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ALGAE FOR MONITORING RIVERS
Analysis of the seasonal dynamics of river phytoplanktonbased on succession rate indices for key event identification
Roman E. Romanov • Vladimir V. Kirillov
Received: 30 December 2009 / Accepted: 14 June 2011
� Springer Science+Business Media B.V. 2012
Abstract The seasonal dynamics of river phyto-
plankton was analyzed using succession rate indices
based on data collected from year-round observations
of two small plain rivers in the Upper Ob Basin
(Western Siberia). The study revealed a generally
clear seasonal pattern of structural changes in the
phytoplankton of the lower reaches of the studied
rivers. The dynamics of succession rate indices reflects
the key events in the life of phytoplankton in the
Bolshaya Losikha and Barnaulka Rivers, showing
mainly changes in the dominant species during the
main phases of the hydrological cycle. The most
significant changes in phytoplankton structure tend to
occur in the period between the spring flood decline
and the beginning of summer–autumn low water.
These changes coincide with the most drastic changes
in both environmental conditions and phytoplankton
successional stages. Use of succession rate indices to
analyze the seasonal dynamics of phytoplankton
allowed us to distinguish between periods of abrupt
change and periods of comparatively low-intensity
changes in plankton composition in small lowland
temperate rivers.
Keywords Phytoplankton � Succession rate �Community change rate � River �Western Siberia
Introduction
According to Margalef (1968), succession is one of
the most important and fruitful concepts in classical
ecology, occupying a place similar to that of evolution
in general biology. Although there is currently no
concise definition of succession, two underlying
components are generally recognized (Lewis, 1978):
(1) succession determines changes in species abun-
dance within a community, and (2) succession is a
directed change. Furthermore, it is far more useful to
express rates of changes in a community quantitatively
rather than just point out the direction of such changes.
A succession index value characterizes the rate of
change in the relative abundance of all components in
a given community. In analysis of community dynam-
ics, it enables complete and concise descriptions of
bulky statistics and the phenomenology of community
succession (Lewis, 1978). It also allows changes in the
succession structure that correspond to significant
environmental changes to be identified (Reynolds,
Guest editors: L. Ector, D. Hlubikova & L. Hoffmann /
Proceedings of the 7th International Symposium ‘‘Use of Algae
for Monitoring Rivers’’, Luxembourg, November 23–25, 2009
R. E. Romanov (&)
Central Siberian Botanical Garden, Siberian Branch of
Russian Academy of Sciences, Zolotodolinskaya St.,
101, Novosibirsk, Russia 630090
e-mail: [email protected]
V. V. Kirillov
Institute for Water and Environmental Problems of SB
RAS, Molodeznaya St., 1, Barnaul, Russia 656038
e-mail: [email protected]
123
Hydrobiologia
DOI 10.1007/s10750-012-1198-6
1984). Moreover, this method allows us to outline the
general character of a community’s dynamics, i.e., to
define whether it is cyclic, directed change (succes-
sion) or stochastic (Collins et al., 2000). Changes in
community structure tend to be sharp or asymmetrical
when they are caused by abrupt shifts in allogenic
factors, and, conversely, gradual changes mean
autogenic species replacement, which corresponds to
ecological succession (Reynolds, 1988; Huszar &
Reynolds, 1997).
Succession rate indices can be used as a universal
approach to analyze succession in various types of
community (Lewis, 1978; Huhta, 1979; Stephenson,
1980; Collins et al., 2000; Foster & Tilman, 2000).
Establishing temporal heterogeneity in the structure of
aquatic communities is one element in the empirical
statistical description model used as a tool in quanti-
tative ecological forecasting and paleoecological
reconstruction.
Phytoplankton lends itself well to succession
research because of the short life cycles of its
components (Huszar & Reynolds, 1997), which leads
to relatively rapid structural responses to environ-
mental change. Use of succession rate indices in
analysis of phytoplankton dynamics has been
severely criticized due to the strong influence of
counting error on the results; thus, succession rate
indices can be applied only when ‘‘uncertainty
derived from counting error is considered’’ (Duarte
et al., 1990), i.e., only to data with the lowest possible
values of counting error. Moreover, these measures
may theoretically be insensitive to community com-
position changes when changes in the fractions
of different species are counterbalanced (Rojo &
Alvarez Cobelas, 1993). Obviously, a succession rate
index as a measure of change intensity ‘‘gives little
information about the nature of that change’’ (Kuhn
et al., 1981).
