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Distribution of the benthic macroinvertebrate fauna in northeast Thailand : variation of faunal assemblages due to environmental changes


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Inmuong, Yanyong 1998 , 'Distribution of the benthic macroinvertebrate fauna in northeast Thailand : variation of faunal assemblages due to environmental changes', PhD thesis, University of Tasmania.

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Current knowledge and understanding of freshwater ecology in tropical
Asia is very limited. This thesis investigated firstly, the spatial and
temporal characteristics of benthic macroinvertebrates across the
monsoonal flood plain of the Pong River catchment, in northeast
Thailand. Secondly, change in the benthic community was examined in
terms of its sensitivity towards environmental impacts including seasonal
and human impacts. Thirdly, the performance of biotic indices and scores
developed for benthic communities in the temperate zone was tested.
Fourthly, the utility of biological data at species or family levels, and
density or binary counts in quantifying water pollution was assessed.
Lastly, the study describes the small scale variation in benthic
community structure in a pristine tropical forest at Phukradueng.
The benthic community varies through time and space over the study
site, and was markedly related to the degree of environmental
degradation. Most benthic taxa were abundant in less impacted
upstream waters but declined in downstream disturbed reaches.
Sensitive mayfly and caddisfly species were more diverse in less polluted
than impacted waters.
The magnitude of forest loss led to high sediment yield in the water
column which reduced benthic larvae colonisation. Certain caddisfly and
mayfly species were especially affected by high suspended solids.
Changes in water quality due to seasonal flooding and human impacts
both caused a significant decrease in taxa. The abundance of most
benthic groups decreased significantly during the rainy season
irrespective of the degree of human impacts. Water pollution caused by
humans is more obvious during the hot season when the pollution impact
gradient is clearly recovered in ordinations of the sites based on benthic
larvae. Classification of sites based on benthic fauna agreed well with
water chemistry results and a self-purification zone along the river was
reflected in a locally increased diversity of certain taxa.
Among indices and scores tested, measures of species richness, family
richness, and Ephemeroptera/Trichoptera best reflected water pollution.
Of several diversity indices tested, the Shannon-Weiner index most
significantly correlated to water pollution, and the biological working
party score (by average score per taxon) was significantly closely
correlated to organic water pollution.
Both density and presence/absence data resolved at species level gave
similar results in classifying sites when analysed by multivariate
methods. At family level, only density data provided a satisfactory
indication of impacted and less impacted sites. The benthic fauna in pristine headwater forests was much more diverse
than in the lower catchment. Trichoptera had the greatest species
richness which correlated to the extent of undisturbed forest land. The
pattern of colonisation by benthic larvae in various substrates, from
boulder to sand, was markedly different. The larger the substrate size,
the more diverse species were found. Colonisation patterns on various
nutrient-bound substrates were also found to be species specific. Benthic
community structure also differed between riffle and pool areas within a
site. However, the intra-site differences due to riffle and pool
microhabitat is overwhelmed by larger scale habitat difference such as
altered riparian vegetation types and modified ecosystems.
This study has demonstrated the feasibility of using benthic
macroinvertebrates for assessing environmental impacts in a monsoonal
tropical climate. These communities at small scales are related to
environmental change at a site, while on a larger scale the diversity of
these taxa can indicate the relative health of the freshwater ecosystem.

Item Type: Thesis - PhD
Authors/Creators:Inmuong, Yanyong
Keywords: Invertebrates, Invertebrate populations
Copyright Holders: The Author
Copyright Information:

Copyright 1998 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1998. Includes bibliographical references

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