Distribution of planktonic cladocerans (Crustacea: Branchiopoda) of a shallow eutrophic reservoir (Paraná State, Brazil)

Abstract

This study focused the spatial and temporal distribution of the composition, abundance, and diversity of planktonic cladocerans from eutrophic, Iraí Reservoir, as well as their relationships with some biotic and abiotic variables. The tested hypothesis was that cladocerans present higher variation in a temporal than in a spatial scale. The samples were taken monthly in 6 stations, from March/02 to July/03. Twenty-four taxa were identified, distributed in 7 families, the richest families being Daphniidae (6 spp.), Chydoridae (6 spp.), and Bosminidae (5 spp.). The most frequent and abundant species were Bosmina hagmanni, Moina minuta, and Ceriodaphnia cornuta. The highest abundances were found in September/2002. Temporally, rainfall influenced organism's distribution, while spatially cladocerans were more affected by reservoir hydrodynamics and wind action. The low species richness could be a reflection of the trophic state of the reservoir, in which a dominance of Cyanobacteria was observed during that study period. Both scales showed high variation, but only the temporal scale showed significant difference to richness and abundance. Nearby the end of this study, higher stable values of species richness were recorded, which could suggest an increase in the water quality due to des-pollutions actions.

Full text

Pan-American Journal of Aquatic Sciences (2009), 4(3): 294-305
Distribution of planktonic cladocerans (Crustacea: Branchiopoda) of
a shallow eutrophic reservoir (Paraná State, Brazil)
ANDRÉ RICARDO GHIDINI1; MOACYR SERAFIM-JÚNIOR2;
GILMAR PERBICHE-NEVES3 & LINEU DE BRITO4
1Programa de Pós-Graduação em Biologia Tropical e Recursos Naturais, Instituto Nacional de Pesquisas da
Amazônia/Universidade Federal do Amazonas. André Araújo Avenue, nº 2638, Manaus, Amazonas, Brazil. CEP:
69060-001. Email: arghidini@yahoo.com.br.
2Universidade Federal do Recôncavo da Bahia, Centro de Ciências Agrárias, Ambientais e Biológicas – Núcleo de
Estudos em Pesca e Aqüicultura (NEPA), CEP 44380-000, Cruz das Almas, BA. Email: moa.cwb@gmail.com
3Curso de Pós Graduação em Zoologia, Universidade Estadual Paulista “Júlio de Mesquita Filho” - UNESP, Distrito
de Rubião Jr., s/nº, Botucatu, São Paulo, Brazil, CEP: 18618-000. Email: gilmarpneves@yahoo.com.br
4Universidade Federal do Paraná, Centro de Estudos do Mar, Beira-Mar Avenue, s/no, Pontal do Sul, Paraná, Brazil.
CEP: 83255-000. Email:lineubrito@yahoo.com.br
Abstract. This study focused the spatial and temporal distribution of the composition, abundance,
and diversity of planktonic cladocerans from eutrophic, Iraí Reservoir, as well as their
relationships with some biotic and abiotic variables. The tested hypothesis was that cladocerans
present higher variation in a temporal than in a spatial scale. The samples were taken monthly in 6
stations, from March/02 to July/03. Twenty-four taxa were identified, distributed in 7 families, the
richest families being Daphniidae (6 spp.), Chydoridae (6 spp.), and Bosminidae (5 spp.). The
most frequent and abundant species were Bosmina hagmanni, Moina minuta, and Ceriodaphnia
cornuta. The highest abundances were found in September/2002. Temporally, rainfall influenced
organism’s distribution, while spatially cladocerans were more affected by reservoir
hydrodynamics and wind action. The low species richness could be a reflection of the trophic state
of the reservoir, in which a dominance of Cyanobacteria was observed during that study period.
Both scales showed high variation, but only the temporal scale showed significant difference to
richness and abundance. Nearby the end of this study, higher stable values of species richness
were recorded, which could suggest an increase in the water quality due to des-pollutions actions.
Keywords: Cladocera, Iguaçu River basin, Iraí Reservoir, eutrophication, Cyanobacteria.
