Researches On The Community Characteristics And Habitat Preferences Of Macroinvertebrates In The Taizi River

Based on sampling of macroinvertebrate communities in Taizi River Basin, the northeastern China, several researches were carried out: 1) the species composition and temporal patterns of macroinvertebrate communities in Taizi River, and their relationships with environmental factors. 2) macroinvertebrates response to agricultural disturbance was discussed using functional feeding groups analysis, cluster analysis, Indicator analysis and ordination analysis. In addition, stream health were assessed by Shannon-Wiener index, Pielou evenness, number of EPT ( Ephemeroptera Plecoptera and Trichoptera) taxa and number of sensitive taxa.3) weight averaging (WA) and nonmetric multidimensional scaling (NMS) methods were used to rank the relative importance of habitat variables (i.e. substrate, velocity and water depth) of macroinvertebrates in the Taizi River, and the Habitat Suitability Model were constructed for the most abundant species, Baetis thermicus.The main results are as follows:1) The spatial distribution of macroinvertebrates were in accordance with Ecoregion of Taizi River.In the upper zone,macroinvertebrate community was almost healty in which sensitive taxa were abundant and diversity was high. The more heavier human disturbance resulted in degradation of community structure indicated by low taxa and more pollution-tolerant species. The most influencial variables were physical factors such as altitude and substrate materials. Electric conductivity, ammonia and oxygen-consumed organic matter were major pollution factors which damaged the macroinvertebrate communities of the middle and low zone of Taizi River;2) The northern stream had a more seriously agricultural disturbance,indicated by significant differences of farmland%, Total nitrogen and electric conductivity between the northern and southern streams. By applying functional feeding groups analysis,cluster analysis,macroinvertebrate community was significant different between northern and southern streams, showing that the relative abundance of Plecoptera sharply decreased in northern stream and gathering collector and filtering collector were the most important groups. Indicator analysis also indicated that the indicator species of the southern stream were almost sensitive species and the moderately tolerant species were dominated in northern streams. Canonical correspondence analysis showed that water temperature, altitude and total nitrogen were the most significantly influencial environmental variables. The macroinvertebrate bioassessment indicated that most sites of the northern and southern streams were healthy;3) All species found in this study showed different preference to habitats. Most species preferred to live in habitat with small cobble substrate. The preference optimal velocities and water depth were different among species, depends on their feeding methods, life types and morphological structures. The most abundant species, Baetis thermicus, preferred to live on small cobble with velocity of 0.4 m/s and depth of 0.2 m. Based on the habitat suitability model, however, the observed numbers of individuals of B. thermicus were lower than the predicted values. This indicated that the habitat variables measured in this study are no the only factors affecting the distribution of B. thermicus. More research is required to understand the effect of other habitat variables on macroinvertebrate distribution.