Density Of Cladocera Research Articles

Cladocera and Copepoda (Cyclopoida, Calanoida) of the mountain part of the Stryi river basin (Ukrainian Carpathians)

The Cladocera, Cyclopoida and Calanoida species diversity of the mountain part of the Stryi river basin is described. The objects of research were found in 48 lenthic water bodies (Zhuravlyne lake, Yavirske reservoir, numerous ponds, puddles, swamps, springs, and wells) and on 7 sections of the Stryi and Yablunka rivers. 24 species of Cladocera, 23 Cyclopoida, and 1 Calanoida are found. The most diverse is the fauna of Lake Zhuravlyne, which is located in the Skole Beskydy National Nature Park. 56% of the species diversity of the mentioned groups is noted in ponds, 42% in puddles and swamps, 8% in springs and wells, 15% in rivers, 10% in Yavirske reservoir, 44% in Zhuravlyne. The fauna of the mountain part of the Stryi river basin includes 44% of the Cladocera, Cyclopoida and Calanoida species diversity of the territory of the Ukrainian Carpathians. Only Eudiaptomus transylvanicus is noted within Calanoida. Alona protzi, Eurycercus lamellatus, Simocephalus expinosus are found only in the study area within the Ukrainian Carpathians. The most common species in this area are Chydorus sphaericus (36% frequency of occurrence in the investigated lenthic water bodies) and Eucyclops serrulatus (55%). These species are the most common in the Ukrainian Carpathians as well. The highest total density of Cladocera and Cyclopoida was 253,5 thous.ind./m3. Daphnia obtusa, Alona protzi, Eucyclops subterraneus, Paracyclops poppei та Grateriella unisetigera are rare species for Lviv region. Eurycercus lamellatus, Simocephalus expinosus, Chydorus latus together with the previous species are rare for the Ukrainian Carpathians in total. 47% of the investigated lenthic water bodies are in oligosaprobic zone. The most valuable communities of the Cladocera, Cyclopoida and Calanoida exist in the Zhuravlyne lake, springs and wells near village Verkhnia Rozhanka, pools of the Vododilnyi masiff, riverbed of Stryi and the along-river reservoirs between the villages Zavadavivka and Yavora, and ponds near the village Dovge.

A review of the Cladocera in Basrah, Iraq

Sixty-five species of freshwater Cladocera belong to twenty-two Genera are reported from Basrah city, based on 15 studies mentioned the species of Cladocera in addition to seven other studies reported only density of Cladocera group. The maximum density of Cladocera was 91225 (ind./m3) recording at Shatt Al-Arab- Al-Hartha region.

Diversity and seasonal changes of zooplankton communities in the Shatt Al-Arab River, Basrah, Iraq, with a special reference to Cladocera

Zooplankton abundance and distribution were studied at four stations in the northern sector of Shatt Al-Arab from September 2008 to August 2009. Monthly zooplankton samples were collected.Oblique hauls were taken at each stationusing a 0.120 mm mesh-sized net with 40 cm mouth opening. Air and water temperatures, salinity, pH, dissolved oxygen, turbidity, chlorophyll-a, total suspended solids and total soluble solids were measured at each station and at each sampling event and were correlated with the density of Cladocera. Like Shannon index, Jaccardʼs similarity index,measures of richness and evenness were calculated. Water temperature ranged from 10 to 28 ºC. Salinity values changed from 0.7 to 4.1 psu with a decline in the summer and an increase in the autumn. pH values were >7, dissolved oxygen varied from 4.9 in the summer to 12.3 mg/l in the winter. Chlorophyll-a values fluctuated between 2.3 in the autumn and winter and 21.4 mg/m3 in Summer.Zooplankton density was the least at station 1 (79-10074 ind/m3) and the most at station 2 (174-65170 ind/m3).Cirripede larvae dominated the zooplankton community at all the stations. Cladocera was second in number, followed by Copepoda.The maximum diversity index (2.11), richness (64.45) and evenness (0.47) were obtained at station 1. The highest similarity was obtained between stations 3 and 4 and the lowest between stations 1 and 2.