Resumo. Distribuição de cladóceros planctônicos (Crustacea: Branchiopoda) em um
reservatório eutrófico raso (Paraná, Brasil). Esse estudo enfocou a distribuição espacial e
temporal da composição, abundância e diversidade de cladóceros planctônicos em um reservatório
eutrófico, reservatório do Iraí, bem como suas relações com variáveis bióticas e abióticas. A
hipótese testada foi que os cladóceros apresentam maior variação em escala temporal do que
espacial. As amostragens foram realizadas mensalmente em seis estações, entre março/02 e
julho/03. Vinte e quatro táxons foram identificados, distribuídos em sete famílias, sendo
Daphniidae (6 spp.), Chydoridae (6 spp.) e Bosminidae (5 spp.) as que ativeram maior número de
espécies registradas. As espécies mais freqüentes e abundantes foram Bosmina hagmanni, Moina
minuta e Ceriodaphnia cornuta. A maior abundância foi registrada em setembro/02.
Temporalmente a pluviosidade influenciou a distribuição dos organismos, enquanto espacialmente
os cladóceros foram mais afetados pela hidrodinâmica do reservatório e pela ação do vento. A
baixa riqueza de espécies pode ser um reflexo do estado trófico do reservatório, no qual a
dominância de Cyanobacteria foi observada quase que constantemente. Ambas as escalas
apresentaram elevadas variações, porém somente a temporal apresentou diferença significativa
para a riqueza e abundância. Próximo do final deste estudo, maiores valores estáveis de riqueza de
espécies foram verificados, a qual pode sugerir uma melhoria na qualidade de água devido a ações
de despoluição.
Palavras-chave: Cladocera, rio Iguaçu, reservatório do Irai, eutrofização, Cyanobacteria.

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Introduction
The importance of continental aquatic
ecosystems as a source of freshwater to human
populations is unquestionable. However,
anthropogenic activities have been degrading these
environments and the water quality, altering its
physical, chemical, and biological properties, a
phenomenon called eutrophication (Bollmann &
Andreoli 2005).
Changes in the nutrients dynamics of a water
body alter the decomposition and production
processes that directly affect the consumption. This
fact can be evidenced studying planktonic
microcrustaceans since its life cycle, development,
and reproduction are influenced by biotic and abiotic
factors of the environment (Branco & Cavalcanti
1999, Bini et al. 2008).
In tropical environments, rain and wind
action are the major forces influencing cladocerans
population structure, promoting the water column
mixing, and stimulating nutrient cycling (Lopes et
al. 1997, Sampaio et al. 2002). Factors as pH,
dissolved oxygen, and nutrients (especially P and N)
directly affect these organisms, because they
strongly influence phytoplankton development
(Bonecker et al. 2001, Matsumura-Tundisi &
Tundisi 2003, 2005). Furthermore, cladocerans
populations can oscillate in response to predation by
other groups, like insect’s larvae and small fishes
(Meschiatti & Arcifa 2002).
Most cladocerans are herbivorous and
phytoplankton feeders, transferring energy to higher
trophic levels (Melão 1999). This is the reason why
generalist’s cladocerans species are able to develop
in a high number of environments, like species of
the Bosminidae family. Some large cladocerans
(Sididae and Daphniidae families) have preference
on the food item ingested, and they became more
selective when there is food limitation (DeMott &
Kerfoot 1982, Ferrão-Filho et al. 2003). Filamentous
algae and presence of toxins affect cladocerans
growth and filtering rates, besides to increase
mortality and polymorphism, which in a spatial-
temporal scale influences the composition,
distribution and species succession (Ferrão-Filho &
Azevedo 2003). This is particularly important in
eutrophic reservoirs where food availability from
cladocerans changes with time since cyanobacteria
blooms, which occur during almost the whole annual
cycle, can develop toxicity (Ferrão-Filho et al.
2003).
Temporal-spatial variations of
microcrustaceans in Brazilian reservoirs have been
extensively studied (Bonecker et al. 2001, Sampaio
et al. 2002, Matsumura-Tundisi & Tundisi 2003,
2005, Corgosinho & Pinto-Coelho 2006). However,
in small and eutrophic reservoirs, as the case of Iraí
Reservoir and which is the aim of this study, the
relationships between cladocerans assemblages and
limnological factors (biotic and abiotic) are poorly
known besides they can affect population structure.
Lansac-Tôha et al. (2005), Velho et al. (2005),
Serafim-Júnior et al. (2005) and Perbiche-Neves et
al. (2007) studied this reservoir and attributed the
homogeneity of zooplanktonic assemblages to the
low depth, long residence time and elevated
production, with the dominance of cyanobacteria.
Pinto-Coelho et al. (1999) made similar observations
to Pampulha Reservoir (MG), which is small,
eutrophic and located in a region of strong
urbanization. In small, shallow and polymictic
reservoirs, Henry (1999) highlighted the wind action
effects on the water column, where daily or
temporary stratifications can occur, but they are
subjected to the vertical homogenization in most part
of the year.
