Polish Journal of Ecology
Pol. J. Ecol. (2014) 62: 431–439
Regular research paper
Lech KUFEL, Katarzyna RYMUZA
Department of Ecology and Environmental Protection, University of Natural Sciences and Humanities,
Prusa 12, 08-110 Siedlce, Poland, e-mail: [email protected] (corresponding author)
COMPARING THE EFFECT OF PHYTOPLANKTON
AND A CHAROPHYTE ON CALCITE PRECIPITATION IN LAKE
WATER: EXPERIMENTAL APPROACH
ABSTRACT: Primary producers are able to
strongly affect calcium budget in hardwater lakes.
The relative contribution of phytoplankton and
charophytes to water decalcification (by precipitation of calcium carbonate) is, however, unclear. In
this study we checked the effect of natural phytoplankton community and a charophyte (Nitellopsis obtusa) on the decline of calcium concentration in experimental outdoor conditions. The
experiment was carried out in original lake water
and two variants of enrichment with inorganic
nitrogen and phosphorus to test the changing efficiency in decalcification by both primary producers. At low nutrient concentrations, N. obtusa
was responsible for calcium decline in original
lake water by 12 mg Ca+2 dm–3 during 20 days of
experiment. In these conditions the effect of phytoplankton was negligible. In lake water enriched
with nutrients, the exponential growth of phytoplankton led to the decrease of calcium concentration from initial 35 mg Ca+2 dm–3 to 9 mg Ca+2
dm–3 in the same time period. The maximum effect of N. obtusa was the same as in original lake
water but manifested itself earlier to decline in the
end of experiment. Supersaturation of water with
calcium carbonate was always more than threefold and saturation index reached 27 in mixed
cultures of phytoplankton and N. obtusa in lake
water enriched with nutrients. In this context we
hypothesise on a possible role of charophytes as
nucleation sites necessary for calcite precipitation. Based on our own and literature data we also
discuss expected immobilisation of phosphate incorporated in calcite precipitated by the growth of
phytoplankton and N. obtusa.
KEY WORDS: calcite, supersaturation, phytoplankton, Nitellopsis obtusa, charophytes
1. INTRODUCTION
Decalcification of lake water and calcium
carbonate deposition in bottom sediments is
important in view of current discussions on
global warming and of the search for mechanisms of carbon dioxide sequestration. Another reason for an interest in calcium cycling in
lake ecosystems is the possibility of co-precipitation of calcite with phosphates (O tsu k i and
Wetzel 1972, Mur phy et al. 1983, Kos chel
1990, Ditt r ich and Kos chel 2002). It is not
clear whether phosphates are incorporated in
crystal structures of minerals like apatite or hydroxyapatite or rather non-stoichiometrically
bound to deposited calcium carbonate. Nevertheless, deposition of calcium-bound P is an
important way of immobilisation of phosphorus in bottom sediments, more so that these
compounds, unlike Fe-bound phosphorus, are
redox insensitive. Experimental enrichment
of hypolimnetic waters with calcium showed
that this mechanism may help recovering a eu-
432
Lech Kufel and Katarzyna Rymuza
trophic lake to mesotrophic status (Ditt r ich
and Kos chel 2002).
Carbonate ions are formed in lake water
as an effect of increased pH and the shift of
inorganic carbon equilibrium caused by photosynthetic activity of aquatic primary producers.
In hardwater lakes these ions combined
with calcium produce hardly soluble calcium
carbonate usually in the form of micro-crystalline calcite (Wetzel 2001). This may results in lake “whiting” accompanying phytoplankton blooms which may even be visible
in satellite images of large lakes (St rong and
E adie 1978). In the effect, settling seston in
such lakes may contain up to 19% calcium (or
47.5% CaCO3) and the annual deposition rate
may reach 200 g Ca m–2 (500 g CaCO3) on dry
weight basis (Stabel 1986). This mechanism is
responsible for a high content of calcium (up to
30% dry weight) in bottom sediments of mesotrophic lakes like e.g. those noted in the Jorka
and Krutynia River systems (Rzep e ck i 2010).
