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Oceanological and Hydrobiological Studies
International Journal of Oceanography and Hydrobiology
Vol. XXXIX, No. 1
Institute of Oceanography
ISSN 1730-413X
(85-94)
2010
University of Gdańsk
eISSN 1897-3191
Copyright© by Institute of Oceanography, University of Gdańsk, Poland www.oandhs.org
Changes in the structure of phytoplankton in the lowest part
of the Cybina River and the Maltański Reservoir
Anna Kozak1
Dept. of Water Protection, Adam Mickiewicz University
ul. Umultowska 89, 61-614 Poznań, Poland
Key words: phytoplankton, taxonomic composition, abundance, biomass,
Abstract
The floristic composition, abundance, and biomass of phytoplankton in the Cybina River and
the Maltański Reservoir were examined from April to October 2005. The analysis of the
phytoplankton in the samples revealed statistically significant differences in both composition and
abundance. The maximum abundance (39.2 × 103 ind. cm-3) and biomass (56.8 μg cm-3) of
phytoplankton was noted in July 2005 at the outlet from the Maltański Reservoir. The lowest
phytoplankton density was most often noted at the site located at the inlet of the Cybina River into
the Maltański Reservoir. The quantitative and qualitative compositions of the phytoplankton
varied at different sites. The highest taxonomical similarity was noted among the samples
collected in the reservoir and at the outflow from it.
1 e-mail: akozak@amu.edu.pl
DOI 10.2478/v10009-010-0003-y
Original research paper Received:
Accepted:
July 03, 2008
January 20, 2010
A. Kozak
Copyright© by Institute of Oceanography, University of Gdańsk, Poland
86
INTRODUCTION
The Cybina River (total length of 41 km) is a right tributary of the Warta
River in the Wielkopolska Region (mid-western Poland). Its catchment area of
195.5 km2 is covered mainly by cultivated fields (Gołdyn and Grabia 1998,
Gołdyn and Kowalczewska-Madura 2005). The contribution of forests to this
area is just 14%. The Cybina River and its tributaries are typical lowland rivers
with mildly sloping riverbeds and many natural lakes and artificial reservoirs
along their courses (Gołdyn et al. 2005). The Cybina River flows through the
Maltański Reservoir just prior to discharging into the Warta River. The
reservoir is a shallow water body of 64 ha, a mean depth of 3.1 m, a maximum
depth of 5 m and a water residence time of 34 days. It is an urban reservoir that
was created in the 1950s for sports and recreation. Recently, substantial efforts
have been made to improve the ecological quality of its water. In the 1980s, the
reservoir was subjected to thorough restoration (Gołdyn et al. 1994), and
biomanipulation was applied by introducing predatory fish species in the 1993-
1996 period (Gołdyn et al. 1997, Kozak and Gołdyn 2004, Kozak 2005).
A 4-year cycle of water drainage was introduced in 1993 (from fall in October
to spring in March).
The species composition of the potamoplankton undergoes dynamic
changes as it passes through reservoirs along the course of the river. The aim of
this study was to establish seasonal changes in the quantitative and qualitative
phytoplankton structure in the Maltański Reservoir and at the inlet and outlet of
the Cybina River to this reservoir.
MATERIALS AND METHODS
The Cybina River is a 41 km long watercourse that debouches into the
Warta River at the 240.5 km of its course (Gołdyn and Garbia 1998). The
current study focuses on the last section of the Cybina River and the Maltański
Reservoir. The main physicochemical data of the water are presented in Table 1.
The taxonomic composition, abundance, and biomass of the phytoplankton
from the Cybina River and the Maltański Reservoir collected fortnightly from
April to October in the year 2005 were analyzed. The samples for analysis were
collected from midstream in the Cybina River at the inlet and outlet to the
Maltański Reservoir and from the center of the reservoir (mean value from the
surface layer and depths of 1, 2, and 3 m).