The comprehension of the relationship
between cladocerans assemblages and
environmental conditions are important to the
development of ecological tools used in
management techniques and environmental
restoration of eutrophic reservoirs. Also, the
knowledge of those relations could be useful to
understand Cladocera ecology in sub-tropical
reservoirs, nevertheless used to water supply to the
city of Curitiba and metropolitan region, composed
of ca. 3.5 million habitants. The hypothesis tested in
this study was that cladocerans variation occurs
mainly in a temporal than in a spatial scale,
associated to the small size of the reservoir, being a
homogeneous assemblage, due the its relation to
some limnological variables and specially to
phytoplankton community, because their food item
selectivity. The aim of this work was to describe: (i)
the temporal-spatial distribution of some ecological
attributes of cladocerans populations and the major
limnological variables influencing them; (ii) the
intensity of eutrophication that affect these
organisms, and (iii) the relation between cladocerans
and the phytoplankton community.
Material and Methods
Study area. The Iraí Reservoir (25º
25’49’’S and 49º 06’40’’W) is located in the basin
of higher Iguaçu River among the cities of Pinhais,
Piraquara, and Quatro Barras. It occupies an area of
14 km2 in the alluvial plain of Iraí River. The mean
water volume is 58x106 m-3, the theoretical residence
time is 300 to 450 days, and the mean depth is 4 m.
(Zmax=10 m). The margins are not vegetated, being

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Pan-American Journal of Aquatic Sciences (2009), 4(3): 294-305
296
composed mainly by pastureland (Andreoli &
Carneiro 2005).
Iraí Reservoir was built in 2001 and its
morphometrical and hydrological features have been
causing Cyanobacteria proliferation since its filling,
complicating water treatment and reducing water
quality (Andreoli & Carneiro 2005).
One of the four main tributaries (Timbú
River) is characterized by an elevated nutrient load,
especially of phosphorus and nitrogen, due to the
disordered urban occupation of the drainage basin.
This fact, associated to the high residence time and
low dept of the reservoir favored the development of
blooms of Cyanobacteria, as Anabaena sp.,
Cylindrospermopsis sp., and Microcystis sp.,
promoting significantly changes in the water quality
of the reservoir (Bollmann & Andreoli 2005).
Field work, samples and data analyses.
The samples were obtained monthly from
March/2002 to July/2003 in six stations in the
reservoir, totalizing 102 samples. Stations 1, 2 and 3
were located in the dam axis (stations 1 and 3, Zmax=
4 m; station 2, Zmax= 8 m), and the others were in the
main body the reservoir (stations 4, 5, and 6, Zmax= 3
m) (Fig. 1).
Two-hundred liters of sub surface water
(due to low depth) were filtered in a conical
plankton net (55 µm mesh size), using a motorized
pump. The samples were narcotized with 4 %
buffered formalin. Countings were made through
subsamples of 1 mL using Stempel pipette, and a
minimum of 200 individuals were counted per
sample in a Sedgewick-Rafter chamber under optical
microscope. Cladocerans are usually quantified in
acrylic gridded Petri dishes using stereomicroscope.
However, in this study, countings in Sedgewick-
Rafter were possible due to the elevate number of
small organisms. Identification of species was based
in specialized literature, as Matsumura-Tundisi
(1984), Elmoor-Loureiro (1998; 2007), Hollwedel et
al. (2003) and Elmoor-Loureiro et al. (2004).
Abundance data were expressed as individuals.m-3.
Figure 1. Localization of Iraí Reservoir (Paraná State) and of sampling stations
Non-parametric tests were used after
Shapiro-Wilk normality test have indicated a not
normal distribution. Organism’s richness and
abundance were analyzed using H Kruskal-Wallis
ANOVA test (p < 0.05) to detect significant
variations between sampling stations and months.
Biotic and abiotic variables for limnological
characterization were not different among the
stations (p > 0.05). It was used data of station 2, in
middle dam zone. Biotic and abiotic variables were
related to the cladocerans abundance. Phytoplankton
species abundance and cladocerans abundance
interactions were analyzed using the Spearman
correlation (p < 0.05). Due to the elevate number of
statistical analyses applied, multiple comparisons
tests between the means of analyzed categories were
used to avoid error type I on null hypothesis.