From among aquatic macrophytes only
charophytes, mainly of the genera Chara and
Nitellopsis, are known to actively decalcify
lake waters. Unlike planktonic algae, charophytes form calcite encrustations on their
thalli. Abundant growth of charophytes is often accompanied by a significant decline in
calcium concentrations in lake water (Pe nte cost 1984). The amount of encrusted calcite
may exceed 80% of plant dry weight (Pe nte cost 1984, Peł e chat y et al. 2013). This
pool of calcium carbonate is deposited in
bottom sediments after plant decay. In lakes
with dense Chara stands, bottom sediments
may contain substantial amounts of calcite.
For example, sediments in Lake Łuknajno in
north-east Poland populated by 7 charophyte
species, which in total cover 50% of lake area
(Króli kowska 1997), contain 62 ± 4.8% of
calcium carbonate (Kufel and Kufel 1997).
Charophytes may form large underwater
meadows in hardwater lakes of moderate trophic status. With the advancement of eutrophication they retreat due to worsening light
conditions (Ozimek and Kowa l c ze wsk i
1984, Blindow 1992). Within a certain range
of nutrient concentrations in shallow lakes,
phytoplankton and charophyte dominance
may alternate depending on external factors
like e.g. weather conditions (S chef fer 1998).
On the other hand, re-oligotrophication may
facilitate the development of charophytes,
which may finally outcompete vascular submerged macrophytes (R ichte r and Gro ss
2013). Therefore, the share of phytoplankton
and charophytes in the total primary production and thus in overall decalcification of lake
waters may vary depending on light conditions and nutrient availability in a given lake.
In this study, we attempted to test experimentally the relative contribution of natural
phytoplankton community and a charophyte
(Nitellopsis obtusa (Desvaux) J. Groves) to the
decline of calcium concentrations in lake water.
2. MATERIAL AND METHODS
Lake water and plant material were collected from five sites in a mesotrophic lake
– Lake Białe Włodawskie (east Poland;
51o29’47”N; 23o31’57”E) – in the end of June
2013. Water samples were taken in lake littoral from a depth of 0.5 m with Patalas sampler and filtered through a 20 µm plankton
net to remove zooplankton. Plant material
(Nitellopsis obtusa (Desvaux) J. Groves) was
collected with a rake sampler from the same
sites at a depth of 2.0–2.5 m. Water pH and
conductivity were measured in situ. Part of
lake water filtered through Whatman GF/C
filter in the laboratory served for chemical
analyses and as a control in the experimental set up. Chemical analyses were performed
on the day of sampling and water for further
experimental use was kept in a refrigerator in
dark at a temperature of 5oC.
The experiment consisted of three variants: GF/C filtered water, unfiltered lake
water with natural phytoplankton and unfiltered lake water with phytoplankton and
2–3 pre-weighed top fragments of N. obtusa
stems (20–25 cm long and 0.76–1.20 g of
combined fresh weight per pot). Five separate
pre-weighed plant samples were taken for the
determination of dry weight, after drying at
105oC to constant weight. Each experimental variant was performed in three nutrient
enrichments: original lake water, lake water enriched with 1.05 mg dm–3 N-NO3 as
NaNO3 and 0.093 mg dm P-PO4 as K2HPO4
(enrichment I) and lake water enriched with
2.10 mg dm–3 N-NO3 and 0.186 mg dm–3
P-PO4 (enrichment II). All combinations of
Calcite precipitation by phytoplankton and charophyte
variants and enrichments were made in 5 replicates.
The experiment was carried out in outdoor conditions at ambient temperature and
light:dark ratio under a polycarbonate roof
additionally covered with polyethylene foil
to adjust light conditions to those noted in
lake water. Light intensity (measured with
LI-250A light meter) on a cloudy day was
139 μM photons m–2 s–1 under the roof and
83 μM photons m–2 s–1 under water surface.
