Biologia 63/4: 566—573, 2008 Section Zoology DOI: 10.2478/s11756-008-0084-1
Zooplankton in a Danube River Arm near Rusovce (Slovakia) Marta Illyová1, Katarína Bukvayová2 & Danka Némethová3 1
Institute of Zoology, Slovak Academy of Sciences, SK-84506 Bratislava, Slovakia; e-mail:
[email protected] Department of Ecology, Faculty of Natural Sciences, Comenius University, Mlynská dolina B-2, SK-84215 Bratislava, Slovakia 3 Research Centre for Environmental Chemistry and Ecotoxicology, Masaryk University, Kamenice 3, CZ-62500 Brno, Czech Republic 2
Abstract: Poor quantity of zooplankton was recorded in a Danube arm situated on the right side of the Danube River in Slovakia (river km 1857) in 2002 and 2003. All over the year the arm is significantly influenced by groundwater by reason of seepage. Because of low mean water temperature (12 ◦C) and poorly developed macrovegetation in particular, the arm reminds gravel pit-like. The annual average of zooplankton biomass was low and ranged from 0.35 g m−3 (2002) to 1.28 g m−3 (2003), because of low crustacean abundance. Total cladoceran abundance was excessively low in both years and ranged from 3.5 N L−1 (2002) to 16.6 N L−1 (2003). Small species, Bosmina longirostris and Chydorus sphaericus were dominant. Only four adult Copepoda – Cyclops vicinus, Thermocyclops crassus, Eurytemora velox and Eudiaptomus gracilis – were recorded in quantitative samples of both years. In the zooplankton assemblage dominated rotifers (Synchaeta pectinata, Synchaeta oblonga, Polyarthra dolichoptera and Keratella cochlearis) which represented 78% and 67% of total abundance respectively. The total of 19 species of rotifers, 34 Cladocera species and 16 taxa of Copepoda were found. Key words: river-floodplain habitats; Cladocera; Copepoda; Rotifera
Introduction The Rusovecké rameno arm, of a plesiopotamal-type (Ward et al. 2002), is situated on the right side of the Danube River (river km 1857) between a floodprotection dike and the main river channel, in the upper part of Žitný ostrov island area near Bratislava city. Throughout the year, the arm is significantly influenced by groundwater as a result of two things: groundwater levels and its natural character. Firstly, groundwater levels increased approximately two meters in this area at the beginning of 1993 after filling-up of the reservoir Hrušovská zdrž, which is a part of hydro-electric power plant (Klinda & Lieskovská 1998). Furthermore, there are some waterworks on the right side of the main channel, situated between the Danube, and Rusovce and Čunovo villages (Rodák & Banský 1995). Secondly, its character, i.e., all-year cold water and poorly developed macrovegetation in particular, remains gravel pits or dams (Horecká et al. 1994; Hudec & Hucko 2000). For these reasons, the Rusovecké rameno arm differs from the other Danube arms, which are situated lower than the Rusovecké and are in the inland delta area. Many zooplankton studies have been conducted in the Danube River floodplain. Heiler et al. (1994) investigated the arms of the right-bank side of the main river channel in an Austrian study. Long-term studies of crustacean assemblages have been conducted on the right side arm of this area in the Szigetk¨ oz floodplain
c 2008 Institute of Zoology, Slovak Academy of Sciences
area of Hungary (Gulyás 1987, 1994; Bothár & Ráth 1994 and others). Zooplankton assemblages of the leftbank area in Slovakia were also investigated (e.g., Vranovský 1974, 1975, 1985, 1991). Cladocera and Copepoda assemblages in the Danube floodplain area are well-recorded for the long-time monitoring area influenced by hydro-electric power plant operations (Vranovský 1997; Illyová & Némethová 2005). To date, there have not been any zooplankton investigations on right-bank Danubian arms in Slovakia, neither of the ones of the upper part of the river. This research examines species composition, seasonal changes in biomass, and abundance of zooplankton assemblages of the Rusovecké rameno arm. The objective of the study was to obtain new information regarding zooplankton quality and quantity in this area, seasonal dynamics of the community, and the factors affecting the afore mentioned.