Nevertheless, this method can be used fruitfully in
analysis of phytoplankton and periphyton dynamics,
and has allowed identification of stages of seasonal
succession or differentiation of parts of reservoirs with
different intensities of phytoplankton succession
(Kuhn et al., 1981; Millie & Lowe, 1983; Reynolds,
1984, 2006; Trimbee & Harris, 1984; Giorgio et al.,
1991; Huszar et al., 1998; Hubble & Harper, 2002; de
Souza Cardoso & da Motta Marques, 2003; Pannard
et al., 2008). This succession rate indices approach
has been applied to potamophytoplankton succession
analysis in only a few cases to date (Giorgio et al.,
1991; Garcıa de Emiliani, 1997).
The aim of this work is to analyze the seasonal
dynamics of river phytoplankton using different
succession rate indices in order to recognize key
events and detect the periods of most significant
change in river phytoplankton composition.
Materials and methods
Study sites
Two lowland rivers of the Upper Ob Basin were
chosen as the study locations: the Barnaulka and
Bolshaya Losikha Rivers. The lower reaches of the
Barnaulka and Bolshaya Losikha Rivers were studied
in 2001–2003 (Fig. 1). Of all the innumerable small
rivers of Western Siberia, the complete seasonal
dynamics of phytoplankton is described only for these
two. Data from these surveys can be used to calculate
succession rate indices by sampling frequency and
duration, yielding comparatively low counting errors
due to accurate sample analysis (see below).
The Bolshaya Losikha River flows into a channel of
the Ob near the Town of Barnaul. According to the
Korytny classification of river systems (2001), the
Bolshaya Losikha is a medium-length river (150 km)
with small catchment area (1,500 km2). The flow
velocity of the Bolshaya Losikha near its mouth varied
from 0.5 to 0.7 m s-1 in the summer–autumn low
water period of 2002. The salinity during spring floods
is 0.1–0.2 mg l-1, rising to 0.5–0.6 g l-1 in summer
(Uryvaev, 1962).
The Barnaulka River flows into the Ob within the
city limits of Barnaul. According to Korytny (2001),
the Barnaulka is a medium-sized river (approximately
200 km in length with 5,700 km2 watershed), catego-
rized as minor by discharge. Measurements conducted
in 2000 showed discharge varying from 0.4 m3 s-1
(March 14) to 7.3 m3 s-1 (April 12), and flow velocity
between 0.3 m s-1 (October 5) and 0.9 m s-1 (April
12) (Temerev et al., 2001). In the summer–autumn
low water period, the water salinity of the Barnaulka
varies from 0.16 to 0.90 g l-1 at various measurement
locations. The concentration of biogens, i.e., inorganic
compounds of phosphorus and nitrogen, is very high,
and increases further downstream. In the middle and
lower reaches, both the water and bottom sediments
Hydrobiologia
123
are contaminated with heavy metals and harmful
organic compounds (Mikhailov et al. 2000; Tret’yak-
ova, 2000; Temerev et al., 2001), as supported by data
on zooplankton and zoobenthos (Bezmaternykh &
Eidukaitene, 2003).
The spring floods on the plain rivers of the Upper
Ob Basin are followed by steady low waters that
remain until the formation of ice before falling further
to the winter low water level. There are, however,
occasional insubstantial floods (one or two per
season). A system of lakes in the upper reaches of
the Barnaulka and the swamped floodplains in its
upper and middle reaches define the low values of
maximal flood discharge and explain the relatively
extended spring flood period (Uryvaev, 1962). The
low water season in the Barnaulka is rarely interrupted
by floods (Shenberg, 1991).