Respective values on a sunny day were 449
and 281 μM photons m–2 s–1 which corresponded well to 275 μM photons m–2 s–1 recorded in full sunlight at a depth of 2.5 m in
Lake Białe Włodawskie.
Forty five PET (polyethylene terephthalate) pots (8 × 8 × 22 cm) with one litre of lake
water in appropriate variant and enrichment
were randomly displaced in larger containers
filled with tap water to mitigate daily variation of ambient temperature. Every day the
content of each pot was gently mixed with
glass rod to prevent phytoplankton settlement. Every fourth day 100 cm3 of water was
sampled from each pot and replaced with the
same volume of water of respective variant
and enrichment. Water losses due to evaporation were supplemented with distilled water.
The experiment lasted 20 days.
Water samples from experimental pots
were filtered through Whatman GF/C filters.
Calcium, alkalinity, pH and conductivity were
analysed in filtrates. In the initial phase of the
experiment, chlorophyll concentrations were
too low to be determined in a 100 cm3 water
sample. Therefore, suspended solids from 5
repetitions were pooled on one glass fibre filter. Only in the end of the experiment it was
possible to determine chlorophyll concentration in each repetition separately.
The concentration of calcium in lake water
and in experimental samples was determined
by EDTA titration, alkalinity – by titration
with 0.1 M HCl (G olter man 1969). Electrolytic conductivity and pH was measured with
portable Combo (Hanna Instruments) pH
and conductivity meter. Chlorophyll was analysed in acetone extracts of ground glass fibre
filters with settled phytoplankton (G olte rman 1969). Total phosphorus (TP) and total
Kjeldahl nitrogen (TKN) in natural unfiltered
lake water was determined as soluble reactive
433
phosphorus (SRP) and ammonium-nitrogen,
respectively, after digestion with concentrated H2SO4 (G olte r man 1969).
Decalcification was assessed from the
decline of Ca+2 concentration in filtered water sampled from each repetition on the assumption that insoluble calcium carbonate
was retained on GF/C filter or encrusted the
stems and branchlets of N. obtusa. The relative contribution of N. obtusa to these losses
was estimated as a difference in Ca concentration between lake water with and without the charophyte. Saturation of water with
calcium carbonate was calculated acc. to the
equation:
SI = [Ca+2] × [CO3-2]/SP 1)
where:
SI – saturation index, [Ca+2] and [CO3–2]
are the molar concentrations of respective
ions, SP is the solubility product of calcium
carbonate = 10–8.39.
The concentration of carbonate ions was
calculated from the equation:
[CO3–2] = K2 × [HCO3–]/[H+] 2)
where:
K2 is the second dissociation constant of
carbonic acid (= 10–10.38), [HCO3–] is the total
alkalinity in moles and [H+] is the molar concentration of hydrogen ions (10–pH) (Nõ ge s
et al. 2003). Saturation index SI> 1 means that
the analysed water sample is supersaturated
with respect to calcium carbonate.
Relative growth rate (RGR) of phytoplankton in both nutrient enrichments was
calculated from the equation:
RGR = (log[chlt]–log[chl0])/t 3)
where:
chlt and chl0 are the concentrations of
chlorophyll (in µg dm–3) at the end and in the
beginning of experiment, respectively, and t
is a time interval in days. The linear regressions of log[chl] on days was significant in
both enrichments.
Obtained results were processed with the
Statistica 10 software. Calcium decline on
subsequent days of the experiment was tested
with the Friedman non-parametric ANOVA.
Significance of differences in the initial and
final biomass of N. obtusa was checked with
the Wilcoxon’s pair test.
434
Lech Kufel and Katarzyna Rymuza
4. RESULTS
Chemical analyses confirmed a hard water and moderately eutrophic status of Lake
Białe Włodawskie (Table 1). Cyanobacteria
were the most numerous taxa in phytoplankton (ca. 52% in the total biomass), the next
abundant were Chrysophyceae, mainly Dinobryon spp. (24%), green algae and diatoms
contributed in several percent to the total
phytoplankton biomass.