Study sites The investigated waterbody is horseshoe-shaped, with a length of 2000 m, width of 100–200 m, and depth of 2–3 m. Bottom material consists of alluvial gravel covered by sand. Macrovegetation cover is poor; communities consist of Ceratophyllum demersum and Myriophyllum spicatum species. The branch bank is covered with Typha angustifolia and T. latifolia.
Zooplankton in a Danube River Arm
567
1200
Water stages (cm)
1000 800 600 400 200 0
IV
V
VI
VII VIII
IX
X
IV
V
2002
VI VII VIII XI X 2003
Fig. 1. The water stages measures at the profile of Bratislava (by SHMU) in 2002 and 2003.
The arm is situated 15 km from Bratislava and is named for the nearby village of Rusovce – (GPS coordinates: 48◦ 03 33 N, 17◦ 09 55 E, 136 m a s. l.) The examined area belongs to the orographic area of the Danubian lowland. Water level in the arm is influenced by seepage water and local surface inflow. Connectivity with the Danube occurs when there is a water level above 400 cm, as measured in Bratislava (Fig. 1), i.e., over 400 cm the arm has flowing water during a flood. The system of waterworks located between the Rusovce and Čunovo villages, consists of 23 wells situated at a distance of about 120 m from the seepage canal (Rodák & Banský 1995). At present the groundwater flows from the Danube towards the system of wells and the Waterworks Rusovce-Ostrovné lúčky-Mokraď, and further inland. The research of zooplankton of the Rusovecké rameno arm was conducted in two hydrologically different years (Fig. 1); during a great flood in August 2002 (Fig. 1), the side arms were flushed out and their water levels increased, and in 2003 when there was a low water level (less than 400–300 cm) for almost the whole season. Methods Samples were collected during the growing season, from March to February and December to November, in 2002 and 2003. No samples were collected in August 2002 because of flooding. Water for physico-chemical analyses, chlorophylla, and quantitative zooplankton samples were collected from the surface layer of open water; samples were integrated from the whole water column. Qualitative zooplankton samples were collected from open water and littoral vegetation. In situ water temperature ( ◦C) was recorded and oxygen concentration (mg L−1 ) was measured according to the Winkler method. Chlorophyll-a (chl-a) was measured by ISO Standard method (ISO 10260:1992). Phytoplankton identification and enumeration were not analysed in detail. Qualitative zooplankton samples were obtained using vertical tows from the bottom to top of water column using plankton net (60–70 µm mesh size). Quantitative samples were acquired with a Patalas-type plankton sampler by collecting 10 L from a water column. Zooplankton was concentrated using a phosphor-bronze sieve (40–50 µm mesh size) and preserved in formalin. Zooplankton abundance (N L−1 ) was assessed in a 1-ml Sedgewick-Rafter chamber. Occurrence was evaluated on a percentage basis (number of samples where the species was present). Biomass (g m−3 ) was established as wet weight calculated from the mean recorded
body lengths and from the body length/biomass ratio using tables compiled from several bibliographic sources by Morducha˘ı-Boltovsko˘ı (1954), Ulomski˘ı (1951, 1961), Nauwerck (1963), D¨ ussart (1966). The Pearson correlation coefficient was used to determine relationships among water temperature, oxygen, chlorophyll-a concentration, and zooplankton density. When necessary variables were logarithmically transformed to normalize the data (e.g., oxygen concentration, and rotifer, cladoceran and copepod densities).