Impact of Fish Farming in floating cages on zooplankton Community in Euphrates River, Iraq

The Impact of floating cages Fish culture on zooplankton in Euphrates river of middle of Iraq was examined from cage and non-cage site at monthly intervals from January 2018 to December 2019. the physical and chemical properties of river water were measured including Water Temperature, Turbidity,Total Solid suspended ( TSS), pH, Electrical Conductivity(EC),Total Dissolved Solids(TDS),Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD5),phosphate (PO4) and Nitrate (NO3),The results indicated that: the, Turbidity,Total Solid suspended ( TSS), pH, Electrical Conductivity, Total Dissolved Solids(TDS), Biochemical Oxygen Demand (BOD5), (PO4) phosphate and (NO3) Nitrate values in cage site were significantly higher than non-cage site (p<0.05) This gives evidence of the effect of fish cages on this properties. In the current study about 48 Taxonomic units of zooplankton were identified, the rotifer was dominate group including 23 taxa to rotifera, 12 taxa belonging to cladocera and 13 taxa to copepod. The Zooplankton showed high density in river 9470 ind/m3 during April in non-cage site while lower1100 ind/m3 in December in cage site also the rotifer recorder density from (425 ind/m3 in cage site to 4925 ind/m3 non-cage site), cladocera density from225 ind/m3 in cage site to 1850 ind/m3 in non-cage site and copepod density from 450 ind/m3 in cage site to 2695 ind/m3 non-cage the high values were in spring and autumn while lowest values were recorded in summer and winter. The results of relative abundance index showed that the species rotifera: Keratella cochlearis,K.valga, Euchlanis delatata while the cladocera Alona rectangular, Bosmina longirostris, Chydorus sphaericus, Simocephalus vetulus and the copepods: nauplii were more abundant in the Euphrates river at cage site. The Shanon-Weiner index of total Zooplankton varied from 1.81 to 4.13 bit/ind while the Shanon index of Rotifer from 1.85 to 3.78 bit/Ind, Cladocera varied from 0.001 to 3.04 bit/Ind and Copeoda varied from 0.35 to 2.71 bit/Ind with greatest values were recorded at April and September in non-cage site while lower values at and June and November in cage site that give evident to effect of cage on zooplankton.

Biodiversity of Rotifera and Cladocera in the upper region of Euphrates River- Iraq

Five representative sampling stations were selected in upper region of Euphrates river. Bimonthly sampling were collected from December 2000 to December 2001. Rotifera showed high density in December 2000 while high density of cladocera which recorded in October .The results of relative abundance index showed that rotifera: Polyarthera dolichoptera , Keratella cochlearis , K. valga, Cephalodella auriculata and cladocera: Bosmina longirostris , B.coregoni ,Chydorus spharicus, were more abundant in study stations. The results of constancy index showed 4 taxa belonged to rotifera and 2 taxa belonged to cladocera which were considered constant in the Euphrates river, where the other species varied between accessory and accidental species in study stations. The index values of Species richness of rotifera varied between 0.41 – 2.8 and cladocera varied between 0.5 - 1.95. The Shanon-Weiner index of rotifera varied between 0.54-1.72 bit/ind., while the Shanon index of cladocera varied between 0.5-1.6 bit/ind. The uniformity index of rotifera varied between 0.41 – 0.99 but the uniformity index of cladocera varied between 0.61- 0.98 .

Long-term plankton community dynamics and influencing factors in a man-made shallow lake, Lake Dishui, China