At low nutrient concentrations in natural
lake water chlorophyll increments were small
(Fig. 1A). Noteworthy, phytoplankton grew
better when accompanied by N. obtusa than
kept alone in water without nutrient enrichment (Table 2). The reverse situation was observed in water with single and double additives of N and P (Fig. 1B and C, respectively).
In both enrichments N. obtusa grew faster than
in original lake water (Fig. 2) and assimilated
part of added nutrients. Therefore, the increments of phytoplankton biomass (expressed
in chlorophyll concentrations) were smaller
in mixed cultures and relative growth rates of
phytoplankton were lower compared with phytoplankton grown in enriched cultures without
the charophyte (Fig. 1B and C and Table 2).
Original lake water was supersaturated
with calcium carbonate already when sampled (SI = 5.7±1.8). In filtered lake water,
the saturation decreased to SI = 3.3±0.8 on
day 4 (mean of original lake water and the
two nutrient enrichments) and remained on
similar level till the end of the experiment. In
unfiltered water, supersaturation increased
along with phytoplankton growth to achieve
the highest values of SI = 13.4±4.1 in enrichment I and 27.4±8.3 in enrichment II on the
20th day of experiment. In mixed cultures of
phytoplankton and N. obtusa, maximum supersaturation of water with calcium carbonate was achieved on day 16 (SI = 12.7±5.2
in enrichment I and 27.1±5.0 in enrichment
II) to decrease in the end of experiment
to SI = 2.8±0.4 and 14.0±2.6, respectively.
Supersaturation observed in phytoplankton
and phytoplankton with charophyte cultures
grown in original lake water varied irregularly but did not exceed SI = 10.
Relatively slow growth of phytoplankton
in original lake water translated into their
negligible effect on calcium concentrations
(Fig. 3A). This effect was significant only in
phytoplankton cultures enriched with nutrients. After a lag time of 8 days in enrichment I and 4 days in enrichment II, calcium
concentrations started to decline. On the 20th
day of experiment Ca+2 concentrations decreased to 11.4±0.83 mg dm–3 in enrichment
I (Fig. 3B) and to 9.1±0.82 mg dm–3 in enrichment II (Fig. 3C). Decalcification of lake
water was accompanied by an increase in pH
(to 9.6±0.10 in enrichment I and to 10.1±0.05
in enrichment II) and by a decline in total alkalinity to 1.2±0.16 and 1.0±0.14 mM dm–3,
respectively. For comparison, initial values of
these parameters are given in Table 1.
The effect of N. obtusa on lake water decalcification was more complex. In original
Table 1. Selected parameters of water from Lake Białe Włodawskie (mean ± SD from 5 sites) taken for
the experiment.
Parameter
pH
Electrolytic conductivity (EC) (μS cm–1)
Soluble reactive phosphorus (SRP) (mg P dm–3)
Total phosphorus (TP) (mg P dm–3)
Total Kjeldahl nitrogen (TKN) (mg N dm–3)
Ca+2 (mg dm–3)
Alkalinity (mM dm–3)
Value
8.4+0.2
200+5
0.014+0.003
0.108+0.012
0.87+0.03
34.7+0.9
2.64+0.09
Table 2. Relative growth rates (in day–1) of phytoplankton in relation to experimental variant and nutrient enrichment. For enrichment’s details see the text.
Enrichment
Lake water
Enrichment I
Enrichment II
Phytoplankton alone
0.046
0.199
0.278
Phytoplankton + Nitellopsis obtusa
0.060
0.127
0.096
Calcite precipitation by phytoplankton and charophyte
435
Fig. 1. The changes of chlorophyll concentrations in original lake water (A), in enrichment I (B) and in
enrichment II (C). Vertical lines indicate ± standard error. Note different scales on y-axes. For enrichment’s details see the text.
lake water, at relatively low phytoplankton
biomass (Fig. 1A), the charophyte was mainly
responsible for calcium decline in lake water.