The phytoplankton samples were preserved with Lugol's solution with
Utermöhl's modification. The abundance of phytoplankton was estimated with a
Sedgwick-Rafter chamber. The biomass was calculated by approximating the
shape of the organisms with geometric figures (Wetzel and Likens 1991). To
Changes in the structure of phytoplankton
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87
assess the statistical significance of the changes in the phytoplankton
community resulting from water flow through the reservoir, the Wilcoxon
matched pairs and Wald-Wolfowitz tests from nonparametric statistics were
applied using Statistica 5.1 software.
The similarity of the phytoplankton composition at the measuring sites (S)
was determined based on the abundance of the particular taxa represented,
according to the formula:
)(
100
wba
w
S−+
=
w - is the number of species noted in both samples analyzed,
a - is the number of species in the first sample,
b - is the number of species in the second sample (Romaniszyn 1970).
Table 1
Range of physicochemical data of the water (according to Kozak et al., in
preparation)
Variables max. min. mean SD
temperature (°C) 23.62 8.02 17.57 4.44
Secchi depth (m) 3.7 0.7 1.09 0.79
pH 9.90 6.61 8.47 0.62
conductivity (μcm-1 S) 1372 948 1168 99
dissolved oxygen (mg dm-3 O2) 14.6 2.6 8.8 3.1
BOD5 (mg dm-3 O2) 8.9 1.0 5.2 2.1
dissolved P (mg dm-3 P) 0.310 0.003 0.12 0.08
total P (mg dm-3 P) 0.57 0.03 0.21 0.12
ammonia (mg dm-3 N) 2.809 0.119 0.825 0.587
nitrite (mg dm-3 N) 0.057 0.002 0.02 0.016
nitrate (mg dm-3 N) 2.80 0.01 0.63 0.95
organic N (mg dm-3 N) 4.17 0.58 2.35 0.71
total N (mg dm-3 N) 9.8 2.39 3.91 1.57
seston (mg dm-3) 22.85 0.42 10.16 4.61
chlorophyll a (μg dm-3) 125.70 0.37 38.79 25.41
A. Kozak
Copyright© by Institute of Oceanography, University of Gdańsk, Poland
88
RESULTS AND DISCUSSION
In its last section, the Cybina River flows through the Maltański Reservoir
and then debouches into the Warta River. The number of taxa representing
particular classes of phytoplankton found in the Cybina River and in the
Maltański Reservoir at all sites was similar. The lowest number of taxa of 152
was observed at the outlet of the river from the Maltański Reservoir, while the
highest of 184 was noted in the samples taken from the middle of the reservoir
(Table 2). The most abundant group of phytoplankton represented by the
greatest number of taxa were green algae, whose contribution at particular sites
varied from 45-48% of all taxa identified. The number of phytoplankton taxa
identified in the water of the Cybina River and the Maltański Reservoir was
within the range specified for similar artificial reservoirs and rivers in Europe,
e.g. 93 in Lake Arancio, an artificial Sicilian water body (Flores, Barone 1998),
118 in the Narew River (Hutorowicz et al. 2002), 323 in the Radunia River
(Gołdyn 1989), 240 in the Bulgarian Srebrna Lake (Stoyneva 1998), 402 in
Estonian rivers (Piirsoo 2001), 426 in the Morava River (Hindak and Hindakova
2004).
The analysis of seasonal changes in phytoplankton revealed a significant
increase in its abundance and biomass in spring and summer. The maximum
phytoplankton abundance was noted in the Cybina River in July 2005, when it
reached 39.2 × 103 ind. cm-3 at the site at the river outlet from Maltański
Table 2
Number of taxa identified at the intlet, outlet, and in Maltański Reservoir
Taxa Cybina inlet Maltański Reservoir Cybina outlet Together
Cyanobacteria 11 16 14 17
Euglenophyceae 10 9 8 12
Cryptophyceae 9 14 12 14
Chrysophyceae 15 19 15 21
Bacillariophyceae 29 26 22 31
Chlorophyceae 78 85 69 101
Dinophyceae 3 3 3 3
Xantophyceae 3 4 2 5
Conjugatophyceae 6 8 7 8
Total 164 184 152 212
Changes in the structure of phytoplankton
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89
Reservoir (Fig. 1). The corresponding biomass of this phytoplankton was
56.8 μg cm-3.