Understanding how long-term environmental variation and biotic interaction determine biological assemblages is critical for evaluating the response of biological communities to anthropogenic and climate changes. We sampled plankton and water quality from a man-made lake monthly from 2006 to 2015 for the period from after creation to 13-year old of the lake. We used correlation, variation partitioning, multivariate autoregressive state-space models, and dynamic factor analyses to disentangle interactions of biotic and abiotic factors in regulating the dynamics of plankton size groups. We found that annual average total abundances decreased 86% for phytoplankton and 78% for zooplankton, while concentrations increased 1.8 times for total nitrogen and 2.7 times for total phosphorus during the study period. We concluded that the decline of plankton abundance was largely attributed to the predation of zooplankton on phytoplankton, fish predation on both phytoplankton and zooplankton, and linkages with the decline of water salinity, pH, and the increase of clarity. The decline of plankton abundance was apparently not resulted from long-term change in nutrient concentrations. These conclusions were further supported by that abundances of nano-phytoplankton and micro-phytoplankton oscillated in opposite direction with extremely low density of Cladocera (< 1 individual/L) during the study period. Our conclusions were also supported by the strong interactions between Rotifera and macro-phytoplankton and between nano-phytoplankton and Copepoda, as well as by the describability of the six plankton size groups in a shared trend that was opposite to the trends of water clarity and planktivorous fish stock density.

Diversity, Abundance, and Distribution of Cladocera at the end of the Tigris River North of Basrah – IRAQ

Seasonal variations of the species composition and abundance of Cladocera were studied in two stations at the end of the Tigris River and one station at the confluence of the Tigris with Euphrates area, at the beginning of the Shatt Al-Arab River in Al-Qurnah North of Basrah Province, from October 2015 to August 2016. Samples of zooplankton were collected by plankton net 100-µm. mesh size. The population density of Cladocera ranged between 1 Ind /m³ during summer and 211 Ind./m³ during winter at station 1 (Al-Jewaber Bridge). A total of 16 species of Cladocera belonging to 12 genera were recorded in the study. The average density of Cladocera ranged from 23.2 ind./m3 at Station 2 (Hamayon Bridge) to 53.7 Ind./m3 at Station 1 (Al-Jewaber Bridge). The results showed that the Bosmina meridionalis was dominant at the three stations 47.8%, while the other species were as follow Moina affinis 15.1%, Daphnia lumholtzi 9.3%, Simocephalus (Simocephalus) vetuloides 8.1% and Daphnia exilis 6.6% of the total Cladocera.

Environmental Study of Zooplankton in the Middle Part of the Shatt Al-Arab River, Basrah, Iraq

An environmental study of zooplankton on the Shatt al-Arab River was carried out in two stations from July until November 2018. A total of 34 taxa of zooplankton were recorded in this study, belong to Cladocera, Copepoda and Rotifera. Some species have disappeared and others have emerged during the study period but varying numbers of dominant species found during the search such as Acarocalanus gibber, and recorded in the station 1 in July and station 2 for all months such as cyclopoid nauplii of Copepoda. Water temperature ranged between (19-35) °C station 1 and between (18- 32) °C at station 2, Salinity values fluctuated between (4.05 and 15.42 ‰), (6.47- 12.2 ‰) at stations 1, 2 respectively. pH values ranged was between (7.3 to 7.9) and (7.1 to 8.5) at stations 1 and 2 respectively. Copepoda density ranged between (0.12 to 88.23) ind. l-1 at station 1 and between (0.94 to 69.73) ind. l-1 at station 2. Density of Cladocera fluctuated between (0.06 and 1.45) ind. l-1. Maximum and minimum densities were at station 1. The population density of Rotifera ranged between (0.06 ind. l-1 to 20.44) ind. l-1 at second station.

Temporal and spatial variations in zooplankton communities in relation to environmental factors in four floodplain lakes located in the middle reach of the Yangtze River, China

A comparative limnological study of the zooplankton communities and their relationship with environmental factors was conducted to test the temporal and spatial changes among lake groups. In our study of four lakes, the lowest gamma (γ) diversity was recorded in January 2017, with a total of 25 zooplankton taxa. The highest γ diversity was recorded in May 2016, with a total of 55 zooplankton taxa. Species turnover in space (β) were from 14.98 to 25.81. Markedly temporal and spatial variations were observed in the zooplankton community. The higher mean cladocera density (57.70 ind. L−1 and 39.85 ind. L−1) was observed in May and August, then decreased gradually with the lowest in January. The mean copepoda density ranged from 8.71 ind. L−1 in January 2017 to 32.04 ind. L−1 in August 2016. The mean rotifera density was significantly higher than that of the other two crustacean zooplankton (p < 0.01), within the range of 89.36–1139.2 ind. L−1. We also observed that zooplankton density exhibited significant seasonal changes from NMDS (Nonmetric multidimensional scaling analysis). Redundancy analysis revealed that environmental factors, such as water temperature and transparency, have significantly influenced the zooplankton community structure.