Multiple comparisons analyses of “p” values (Z, p >
0.05) were performed on the significance tests of H
Kruskal-Wallis ANOVA and Bonferroni correction
(β, p > 0.05) on Spearman correlations. Despite the
corrections, infringements about null hypothesis

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Pan-American Journal of Aquatic Sciences (2009), 4(3): 294-305
297
were not significant. Biotic and abiotic variables
were correlated with Cladocera using Factorial
Analysis (p < 0.05) with extraction by Principal
Component Analysis. Mantel test with 1000
permutations for dissimilarity matrices between
cladocerans data versus phytoplankton data (also
with Bray Curtis distances) versus abiotic data (with
Euclidian distances) was performed, but a significant
correlation was not obtained. Factorial Analysis was
performed using Statistic 6.0 software (Statsoft
2002), and the other analyses were carried out using
“R Development Core Team” (2009).
Data of abundance, composition and
phytoplankton biomass, and water physical-chemical
parameters (chlorophyll-a, pH, temperature,
dissolved oxygen, electric conductivity, turbidity,
organic nitrogen and total phosphorus) were
obtained in same stations and months through the
data base of "Projeto multidisciplinar de pesquisa
em eutrofização de águas de abastecimento público”.
For further details of sampling methodologies and
analyses, as well as the responsible authors, see
Andreoli & Carneiro (2005). Monthly mean
pluviosity was obtained from data base of
Technological Institute SIMEPAR.
Results
Species richness (S) values varied
significantly during the studied months (H=71.23,
p < 0.00), with lower mean value in March/2002
(S = 4.2), and higher mean value in December/2002
(S = 12) and November/2002 (S = 11.5). From
November/2002 to February/2003 (rainy season),
the highest means, maximum values and variation
(standard deviation and min/max) in species richness
were observed among the stations (Table I). After
this, richness tended to stability from July (S: 7.5-
10; mean: 8.7). Significant spatial variation of
richness was not observed (H = 1.59, p = 0.97,
Z = p > 0.05).
Table I. Cladocerans richness species (Mean, Standard deviation - SD and Minimum/Maximum - Min/Max)
at Iraí Reservoir from March/2002 and July/2003 (N = 102).
2002 Mean SD Min/Max 2003 Mean SD Min/Max
Mar 4.2 ±1.17 3-6 Jan 10.8 ±2.64 8-15
Apr 6.0 ±1.26 4-8 Feb 9.5 ±1.64 7-12
May 5.5 ±1.52 4-8 Mar 7.5 ±1.05 6-9
Jun 6.7 ±0.82 6-8 Apr 8.3 ±2.16 5-11
Jul 6.5 ±1.38 6-8 May 9.3 ±1.63 9-12
Aug 6.3 ±1.63 4-9 Jun 10.0 ±0.63 9-11
Sep 7.7 ±1.51 6-10 Jul 7.7 ±2.07 8-11
Oct 8.8 ±1.47 7-11
Nov 11.5 ±1.87 9-14
Dec 12.0 ±1.79 9-13
A total of 24 species was identified (Table
II). The most frequent cladocerans species in the
samples were Bosmina hagmanni (94%), followed
by Moina minuta (84%), Ceriodaphnia cornuta
(70%), Bosmina longirostris (67%), and
Ceriodaphnia silvestrii (64%). Bosmina hagmanni
was also the most abundant species during the whole
study period (relative abundance = 65 %).
Chydoridae and Daphniidae families presented
higher richness (six species), and the last family was
the most abundant. Five Bosminidae species were
recorded (Table II).
In a temporal scale, a significant difference
in cladoceran abundance was observed along the
studied months (p < 0.00, H = 70.68), but with no
distinguished pattern of variation. Lower
abundances were found in March/2002 and 2003,
and in June and July/2003. A peak of abundance was
observed in September/2002, and to the following
months, elevated densities were observed until
January/2003. In May/2003 values also increased
(Fig. 2).
Most cladocerans species, mainly the more
abundant, followed the variation showed in Figure 2.
The variation was especially evident to smaller
cladocerans, as B. hagmanni responsible for the
density peak during September/2002, when densities
were more than 12 fold higher compared to previous

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months (≈ 600,000 org.m-3). In October/2002,
abundance of that species decreased progressively
until its absence in March and April/2003. Moina
minuta higher densities were found in May/2002
(≈ 55,000 org.m-3), and population declined in
August and September/2002. A peak of
Ceriodaphnia cornuta was observed in
October/2002 (≈ 60,000 org.m-3).
Table II. Recorded species at Iraí Reservoir, relative abundances (Ab %), and frequency of occurrence (Fr
%) in the samples, from March/2002 to July/2004.