The largest phytoplankton biomass was most frequently noted at the site
located in the middle of the Maltański Reservoir, while the lowest values were
observed at the site of the inlet of the Cybina River to the Maltański Reservoir.
The greatest differences between the maximum and minimum abundance
and biomass observed at the three sites studied were noted at the outlet of the
Cybina River from the Maltański Reservoir (Fig. 1), while the lowest
differences were at the inlet of the Cybina River to the reservoir. Usually,
phytoplankton density was greater in the samples collected in the middle of the
reservoir than in those collected at the inlet. An increase in the phytoplankton
density at the outlet was noted at the end of spring and in summer (in April,
July, and August). In other months, the amount of phytoplankton at the outlet
was lower. The differences in the abundances of particular species and in their
Fig. 1.
A
bundance and biomass of phytoplankton throughout the investigated
period.
A. Kozak
Copyright© by Institute of Oceanography, University of Gdańsk, Poland
90
biomass at different sites were statistically significant, and the greatest
differences were noted between the samples collected at the inflow and outflow
of the reservoir (p=0.001, n=119).
The Cybina River ecosystem was significantly affected by its passage
through the Maltański Reservoir, and the phytoplankton density was usually
greater in the reservoir than at the outlet. The intense development of
phytoplankton occurs in reservoirs in which the water residence time is long
enough for phytoplankton growth (Sullivan et al. 2001, Zeng et al. 2006).
The contribution of individual taxonomic groups to the total abundance of
phytoplankton confirmed there were significant temporal and spatial changes
(Fig. 2). Two peaks of abundance were observed in spring and in summer at the
inlet of the Cybina River to the reservoir. The greatest contribution to total
abundance in spring was by Chrysophyceae, Bacillariophyceae, Cryptophyceae,
and Chlorophyceae. The most abundantly represented at that peak were
Chrysococcus minutus (Fritsch) Nygaard 2.4 × 103 ind. cm-3, Dinobryon sociale
Ehrenberg 4.1 × 103 ind. cm-3, Erkenia subaequiciliata Skuja 1.8 × 103 ind. cm-3,
Asterionella formosa Hass.1.2 × 103 ind. cm-3, Fragilaria ulna var. acus
(Kutzing) Lange-Bertalot 2.8 × 103 ind. cm-3, Nitzchia acicularis W. Sm. 10.2 ×
103 ind. cm-3, and Stephanodiscus hantzschii Grun. 3.2 × 103 ind. cm-3. Among
the Cryptophyceae the most abundant were Cryptomonas marssonii Skuja and
Rhodomonas lacustris Pascher et Ruttner, whose numbers reached 3.2 × 103 and
2.0 × 103 ind. cm-3, respectively. The importance of green algae was also noted,
and it was represented mostly by Scenedesmus communis Hegewald, Oocystis
lacustris Chodat, Monoraphidium contortum (Thur.) Kom.-Legn, Crucigenia
tetrapedia (Kirchner) W et G. S. West., and Tetrastrum triangulare (Chodat)
Komarek. A large contribution to total biomass was made by Pediastrum tetras
(Ehrenberg) Ralfs and P. duplex Meyen, P. boryanum (Turp.) Menegh. The
green algae that were represented by the greatest number of taxa were rarely
dominant in the abundance or biomass of the phytoplankton. Their domination
was noted only at the inflow in the period from July to September (Figs. 2, 3).