Combining sediment Cladocera remains and geochemistry to reveal the role of a large catchment in driving changes in a small subalpine lake (Lake Ledro, N-Italy)

&lt;p&gt;Sediment Cladocera remains and geochemistry were analyzed at Lake Ledro, a small subalpine lake with a large catchment area located in northern Italy. The aim of the study was to investigate human, climate and hydrological impacts on the Cladocera community and on the geochemical components during the last few centuries. A sediment core was collected from the deepest point of Lake Ledro and radiometrically dated. Cladocera remains were analyzed to track the trophic lake evolution. The core bottom section revealed the dominance of Bosminidae in concomitance with nutrient pulses entering into the lake during major flood events. The abundance of species preferring cold water temperatures confirmed the deposition of this core section during the Little Ice Age. The flood event occurred in the first half of the 19&lt;sup&gt;th&lt;/sup&gt; century produced a drastic increase in littoral species, due to the development of new habitats. The decrease in Cladocera densities during the following lake stage was followed by a rapid increase in planktonic species during the nutrient enrichment after the 1960s. Statistical analyses revealed a clear response of Cladocera community to climate variability during oligotrophic periods, while no relation to temperature changes was recorded during high nutrient levels. A preliminary study on Bosminidae and Daphnidae body size and appendages length was carried out to reconstruct major changes in the lake food web. Only &lt;em&gt;Bosminia&lt;/em&gt; spp. revealed clear body size changes: minor shifts were recorded before the 1930s in relation to the low nutrient concentrations, while the major changes occurred during the 1980s were interpreted as related to the appearance of Cladocera invertebrate predators. Geochemical components were studied using X-ray fluorescence spectroscopy (XRF) analysis in order to recognize the impact of the large catchment area and from the lake-level regulations on the lake hydrology. Moreover the Si:Al ratios profile confirmed the increase in lake productivity after the 1960s. Although both Cladocera and geochemical analysis indicate major changes since the 1960s, they also revealed diverse responses to common external and local forcing, thus confirming the value of a multi-proxy approach for disentangling the lake responses to different environmental stressors. Moreover, it outlined the importance of larger catchment areas on small lakes as they are to a larger extent influenced by the modifications occurring in the drainage basin.&lt;/p&gt;

Seasonal variations of the Cladocerans in the Shatt Al-Arab River, Southern Iraq

Samples were collected seasonally from three stations (Al-Ashar, Abu Al-Khasib and Al-Faw) in the Shatt Al-Arab River by a plankton net (85 μm mesh-size and 40 cm mouth aperture), from January to November 2013. Some physical and chemical parameters of the water were monitored such as, water temperature, salinity, pH, dissolved oxygen, Total Dissolved Solids (TDS) and turbidity. The density of Cladocera ranged between 0.0 ind/m3 during spring and summer at Al-Faw station to 18922 ind/m3 during summer at Al-Ashar station. Five, two and one species of Cladocera were recorded at the three stations, respectively. Moina affinis and Diaphanosoma brachyurum were the dominant species at study area. Maximum diversity index (H) (0.7) was obtained at stations 1 and 2 during winter and spring respectively and higher evenness value (J) (0.4) was recorded at station 1 and 2 during winter, while higher richness (D) (6.1) was obtained at station 1 during winter and lowest value (0.0) at station 3. Jaccard׳s index revealed higher similarity between stations 1 &amp; 2 and lower values between station 1 and 3.