Results Temperature, oxygen In the both years low water temperatures, less than 10 ◦C, were maintained for a long time into the spring season. Seepage water from the main channel and groundwater were the main reasons for these low mean water temperatures in the arm (Table 1). There was no significant increase in temperatures before July of either year (15 ◦C and 18 ◦C, respectively); the highest temperature (20 ◦C) occurred in September (Fig. 2). Seasonal presence of oxygen had balanced values during the two years, but the average annual values were not similar: 7.71 mg L−1 (2002) and 9.34 µg L−1 (2003). The highest value (12.48 mg L−1 ) was recorded in September 2003. This value correlates with the increase of chlorophyll-a maxima in September. The oxygen correlated negatively with water temperature (r = −0.478, P = 0.038). Seasonal dynamics of zooplankton density Rotatoria In both years rotifers dominated abundance values (78% and 67%) and the average annual value of rotifer quantity was similar in both years (Table 1). Typical spring development of rotifers (Devetter 1998) was insignificant in both years. In pelagial areas the species Synchaeta pectinata (84%), Polyarthra dolichoptera (74%), and Keratella cochlearis (61%) had the highest occurrences. The density of rotifers correlated significantly with water temperature (r = 0.486, P = 0.035)
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Table 1. Mean annual values of some physicochemical and biological parameters in Rusovecké rameno arm in the production period of 2002 and 2003. Unit Maximum water temperature
Total density Total wet biomass
2003
19.0 ( ◦C)
20.5 ( ◦C)
Mean
SD
Mean
SD
( ◦C) (mg L−1 ) (µg L−1 ) (N L−1 ) (N L−1 ) (N L−1 ) (N L−1 ) (N L−1 ) (N L−1 ) (N L−1 ) (N L−1 ) (N L−1 )
12.1 7.7 19.6 73.6 18.1 7.2 10.6 25.8 3.5 2.7 0.4 16.3
4.5 0.7 11.7 44.1 21.4 6.4 13.4 27.4 3.9 4.2 0.7 8.3
12.8 9.3 21.5 73.4 8.2 10.0 5.9 38.4 16.6 2.4 10.0 20.3
6.6 2.0 9.2 84.1 10.7 6.9 7.1 46.4 30.5 3.4 25.7 13.4
(N L−1 ) (g m−3 )
93.4 0.35
50.3 0.41
110.2 1.28
92.4 2.14
Oxygen
Temperature
Temperature ( o C)
25
14 12
20
10 15
8
10
6 4
5
Oxygen (mg L -1)
Water temperature Oxygen Chlorophyll-a Rotifera Asplanchna priodonta Keratella cochlearis Polyarthra dolichoptera Synchaeta pectinata Cladocera density Bosmina longirostris Chydorus sphaericus Copepoda density
2002
2
0
0 III. IV. V. VI. VII. VIII IX. X. XI. XII. 2002
II.
III. IV. V. VI. VII. VIII. IX.
X. XI.
2003
Fig. 2. Seasonal changes of water temperature and oxygen in Rusovecké rameno arm and the temperature in main channel in 2002 and 2003.
and with concentration of chl-a (r = 0.458, P = 0.049). Rotifer density was not significantly correlated to oxygen concentration (r = −0.289, P = 0.230). In 2002, the distribution of rotifer abundance was almost identical to the distribution of total zooplankton abundance (Fig. 3). In the first half of a growing season Synchaeta pectinata had the highest density (April, 86 N L−1 ), in summer Asplanchna priodonta predominated (July, 39 N L−1 ). These big rotifer species were also dominate from September (A. priodonta, 57 N L−1 ) to October. In 2003, only a moderate increase in abundance of rotifers was recorded in spring. The decrease in abundance that followed in May can be related to the presence of a predator Cyclops vicinus (Devetter & Seďa 2003). Maximum abundance of rotifers was recorded in summer (July, 315 N L−1 ). The highest density at that time was for S. pectinata (168 N L−1 ), which is also the highest individual quantity value of rotifers recorded in the two years. Cladocera In 2002, cladocerans comprised 4% of total abundance; in 2003 they made up 14%. Pelagic zooplankton was
essentially free of Daphnia spp., and other cladocerans were also rare. During both years, Chydorus sphaericus (54%) and Bosmina longirostris (53%) had the highest occurrence. There was no statistically significant correlation of cladoceran density with water temperature, chl-a concentration, or oxygen concentration (in all cases P > 0.05). Total Cladocera abundance was excessively low in both years (Table 1, Fig. 3). In 2002, abundance values of individual species varied from > 1 N L−1 to 12.5 N L−1 . Most species (Ch. sphaericus and Pleuroxus aduncus), except for B. longirostris (max. 12.5 N L−1 , October), occurred in densities lower than 1 N L−1 . The first increase in cladoceran density and maximum of the two seasons (107 N L−1 ) was recorded in May 2003. During that time Ch. sphaericus (87 N L−1 ) had the highest abundance. Values of cladoceran abundance were low in the following period; B. longirostris (max. 9.5 N L−1 , July) was dominate from June to August; filter feeding species, such as Daphnia spp. and Diaphanosoma spp., were only found occasionally in summer samples. In the second half of
Zooplankton in a Danube River Arm
569
Rotatoria
Copepoda
Cladocera
Total density
Abundance [N.L-1]
400
300
200
100
0 III.
IV.