Phytoplankton sampling and analysis
Phytoplankton in the Barnaulka was sampled 1 km from
the river mouth from November 2001 to February 2003,
and samples in the Bolshaya Losikha were collected
6.5 km from the mouth from December 2001 to
December 2002 at 10–15-day intervals. The samples
were fixed with 40% formaldehyde solution to final
concentration of 2–4%, and filtered through Vladipor
no. 6 membrane filters with pore diameter of
0.55–0.65 lm. A total of 59 samples were analyzed
by light microscopy using standard techniques (Wasser,
Fig. 1 Map of the Upper
Ob drainage basin showing
the location of two sampling
sites at two rivers
Hydrobiologia
123
1989): 32 from the Barnaulka and 27 from the Bolshaya
Losikha. At least 500 individuals, and all cells in all 500
individuals, were counted in each sample to achieve the
lowest possible count error (*10%). To calculate the
biomass (biovolume), cell volumes were approximated
as simple or combined geometric figures. Diatoms were
identified in permanent preparations.
The numbers of cells and individuals (solitary cells,
colonies, coenobia, filaments, temporary cell aggregates)
were counted independently, resulting in two indepen-
dent sets of values for the Barnaulka and Bolshaya
Losikha Rivers. The cell and individual counts are not
interchangeable, and their integration into a single set of
values is impossible. Using both of these independent
measurements simultaneously instead of the more com-
monly used cell count method allowed more precise
evaluation of the role of species and of the size groups of
phytoplankton (Shtin, 1945; Mikheyeva & Lukyanova,
1999, 2000). Noncolonial centric diatoms (mostly Step-
hanodiscus spp. and Cyclotella spp.) were counted in
bulk without regard to the particular species since it is
impossible to distinguish them adequately under light
microscopy and in uncleaned material. Species of
Gymnodinium, Chlamydomonas, and Cryptomonas were
counted and used for index calculation (see below) as
aggregate components (Gymnodinium spp., etc.) since
the exact identification of individual cell types is
impossible in formaldehyde-fixed material.
Data analysis
Succession rate indices (SD, ED, WG) were calculated
using the following three formulae:
SDt1;t2 ¼Xn
k¼1
pk2� pk1
j j !,
t2 � t1ð Þ;
EDt1;t2 ¼Xn
k¼1
ðpk2� pk1
Þ2" #1=2,
ðt2 � t1Þ;
WGt1;t2
¼Xn
k¼1
pk2log2 pk2
�Pn
k¼1
pk2log2 pk2
� pk1log2 pk1
�Pn
k¼1
pk1log2 pk1
2
664
3
775
20
BB@
1
CCA
1=2
,
ðt2 � t1Þ;
pkiis the share of species k in the total abundance of a
community at time point ti; n is the number of species
in the community at time points t1 and t2 (Williams &
Goldman, 1975; Lewis, 1978; Stephenson, 1980),
however only for periods of comparable sampling
intensity.
The numerator in SD corresponds to an n-dimen-
sional vector rate. Its start–end coordinates describe
two points in an n-dimensional space. In our case,
these points describe the set of species of phytoplank-
ton at t1 and t2; the numerator in ED corresponds to the
n-dimensional vector length mentioned above
(Euclidean distance). Both expressions conform to
the distance function definition and are a particular
case of the lp-norm (Duran & Odell 1974) and a
particular case of the Minkovsky distance metric
function. The WG index, where the numerator also
obeys the definition of a distance function, is the rate
of community movement through the diversity space
and assigns a value to the relative contribution of a
single species to the diversity of the whole commu-
nity. If the species composition has changed but the
community diversity has stayed the same, WG will be
greater than zero (Williams & Goldman, 1975). SD is
less sensitive to counting error than the index proposed
by Jassby & Goldman (1974); the latter was not used
in our research. Due to the large influence of counting
errors on succession rate index values (Duarte et al.,
1990), only prominent differences in rate index values
(at least threefold) were taken into account.
Results
Taxonomic richness
A total of 383 species belonging to 138 genera and 63
families were found in the phytoplankton of the
Barnaulka River (Romanov & Kirillov, 2009). The
phytoplankton richness in the Bolshaya Losikha was
somewhat lower: 362 species in 128 genera and 55
families. The highest richness was seen among the
green algae, diatoms, euglenoids, and cyanobacteria.
The green algae were always superior in richness
compared with diatoms, and euglenoids were enriched
compared with cyanobacteria. The taxonomic richness
of the other algal groups was very low.