Diversity and seasonal changes of zooplankton communities in the Shatt Al-Arab River, Basrah, Iraq, with a special reference to Cladocera

Zooplankton abundance and distribution were studied at four stations in the northern sector of Shatt Al-Arab from September 2008 to August 2009. Monthly zooplankton samples were collected. Oblique hauls were taken at each station using a 0.120 mm mesh-sized net with 40 cm mouth opening. Air and water temperatures, salinity, pH, dissolved oxygen, turbidity, chlorophyll-a, total suspended solids and total soluble solids were measured at each station and at each sampling event and were correlated with the density of Cladocera. Like Shannon index, Jaccard ʼ s similarity index, measures of richness and evenness were calculated. Water temperature ranged from 10 to 28 o C. Salinity values changed from 0.7 to 4.1 psu with a decline in the summer and an increase in the autumn. pH values were >7, dissolved oxygen varied from 4.9 in the summer to 12.3 mg/l in the winter. Chlorophyll-a values fluctuated between 2.3 in the autumn and winter and 21.4 mg/m 3 in Summer. Zooplankton density was the least at station 1 (79-10074 ind/m 3 ) and the most at station 2 (174-65170 ind/m 3 ).Cirripede larvae dominated the zooplankton community at all the stations. Cladocera was second in number, followed by Copepoda. The maximum diversity index (2.11), richness (64.45) and evenness (0.47) were obtained at station 1. The highest similarity was obtained between stations 3 and 4 and the lowest between stations 1 and 2 .

ABUNDANCE AND DIVERSITY OF ZOOPLANKTON IN THE KÖPRÜÇAY ESTUARY, TURKEY

The physicochemical features and species composition and density of zooplankton of Koprucay estuary inves­tigated monthly sampling from selected 5 stations be­tween January and December, 2009. In this study, Zo­oplankton which are Rotifera (20), Cladocera (6), Co­pepoda (34), and Cnidaria, Tubilariidae, Foraminifera, Tintinida, Cirripedia, Gastropoda, Polychaeta, Chae­tognatha, Decapoda, Ichthyoplankton one of each of determined 70 taxons in Koprucay River estuarin zone. The dominant taxa in Koprucay River estuarin zone consist of Oithona nana, Clausocalanus arcui­cornis, Acartia discaudata, Paracalanus parvus, Eu­chlanis dilatata and Cephalodella gibba and these species are eurohalin character types of zooplankton. In Koprucay River estuarin zone, the highest and the lowest Copepoda density semptember (25627.33 ±8369 ind./m 3 ) and february (3050 ±1701 ind./m 3 ), ; the highest and the lowest Rotifera density january (12152 ±6835 ind./m 3) and september (187 ±76 ind./m 3 ); the highest and the lowest Cladocera density august (2687 ±604 ind./m 3 ) and february (0 ±0 ind./m 3 ); the highest and the lowest other organisms february (3226,33 ±586 ind./m 3 ) and may (648 ±178 ind./m 3 ), respectively. This article was prepared from the doctoral thesis.

Biomass-dependent effects of age-0 common carp on aquatic ecosystems

Fishes play a functional role in structuring aquatic ecosystems through top-down and bottom-up processes. Adult common carp (Cyprinus carpio )a re well recognized for their middle-out effects on aquatic ecosystems that can shift shallow lakes from the clear- to turbid-water stable state through benthic foraging activities. However, less is known about ecosystem effects of age-0 common carp. Age-0 common carp are planktivorous and can be highly abundant, suggesting that large year classes may also produce undesirable ecosystem effects. We evaluated the effects of four age- 0 common carp densities (0, 175, 475, and 812 kg/ha) on water quality (ammonium, total phosphorus, total Kjeldahl nitrogen, and turbidity) and primary (macro- phytes and phytoplankton) and secondary (zooplankton and benthic invertebrates) production. Common carp increased nutrient availability and phytoplankton pro- duction and decreased water transparency with effects increasing with carp biomass. Common carp also reduced macrophyte coverage and cladocera density (through effects on chydorus and ceriodaphnia) and body size, but effects were not density dependent. In contrast, common carp did not appear to affect copepod, rotifer, chironomid, or gastropod densities. These results suggest that even relatively low age-0 common carp densities ((175 kg/ha) may have many comparable ecosystem effects as adult carp, although effects may be accrued through different pathways.

