Diaphanosoma Brachyurum Research Articles

Spatial and Temporal Changes of Planktonic Microcrustaceans (Cladocera, Copepoda) and their Relationship with Physicochemical Parameters in Kırklareli Reservoir (Kırklareli-Türkiye)

The present study focused on monthly densities and abundances of planktonic microcrustaceans (Cladocera and Copepeda) in Kırklareli reservoir, as well as their relationship with some physicochemical parameters at three stations for the period from May 2018 to April 2019. In the present study, a total of 26 planktonic microcrustaceans species, 14 from Cladocera and 12 from Copepoda were identified. The mean annual microcrustacean abundance recorded during the study was 24076 ind/m3, 67% of which was Cladocera (16054 ± 12414 ind/m3) and 33% was Copepoda (8022 ± 5564 ind/m3). The maximum abundance of planktonic microcrustaceans were found in September (51521 ind/m3) and the minimum was found in January (2919 ind/m3). The most common species in the reservoir were Bosmina longirostris, Daphnia pulex, Daphnia cucullata, Daphnia galeata, Daphnia longispina and Diaphanosoma brachyurum from Cladocera and Cyclops abyssorum, Cyclops vicinus, Eudiaptomus vulgaris and Arctodiaptomus wierzejskii from Copepoda. The environmental parameter values measured in the reservoir were acceptable to support aquatic life, especially the zooplankton community. The total density and abundance of zooplanktonic microcrustaceans showed positive correlation with the water temperature and Chlorophyll-a. According to these results, we concluded that Kırklareli reservoir has a mesotrophic character in terms of the microcrustacean fauna and the physicochemical parameters.

Distribution of Diaphanosoma (Diplostraca: Sididae) genus in Central Europe – morphological and molecular approach

Diaphanosoma brachyurum is a dominant component of summer zooplankton in Central Europe. So far only this species has been known from Poland, and other species from this genus have been found in neighboring countries. The aim of the present study was to present the factual distribution of Diaphanosoma species in Central Europe. We investigated Diaphanosoma individuals in 109 water bodies in Central Europe (mostly from Poland) by combining morphological analyses and molecular methods (mtDNA COI gene). Our research confirmed the presence of three other species - D. orghidani, D. mongolianum, and D. cf. lacustris. We provided a detailed morphological description for every species and pointed out that each species can be easily distinguished morphologically by armament of postero-ventral valve margins. The results of phylogenetic analysis based on 27 haplotypes of mtDNA COI gene lead to the same conclusion as morphology. Our genetic and morphological analysis confirms a close affinity between D. mongolianum and D. lacustris, as well as the presence of hybrids between these species. Nevertheless, the most common was D. brachyurum - it was found in 97 water bodies, and other Diaphanosoma species begin to penetrate Central Europe via rivers.

Diversity of crustaceans in the euphrates River/Najaf province-Iraq

To study the biodiversity of crustaceans, five sites were taken with three replicates from each sample over a period of six months, from November 2021 to April 2022. Samples were also taken. Water is used to measure some chemical and physical properties. The density of crustaceans ranged from (4-773) individuals / liter, and the month of March recorded the highest density. The results of the isolation and identification of crustaceans showed the following species of cyclops, Diaptomidae, Acroperus harpae, Daphnia sp, Bosmina sp, Ceriodaphnia quadrangula, Daphnia galeata, A amphipod Hyallela, Diaphanosoma brachyurum, Simocephalus vetulus and Bosmina sp. According to the relative abundance index (Ra) of crustaceans, the first site throughout the research period had the highest density of cyclops, while the remaining sites had the highest density of Bosmina sp. It also showed The Crustacean Species constancy Index (S) also showed that among the species at the research sites, Cyclops, Diaptomidae, Daphnia sp. and Bosmina sp. The Ceriodaphnia quadrangula is the most persistent. The values of the species richness index (D*) ranged between 0.67-4.66. While the Shanon-Weiner index ranged between 0.346-2.76 bit/ind. While the values of the species homogeneity index (E) ranged between 0.499-1.256.