Taxa Ab% Fr% Taxa Ab% Fr%
Bosminidae
Ilyocryptidae
Bosmina hagmanni Stingelin, 1904 65.4 94.1 Ilyocryptus spinifer Herrick, 1882 <0.1 3.3
Bosmina huaronensis Delachaux, 1918 2.3 40.3
Macrothricidae
Bosmina longirostris Müller, 1785 4.8 58.8 Macrothrix squamosa Sars, 1901 <0.1 0.8
Bosmina tubicen Brehm, 1953 <0.1 2.5
Moinidae
Bosminopsis deitersi Richard, 1895 1.5 40.3 Moina micrura Kurz, 1874 <0.1 3.3
Chydoridae Moina minuta Hansen, 1899 6.6 84.0
Alona guttata Sars, 1862 <0.1 10.0 Moinodaphnia macleayi King, 1853 <0.1 0.8
Alona intermedia Sars, 1862 <0.1 2.5
Sididae
Alona monocantha Sars, 1901 0.1 15.1 Diaphanossoma birgei Korineck 1981 0.4 35.2
Alonella dadayi Birge, 1910 <0.1 3.4 Diaphanossoma brevireme Sars 1901 0.1 11.7
Chydorus eurynotus Sars, 1901 1.3 37.8 Diaphanossoma spinulosum Herbst, 1967 0.1 11.7
Chydorus nitidulus Sars, 1901 0.2 11.7
Daphniidae
Ceriodaphnia cornuta Sars, 1886 5.0 73.1
Ceriodaphnia cf. laticaudata Müller, 1867 0.6 24.3
Ceriodaphnia reticulata Jurine, 1820 2.7 43.7
Ceriodaphnia silvestrii Daday, 1902 3.7 72.2
Daphnia gessneri Herbst, 1967 <0.1 8.4
Considering larger cladocerans (> 1.00 mm),
their densities were less representative compared to
smaller species. Diaphanosoma birgei reached a
peak in November/2002 (≈ 2,000 org.m-3) and was
always recorded since then. This species was absent
in the previous samples (June, August, and
September/2002). Daphnia gessneri was not found
in the first months, appearing in the samples in
October/2002, with increasing populations densities
in the following months.
Figure 2. Cladocerans mean densities (individuals.m-3 x103) from March/2002 to July/2003, at Iraí Reservoir (N=102).

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Pan-American Journal of Aquatic Sciences (2009), 4(3): 294-305
299
Inside Iraí Reservoir, B. hagmanni
population densities were, generally, slightly higher
in stations 1 and 3, located in the left and right
margins of the dam, while C. cornuta was more
abundant at station 5, followed by stations 1 and 3.
Some larger species, like D. birgei, presented
elevated maximum abundances in stations 4 and 5,
and D. gessneri in station 6 (Fig. 3). It was not
detected any significant difference between total and
species abundance among sampling stations
(H = 4.54, p = 0.60, Z = p > 0.05).
Significative Spearman correlation (R)
between dominant cladocerans abundance and
phytoplankton densities showed positive correlation
with two Ceriodaphnia and two Chydoridae species
with densities of Microcystis aeruginosa, one of the
most abundant Cyanobacteria present in the
reservoir in this study. There were no positive
correlations between cladocerans and the other algae
genera (β = p > 0.05) (Table III).
Figure 3. Spatial distribution of some cladocerans species inside Iraí Reservoir. Dark paths represent higher mean
abundances from March/2002 to July/2003. For localization of stations sampling, see Figure 1.
Table III. Significative Spearman correlations between cladocerans and phytoplankton considering the mean
population density during the studied period (p<0.05). Aual- Aulacoseira alpigena, Miae- Microcystis
aeruginosa, Momi- Monoraphidium minutum, Peum- Peridinium umbonatum, Scen- Scenedesmus sp., Tetr-
Tetraedon sp, Uros- Urosolenia sp.
Aual Miae Momi Peum Scen Tetr Uros
C. cornuta 0.72 -0.63 -0.72
C. reticulata -0.63 -0.69
C. silvestrii 0.73 -0.76 -0.64
C. eurynotus 0.73 -0.79 -0.67
C. nitidilus 0.79 -0.69 -0.71 -0.72
D. gessneri -0.79 -0.77 -0.66
D. birgei -0.79
D. brevireme -0.75
Spearman correlations were not significant
(p < 0.05) among environmental variables (dissolved
oxygen, pH, electric conductivity, total phosphorus,
organic nitrogen, water transparency, and
chlorophyll-a) and cladocerans population densities
(β = p > 0.05). Results from Factor Analysis (Factor
1: 31.59%, Factor 2: 22.10%) indicated a close
relation between cladoceran abundance and mean
pluviosity (Fig. 4). Slightly correlation among
Cladocera with phytoplankton and turbidity in the
second factor were observed.
