The effect of water hyacinth infestation on the abundance, distribution and species

composition of zooplankton in Awba Reservoir were investigated. Samples were collected in each

of the sampling areas (water hyacinth infested and open water) by vertical zooplankton hauls using

§1Yro bolting silk net. The species composition of the zooplankton from the sampled areas

consisted of 3 taxa, comprising of 6 species of Cladocera (Moina sp.,Ceriodaphnia sp.,Pleuroxus

sp.,Diaphanosoma sp.,Chydorus sp., and Leydigia sp.,) 6 species of Rotifers(Asplanchna

sp.,Trichocerca.,Filinia sp., Polyarthra sp.,Brachionus sp.,and Lecane sp.) and 3 species of

Copepoda(Cycloid copepods, Copepodite nauphii and Calanoid copepods). However, the study

showed that the Rotifers had higher numerical abundance in the study areas. Water hyacinth

infested area had a total density of 95 individuals/I while open water had 225 individuals/I. The

study showed that the density of zooplankton was significantly lower (P<0.05) in the infested area.

Biotic indices such as Margalefs, and Simpson's indices were lower in the infested area while

Shannon-Weiner diversity index was significantly lower (P<0.05). The result suggests that water

hyacinth dense mats affected the numerical abundance of the zooplanktons

Chukwuka, K.S.

Daddy, F.