Chlorophyceae were dominated by species from other taxonomic groups in the
samples taken at the outflow and in the middle of the reservoir.
At the outlet in early spring the dominants were Bacillariophyceae and
Chrysophyceae, while from June to September it was Cyanobacteria, which
were only sporadically noted at the inlet. The dominant species of
Cyabobacteria was Aphanizomenon flos-aquae (L.) Ralfs and it occurred at the
maximum density in July 2005 reaching an abundance of 30.7 × 103 ind. cm-3
and a biomass of 48.6 µg cm-3. This species, which is frequently toxic to
humans, appeared in great abundance in the reservoir the first year after it was
refilled. Similar observations were made in the first years after refilling in 1990
and 1993 (Gołdyn et al. 1994, Kozak and Gołdyn 2004, Kozak 2005). Intense
Changes in the structure of phytoplankton
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91
water blooms caused by this species have also been reported in many other dam
reservoirs and rivers in Europe, e.g., Goczałkowicki Reservoir, Sulejów
Reservoir, the Morava River (Pająk 1986, Galicka et al. 1992, Rakowska et al.
2005, Marvan et al. 2004). Other species representing Cyanobacteria in the
samples collected from the Cybina River and Maltański Reservoir included:
Planktothrix agardhii (Gom.) Anagnostidis & Komarek, Anabaena flos-aquae
Brebisson, ex Bornet et Flahault, Microcystis aeruginosa Kutzing,
Fig. 2. Share of main taxonomic groups in the total abundance of
phytoplankton at the inlet and outlet of the Cybina River to the Maltański
Reservoir and in the reservoir.
A. Kozak
Copyright© by Institute of Oceanography, University of Gdańsk, Poland
92
Fig. 3. Biomass distribution of taxonomic groups of phytoplankton in the lowest
part of the Cybina River and the Maltański Reservoir.
Changes in the structure of phytoplankton
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93
Pseudanabaena limnetica Lemmermann from Geitler, and Woronichinia
naegeliana (Unger) Elenkin. The species Anabaenopsis arnoldii Aptekarj, a
new Cyanobacteria species in Poland (Gołdyn et al. 2003), was also identified;
however, its abundance was low and reached 80 ind. cm-3 in August 2005 in the
samples from the middle of the reservoir.
Diatoms and green algae were among the other groups abundantly
represented, in particular by Aulacoseira granulata m. curvata (Echrenberg)
Simonsen, noted almost exclusively in the reservoir and at the outflow, Oocystis
lacustris Chodat, Manoraphidium contortum (Thur.) Kom.-Legn., and
Scenedesmus communis Hegewald. A. granulata m. curvata was numerous from
the end of August to October 2005 and reached the maximum value of 3.7 × 103
ind. cm-3 and a biomass of 11.21 μg cm-3 at the beginning of September. It was
not, however, noted in 1993-1996 (Kozak 2005).
The qualitative composition of the phytoplankton samples was most similar
in the samples collected from the reservoir and at the outflow from it (S=40%,
on average). The similarity of phytoplankton composition between the samples
collected at the inflow and in the reservoir was lower (S=36%, on average). The
taxonomic composition of the phytoplankton changed significantly as the river
flowed through Maltański Reservoir, which is confirmed by the lowest
similarity in taxonomic composition of the samples collected at the inflow and
outflow (S=28%, on average).
In addition to quantitative changes in the phytoplankton, the passage of the
Cybina River through Maltański Reservoir also caused significant qualitative
changes in the water. This was particularly apparent in the summers in the
1990s (Gołdyn et al. 1994, Gołdyn and Szeląg-Wasielewska 2005) when the
taxonomic composition shifted from the dominance of: Chlorophyceae,
Bacillariophyceae, and Cryptophyceae at the inflow into the dominance of
Cyanobacteria at the outflow. Similar changes have been noted in other dam
reservoirs (Zeng et al. 2006, Marvan et al. 2004).
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