Effects of flooding regime and diel cycle on diet of a small sized fish associated to macrophytes

AIM: In this paper we assessed the effects of flooding (low and high water period) on the feeding activity and diet composition of Serrapinus notomelas in patches of the macrophyte Eichhornia azurea in a shallow floodplain lake (upper Paraná River Floodplain, Brazil). We also assessed the variations of diet composition and feeding activity along the diel cycle. METHODS: Traps were used to catch the fish inside of macrophyte patches monthly from June/2007 to May/2008. A total of 1038 stomachs were examined. We assessed the feeding activity with the mean stomach fullness degree method. To summarize and support the results of diet composition in the different periods (low and high water periods) and times (dawn, light period, and dusk), was applied a nonmetric multidimensional scaling (NMS). RESULTS: The feeding activity of S. notomelas did not differ between low and high water periods, but it differed along the diel cycle. The feeding activity was higher during the light period and dusk, at both the low and high water period. The diet composition differed significantly between low and high water periods, and also along the diel cycle. In the low water the diet of S. notomelas was composed mainly by algae and in the high water by Cladocera. Algae were consumed mainly during the light period while Cladocera in dawn and dusk. CONCLUSIONS: Our results indicate that the oscillations in the water level affect the diet composition, but not the feeding activity of S. notomelas. These seasonal changes are probably related to the temporal abundance of food resources, thus, when Cladocera density was low (low water), S. notomelas consumed mainly algae but when Cladocera was more abundant (high water), it became a common food resource.

Respostas da comunidade zooplanctônica à formação do reservatório de Dona Francisca, Rio Grande do Sul, Brasil

Nós investigamos as mudanças na riqueza, densidade e composição da comunidade zooplanctônica em resposta à formação de um reservatório na área da usina hidrelétrica Dona Francisca. Amostras de zooplâncton foram coletadas trimestralmente durante quatro anos, compreendendo dois anos antes e dois anos após a formação do reservatório. A riqueza de espécies e a densidade de Cladocera, Copepoda e Rotifera aumentaram após o enchimento do reservatório. Além disso, a comunidade zooplanctônica apresentou uma nítida alteração na composição de espécies entre os períodos antes e após a formação do reservatório. A distinta composição de espécies entre os dois períodos esteve relacionada às alterações nas características limnológicas decorrentes da formação do reservatório.

Plankton Richness and Abundance in Several Different Hydrological Situations in Lakes Lateral to a River: A Case Study in the Mouth Zone of a Tributary into a Tropical Reservoir

A descriptive analysis of the responses of plankton from lakes lateral to a river in its mouth zone into a tropical reservoir to water level variations is presented. Three situations were reported: 1) a comparison of species richness and diversity and of algae population abundance in prolonged drought and in periods of connection of lakes to the river, 2) the spatial distribution of abundance and richness of Rotifera species in four isolated water bodies formed by fragmentation of a lateral lake during a period of prolonged drought and in the same areas during a period of integrity as an ecosystem, 3) the variability of total zooplankton and Cladocera densities at the end of the isolation period of a lateral lake and after the recovery of connection with the river and in a year of continuous connection with the lotic ecosystem. Various idiosyncrasies were observed in connected lateral lakes, like the surface hydrologic connectivity, a primary factor in species richness modifications and a secondary controlling factor of plankton abundance. Underground hydrologic connectivity, through the river - lake water flux during the high-water period and lake - river during drought period, appears to have an important role in richness and abundance variations of planktonic populations in the lake isolated from the river.