Uka, U.N

Aquatic Commons

Uka, U.N.1, Chukwuka, K.S.2 and Daddy,F.1
1 National Institute for Freshwater Fisheries Research, New-Bussa, Nigeria
2 Department of Botany and Microbiology, University of Ibadan, Ibadan, Nigeria
.//,'
Abstract /
The effect of water hyacinth infestation on the abundance, distribution and species
compositionof zooplankton in Awba Reservoir were investigated. Samples were collected in each
ofthesampling areas (water hyacinth infested and open water) by vertical zooplankton hauls using
§1Yro bolting silk net. The species composition of the zooplankton from the sampled areas
consistedof 3 taxa, comprising of 6 species of Cladocera (Moina sp.,Ceriodaphnia sp.,Pleuroxus
sp.,Diaphanosoma sp.,Chydorus sp., and Leydigia sp.,) 6 species of Rotifers(Asplanchna
sp.,Trichocerca.,Filinia sp., Polyarthra sp.,Brachionus sp.,and Lecane sp.) and 3 species of
Copepoda(Cycloid copepods, Copepodite nauphii and Calanoid copepods). However, the study
showedthat the Rotifers had higher numerical abundance in the study areas. Water hyacinth
infestedarea had a total density of 95 individuals/I while open water had 225 individuals/I.The
studyshowed that the density of zooplankton was significantly lower (P<0.05) in the infested area.
Bioticindices such as Margalefs, and Simpson's indices were lower in the infested area while
Shannon-Weiner diversity index was significantly lower (P<0.05). The result suggests that water
hyacinthdense mats affected the numerical abundance of the zooplanktons.
Keywords: Eichhomia crassipes, Zooplankton, abundance, diversity, Species richness Awba
Reservoir.
Introduction
Eichhornia crassipes (Mart Solms) popularly known as water hyacinth, is a free-floating aquatic
weedwhich belongs to the family Pontedriaceae (Cronk and Fennessy, 2001 ).This aquatic weed
has infestedd fresh and brackish waters in 20 out of 36 States and Federal Capital Territory of
Nigeria(Bolorunduro,2000),
. Awba Reservoir a repository of domestic waste from the Halls of residence and Staff
quartersof University of Ibadan, Nigeria, has experienced an explosive growth of this weed. It has
beenreported that such alien species as water hyacinth alters the ecosystem functions and thus
:: : : : :: < ::: 199) ,.: ::: :: :-: ::
EFFECT OF WATER HYACINTH ( EICHHORNIA CRASSIPPES) INFESTATION ON
ZOOPLANKTON POPULATIONS IN AWBA RESERVOIR, IBADAN, SOUTH-WEST
NIGERIA.
Zooplankton Composition, Density and Distribution
A total of 15 species of zooplankton were identified in the study (Table 2). The total number of
species and individuals present (in parenthesis) at the sampled areas (water hyacinth infested and
open water) are 8 (95) and 15 (225) respectively (Table 3). Analysis of Variance(ANOVA) showed
that water hyacinth infested area was significantly fewer (P< 0.05) number of species and
individuals than the open water area. Rotifers were the dominant zooplankton group in the infested
and open water accounting for 61.1 % and 44.1 % respectively; it was followed by Cladocerans
16.9% and 28.1 % respectively, while the least was Copepoda 22.1 % and 28% respectively in the
sampled areas as shown in Table 3.
Results
Physico-chemical Properties
The variations in the physicochemical parameters of the study areas are shown in Table 1 below.
Water temperature and alkalinity were not significantly different (P>0.05).While dissolved Oxygen,
pH, turbidity and total suspended solids were significantly different (P<0.05) between infested and
open water areas.
Sampling Areas and Procedures
The study was carried out between July and November, 2005. The reservoir was divided into 2
sampling areas viz water hyacinth infested and open water areas for the purpose of the study.
Samplings for water quality parameters and zooplankton were carried out fortnightly between 0700
and 1100 hrs on each sampling day. Zooplankton were collected using 64um bolting plankton net.
Plankton samples concentrated into 1 litre container were immediately preserved in 4% formalin
(Jeje, 1990). Zooplanktons were identified using the taxonomic keys of Jeje and Fernando (1986),
Jeje (1990) and Boney (1983). All results were expressed as number of organisms per litre.
The percentage occurrence and relative numerical abundance of zooplankton were calculated. The
total density of zooplanktons in the infested area was compared with that of the open water area
using Analysis of Variance(ANOVA). The biotic indices such as Margalef's (Margalef, 1949),
Shannon-Weiner (Shannon-Weiner, 1949) and Simpson's (Simpsons'1949)indice were used to
estimate diversity. Shannon-Weiner diversity values of the sampling areas were further subjected
