Diversity and Distribution Patterns of Freshwater Macroinvertebrates in Modi River System, Gandaki Province, Nepal
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Department of Botany
Abstract
In the face of several stressors in Modi River system, this research was conducted
with the aim of assessing diversity and distribution patterns of benthic
macroinvertebrates along the altitudinal gradient including the ecological health of a
River system. Benthic macroinvertebrates sampling was conducted in 20 different
(13-river's mainstem and 7- tributaries) following a multi-habitat sampling approach
based on Moog (2007). Macroinvertebrates were collected by kicking the substrate or
jabbing with a D-frame dip net and transferred into labeled vials and preserved in
99.9% ethanol for sorting and identification in the lab. Threats were identified from
direct observation and key informant interview. Taxa richness was assessed using
Shannon Diversity Index, Simpson Diversity Index, and Evenness. Similarly,
Shapiro-Wilk normality test, One way ANOVA, Turkey HSD test and Wilcoxon pair
test were conducted to know the difference between groups. R studio (1.2.5 version)
and CANOCO (4.5 version) was used for statistical analysis. In total, 40 families
belonging to 10 orders were recorded in the study area. 29 families belonging to eight
orders were recorded in river’s mainstem while 39 families belonging to 9 orders
were recorded in tributaries. Lowest numbers of taxa were recorded at higher
elevations of both river (9 families at 1654m) and tributaries (14 families at 1719m).
Among 40 families, order Diptera has the highest family richness. Turkey HSD test
showed taxa richness between 1550-1800m and 1050-1300m (p=0.0004), and 15501800m
and
1350-1500m (p=0.0389) differ significantly. Taxa richness is highest at
the elevation of 1050-1300m and lowest at 1550-1800m. Similarly, Shannon
Diversity index is highest in the sampling sites located at 1265m elevation and lowest
at 1533m. Test Showed that the diversity index differs significantly (p=0.049) with
altitude. Wilcoxon pair test did not show the difference in the Simpsons Diversity
Index between river's mainstem and tributaries (p=0.195). Likewise, RDA diagram
showed the temperature as the most important variable governing the BMI
composition . Furthermore, river's mainstem are less polluted than the tributaries.
Hydropower construction, sewage, sand and stone quarry, waste dumping, bathing
and washing were the major threats for the river system.
Keywords: Benthic macroinvertebrates, freshwater, diversity, distribution, stressors