Precipitation of calcium started on the 4th day
of experiment and attained its maximum of
ca. 12 mg dm–3 of calcium loss on day 12th.
No further losses of calcium were noted until
the end of the experiment (Fig. 4A). Similar
maximum calcium loss of ca. 12 mg dm–3 attributed to N. obtusa was noted on the 12th day
of experiment in both enrichments (Fig. 4B
and C). However, statistical analyses showed
significant differences in calcium losses with
time only in enrichment I (Fig. 4B) but not in
enrichment II (Fig. 4C).
The decline of calcium concentrations
was closely correlated with chlorophyll concentration (as a proxy of actual phytoplankton biomass) across all enrichments (Fig. 5).
Chlorophyll explained 88 and 90% of calcium
variability in enrichment I and II, respectively.
5. DISCUSSION
Decalcification of lake water observed in
our experiment was an outcome of the interplay between phytoplankton and N. obtusa,
which in turn depended on nutrient concentrations. N. obtusa was apparently nutrient limited in original lake water but most
probably light limited in both enrichments,
especially in the end of the experiment. The
first effect manifested itself in low biomass
increments when the charophyte was grown
in original lake water (Fig. 2); the second –
in declining efficiency of Ca+2 precipitation
(because of decreasing primary production
rate) at exponentially increasing chlorophyll
concentrations in water enriched with nutrients (Fig. 4). Nevertheless, the presence of N.
obtusa in mixed cultures led to the fourfold
decrease of calcium concentration in lake water at relatively low phytoplankton biomass
(Fig. 5). The same final effect was obtained
in phytoplankton cultures only when chlorophyll concentrations exceeded 250 µg dm–3.
Percent of calcite encrustation calculated from biomass increments, percent of
dry weight in fresh biomass of N. obtusa
(9.4%) and a maximum Ca+2 loss from water
(12 mg Ca+2 dm–3 on average) was 24% dry
wt. in enrichment I and 16% dry wt. in enrichment II. This is far less than 70.5% of calcite
per dry weight of N. obtusa growing in Lake
436
Lech Kufel and Katarzyna Rymuza
Fig. 2. Initial and final fresh weight of Nitellopsis obtusa grown in: original lake water (A), enrichment I
(B) and enrichment II (C). Significant (P <0.05) increments of charophyte biomass were noted only in
B and C. For enrichment’s details see the text.
Fig. 3. The changes of calcium concentration caused by phytoplankton grown in: original lake water
(A), enrichment I (B) and enrichment II (C). The same small letter above plots means no significant
differences at P <0.05. For enrichment’s details see the text.
Calcite precipitation by phytoplankton and charophyte
437
Fig. 4. Contribution of Nitellopsis obtusa to the decline of Ca+2 concentrations in mixed cultures in:
original lake water (A), enrichment I (B) and enrichment II (C). The same small letter above plots
means no significant differences at P <0.05. For enrichment’s details see the text.
Białe Włodawskie (Kufel et al. 2013). The
reason for this discrepancy might be in lightlimited growth of the plant in the second half
of experiment and at the same time the declining content of dissolved calcium in water.