V.
VI. VII. VIII IX.
X.
XI. XII.
II.
III.
IV.
2002
V.
VI. VII. VIII. IX.
X.
XI.
2003
Fig. 3. Abundance (N L−1 ) of zooplankton in the Rusovecké rameno arm during the season in 2002–2003.
Rotatoria
Copepoda
Cladocera
chl-a
2.5
45
7.5 40
30 1.5 25 20 1 15
F
Chlorophyll-a (µg L-1)
35
-3
Zooplankton (g m )
2
10
0.5
5 0
0 III.
IV.
V.
VI.
VII.
VIII
IX.
X.
XI.
XII.
2002
II.
III.
IV.
V.
VI.
VII.
VIII.
IX.
X.
XI.
2003
Fig. 4. Development of wet biomass (g m−3 ) of zooplankton (Rotatoria, Cladocera and Copepoda) with relation to chlorophyll-a (µg L−1 ) in the Rusovecké rameno arm during the season in 2002–2003.
a growing season (in 2003) the occurrence of phytophilous species (P. aduncus, Simocephalus vetulus, and others) was recorded in pelagial; and Sida crystallina (6 N L−1 , September) was of the highest abundance. Copepoda The proportion of copepods in total abundance of zooplankton was low in both years: 17% (2002) and 18% (2003). Copepods density did not correlate significantly with oxygen (r = −0.018, P = 0.942). However, the correlation of copepods density and water temperature (r = 0.542, P = 0.017), as well as with chl-a concentration (r = 0.615, P = 0.005) was statistically significant. Developmental nauplia and copepodites were commonly present during both years. Actually, no adult Copepoda were recorded in quantitative samples in 2002. In 2003, there were 4 adult species present. Cyclops vicinus (3.5 N L−1 ) was recorded only in May, Thermocyclops crassus (1 N L−1 ) was found in September and the species Eurytemora velox and Eudiaptomus gracilis occurred (0.5 N L−1 both) in October and November.
Seasonal dynamics of zooplankton biomass and chlorophyll-a In 2002, the percentage of individual zooplankton groups in total biomass was: Rotifers 78, Cladocera 20, and Copepoda 2. The mean value of wet zooplankton biomass was 0.35 g m−3 , and average concentration of chl-a was 19.6 µg L−1 (Table 1). Values of zooplankton biomass were significantly below average in spring (> 0.30 g m−3 ), while the highest chl-a values were recorded at that same time (April, 39.07 µg L−1 ) (Fig. 4). However, after the spring increase in the algal population there was no subsequent, typical increase in zooplankton biomass, as expected. Zooplankton biomass was poor throughout the whole summer period (Fig. 4). In September 2002, the second increase of chl-a (31.9 µg L−1 ) was recorded in conjunction with a very low zooplankton biomass (1.38 g m−3 ). A considerable portion of the biomass was represented by rotifers (0.25 g m−3 ), with Asplanchna priodonta (92%) predominating. A relatively higher amount of biomass was maintained in October and November (Fig. 4), when there was a significant increase in Cladocera, particularly of Bosmina longirostris. In 2003, the percentage of individual zooplankton
570 groups in total biomass was: Rotifers 20%, Cladocera 70%, and Copepoda 10%. Average zooplankton biomass was 1.28 g m−3 , and average chl-a concentration was 21.5 µg L−1 . The first significant increase in chl-a values was recorded in May (27.2 µg L−1 ), with a maximum increase (35.5 µg L−1 ) occurring in August. These chl-a values classify the arm as highly eutrophic (Straškraba et al. 1993). There were three peaks of increase in seasonal dynamics of zooplankton biomass; the first increase in biomass was recorded in May (1.98 g m−3 ), with phytoplankton development peaking at the same time. Planktonic crustaceans Ch. sphaericus (43%) and C. vicinus (44%) predominated. The second peak of zooplankton growth was recorded in July (1.43 g m−3 ), which was affected by rotifers (Synchaeta spp.). Lastly, the maximum of zooplankton biomass was recorded in September (7.5 g m−3 ), when Sida crystallina (97%) predominated. Rotatoria, Cladocera and Copepoda Nineteen Rotatoria, 34 Cladocera and 16 Copepoda species were found in 2002–2003 (Appendix 1). Discussion Very low average temperatures of