The seasonal dynamics of the numbers of simulta-
neously vegetating species (including their varieties
and forms) was similar in the studied rivers
Hydrobiologia
123
(hereinafter referred to as simultaneous species
richness, SSR). Minimum SSR was registered during
winter low water and during floods (11–54 species,
varieties, and forms); maximum SSR was registered
during summer and autumn low water when the water
temperatures are highest (90–129 species, varieties,
and forms). The SSR peaked dramatically with the
decline of floods (Romanov, 2006).
Seasonal dynamics of abundance and composition
Planktonic forms, diatoms, green algae, and, in a few
cases, cyanobacteria form the core of phytoplankton in
the studied rivers.
The abundance of the fluctuation range of phyto-
plankton in the Bolshaya Losikha was significantly
broader compared with that of the Barnaulka (Table 1).
Cell count, individual count, and gross biomass of
phytoplankton in the Barnaulka River were approxi-
mately the same during the winter low water season
and spring floods (less than 0.23 9 106 cells l-1,
0.15 9 106 individuals l-1, 0.2 g m-3; Fig. 2). The
counts rose dramatically during the flood decline along
with the fall in water level. The maximum values for cell
count, individual count, and gross biomass were
recorded during periods that were relatively stable
hydrologically, with water temperatures above 10.0�C,
primarily during the summer–autumn low water season
(early May through early September).
Similarly to the Barnaulka, noncolonial centric
diatoms were the dominant group throughout the larger
part of the year. Their abundance reached 31.6 9 106
cells or individuals l-1, 16.1 g m-3, and their share
of total phytoplankton abundance was 58.4, 63.8,
and 89.0%, respectively. Monoraphidium contortum
(Thuret) Komarkova-Legnerova and Chrysococcus
rufescens f. tripora J.W.G. Lund had the top cell and
individual counts (up to 11.7 9 106 cells or individu-
als l-1, 21.9% of total phytoplankton cell count, 22.7%
of total individual count, and up to 4.2 9 106 cells or
individuals l-1, 46.9% of total phytoplankton cell
count, 37.0% of total individual count, respectively),
while Chlamydomonas spp. dominated the gross bio-
mass (up to 1.2 g m-3, 84.3% of total biomass).
The studies revealed two seasonal peaks of abun-
dance in Barnaulka River phytoplankton (Fig. 3). The
first peak corresponded to the spring flood decline (up to
6.0 9 106 cells l-1, 4.6 9 106 individuals l-1, 3.7 g
m-3), and the second, stronger peak to the season
preceding ice cover formation (up to 35.1 9 106
cells l-1, 9.6 9 106 individuals l-1, 4.6 g m-3). The
cell count, individual count, and gross biomass of
phytoplankton were low (up to 1.0 9 106 cells l-1,
0.6 9 106 individuals l-1, 0.6 g m-3) in the winter low
water of 2001–2002. On the contrary, phytoplankton
abundance was higher in the first half of the winter low
water of 2002–2003 due to significant development of
noncolonial centric diatoms and Limnothrix redekei
(Van Goor) Meffert (up to 27 9 106 cells l-1, 2.3 9
106 trichomes l-1, 0.4 g m-3; 77.3, 24.1, and 7.8% of
total phytoplankton abundance, respectively). The cell
count, individual count, and gross biomass of phyto-
plankton were in the same order during the winter low
water of 2001–2002 and the following spring flood. The
abundance of phytoplankton increased significantly
with the flood decline, due mainly to an outburst of
noncolonial diatoms and Chlamydomonas spp., reach-
ing 0.5–3.2 9 106 cells l-1, 0.2–2.4 9 106 individu-
als l-1, and 0.3–3.6 g m-3. Noncolonial centric
diatoms often dominated all three values—cell count,
individual count, and gross biomass (up to 68.6, 71.2,
and 73.4% of total abundance of phytoplankton,
respectively)—and M. contortum by cell count and
individual count (up to 40.0 and 43.8% of total
abundance of phytoplankton, respectively). The maxi-
mal abundance of noncolonial centric diatoms
was 6.4 9 106 cells l-1, 5.9 9 106 individuals l-1,
and 2.75 g m-3; that of M. contortum was up to
758.0 9 103 cells or individuals l-1.