Although lake water was supersaturated
with calcium carbonate, no substantial decline of dissolved calcium concentrations was
noted either in filtered lake water or in lake
water with phytoplankton but not enriched in
nutrients (Fig. 3A). Also in nutrient-enriched
phytoplankton cultures, measureable decrease
of calcium concentrations was noted not earlier then on the 4th or 8th day of the experiment (Fig. 3B and C). Supersaturation of water with calcium carbonate was often recorded
in lakes. Nõges et al. (2003) noted less than
fivefold supersaturation in a Chara-dominated lake and more than fivefold supersaturation in a phytoplankton-dominated lake in
Estonia. Similar supersaturation of water was
found by St ab el (1986) in Lake Constance
whose surface waters had saturation index >2
during entire vegetation period of two subsequent years. Occasionally, saturation index
reached 9 there. However, a peak of saturation
index did not correlate with significant reduc-
tion in calcium concentration. Instead, intensive precipitation of calcite usually followed
maximum biomass of phytoplankton algae
(different species on different sampling occasions). From these measurements and from
microscopic examination of precipitating
calcite crystals St ab el (1986) concluded that
calcium precipitation in a form of calcite crystals needed (apart from large supersaturation)
also the nucleation (seeding) by algal cells.
Similarly, Ditt r icht and O bst (2004) underlined the importance of small phytoplankton, particularly of autotrophic cyanobacteria,
for the initiation of calcite crystal formation.
This mechanism probably also applied to our
results and would explain a lag time needed
by calcium to precipitate in phytoplankton
cultures. This could also explain the decline
of calcium concentrations attributed to N.
obtusa of relatively small biomass increments
(Fig. 2A and 4A). Here, at low biomass of phytoplankton, thalli of the charophyte provided
sufficient nucleation sites to allow calcite
precipitation. A lack of such sites allowed for
maintaining over threefold supersaturation of
GF/C filtered water in the control variant of
our experiment.
438
Lech Kufel and Katarzyna Rymuza
6. CONCLUSIONS
Fig. 5. The decline of calcium concentrations in
relation to chlorophyll in lake water. Data are
pooled from three enrichment levels. Each dot
represents the mean from 5 replications.
According to an earlier study (Kufel et al.
2013) N. obtusa from Lake Białe Włodawskie
contained 1.32±0.29 mg P per gram dry wt.
Out of this amount, 0.29±0.06 mg P g-1 was
inorganic fraction loosely bound to the plant
and 0.33±0.14 mg P g–1 was a fraction associated with calcite encrustation. However,
the sum of the two inorganic P fraction did
not correlate with the amount of calcite encrustation when assessed across various taxa
and lakes. On the other hand, D anen-L ou wers e et al. (1995) based on their own and
literature data presented significant empirical relationship between ambient phosphate
concentrations and precipitating calcite in the
form: Y = 10.9 X0.5 (r2 = 0.50) where Y – incorporation of dissolved phosphate-P in CaCO3
(in mg P g–1 Ca+2) and X – the dissolved phosphate-P concentration in mg dm–3. The relationship applied to phytoplankton growth in
enrichment II of our experiment shows that
on average 0.122 mg P could be incorporated
into precipitating calcite i.e. 61% of phosphate-P present in lake water in the beginning
of the experiment. Due to rather moderate
predictive power of D anen-L ouwers e et
al’s (1995) formula and to many factors affecting coprecipitation of P with calcite (complexation of Ca+2 with organic substances,
negative effect of magnesium on calcite precipitation etc.) one should take above results
with care. Anyway, further studies are needed
to elucidate the role of phytoplankton and
charophytes in phosphorus immobilisation
accompanying calcite precipitation.
N. obtusa was more efficient in decalcification of lake water at low nutrient concentrations and phytoplankton biomass. This effect
consisted in the formation of calcite encrustation and probably in providing nucleation
sites necessary for calcite to precipitate from
supersaturated solutions.
At higher nutrient concentrations phytoplankton took the superiority in decalcification because of exponential growth, the rise
of pH and carbonate concentrations and due
to negative light limitation exerted on accompanying charophyte.
Nutrient concentration seems to be the
chief driving factor in lake water decalcification by aquatic primary producers.
ACKNOWLEDGEMENTS: Dr Małgorzata
Strzałek kindly provided data on phytoplankton
composition in water of Lake Białe Włodawskie.
7. REFERENCES
Blindow I. 1992 – Decline of charophytes during eutrophication: comparison with angiosperms – Freshw. Biol. 28: 9–14.