water were recorded (12 ◦C) in both of the years, while summer maxima did not exceed 21 ◦C. The high long-term air temperatures in summer of 2003 did not increase the water temperature in the arm. It is because the arm is enriched with groundwater and seepage water. Cold water is rather typical for the Danube and its side arms. However, summer temperatures in the arms are usually higher than those of the main river channel that can reach 28 ◦C (Vranovský 1985). Average annual values in chl-a in the arm were relatively high and maximum values of chl-a corresponded with high eutrophication (Straškraba et al. 1993) of a biotope. Considering low water temperature in the arm one would expect also low biomass of phytoplankton, resembling that of oligosaprobic gravel pits (from 2.1 µg L−1 to 4.8 µg L−1 ) (Horecká et al. 1994) or waterworks reservoirs (from 8.80 µg L−1 to 21 µg L−1 ) (Hudec & Hucko 2000). However, the values obtained from the Rusovecké arm corresponded more with the values recorded in other Danubian arms. Štefková (1998) recorded chl-a values in the Danube arms of 11.7 µg L−1 to 36.9 µg L−1 , depending on their hydrologic regime and presence of macrovegetation. Similar average annual values of chl-a (32.8 µg L−1 or 27.8 µg L−1 ) were recorded by Vranovský (1974) in the two side arms of the Danube at Baka (1,820.5– 1,825.5 river km). Relatively high values of chl-a in the Rusovecké rameno arm from April to September can be explained by (i) the structure of zooplankton, i.e., predomination of rotifer and small cladoceran species, and (ii) minimal macrovegetation in littoral zone. During both years rotifers were dominated plankton abundance, while filtrate-feeding crustaceans (genera Daphnia, Diaphanosoma, Eudiaptomus) were poorly repre-
M. Illyová et al. sented. Thus, there was no decrease in phytoplankton as a consequence of herbivore grazing in a sense of PEG model (Sommer et al. 1986). Poor development of macrovegetation was probably affected by high groundwater level. Amoros & Bornette (1999) detected that connectivity of the arm and groundwater could indirectly affect diversity of water plants, and presence or absence of submerged and natant vegetation. The increase in chl-a values in September 2002 could be related to flooding in August. Heiler et al. (1994) stated that the increase in chl-a after flooding is linked with the increase in phosphorus concentration. However, we did not record expected increase of zooplankton biomass after increasing of phytoplankton biomass. According to Terek (1990), there should be a significant increase in zooplankton biomass within two weeks of a flood receding, and there should be an increase in proportion of planktonic crustaceans as well. This was not the case, and was probably due to low water temperatures in the arm as previously mentioned. Low water temperature was the major factor affecting zooplankton development in the Rusovecké rameno arm, as was manifested in low abundance and also low biomass values. Considering all year-round low water temperature and low value of zooplankton biomass the Rusovecké arm met the characteristics of gravel-pits (Horecká et al. 1994) or reservoirs (Hudec & Hucko 2000; Hudcovicová & Vranovský 2000), rather than meeting the biomass values of Danubian arms (Table 2). All year-round low zooplankton biomass was in a gravel-pit Senec, with the maximum of 0.845 g m−3 in October (Horecká et al. 1994). Low biomass values were also typical for a middle-sized dimictic valley reservoir Dubnik II (1.9 and 1.7 mg L−1 ), as a consequence of high fish stocking (Hudcovicová & Vranovský 2000). In Zemplínska Šírava reservoir, there were low zooplankton biomass values (4.3 mg L−1 and 1.7 mg L−1 ) despite biotopic eutrophication (Hudec & Hucko 2000) (Table 2). However, neither Danubian arms can be described as significantly high in zooplankton biomass (Table 2). To data, the average annual