The pluviometric means at Iraí Reservoir
region showed an increase in rainfall episodes in
September/2002, indicating the beginning of rainy
period (Fig. 5). In the same month, the peak of B.
hagmanni density was observed in station 2, calling
attention a peak in phytoplankton abundance one
month before (August/2002). In dry period of 2002
(May from August) were recorded a decrease in the
pluviometric indexes, as to April to June of 2003,
when cladocerans abundances were also low, except
in May/2003.

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Figure 4. 2D loadings for factors 1 and 2 of the Factor Analysis of station 2. ac: a-chlorophyll; Clad: cladocerans total
density; Cond: electrical conductivity; O: dissolved oxygen; OrgN: organic nitrogen; Phyto: phytoplankton’s species
richness; TotP: total phosphorus; Rain: mean rainfall for each month; Transp: Secchi’s transparency; Turb: turbidity;
Tw: water temperature.
Figure 5. Mean pluviosity, total Cladocera and phytoplankton abundance in station 2 between April/2002 and
June/2003.
Discussion
Most species recorded in this study are
commonly found in the basin of Paraná River,
especially the dominant planktonic, as B. hagmanni,
M. minuta, and C. cornuta (Nogueira et al., 2008).
These species were also found in other aquatic
Brazilian environments (Robertson & Hardy 1984,
Santos-Wisniewski et al. 2000). In general,
Bosminidae, Moinidae, and Daphniidae families are
dominant in lenthic aquatic ecosystems like
reservoirs as verified by Sampaio et al. (2002).
Lansac-Tôha et al. (2005) also found the dominance
of these families at Iraí Reservoir.
Representants of Macrothricidae and
Ilyocryptidae families were less common in this
study. They living in the littoral zone or nearby
(Serafim-Júnior et al. 2003), and their presence in
limnetic zone is accidental. The same consideration
can be done to the Chydoridae family, but C.
eurynotus and C. nitidilus were found in relatively
high abundances compared to the other species of
this family. Records of Chydoridae in the limnetic
zone were found by Paggi & José de Paggi (1990)
that considered some Alona species as
pseudoplanktonic since its abundance was higher in
the limnetic zone compared to the littoral zone of
river channel and floodplain lakes.
Cladocerans are affected by several factors

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at Iraí Reservoir, mainly due to its shallowness,
presenting a large superficial area as shown in
Figure 1. In the beginning of the rainy season,
increased nutrients availability to the water column
allowed their incorporation by the aquatic
communities (Nogueira et al. 2008, Serafim-Júnior
et al. 2005). The low depth and the geomorphology
of the reservoir induce organic matter and nutrients
accumulation, and consequently, phytoplankton
presence in areas next to the margins, favoring the
development of small cladocerans. Larger species,
however, are distributed in areas far from the dam.
The great amplitude variation of species
richness in the rainy season can be related to two
factors. First, the spatial heterogeneity of
cladocerans, which explore the environment in
different ways (Pinel-Alloul 1995), searching for
adequate conditions for their development, for
example, when an increase in altimetric quote and
volume of the reservoir raises food availability and
alter the phytoplankton community. Second, rain
effect is noticeable because it causes the transport of
autochthonous (from littoral zone) and allochtonous
materials (from tributaries and other smaller lakes in
the same basins). Lansac-Tôha et al. (2005) found
slightly higher cladocerans richness at Iraí Reservoir
during the rainy period.
Generally, there was an increase in
cladocerans species richness during this study,
possibly reflecting the processes of colonization and
stabilization of the water column, a fact also
observed in other reservoirs (Esteves & Camargo
1983). A trend of cladoceran temporal variation was
observed after November/2002, when a richness
peak was observed, followed by stable values, with a
mean of 8.7 species. In contrast, in the same period,
considering other plankton communities, Fernandes
et al. (2005) did not find a pattern of species
richness variation and abundance of the
phytoplankton in Iraí Reservoir, as well as Perbiche-
Neves et al. (2007) studying copepods. Also
despollution actions were made in Iraí drainage
basin and it can reflect in better quality water
conditions. Elmoor-Loureiro et al. (2004) verified
similar conditions in Paranoá Reservoir (Brazil),
with new cladoceran records after a long period of
water quality treatment of this reservoir.