Degradation of dead cladoceran zooplankton and their contribution to organic carbon cycling in stratified lakes: field observation and model prediction

Abstract The contribution of dead zooplankton biomass to carbon cycle in aquatic ecosystems is practically unknown. Using abundance data of zooplankton in water column and dead zooplankton in sediment traps in Lake Stechlin, an ecological-mathematical model was developed to simulate the abundance and sinking of zooplankton carcasses and predict the related release of labile organic matter (LOM) into the water column. We found species-specific differences in mortality rate of the dominant zooplankton: Daphnia cucullata, Bosmina coregoni and Diaphanosoma brachyurum (0.008, 0.129 and 0.020 day−1, respectively) and differences in their carcass sinking velocities in metalimnion (and hypolimnion): 2.1 (7.64), 14.0 (19.5) and 1.1 (5.9) m day−1, respectively. Our model simulating formation and degradation processes of dead zooplankton predicted a bimodal distribution of the released LOM: epilimnic and metalimnic peaks of comparable intensity, ca. 1 mg DW m−3 day−1. Maximum degradation of carcasses up to ca. 1.7 mg DW m−3 day−1 occurred in the density gradient zone of metalimnion. LOM released from zooplankton carcasses into the surrounding water may stimulate microbial activity and facilitate microbial degradation of more refractory organic matter; therefore, dead zooplankton are expected to be an integral part of water column carbon source/sink dynamics in stratified lakes.

Application of species-specific primers to estimate the in situ diet of Bythotrephes [Cladocera, Onychopoda] in its native European range via molecular gut content analysis.

The study of invasive species often focuses on regions of recent introduction rather than native habitats. Understanding an invasive species in its natural environment, however, can provide important insights regarding the long-term outcome of invasions. In this study we investigated the diet of the invasive spiny water flea, Bythotrephes longimanus, in two Austrian perialpine lakes, where it is native. The gut contents of wild-caught Bythotrephes individuals were estimated by quantitative polymerase chain reaction, targeting species-specific fragments of the barcoding region of the cytochrome c oxidase I gene of potential prey. The observed prey spectrum of Bythotrephes in the study lakes consisted primarily of Eudiaptomus gracilis and Diaphanosoma brachyurum. The Daphnia longispina complex, Leptodora kindtii and Mesocyclops leuckarti also contributed to the diet. Results indicate that Bythotrephes is a generalist feeder with a preference for epilimnetic prey.

SPATIOTEMPORAL VARIABILITY OF DAPHNIA CRISTATA SARS, 1862 AND DIAPHANOSOMA BRACHYURUM (LIÉVIN, 1848) POPULATIONS IN LAKE LESCHOVOYE IN 2016–2020

The article presents results on the spatiotemporal variability of two zooplankton species – Daphnia cristata and Diaphanosoma brachyurum, in Lake Leschovoye. Surveys were conducted from June to September in 2016–2020. According to monitoring data from this period, the abundance of these species varied widely over time. Specific surveys at six sites in July–August 2019–2020 revealed also high spatial variation of the species’ abundances. Compared to the other species, D. cristata dominated in the lake with a 71 % share in Cladocera abundance. In 2020, however, D. brachyurum abundance was relatively high. In this period, its share in the cladoceran zooplankton reached 31 % and was twice that of D. cristata that year. A positive effect of water transparency on D. brachyurum abundance was observed. The study found no significant effect of other limnological parameters (gas conditions, pH, dissolved organic matter concentration, water color and turbidity) on the species. Another factor potentially influencing the species abundance is interspecific competition for food, as the range of particles consumed by the species is similar. Alongside competition, predation of plankton-feeding fishes and organic matter input with runoff from managed meadows can affect the abundance of the species. The effect of the runoff, nonetheless, can be dual. In some years, large amounts of allochthonous organic matter can lead to suppression of both species by clogging their filtration system. In other periods, runoff can lower water transparency thereby reducing the hunting efficiency of plankton-feeding fishes and leading to an increase in D. brachyurum abundance.

Can zooplankton species be used as indicators of trophic status and ecological potential of reservoirs?

The European Water Framework Directive implements the policies to achieve a good ecological status of all European waterbodies. To determine the ecological potential in freshwater environments, abiotic (morphology, physical and chemical variables) and biotics (algae, fishes, etc.) metrics are used. Despite their importance in trophic web, zooplankton was not included as one of the Biological Quality Elements (BQE) to determine the water quality. In the present research, we studied the zooplankton species that can be considered as indicators of trophic status and ecological potential for more than 60 water reservoirs. The data were obtained from more of 300 samples collected during 10 years from reservoirs at Ebro River watershed, which is the largest basin in Spain. According to their physicochemical and biological elements, the trophic status and ecological potential of these reservoirs were established. More than 150 zooplankton species were identified during the study. The results from this research indicate that species that are related with low water quality are: Acanthocyclops americanus, Ceriodaphnia spp., Daphnia cucullata, Daphnia párvula, Diaphanosoma brachyurum, Brachionus angularis, Keratella cochlearis and Phompolyx sulcata. An indicator of moderate quality was Bosmina longirostris, while Daphnia longispina, Ascomorpha ovalis and Ascomorpha saltans were considered as indicators of good water quality. The data obtained suggest that zooplankton species can be used as a valuable tool to determine the water quality status and should be considered, in a near future, as one more of the BQE within the WFD metrics.