to Student's T-test. Sorenson's and Jaccard indices of community similarity were used to determine
how zooplankton in both areas are closely related.
Materials and Methods
Study Area
Awba reservoir is located within the University of Ibadan Campus at an altitude of 185 meters above
sea level .It lies between latitude 3° 53' E and 1r 26' N(Akin- Oriola, 2003).The reservoir has a
surface area of 6 hectares, maximum depth of 5.5 meters and maximum length of 700m
(Omotosho, 1981). Located in the rainforest bell of Nigeria the reservoir experineces two seasons,
the Wet and Dry seasons. Wet season occurs between April and October while Dry season is
between November and March.The dominant aquatic plants on the fringes of the reservoir are Pistia
stratiotes ,Nymphaea lotus, Canna indica, Bahimasp. and Typhaaustralis.
constitute a threat to biological diversity of organisms (aquatic flora and fauna) in such ecosystems
and food chains associated with them (Luken and Thieret, 1997). Zooplanktons play important role
in channeling primary production into fish production (D~jen et a/2004).Zooplankton studies are
necessary since these organisms play important role in theenerqy transfer from primary producers
to organisms of higher trophic levels (Aoyagui and Bonecke,2004).Therefore variations in terms of
species richness of zooplankton may negatively affect the ecosystem function. The quest for factors
that influence zooplankton diversity is of great interest to researchers. According to Serafin (1997);
Aoyagui and Bonecka, (2004), dissolved oxygen, pH, conductivity and Environmental morphometry
have great effect on zooplankton. -
The objective of the study therefore is to examine the influence of water hyacinth infestation
on the composition, abundance and distribution of zooplankton inAwba Reservoir.
£_ .. J .:
:= ':.
Pindicates significance of One way ANOVA
* = Significant P«0.05)
NS= Not significant P(>0.05)
PARAMETER WATER OPEN P-VALUE ANOVA
HYACINTH WATER Probability
INFESTED
Water Zl?16it 7JE7tUH3 0.28 P>0.05N::>
temperature
Dissolved 11~ ffifmJS 0.00 P< 0.05*
Oxygen
Alkalinity 4mID!I 3m.11ffi @ 0.07 P>0.05N::>
pH ffitl.I 717l11B 0.00 P<0.05*
Turbidity ~17"l:i5l ffflfE7i9 0.00 P<0.05*
TSS 9224$ ~f) 0.00 P<0.05*
Cladoceranswere represented by three families: Moinidae with one genus Moina sp; Daphninidae
comprisingof one species Ceriodaphnia corn uta ,Chydoridae comprising of one species namely
Pleuroxusimiles which was absent in the infested area. Chydorus sp. and Leydigia sp. were also
notrepresented in the infested area. Cladocerans had a density of 16 individuals per litre (16/1) in
theinfestedarea as against open waters 63/1 (Table 3)
Rotiferanswere represented by 6 families: Asplanchnidae made up of one genus Asplanchna sp;
Trichocerchidae,Synchaetidae and Brachionnidae comprised of one genus each and they were
representedby Trichocerca sp, Polyarthra sp and Brachionus sp respectively .These genera were
absentinthe infested area. Filinidae and Lecanidae were made up of one genus each represented
by Filiniasp. and Lecane sp. respectively. In the water hyacinth infested area Rotiferans were
580rg/l while open water had 99 org/l.(Table 3)
. Copepods were represented by cylopoid copepods, calanoid copepods and
somecopepodite nauplic in water hyacinth infested area had a density of 21orgll while in the open
water,itaccounted for 630rg/l. (Table 3).
Margalefs species richness, Shannon-Wieners index as well as Simpson's index
werelower in the water hyacinth infested area when compared to open water. Shannon wieners
indexwassignificantly lower (t<0.05) in water hyacinth infested area when subjected to Students t
Testthan in open water (Table 4). However, Sorensen's and Jaccard Coefficients of Community
Similarityshowed that zooplankton in the sampling area were related.
Table 1 Variations in water quality (Mean-standard error) between water hyacinth infested and
openwaterareas inAwba Reservoir between July and November, 2005.
Table 2: Zooplankton species identified in Awba dam during the study period'
Division SINo Species Water hyacinth Open wateinfested
CLADOCERA 1 Family: Moinidae
Moinasp + +
Goulden, 1968
2 Family: Daphinidae
Ceriodaphnia com uta + +
Sars, 1888
3 Family: Chydoridae
Pleuroxus similes +
Vavra, 1900
4 Family: Sididae
Diaphanosoma sp +
Fischer, 1850
5 Family: Chydoridae
Chydorussp + +
Leach, 1816
6 Family: Chydoridae
Leydigicsp +
Kurz, 1875
ROTIFERA 7 Family: Asplanchnidae
Asplanchna sp + +
Crosse, 1850
8 Family: Trichocerchidae
Trichocerca sp +
Lamarck, 1801
9 Family: Filinidae
Filiniasp + +
Bory de st. Vincent,
1925
10 Family: Synchaetidae +
Polyarthra sp
Ehrenberg, 1834