Seasonal dynamics of succession rate indices
Use of SD and ED indices (linear correlation coeffi-
cient for Bolshaya Losikha and Barnaulka, k =
0.85–0.98; Table 2), cell count and individual count
Table 1 Abundance of phytoplankton in the Bolshaya Losi-
kha and Barnaulka Rivers
Abundance index, season, unit Bolshaya
Losikha
River
Barnaulka
River
Cell count, all seasons,
106 cells l-10.02–95.68 0.19–35.10
Individual count, all seasons,
106 individuals l-10.01–57.83 0.13–9.65
Biomass, all seasons, g m-3 0.01–18.80 0.08–4.57
Arithmetical mean biomass,
open water period, g m-34.94 ± 1.47 1.53 ± 0.28
Hydrobiologia
123
(k = 0.72–0.87) yielded very similar results. The
seasonal dynamics of the SD and WG indices were
similar only in their general features (Figs. 4, 5).
The seasonal dynamics of values of succession rate
indices by cell count, individual count, and gross
biomass of the Bolshaya Losikha phytoplankton share
two features. Firstly, they peaked in the second third of
the low water season of 2001–2002 and during the
flood decline. Secondly, they showed reduced vari-
ability from the summer–autumn low water through
the first half of the winter low water season of
2002–2003 (Fig. 4). The latter was less obvious by
the cell-count-based SD. There were no peaks in the
second half of the winter low water in the seasonal
dynamics of the biomass-based ED.
The maximum values of the succession rate indices
at the flood decline reflect the sharp change of
dominants from Chlamydomonas spp. to noncolonial
centric diatoms, just as in the Barnaulka River.
Presumably this was due to the significant decrease
in velocity, level decline, and increase in the residence
time of the river waters.
Only two peaks in the individual-count-based SD
values for the Barnaulka exceeded 0.1 day-1.
Reynolds (1984) used this threshold to analyze
phytoplankton succession in a number of lakes and
Fig. 2 Seasonal dynamics
of phytoplankton abundance
in the lower reach of the
Bolshaya Losikha in 2002
Fig. 3 Seasonal dynamics
of phytoplankton abundance
in the lower reach of the
Barnaulka in 2002
Hydrobiologia
123
experimental mesocosms. The first maximum at the
flood decline (Fig. 5) reflects the change of dominants
from Chlamydomonas spp. to noncolonial centric
diatoms; the second maximum at the beginning of the
summer–autumn low water season corresponds to the
change from the apparent dominance of the latter
group to M. contortum and Nitzschia acicularis (Kut-
zing) W. Smith subdominance. The SD values vary
greatly in the summer–autumn and winter low water
seasons. The peak at the boundary between the
summer–autumn and winter low water seasons is
more prominent, especially in terms of the cell count,
and reflects the onset of L. redekei dominance. The
cell-count- and individual-count-based WG are less
informative; their dynamics shows a clearer peak at
the flood decline.
The values of biomass-based ED varied greatly
throughout the year and were relatively higher in the
period from the second half of the spring floods to the
beginning of the summer–autumn low water season,
when a sharp decline in the water level takes place.
Above all, these peaks reflect the changes in the
relative abundance of noncolonial centric diatoms.
A peak of the biomass-based ED in the first half of the
winter low water after ice cover formation also reflects
the increase of the L. redekei share.
The biomass-based WG values for the Barnaulka
did not vary much throughout the year; there was,
however, a noticeable peak at flood decline. Observa-
tions of the first half of the winter low water season of
2002–2003 yielded stable, low values.
The most significant and relatively rapid changes in
the composition and the increase in SSR and abundance
of phytoplankton in the Bolshaya Losikha and Barnaulka
tend to occur in the period between the spring flood
decline to the beginning of the summer–autumn low
water season. In the Barnaulka River, the sharpest
changes were registered a month earlier. This can
probably be explained by its specific hydrological regime
due to a system of flood lakes in its upper reaches.