Spatial variation of the most limnological
features of the reservoir was very similar and
homogeneous (Andreoli & Carneiro 2005), except
by the concentration of nitrogenates and phosphates
forms due to the tributaries rivers. Except the
nutrients, homogeneous conditions can be associated
to the constant cladocerans species numbers among
sampling stations, probably related to the carrying
capacity of the reservoir. Begon (2007) comments
about this for ecological communities in general.
Generally, in small and shallow reservoirs, two
important parameters that promote water column
mixing in reservoirs are the tributaries water velocity
and wind dynamics. At Iraí Reservoir, wind effect is
very important because its action on water surface
causes accumulation of nutrients and algae in areas
next to the dam (Gobbi et al. 2005), also
influencing, as an example, the phytoplankton
community (Fernandes et al. 2005) and the spatial
distribution of copepods (Perbiche-Neves et al.
2007). Wind can also affect cladocerans spatial
distribution, but a significant difference was not
detected in the total abundance of cladocerans
assemblages, as well as of species richness in this
study.
Considering cladoceran temporal abundance
peaks, was noticed the dominance of small
organisms, especially B. hagmanni. In contrast,
Elmoor-Loureiro (1988) states that to B.
longirostris, B. hagmanni have never been
associated to eutrophic environments and that
elevated densities of these species were found in
lakes with low nutrients. Thus, B. hagmanni
dominance can be related with other variables not
favorable to the dominance of B. longirostris, but
detailed studies, as laboratory bioassays must be
carried out to evaluate this relations. Dominance of
small cladocerans like bosminids in eutrophic
reservoirs was also found in other Brazilian studies
(Branco & Cavalcanti 1999, Pinto-Coelho et al.,
1999, Sendacz et al., 2006). It can be suggested that
the dominance of B. hagmanni was favored by the
eutrophication of Irai Reservoir, because this species
corresponded to more than half of the total relative
abundance. On the other hand, other species of the
Daphniidae, Sididae, and Moinidae families were
dominant in oligo/mesotrophic environments like
some reservoirs of high Paranapanema River
(Nogueira et al., 2008).
Although not so abundant as B. hagmanni,
M. minuta and C. cornuta elevated abundances can
be explained by the adaptation of these species to
food resources. They fed not only on phytoplankton,
but also on detritus and bacteria (DeMott & Kerfoot
1982, Dole-Olivier et al. 2000). Furthermore, they
have a fast development, associated to the high
water temperature in the rainy season and to the
great offer of food during the whole year at Iraí
Reservoir, represented by Cyanobacteria. According
to Monakov (2003), predation of cladocerans on
bacterioplankton is one of the reasons of the
development success of these organisms in adverse
conditions. Success of this species was verified in

A. R. GHIDINI ET AL.
Pan-American Journal of Aquatic Sciences (2009), 4(3): 294-305
302
many reservoirs in Paranapanema River (Brazil)
(Nogueira et al., 2008).
Generally, large cladocerans abundance is
low when compared to small cladocerans, however,
their biomass is high, balancing the contribution of
these organisms to the community (Sendacz et al.,
2006; Corgosinho & Pinto-Coelho, 2006). Studies
indicate that large cladocerans fed on algae, few
species are detritivorous, and most species are
selective to food quality (DeMott & Kerfoot 1982,
de Bernardi et al. 1987). Other studies show that
herbivory on large phytoplankton, as large colonies
of Cyanobacteria by zooplanktonic filter feeders is
difficult and energetically poor, especially if it
involves algae toxicity (Ferrão-Filho & Azevedo
2003). Considering Ceriodaphnia cornuta, a
dominant cladoceran in this study, the explanation of
the high correlation with M. aeruginosa could be the
great niche variety that this species could occupy,
feeding, in this case, on Cyanobacteria early
associated with cyanotoxins in Iraí Reservoir
(Fernandes et al. 2005).
Ferrão-Filho & Azevedo (2003) found that
feeding on colonial (Microcystis) and filamentous
algae is difficult to small cladocerans and that they
feed mainly on individual or in decomposition cells.
Apparently, only large cladocerans, as Daphnia, are
able to feed on individual cells or colonies of
Microcystis (Rohrlack et al. 1999, Nandini 2000).
Kobayashi et al. (1998) also state that large
cladocerans are able to feed efficiently on large
Microcystis colonies and that this can be influenced
not only by alga toxicity, but also by colony
disaggregation. The same was observed in Trabeau
et al. (2004) experiments, that rising alga biovolume
and microcystin production observed a decline of
Daphnia populations, associated to an increase in
energetic costs of feeding. Conversely, Alva-
Martinez et al. (2001) detected an increase of
population growth of one species of Daphnia and
one of Ceriodaphnia when fed with increasing
concentrations of Microcystis aeruginosa. Similar
results could be expected in Iraí Reservoir, but
laboratory bioassays are needed to test the influence
of food on cladocerans populations.
