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Zooplankton-based
assessment of the trophic state of a tropical forest river
ImoobeTunde Ohiokhioya Thadeus* and Adeyinka Muideen
Lekinson
Department of Animal and Environmental Biology, University of
Benin, Benin City, Edo State, P. M. B. 1154, Nigeria.
*Corresponding author. E-mail:
timoobe@yahoo.co.uk. Tel: +2348023322605.
Accepted
5 January, 2010 |
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In this
study, we explored the usefulness of zooplankton as a tool
for assessing the trophic status of a Nigerian forest river.
The river was sampled monthly and investigated for water
physico-chemistry and zooplankton community structure using
basic statistical measurement of diversity indices to
characterize the zooplankton fauna. The trophic status of
the river evaluated from the physico-chemical parameters
indicates that the river is oligotrophic. The zooplankton
composition was typical of a tropical freshwater river, with
a total of 40 species made up of 16 rotifers, 12 cladocerans
and 12 copepods and their developing stages in the following
order of dominance; Rotifera > Cladocera > Cylopoida >
Calanoida. The zooplankton community was dominated by
numerous species of rotifers and crustaceans, which are
typical of oligotrophic to mesotrophic systems, amongst
these includes Conochilus dossuarius and Synchaeta
longipes. However, the most dominant zooplankton species
in West Africa freshwater ecosystems namely, Keratella
tropica, Keratella quadrata, Brachionus angularis,
Trichocerca pusilla, Filinia longiseta,
Pompholyx sulcata, and Proales sp. amongst others
which are indicator species of high trophic levels were not
recorded in the river. We therefore, conclude based on these
facts that the river is clear, oligotrophic and it can be
used for all manner of recreational activities.
Key
words:
Trophic
status, zooplankton, forest river.
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