Discussion
On the whole, the observed structural and quantitative
dynamics of phytoplankton in the lower reaches of the
Barnaulka and Bolshaya Losikha was seasonal. The
wider annual abundance fluctuation range in the
Bolshaya Losikha compared with that of the Barna-
ulka most likely reflects the hydrology specifics of the
latter due to the presence of a system of lakes in its
upper reaches. Taking into account the high content of
ammonium, nitrogen, nitrite, and phosphates in the
water of the Barnaulka (Tret’yakova, 2000), it can be
assumed that growth of algae and cyanobacteria is not
limited by biogens, or at least that it has not been since
the 1960s (Maslov, 1969) until the present day, when
the river has become essentially a sewer. In terms of
the seasonal dynamics of phytoplankton biomass, the
Bolshaya Losikha is similar to the lowland river
Berounka (139.1 km in length), a small tributary of the
River Vltava (Desortova & Puncochar, 2010).
Table 2 Linear correlation indices of phytoplankton succes-
sion rate of the lower reaches of the Barnaulka (n = 28; above
the diagonal from the upper left to the lower right corner) and
the Bolshaya Losikha (n = 25; below the diagonal); with
assurance by Student criterion at * P \ 0.05; ** P \ 0.01;
*** P \ 0.001
ED by
cell count
ED by
individual
count
ED by
biomass
SD by
cell count
SD by
individual
count
SD by
biomass
WG by
cell count
WG by
individual
count
WG by
biomass
1 2 3 4 5 6 7 8 9
1 – 0.82 0.54 0.95 0.84 0.43 0.56*** 0.47 0.59
2 0.72 – 0.47 0.80 0.98 0.52 0.49 0.56*** 0.46
3 0.65 0.72 – 0.58*** 0.53*** 0.88 0.45 0.34 0.71
4 0.85 0.64 0.46** – 0.82 0.49 0.57*** 0.51 0.69
5 0.64 0.91 0.53 0.76 – 0.57 0.59 0.63 0.58
6 0.53*** 0.69 0.88 0.57 0.65 – 0.51 0.50 0.57***
7 0.60*** 0.29* 0.16* 0.59*** 0.41** 0.20* – 0.83 0.68
8 0.49** 0.48** 0.17* 0.62 0.67 0.33* 0.87 – 0.61
9 0.53** 0.38*** 0.30* 0.52*** 0.46** 0.42** 0.85 0.82 –
Hydrobiologia
123
Fig. 4 Seasonal dynamics
of succession rate indices in
the lower reach of the
Bolshaya Losikha in 2002:
a by cell count, b by
individual count, and c by
biomass
Hydrobiologia
123
As a rule, the maximal abundance and SSR were
recorded during the summer–autumn low water season
at the lowest current velocity, discharge, and water level
(Weber & Moore, 1967; Okhapkin, 2000; Zalokar de
Domitrovic, 2002). Judging by the arithmetic mean
biomass values of phytoplankton from the open water
period (Table 1), the Bolshaya Losikha is meso-eutro-
phic, and the Barnaulka mesotrophic (Okhapkin, 2002).
Application of formal methods to data analysis of
phytoplankton richness and abundance in different
Fig. 5 Seasonal dynamics
of succession rate indices in
the lower reach of the
Barnaulka in 2002: a by cell
count, b by individual count,
and c by biomass
Hydrobiologia
123
seasons of the year performed on two plain rivers of
the Upper Ob Basin has thus revealed more precisely
the patterns of seasonal heterogeneity in phytoplank-
ton distribution.
The seasonal succession of river phytoplankton
based on succession rate indices has been analyzed
only occasionally (Giorgio et al., 1991; Garcıa de
Emiliani, 1997), and only once (this work) to identify
the key events in the seasonal dynamics of potamo-
plankton. Consequently, a wider comparison of
different types of rivers on the basis of the approach
realized here is virtually impossible at the moment.
It is possible that, in some cases, the phytoplankton of a
lotic ecosystem shows less structure and diversity
compared with that of a floodplain lake, as in the case
of the Parana River canal and a small floodplain lake
connected with this canal during floods (Garcıa de
Emiliani, 1997). In the Parana River canal, biomass-
based SD values varied from 0.03 to 0.11 day-1
(sampling was done twice a week) and exceeded the
threshold of 0.1 day-1 in only two cases: at the beginning
of the flood decline along with the decrease in water level,
and during the summer–autumn low water season (Garcıa
de Emiliani, 1997). In a tributary of the Parana River, the
cell-count-based SD values varied between 0.03 and
0.16 day-1 (Giorgio et al., 1991).