D anen-L ouwers e H.J., L ijk lema L.,
C o enraats M. 1995 – Coprecipitation of
phosphate with calcium carbonate in Lake Veluwe – Water Res. 29: 1781–1785.
Ditt r ich M., Kos chel R . 2002 – Interactions
between calcite precipitation (natural or artificial) and phosphorus cycle in the hardwater
lake – Hydrobiologia, 469: 49–57.
Ditt r ich M., O bst M. 2004 – Are picoplankton responsible for calcite precipitation in
lakes? – Ambio, 33: 559–564.
G olter man H.L. 1969 – Methods for Chemical
Analysis of Fresh Waters – Blackwell Scientific
Publications, Oxford and Edinburgh, 172 pp.
Kos chel R . 1990 – Pelagic calcite precipitation
and trophic state of hardwater lakes – Arch.
Hydrobiol. Beih. 33: 713–722.
Króli kowska J. 1997 – Eutrophication processes in a shallow, macrophyte-dominated lake
– species differentiation, biomass and the distribution of submerged macrophytes in lake
Łuknajno (Poland) – Hydrobiologia, 342/343:
411–416.
Kufel I., Kufel L. 1997 – Eutrophication processes in a shallow, macrophyte-dominated
lake – nutrient loading to and flow through
Lake Łuknajno (Poland) – Hydrobiologia,
342/343: 387-394.
Calcite precipitation by phytoplankton and charophyte
Kufel L., Bi ardzka E., St rzałek M. 2013
– Calcium carbonate incrustation and phosphorus fractions in five charophyte species –
Aquat. Bot. 109: 54–57.
Mur phy T.P., Ka li K.J., Yes a k i I. 1983 –
Coprecipitation of phosphate with calcite in a
naturally eutrophic lake – Limnol. Oceanogr.
28: 56–96.
Nõges P., Tuv i kene L., Feldmann T.,
Tõnno I., Künnap H., Luup H., Sa luj õ e J., Nõges T. 2003 – The role of charophytes in increasing water transparency: a case
study of two shallow lakes in Estonia – Hydrobiologia, 506–509: 567–573.
O tsu k i A., Wetzel R .G. 1972 – Coprecipitation of phosphate with carbonates in a marl
lake – Limnol. Oceanogr. 17: 763–767.
Ozimek T., Kowa lcze wsk i A. 1984 – Longterm changes of the submerged macrophytes
in eutrophic Lake Mikołajskie (North Poland)
– Aquat. Bot. 19: 1–11.
Pełe chat y, M., Pu kacz A., Ap olinarska
K., Pełe chat a A., Siep a k M. 2013 – The
significance of Chara vegetation in the precipitation of lacustrine calcium carbonate – Sedimentology, 60: 1017–1035.
439
Pente cost A. 1984 – The growth of Chara globularis and its relationship to calcium carbonate deposition in Malham Tarn – Field Studies,
6: 53–58.
R ichter D., Gross E.M. 2013 – Chara can
outcompete Myriophyllum under low phosphorus supply – Aquat. Sci. 75: 457–467.
Rzep e ck i M. 2010 – The dynamics of phosphorus in lacustrine sediments: contents and
fractions in relation to lake trophic state and
chemical composition of bottom sediments –
Pol. J. Ecol. 58: 409–427.
S chef fer M. 1998 – The Ecology of Shallow
Lakes – Chapman and Hall, 357 pp.
St ab el H.-H. 1986 – Calcite precipitation in
Lake Constance: chemical equilibrium, sedimentation, and nucleation by algae – Limnol.
Oceanogr. 31: 1081–1093.
St rong A.E., E adie B.J. 1978 – Satellite observations of calcium carbonate precipitations
in the Great Lakes – Limnol. Oceanogr. 23:
877–887.
Wetzel R .G. 2001 – Limnology: lake and river
ecosystems. 3rd edition – Academic Press, San
Diego, 1006 pp.
Received after revision April 2014