11 Famly: Brachionidae +
Brachionussp
Pallas, 1776
12 Family: Lecanidae + +
Lecanesp
COPEPODA Nitzsch, 1827
13 Family: Cyclopodae + +
Cycloid copepods
14 Family: Cyclopidae + +
Copepodite nauphii
15 Family: Cyclopidae + +
Ca/anoid copepods
Key:+Present
Absent
::== :~: ao71. :: :-- :,': H·e~MFcfi1' Ph
-
,...... .
Discussion
It nas been reported that zooplankton composition and diversity give an insight into the
characteristics and quality of water body (Marson, 1983). The abundance of zooplanktons were
low inwater hyacin.th infested area when compared to open water. The reason could be due to the
formation of dense mats of water hyacinth on the water surface, thus a reduction of dissolved
oxygencontent of the infested area. This is in agreement with Rommens et al. (2003) report that
lowoxygen level inhibited the growth of zooplanktons in a water hyacinth infested sub tropical
impoundment. According to Serafin,(1997) and Aoyagui and Bonecka, (2004), dissolved oxygen,
pH, conductivity and environmental morphometry have the greatest effect on zooplankton
Therefore the low diversity of zooplankton in the infested areas can also be attributed to dense
mats of water hyacinth in the infested area which affects the physicochemical variables of the
area.
SAMPLING AREAS
INDICES WATER HYACINTH OPEN WATER
INFESTED
Number of species 8 15
Marqalefs Species Richness 1.53 2.60
ShannoAWeiner Index (H) 0.65 0.84
Simpson Diversity Index 0.50 0.79
Coefficients of Community Similarity
Sorensons Index 69%
Table 4: Diversity of zooplanktons in the sampling areas of Awba Reservoir
Water hyacinth Open water
Division Species Freq. % Fre_q. %
Cladocerans Moinasp 10 10.5 40 17.8
Ceriodaphnia sp 3 3.2 8 3.6
Pleuroxus sp O· 0 4 1.8
Diaphanosoma sp 0 0 3 1.3
Chydorus sp 3 3.2 4 1.8
Leydigia sp 0 0 4 1.8
SUBTOTAL 16 16.9 63 28.1
Rotifera AsplanchncI5p 3 3.2 2.0 0.9
Tnchocerceso 0 0 6 2.7
Filiniasp 4 4.2 4 1.8
Polyarthrc£p 0 0 6 2.7
Brechionusu: 0 0 4 1.8
Lecanesp 51 53.7 77 34.2
SUBTOTAL 58 61.1 99 44.1
Copepoda Cyclopoid copepods 14 14.7 54 24.0
Copepodite nauphii 7 7.4 5 2.2
Calanoid copepods 0 0 4 1.8
SUBTOTAL 21 22.1 63 28
TOTAL ZOOPLANKTON 95 225
Table3: Percentage Composition and Abundance of Zooplankton in water hyacinth infested
and Open water areas of Awba dam during the study period.
=
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The two sampled areas were closely related based on the estimated Sorenson's (C, and Jaccard's
(C) indices of Community Similarity. The 69% (Cs) and 53% (Cj) are greater than the critical values
of 50%. This suggests that the higher the joint occurrence (S or j); the higher the similarity. It canbe
deduced from these results that water hyacinth infestation did not support zooplankton abundance
and diversity. Efforts should be intensified towards its management and control.
The Shannon-Weiner zooplankton diversity was significantly lower (P<0.05) in water hyacinth
infested area because of non-mixing of autochthonous materials due to dense mats of water
hyacinth on the surface of the water body. Evans (2003) reported that the mixing of autochthonous
materials in a water body facilitates primary production resulting in zooplankton abundance.
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food utilization. Ward and Whipple(1966 also opine that, rotifers have the ability to dessicate and
the possession of an intra-epidermal cuticle which has developed into a thick case or lorica insome
species, gives extra protection to rotifers and as well enhances its survival and proliferation under
adverse environmental conditions.
Zooplankton abundance was low in the infested areas because of high turbidity in the infested area.
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suspended matter boosts zooplanktons population as a result of transfer in the food chain. Sothe
high level of turbidity as a result of heavy load of suspended particles in the infested area will affect
the composition and abundance of zooplankton organisms. Also the ability of Eichhornia crassippes
to absorb and utilize nutrients deprives other Phytoplankton's of those nutrients,
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t :::!-; : M ~ =_: :- :: :: :: -~= : S): :.:::;--::i
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Effect of water hyacinth (Eichhornia crassippes) infestation on zooplankton populations in Awba Reservoir, Ibadan, south-west Nigeria

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Effect of water hyacinth (Eichhornia crassippes) infestation on zooplankton populations in Awba Reservoir, Ibadan, south-west Nigeria

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