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Asia Center of The Academy of Natural Sciences

Aquatic Insect Research

Enkhtaivan Sanaa
Chuluunbat Suvdtsetseg

Objectives

  • Identification of genera and species (where possible) of target aquatic insect groups, particularly Ephemeroptera, Plecoptera, and Trichoptera.
  • Contribute new information on biological diversity, species composition and food web structure of aquatic insects for Lake Hovsgol basin streams and Mongolian freshwater habitats through definition of major functional feeding groups.
  • Determine impact on diversity and ecosystem structure of streams from livestock grazing
  • Determine impact of climate change and permafrost thaw on stream biota
  • Determine combined impacts of climate change and grazing interactions on stream biota and ecosystem structure and food webs.
  • Compare six stream valleys weekly for distribution and abundance of mature aquatic insect groups using Malaise traps.
Figure 1 aquatic insect study sites

Figure 1: Site Map

Research description

A biological assessment of impact and possible impairment from grazing was done on six streams that flow into Lake Hövsgöl along its eastern shore. Upstream, midstream and downstream sites were located on streams that drained valleys with a gradient from high to low or no grazing (Figure 1). Water quality data, physical and habitat data, and macroinvertebrates were collected during June, July, and August in 2003 and in June and August in 2004. Macroinvertebrates were collected using semi-quantitative methods modified from the U.S. EPA Rapid Bio-Assessment Protocol.

A total of 49 taxa were identified representing 7 insect orders and 30 families. The mayfly genus Baetis was numerically dominant at all sites. Principal Components Analysis (PCA) was used to reduce the number of interrelated chemical variables in the analysis. Metrics based on functional percent feeding group, Shannon-Wiener Diversity, V-Evenness, and a modified Hilsenhoff Biotic Index (HBI) were used along with the chemical parameters in Multidimensional Scaling (MDS), cluster analyses and Canonical Correlation. Results from these analyses were used to define patterns in the 18 sites relative to the environmental gradients observed.

Figure 2 Multidimensional Scaling

Figure 2. Multidimensional Scaling (MDS) of Macroinvertebrates (TRG = Turag, SHL = Shagnuul, NYN = Noyon, SVL = Sevsuul, DLB = Dalbay, BRG = Borsog; _U = upper site, _M = middle site, _L = lower site)

Patterns of the sites analyzed by MDS (Figure 2) were based primarily on a gradient of salinity, with the sites located in the lower parts of valleys intensively grazed having the highest salinity concentrations. Also, percent filter feeders and scrapers increased between sites from less grazing to those with the most grazing. The middle and lower sites located on Shagnuul Gol, a stream that drains the valley with the most intensive grazing, formed distinct clusters in all cluster analyses.

Figure 2 cluster analysis

Figure 3. Clustering of macroinvertebrates relative to envirionmental gradients (TRG = Turag, SHL = Shagnuul, NYN = Noyon, SVL = Sevsuul, DLB = Dalbay, BRG = Borsog; _U = upper site, _M = middle site, _L = lower site)

Clusters (Figure 3) were attributed to high concentrations of salinity, hardness and HCO3 as well as higher percent scrapers and filter feeders and a higher HBI. Two sandy bottom streams in the study also consistently formed a cluster, based on temperature and moderately low concentration of dissolved oxygen.

Figure 4 canonical correlations

Figure 4. Canonical Correlations (TRG = Turag, SHL = Shagnuul, NYN = Noyon, SVL = Sevsuul, DLB = Dalbay, BRG = Borsog; _upp = upper site, _mid = middle site, _low = lower site)

Sites with moderate levels of grazing exhibited some of the highest diversity values and V-Evenness. The upstream site on Borsog Gol, a stream that flows through the valley with no grazing, had the highest HBI. Canonical Correlations (Figure 4) were based on genera and families of benthic macro invertebrates correlated with chemical parameters. Patterns observed on figure 3 show that 18 of our study sites were different by Chironomidae (Diptera), Heptagenia (Ephemeroptera), Rhithrogena (Ephemeroptera), Paraleptoplebia (Ephemeroptera) and Arcynopteryx (Plecoptera) along gradients of salinity, hardness and HCO3 of those sites. As cluster and MDS analysis showed, the sites located in the lower parts of valleys where intensive livestock grazing occured had the highest salinity concentrations. Results indicate a clear pattern of impact from grazing and are used to form hypotheses of impact and impairment to be studied in combination with increased impact from permafrost thaw in the region.

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