1.2.3. Aquatic biota
The aquatic fauna of the Republic of Moldova includes about 2130 species and subspecies of 55
taxa 32. Algae are represented by over 2800 species and varieties. The dominant groups are
Chlorophyta – 1566 species and varieties (44.2%), Euglenophyta – species and varieties
(12.26%), Bacillariophyta – 556 species and varieties (24%), Cyanophyta – 291 species and
varieties (12.56%). The number of algae species that can be found in the river courses is given in
table 1.9.
Table 1.9
The average of algae species in the river courses of the Republic of Moldova
Water course
Dniester
river
Raut river
Danube river
(Giurgiuleşti)
Small rivers
Algae groups
Chri
Chlorophyta
soVol
ChloUlophy
voci
rococ
trichi
ta
neae cineae neae
Cya
nophy
ta
Eu
gle
nophy
ta
Baci
llario
phyta
Xan
tophy
ta
Dino
phyta
82
234
215
9
26
17
12
278
124
169
112
127
218
293
6
15
10
7
10
22
16
24
47
130
73
9
4
11
17
Total
Conjuga
teae
Charophyta
17
22
7
919
174
186
10
12
18
67
2
700
922
212
6
20
1
530
According to the surveys conducted in 2002, the diversity of phytoplankton in the surface waters
varies between 39 species (in the lower Dniester) and 79 species (in the Dubasari reservoir),
mostly represented by Cyanophyta, Bacillariophyta, Pyrrophyta and Chlorophyta. The average
of phytoplankton density is in the range of 1.7-10.1 million cells/dm3 and biomass, between 2.6
and7.0 g/m3. In the Dniester river the phytoplankton comprises 330 species with 363 taxa.
Diathoms (43.5%) and green algae (31%) prevail; blue-green algae account for 15.2% and the
other components of phytoplankton, 11.2%. The development of phytoplankton in Dniester and
Prut rivers hits two maxima: in spring, determined by the mass development of Stephanodiscus,
Cyclotella, Synedra, Asterionella and Diatoma and in autumn (the highest one), conditioned by
the intensive development of diatoms and Protococcophyceae. In different phases of the survey,
the phytoplankton of the Dniester included between 29 and 67 species indicators of saprobity.
An important role is played by -β-mezosaprobic (9.7-16.6%) and β-α-mezosaprobic forms (9.711.9% of total number).
The number of species of protozoa, zooplankton and zoobenthos does not differ much in
different water streams of the republic. Protozoas include 26-34 species, with an average density
of 258,800-545,600 ex/m3 and biomass of 0.2-0.4 g/m3. Zooplankton (30-38 species) includes
Rotifera, Cladocera and Copepoda, its density varies from 2,300 to 10,100 ex/m3 and biomass –
from 0.01 to 0.06 g/m3. The zooplankton communities of Dniester river are very poor. The
microzooplankton includes a large group of Infusoria (216 species and subspecies), and 105 taxa
of rizopods. In total, there are about 570 taxa of organisms. The zoobenthos predominantly
consists of mollusks, crustaceans, worms and Chironomidae, with a total average density
between 2,620 organisms per m2 (middle Dniester) and 16,000 org./m2(lower Dniester), and a
total biomass between 85.8 g/m2 in the Prut river and 400.4 g/m2 in the lake Cuciurgan. The
middle reach of the Dniester is poorer than downstream reaches both in the biomass of protozoa,
zooplankton and zoobenthos as well as in the average density of species.
The ichthyofauna of the middle Dniester is represented by 40 species and subspecies of fish
belonging to 10 families. During the last 15 years, the populations of commercially valuable
species (bream, sea-roach, zander, goldfish, etc.) are in decline and are increasingly replaced by
species of less economic interest (chub, ruff, gudgeon, bleak, etc). This trend is due to changes in
the hydrological and thermal regime of the river induced by the operation of the Novodnestrovsk
hydropower station (Ukraine) which leaded to anomalies in water ecosystems and had a
deleterious effect on the life cycle of certain species of fish. This has a negative impact on the
natural reproduction of fish downstream, particularly strong in the middle Dniester. Between
1959-1984 about 30 valuable fish species reproduced in the middle and superior reaches of the
river. Nowadays, the natural reproduction of thermophilic species, spawning at 15-22ºC (sterlet,
barbel, coddling, bream, carp, sheat-fish, goldfish), is totally compromised or severely
hampered. In the same time, even species spawning at 4-10ºC (rapacious carp, perch, zander,
broad snout) were indirectly affected. At present fish resources of the Dniester river and
Dubasari reservoir dropped by 96% compared to the period before the construction of the
Dubasari barrage 32.
The specific diversity of the ichthyofauna of lower Dniester is richer including 46 species and
subspecies of fish. About 18% of them are valuable species and 78% are species of lower
economic value (rudd, gudgeon, rhodeus, bleak, etc.). In Dubasari reservoir there are 38 species
and subspecies of fish, of which only 15 species (roach, sterlet, coddling, barbel, carp, goldfish,
sheatfish, rapacious carp, zander, ictalurus, etc) are of economic importance. The numeric share
of valuable populations constitutes only 20% with a downward trend. Similar diversity and
trends are characteristic for the ichthyofauna of the Cuciurgan lake.
The Prut river (lower part) is populated by 36 species and subspecies. The dominant species are
bleak, gudgeon, roach, goldfish, Danube herring, zander, rapacious carp. The populations of the
following species also reach significant numbers: bream (5,2%), sheatfish (4,7%), chub (2,9%).
The situation described above reveals the mesotrophic status of the large rivers and water bodies
in Moldova, with a reduced biodiversity, poor fish productivity and many non-valuable fish
populations.
The semi-aquatic terrestrial vertebrates are represented by 125 species: mammals – 4, birds –
109, reptiles – 3 and amphibians – 9.
As to the aquatic flora, its biodiversity is the highest in the Cuciurgan lake, 1280 species, the
Dubasari reservoir, 996 species, the Dniester river, 930 species, and the Prut river, 710 species
and 4,6,9,13,14. Phytobenthos and periphyton are particularly rich in algae. 90% of the 566
species of diatoms are typically benthic and the same is characteristic for green algae.
Charophyts have almost totally disappeared from the surface waters and this is an alarm signal
since they are indicators of clean waters. The number of Chrisophyta, Dinophyta and
Desmidiaceae has being reduced as well. The intensive pollution of surface waters over the past
decades has adversely influenced the water ecosystems; the total number of species in the main
water courses decreased by 15-30%.
The aquatic angiosperm plants are represented by 175 species from 42 families. The taxonomic
structure of plant communities in the majority of water bodies is continuously degrading. Only
the plant communities of the wetland zones have relatively maintained their integrity.