biomass in the Žofin arm ranged from 16 to 8.4 and 7 g m−3 (Vranovský 1975). Similarly, in a plesiopotamal-type arm, near Trstená village, the biomass of the medial zooplankton reached the average of 10.4 g m−3 (Vranovský 1991) during the warm part of the year. In the two side arms of the Danube at Baka (1,820.5–1,825.5 river km) the author found average biomass values of 6.0 g m−3 and 7.5 g m−3 , in the following years the values were lower: 2.0 g m−3 a 3.0 g m−3 (Vranovský 1974, 1985). According to Vranovský (1995), the water temperature and current velocity are considered to be the most important factors influencing the zooplankton biomass in the arm system. We have learned that the open water zone was dominated by rotifers, particularly Brachionus spp. In a similar way, rotifers dominated zooplankton in the arm system on the right bank of the Danube (Austria), in both number of species and their density (80%) (Heiler et al. 1994). Unlike our results, the species Bra-
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571
Table 2. Comparison of mean zooplankton biomass in Danube arms and reservoirs.
Danube Rusovce arm Danube Rusovce arm
Year
Mean biomass (g m−3 )
Reference
2002 2003
0.35 1.28
this study this study
Danube arms Žofín arm Žofín arm Žofín arm Trstená n.Ostrove Baka arm Baka arm Baka arm A Baka arm A Baka arm B
1971 1972 1973 1989 1971 1972 1976–1977 1977–1978 1977–1978
Reservoirs Senec gravel-pit Senec gravel-pit Dubník II Dubník II Zemlínska Šírava Zemlínska Šírava
1989 1990 1996 1997 1998 1999
16 8.4 7 10.4 7.5 6 5.2 3 2
chionus calyciflorus, B. angularis, Polyarthra vulgaris, and Keratella cochlearis dominated, and these are indicators of eutrophic conditions. Naidenow (1998) also reported a high dominance of these species, up to 97%, in the main river channel of the Danube and its side arms. Species Polyarthra dolichoptera and Keratella chochlearis predominated, often occurring in mass in spring (Devetter 1998) together with Synchaeta pectinata. All three dominant rotifer species are typical for large Slovakian reservoirs (Hudec 2000). Some differences were recorded in biomass peaks (mainly cladoceran) between the two years. In 2003, there was an increase in biomass of Cladocera. This year was different from the previous one because of a more stabile hydrologic regime, development of submerged plants (Ceratophyllum demersum, Myriophyllum sp.), and planktonic crustacean increases. The number of cladoceran (34) and copepod (16) species is relatively high and corresponds with other Danubian arms (Gulyás 1994; Bothár & Ráth 1994; Illyová & Némethová 2005). The number of cladoceran species found in the Rusovecké rameno arm represents as much as a half (54%) of all the species recorded in a (15 years) long-term monitoring of cladoceran assemblages in the Danube floodplain area (Illyová & Némethová 2005). Similarly, the number of copepod species in the arm is a half of the number of species (30) recorded in monitoring of the Danube river-basin waters by Vranovský (1997). Considering the number of species – according to classification of biotope origin (Hudec 1999) – the Rusovecké rameno arm can be classified into an original biotope category. Although rotifer species were the most prevalent zooplankter in this study, their low numbers in comparison to other studies is most likely due to sampling methodology; our
Vranovský Vranovský Vranovský Vranovský Vranovský Vranovský Vranovský Vranovský Vranovský
0.15 0.16 1.9 1.7 4.3 1.78
(1975) (1975) (1975) (1991) (1974) (1974) (1985) (1985) (1985)
Horecká et al. (1994) Horecká et al. (1994) Hudcovicová & Vranovský (2000) Hudcovicová & Vranovský (2000) Hudec & Hucko (2000) Hudec & Hucko (2000)
evaluation of species spectrum only from an open water zone wherein littoral was not included. These make only 27% out of 70 rotifer species recorded in the late 1990’s in the Danubian arms (Naidenow 1998).