The values of biomass- and cell-count-based SD in
the Bolshaya Losikha were within the same limits as
those reported for the lotic ecosystems of the Parana
River system; the values registered in the Barnaulka
during the first half of the winter low water season
were lower. Further sampling with comparable inten-
sity is required before more meaningful comparison
with data for other rivers can be made.
Quite in accordance with the results of Williams &
Goldman (1975) on phytoplankton succession in five
lakes of different types, we conclude that, in phyto-
plankton of small lowland rivers of the Upper Ob
Basin, the ‘‘maximum succession rates (also) occur
after community independent environmental pertur-
bations which are usually but not necessarily corre-
lated with periods of high primary productivity’’ and
‘‘in the absence of disturbance succession rates decline
and remain low, partly because of community depen-
dent processes’’ (Williams & Goldman, 1975).
The key events in the seasonal dynamics of phyto-
plankton correspond to the main hydrological seasons of
the small lowland rivers of the Upper Ob Basin. This is
concordant with data from numerous publications on
the key role of hydrological factors in potamophyto-
plankton succession (Reynolds, 1984; Ibelings et al.,
1998; Zalokar de Domitrovic, 2002; Desortova &
Puncochar, 2010). The intensity and frequency of
disturbances caused by precipitation and water discharge
fluctuation are the most important factors determining
potamophytoplankton dynamics (Reynolds, 1988;
Ha et al., 1998). We consequently assume that river
phytoplankton succession is mainly allogenic; however,
the potamophytoplankton could be a subclimactic
community, i.e., the aquatic analog of the plagioclimax
(Reynolds, 1993; Garcıa de Emiliani, 1997).
The spatiotemporal heterogeneity of the structure
and abundance of potamoplankton is determined by
the formation of water runoff, and reflects the age
heterogeneity of the water masses in a river from the
source to the mouth. We can assume that the sequence
of changes in phytoplankton structure and abundance
observed at a stable sampling point on a river during
the year is not in fact ‘‘true succession’’. More likely, it
results from the superposition of two processes: (1) the
succession of phytoplankton along the course of
the river downstream (Margalef, 1968), and (2) the
seasonal succession of phytoplankton (Trifonova,
1986). The different water residence time probably
determined the observed ‘‘result’’ of this superposition
at a stable, year-round sampling point on the river.
This chronosequence is usually described as the
seasonal dynamics of potamophytoplankton.
Since there is no consensus on what causes species
changes in phytoplankton communities (Mikheyeva,
1983), the effectiveness of succession rate indices for
indicating and reconstructing specifics of annual
dynamics of phytoplankton communities in reservoirs
depending on their geographical location and the
degree and character of external impact makes use
of these indices for typological assessment of aquatic
ecosystems reasonable. Comparing the succession
rates for the same water body in different years can
be used as the basis for assessment of succession
character, including the rate of eutrophication pro-
cesses. The latter is of great importance for environ-
mental quality management.
Conclusions
The results of this study reveal a generally clear
seasonal pattern of changes in phytoplankton species
Hydrobiologia
123
structure in the lower reaches of small rivers, which is
probably due to sufficient water residence time and the
smaller influence of rainfall floods on their hydrology.
The dynamics of succession rate index values clearly
reflects key events in the life of river phytoplankton
that are connected with changes in dominant species
complexes according to the main hydrological sea-
sons. The most significant and rapid changes in
structure, as well as increases in species richness and
abundance of phytoplankton in the Bolshaya Losikha
and Barnaulka Rivers, tend to occur in the period
between the flood decline to the beginning of the
summer–autumn low water season. The dynamics
reflect both the most important and abrupt changes in
the environment and changes in the recorded stages of
phytoplankton succession.
Acknowledgments The authors are greatly indebted to
anonymous reviewers and Dr. Eduardo A. Morales for
valuable comments and to Dr. Helen Rothnie and Tatyana M.
Bulyonkova for improvement of the English manuscript.
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