Biomanipulation of hypereutrophic ponds: when it works and why it fails

Phytoplankton, zooplankton, submerged vegetation and main nutrients have been monitored in 48 eutrophic ponds from the Brussels Capital Region (Belgium) between 2005 and 2008. Nine ponds have been biomanipulated in order to improve their ecological quality and prevent the occurrence of noxious cyanobacterial blooms. The 4-year study of a large number of ponds allowed identification of the factors having the strongest influence on phytoplankton growth. Continuous monitoring of the biomanipulated ponds allowed the significance of changes caused by biomanipulation to be tested as well as the main reasons of biomanipulation successes and failures to be elucidated. The main factors controlling phytoplankton in the ponds studied appeared to be grazing by large cladocerans and inhibition of phytoplankton growth by submerged vegetation. Biomanipulation resulted in a significant decrease in phytoplankton biomass in general and biomass of bloom-forming cyanobacteria in particular that were associated with a significant increase in large Cladocera density and size. In six out of nine ponds biomanipulation resulted in the restoration of submerged vegetation. The maintenance of the restored clearwater state in the biomanipulated ponds was strongly dependent on fish recolonisation and nutrient level. In the absence of fish, the clearwater state could be maintained by submerged vegetation or large zooplankton grazing alone. In case of fish recolonisation, restoration of extensive submerged vegetation could buffer, to a considerable degree, the effect of fish except for ponds with high nutrient levels.

Restoration potential of biomanipulation for eutrophic peri-urban ponds: the role of zooplankton size and submerged macrophyte cover

Eight hypereutrophic phytoplankton dominated ponds from the Brussels Capital Region (Belgium) were biomanipulated (emptied with fish removal) to restore their ecological quality and reduce the risk of cyanobacterial bloom formation. Continuous monitoring of the ponds before and after the biomanipulation allowed the effects of the management intervention on different compartments of pond ecosystems (phytoplankton, zooplankton, submerged vegetation and nutrients) to be assessed. Fish removal resulted in a drastic reduction in phytoplankton biomass and a shift to the clear-water state in seven out of eight biomanipulated ponds. The reduction in phytoplankton biomass was associated with a marked increase in density and size of large cladocerans in six ponds and a restoration of submerged macrophytes in five ponds. The phytoplankton biomass in the ponds with extensive stands of submerged macrophytes was less affected by planktivorous fish recolonisation of some of the ponds later in the summer. The two non-vegetated ponds as well as one pond with sparse submerged vegetation showed a marked increase in phytoplankton biomass associated with the appearance of fish. Phytoplankton biomass increase coincided with the decrease in large Cladocera density and size. One pond lacking submerged macrophytes could maintain very low phytoplankton biomass owing to large Cladocera grazing alone. The results of this study confirmed the importance of large zooplankton grazing and revegetation with submerged macrophytes for the maintenance of the clear-water state and restoration success in hypereutrophic ponds. They also showed that large Cladocera size is more important than their number for efficient phytoplankton control and when cladocerans are large enough, they can considerably restrain phytoplankton growth, including bloom-forming cyanobacteria, even when submerged vegetation is not restored. The positive result of fish removal in seven out of eight biomanipulated ponds clearly indicated that such management intervention can be used, at least, for the short-term restoration of ecological water quality and prevention of noxious cyanobacterial bloom formation. The negative result of biomanipulation in one pond seems to be related to the pollution by sewage water.

Biodiversity of Rotifera and Cladocera in the upper region of Euphrates River- Iraq

Five representative sampling stations were selected in upper region of Euphrates river. Bimonthly sampling were collected from December 2000 to December 2001. Rotifera showed high density in December 2000 while high density of cladocera which recorded in October .The results of relative abundance index showed that rotifera: Polyarthera dolichoptera , Keratella cochlearis , K. valga, Cephalodella auriculata and cladocera: Bosmina longirostris , B.coregoni ,Chydorus spharicus, were more abundant in study stations. The results of constancy index showed 4 taxa belonged to rotifera and 2 taxa belonged to cladocera which were considered constant in the Euphrates river, where the other species varied between accessory and accidental species in study stations. The index values of Species richness of rotifera varied between 0.41 – 2.8 and cladocera varied between 0.5 - 1.95. The Shanon-Weiner index of rotifera varied between 0.54-1.72 bit/ind., while the Shanon index of cladocera varied between 0.5-1.6 bit/ind. The uniformity index of rotifera varied between 0.41 – 0.99 but the uniformity index of cladocera varied between 0.61- 0.98 .