suitability was reduced after the Three Gorges Dam began filling. Macro-invertebrate species number and fishery harvest reduced sharply after riparian lakes were cut-off from the Yangtze River. Invasion and dense attachment of mussels on water transfer tunnel walls have caused biofouling in many countries. An effective control strategy, using hydraulic control methods for the golden mussel invasion is proposed. Erosion, sediment transportation, and deposition create and change habitats for many macro-invertebrate species. The biodiversity and number density of individual invertebrates are high in stable streams, lower in incised streams and streams experiencing sedimentation, and lowest in streams with intensive sediment transport. In stable streams, macro-invertebrates colonized a layer of bed sediment up to 60 cm, in which different species preferred different depths. For incised streams, the ecosystem was restored with artificial step-pools, which stabilized the channel bed and created high-habitat diversity. The problems and studies presented in this paper indicate the growth points of the discipline of eco-hydraulics and eco-sedimentation.

An exploratory analysis of benthic macroinvertebrates as indicators of the ecological status of the Upper Yellow and Yangtze Rivers

This study presents findings of the first systematic analysis of aquatic biotic assemblages in the source region of the Yellow and Yangtze Rivers. It provides an initial basis with which to select representative organisms as indicators to assess the aquatic ecological status of rivers in this region. Macroinvertebrates are considered to be good indicators of long-term environmental changes due to their restricted range and persistence over time. Field investigations of macroinvertebrates were conducted in August 2009 in the source region of the Yellow River, and in July 2010 in the source region of the Yangtze River. Altogether 68 taxa of macroinvertebrates belonging to 29 families and 59 genera were identified. Among them were 8 annelids, 5 mollusks, 54 arthropods and 1 other animal. In the source region of the Yellow River, taxa number, density and biomass of macroinvertebrates were 50, 329 individuals m−2 and 0.3966 g dry weight m−2, respectively. Equivalent figures for the source region of the Yangtze River were 29, 59 individuals m−2 and 0.0307 g dry weight m−2. The lower benthic animal resources in the source region of the Yangtze River are ascribed to higher altitude, higher sediment concentration and wetland degradation. Preliminary findings of this exploratory study indicate that hydroelectric power stations had a weak impact on benthic dwellers but wetland degradation caused by a series of human activities had a catastrophic impact on survival of macroinvertebrates. Ecological protection measures such as conservative grazing and vegetation management are required to minimize grassland degradation and desertification, and reduce soil erosion rate and river sediment discharge.

The assemblage characteristics of benthic macroinvertebrates in the Yalutsangpo River, the highest major river in the world

Aquatic ecosystems of highland rivers are different from those of low altitude rivers because of the specific topography and environmental parameters associated with high altitudes. Yalutsangpo, the upper course of the Brahmaputra River, is the highest major river in the world, flowing from west to east across Tibet, China and pouring into India. Macroinvertebrates were sampled from Yalutsangpo and its tributaries, the Lhasa, Niyang, and Parlong Tsangpo Rivers, from October 2009 to June 2010, to study characters of the highland aquatic ecosystem. Altogether, 110 macroinvertebrate taxa belonging to 57 families and 102 genera were identified from the basin. The biodiversity and composition of macroinvertebrate assemblages were strongly affected by altitude gradients. Local diversity represented by taxa richness and the improved Shannon-Wiener index were high at altitudes of 3,300–3,700 m, among which suitability of habitat was higher due to the better integrated environmental conditions of water temperature, dissolved oxygen, and aquatic vegetation, etc. Macroinvertebrates were grouped into shredders, scrapers, predators, collector-filterers, and collector-gatherers according to their feeding behaviors. It was found that the distributions of the functional feeding groups varied with habitat altitudes. Shredders were present at altitudes of 2,900–4,400 m, while scrapers mainly inhabited altitudes of 3,500–4,500 m, and collector-filterers preferred 3,500–4,000 m.Even though the local taxa richness was not high at each site, the taxonomic composition and density of the assemblages varied greatly among the different sites, resulting in much higher regional diversity compared to the lowland river with similar flow and substrate conditions. The regional cumulative taxa richness of Yalutsangpo decreased and more families were lost as the altitude increased. However, some families that were newly present as the altitude increased were essential for sustaining the high regional biodiversity. The ordination diagram obtained from Detrended Correspondence Analysis indicated that altitude, river pattern, riverbed structures, bank structures, and flow conditions were the main factors that influenced the macroinvertebrate assemblages in the Yalutsangpo basin.

Macroinvertebrate distribution and aquatic ecology in the Ruoergai (Zoige) Wetland, the Yellow River source region

The Ruoergai (Zoige) Wetland, the largest plateau peatland in the world, is located in the Yellow River source region. The discharge of the Yellow River increases greatly after flowing through the Ruoergai Wetland. The aquatic ecosystem of the Ruoergai Wetland is crucial to the whole Yellow River basin. The Ruoergai wetland has three main kinds of water bodies: rivers, oxbow lakes, and marsh wetlands. In this study, macroinvertebrates were used as indicators to assess the aquatic ecological status because their assemblage structures indicate long-term changes in environments with high sensitivity. Field investigations were conducted in July, 2012 and in July, 2013. A total of 72 taxa of macroinvertebrates belonging to 35 families and 67 genera were sampled and identified. Insecta was the dominant group in the Ruoergai Basin. The alpha diversity of macroinvertebrates at any single sampling site was low, while the alpha diversity on a basin-wide scale was much higher. Macroinvertebrate assemblages in rivers, oxbow lakes, and marsh wetlands differ markedly. Hydrological connectivity was a primary factor causing the variance of the bio-community. The river channels had the highest alpha diversity of macroinvertebrates, followed by marsh wetlands and oxbow lakes. The density and biomass of Gastropoda, collector filterers, and scrapers increased from rivers to oxbow lakes and then to marsh wetlands. The river ecology was particular in the Ruoergai Wetland with the high beta diversity of macroinvertebrates, the low alpha diversity of macroinvertebrates, and the low taxa richness, density, and biomass of EPT (Ephemeroptera, Plecoptera, Trichoptera). To maintain high alpha diversity of macroinvertebrates macroinvertebrates in the Ruoergai Wetland, moderate connectivity of oxbow lakes and marsh wetlands with rivers and measures to control headwater erosion are both crucial.

Ecological Impacts of Seabuckthorn in the Pisha Sandstone Area

There is an area of more than 11,000 km2 in northwest China which is covered by Pisha Sandstone, a kind of loosely bonded sandstone which was formed during the Tertiary period. The sandstone is hard when it is dry and easily changes into sand when wet. The area has a very high erosion rate (over 20,000 t/km2·yr) and very poor vegetation. Seabuckthorn (Hippophae rhamnoides Linn) has been successfully used to reforest gullies and control erosion in the area. Field investigations have been carried out in the Xizhao gully to study the effects of the species on sediment trapping and ecological improvement. It is found that the seabuckthorn mutualizes with Clinelymus dahurcus Turcz, and the two species form dense double-layer vegetation with well developed middle and understory plant communities. The vegetation cover in the gullies reaches 95%. The forest was developed in the late 1990s (first introduced in 1995), with a sediment trapping efficiency of more than 90%. Rainstorm water has also been stored in the gully within the trapped sediment. The water content in the vegetated gully is about twice as high as the uncontrolled plot. The understory community of the seabuckthorn vegetation is much better than in areas forested with poplar or willow. The taxa richness and the thickness-coverage of the sublayer vegetation in the seabuckthorn area are about twice as high as in the latter two.