Other phytoplankton species demonstrated
negative correlation with cladocerans, as D.
gessneri, that showed a negative correlation with A.
alpigena, M. minutum, and Tetraedon sp. Lampert
(1987) states that Daphnia feeding apparatus is
specialized to feed on nanoplankton (5-60µm,
according to Hutchinson 1967), and that ingested
algae species can vary with the animal body size.
Considering the three cited algae species, they are
too large to be consumed by D. gessneri, explaining
the negative correlation found in this study.
Diaphanosoma birgei and D. brevireme
showed a negative correlation with the diatomacean
Urosolenia sp. Despite baccilariophyceans are
considered an indispensable food item to
cladocerans that feed on periphyton, they are not
commonly ingested by planktonic cladocerans
(Nogueira et al. 2003). In the other hand, for
copepods, Perbiche-Neves et al. (2007) found a high
positive correlation with the diatomaceans during
the same period of the present study at Iraí
Reservoir.
After B. hagmanni peak in September/2002
there was a subsequent decline of Bosmina
population’s densities, when Microcystis aeruginosa
cells densities was higher within chlorophyll-levels
until January/2003. This decline could be related to
the difficult of cladocerans in feeding on
Cyanobacteria colonies, or due to the toxicity of the
alga. The fact that M. aeruginosa and cladocerans
densities decreased in October/2002 and that
cladoceran species richness raised after October can
indicate an increase in the food offered to
cladocerans. M. aeruginosa blooms can also be
associated with the population increase or
appearance of the larger cladocerans Daphnia and
Diaphanosoma in the lake that could be favored by
the development of this alga.
Pinel-Alloul et al. (1988), studying the
spatial distribution of zooplankton suggests that
developmental stage, body size, and periodicity are
factors that can influence data obtainment of
population density horizontal variation and
zooplankton species richness. However, tropical
lakes are generally small, shallow, and it is difficult
to establish a large scale of spatial heterogeneity
(Rocha et al. 1995, Sarma et al. 2005). In these
cases, density and species richness spatial variation
can only be determined when adjacent regions of
lenthic zones are included in the sampling program.
Areas next to the margins, where detritus and
cyanobacterians accumulate due the low water flux
and wind direction, favor the development of small
cladocerans, while larger species find better habitat
conditions and greater food diversity in areas far
from the dam.
Through the studied months, elevated rain
episodes promoted water column mixing,
occasioning slightly relation with turbidity in factor
analysis, returning nutrients and organic matter to
the water column, causing the abundance peak of B.
hagmanni in September/2002. The water column
mixing increased the nutrients availability to the
primary producers, and, in this case, high abundance
of cyanobacterians favored the appearance and

Distribution of planktonic cladocerans of a shallow eutrophic reservoir
Pan-American Journal of Aquatic Sciences (2009), 4(3): 294-305
303
development of larger cladocerans. This can also be
associated to an increase of the food quantity and
quality available, promoting the development of
more species, explaining the elevated cladoceran
species richness during the summer of 2002 and
2003 years. But in the absence of higher pluviosity,
it was also verified a peak of phytoplankton
abundance, like in August/02, represented by
strategic cyanobacterians that can development in
such conditions.
Both spatial and temporal variations were
relevant but the first was not significant, rejecting in
part the hypothesis that the temporal variation was
more probable. Spatial variation was influenced
mainly by morphometrical characteristics of the
reservoir, and temporal variation by climatic
changes in the sampling period, especially pluviosity
and water temperature, very contrasting events in
sub-tropical regions. Seasonal and temporal
variation of species richness and population
densities described in this study probably is due to
alterations in the hydrological and biological
characteristics of the reservoir. The modifications
can be considered responses to natural processes of
colonization and to environmental natural changes,
or also a result of the management performed by the
responsible sanitation company in the reservoir, in
consequence of the degradation of water quality.
Acknowlodgements
To GECIP/SANEPAR for logistic support
and development of the Interdisciplinary Project, Dr.
Luciano F. Fernandes (UFPR), IAP-PR, Dr. Harry F.
Bollman and Technological Institute SIMEPAR for
the conceded phytoplankton, abiotic and
pluviometric data, respectively, PUC-PR to the use
of the plankton laboratory installations and the two
anonymous referees for valuable suggestions.
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Received April 2009
Accepted July 2009
Published online August 2009