Acknowledgements This study was partially supported by grant No. 1/4353/07 from Slovak Grant Agency for Science VEGA. The manuscript preparation was supported by the Ministry of Education, Youth and Sports of the Czech Republic (grant No. 0021622412).
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Received June 12, 2007 Accepted March 5, 2008
Appendix 1. Presence of zooplankton species in the Rusovecké rameno arm in 2002 (1) and 2003 (2). Month
F 1
Rotatoria Asplanchna brightwelli Gosse, 1850 A. priodonta Gosse, 1850 Bipalpus hudsoni Wierzejski et Zacharias, 1893 Brachionus angularis Gosse, 1851 B. calyciflorus Pallas, 1766 Colurella uncinata O.F.M¨ uller, 1773 Euchlanis dilatata Ehrenberg, 1832 Filinia longiseta Ehrenberg, 1834 Keratella cochlearis Gosse, 1851 Keratella quadrata (O.F.M¨ uller, 1786) Lecane luna O.F.M¨ uller, 1776 Lepadella triptera Ehrenberg, 1832 Notholca acuminata Ehrenberg, 1832 N. squamula O.F.M¨ uller, 1786 Polyarthra dolichoptera Idelson, 1925
M 2
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Zooplankton in a Danube River Arm
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Appendix 1. (continued) Month
F 1
P. euryptera Wierzejski, 1891 P. remata Slorikov, 1896 Synchaeta oblonga Ehrenberg, 1832 S. pectinata Ehrenberg, 1832 Cladocera Acroperus harpae (Baird, 1834) Alona affinis (Leydig, 1960) A. costata Sars, 1862 A. guttata Sars, 1862 A. quadrangularis (O.F.M¨ uller, 1785) A. rectangula Sars, 1862 Alonella nana (Baird, 1850) Bosmina coregoni Baird, 1857 B. longirostris (O.F.M¨ uller, 1785) Camptocercus rectirostris Schoedler, 1862 Ceriodaphnia pulchella Sars, 1862 Daphnia ambigua Scourfield, 1948 D. cucullata Sars, 1862 D. longispina O.F.M¨ uller, 1785 D. parvula Fordyce, 1901 Diaphanosoma mongolianum Ueno, 1939 D. orghidani Negrea, 1982 Disparalona rostrata (Koch, 1841) Eurycercus lamellatus O.F.M¨ uller, 1875 Chydorus sphaericus (O.F.M¨ uller, 1785) Ilyocryptus agilis Kurz, 1878 Leydigia leydigii Schoedler, 1863 Macrothrix laticornis (Jurine, 1820) Moina micrura Kurz, 1874 Pleuroxus aduncus (Jurine, 1820) P. denticulatus Birge, 1875 P. laevis Sars, 1862 P. truncatus (O.F.M¨ uller, 1785) P. uncinatus Baird, 1850 Polyphemus pediculus (L., 1761) Scapholeberis mucronata (O.F.M¨ uller, 1785) Sida crystallina (Koch, 1776) Simocephalus serrulatus (Koch, 1841) S. vetulus (O.F.M¨ uller, 1776) Copepoda Acanthocyclops robustus (Sars, 1863) Cyclops strenuus Fischer, 1851 C. vicinus Uljanin, 1875 Diacyclops bicuspidatus (Claus, 1857) Ectocyclops phaleratus Koch, 1838 Eucyclops serrulatus (Fischer, 1851) E. macruroides (Lilljeborg, 1901) E. speratus Lilljeborg, 1901 Eudiaptomus gracilis (Sars, 1863) Eurytemora velox (Lilljeborg, 1853) Macrocyclops albidus (Jurine, 1820) M. fuscus (Jurine, 1820) Mesocyclops leuckarti (Claus, 1857) Nitocra hibernica (Brady, 1880) Thermocyclops crassus (Fischer, 1853) T. oithonoides (Sars, 1863)
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