ЗООПЛАНКТОН МАЛЫХ ОЗЕР ВОСТОЧНОЙ ЧАСТИ ВОДОСБОРА ОЗЕРА ВОЖЕ (ВОЛОГОДСКАЯ ОБЛАСТЬ)

In the summer period of 2017–2020, the authors studied the composition, dominant complex and the abun-dance of zooplankton in 23 small lakes in the eastern part of the Lake Vozhe catchment area (Vologda oblast). The lakes are located in lacustrine-glacial, moraine-hilly and moraine-plain landscapes. A total of 121 species are recorded in zooplankton of the lakes (Rotifera – 38, Cladocera – 56, Copepoda – 27) including Holopedium gibberum, Daphnia pulex, Bunops serricaudata, Paralona pigra, Chydorus ovalis, Acanthodiaptomus denticornus denticorn that are relatively rare species for the region. The highest occurrence is typical for eurybiontic species. The planktonic fauna of the waterbodies of lacustrine-glacial terrains is sui generis (the index of similarity with other lakes is 0.4). The level of similarity in the composition of zooplankton in moraine lakes is 0.7 on average. Zooplankton in the lakes of different landscape types differs in the structure of dominant complex. The set of dominants in the reservoirs of the lacustrine-glacial terrains is sui generis (Keratella cochlearis, Daphnia galeata, Eudiaptomus graciloides, Heterocope appendiculata). The composition of zooplankton dominants in moraine lakes is more diverse. Most of these waterbodies are dominated by Kellicottia longispina, Keratella cochlearis, Bosmina longirostris, Thermocyclops oithonoides. In the lakes of the moraine-hilly landscape, the set of dominants also includes Eudiaptomus gracilis and E. graciloides, and in the moraine-plain water bodies Asplanchna priodonta, Diaphanosoma brachyurum, Ceriodaphnia pulchella, Polyphemus pediculus are dominant. The highest average abundance (137.7 thousand ind./m3) and biomass (1.8 g/m3) are typical for the lakes in moraine-plain landscapes. The morphology of the depressions of these lakes contributes to the development of macrophyte thickets. The abundance and biomass of zooplankters in waterbodies of the lacustrine-glacial landscapes are 58.9 thousand ind./m3 and 0.8 g/m3, respectively. The development of macrophytes in these reservoirs is limited by a rapid increase in depth and the predominance of peat and peat-silt soils.

The relationship between zooplankton community and environmental factors of Ghrib Dam in Algeria.

The effect of environmental factors on zooplankton diversity, abundance, and distribution in the Ghrib Dam water body was investigated for 2years from June 2013 to May 2015. A total of 61 species of zooplankton were recorded, including 45 rotifers, 13 cladocerans, and 3 copepods. The zooplankton abundance fluctuated between 4 and 3363ind.L-1, and its Shannon-Wiener index of zooplankton diversity in Ghrib Dam varied from H' = 1.15 to 3.77 during the 2-year study period. The highest diversity index was recorded at sampling site S1 in January 2015, due to the increase of specific richness (Ni = 27, Dmg = 5.75). Canonical correspondence analysis (CCA) was used to determine the influence of environmental factors in structuring the zooplankton species for each group. The results of CCA revealed that the most significant environmental factors influencing zooplankton community were water temperature (WT), dissolved oxygen (DO), phosphorus (PO4-), and NO3- (p < 0.05, Monte Carlo permutation test). Meanwhile, the appearance of Hexarthra sp., Collotheca pelagica, and Diaphanosoma brachyurum indicated a rise in WT. The existence of Filinia longiseta, Keratella quadrata, and Cyclops strenuus correlated with a rising of DO. Brachionus urceolaris, Filinia passa, Keratella tecta, Notholca acuminata, and Polyarthra dolichoptera positively coexisted in an increased PO4-. Daphnia longispina and Oxyurella tenuicaudis were positively associated with high concentration of NO3-.

The Effects of Microalgal Diet With Enrichment of Fermented Organic Matters (Tofu Waste, Rice Bran and Fish Meal) on Growth and Reproduction of Diaphanosoma brachyurum

Diaphanosoma brachyurum is one of cladocerans that potentially used as live food organism for larval rearing in fish and shrimp hatcheries. In the culture of D. brachyurum, it usually uses live food from phytoplankton cells, but researches on the diet enrichment from fermented organic matters has not been widely informed. This study was aimed to investigate the different effects among different microalgal diets and a combination of the best microalgal diet with fermented organic matters on growth and reproduction of D. brachyurum. Two experiments were carried out in this study and those designs applied Completely Randomized Design (CRD). The first experiment, the different microalgal diets divided into four treatments with four replication and those were C. vulgaris (A); C. calcitrans (B); N. oculata (C); and T. chuii (D). The second experiment, the combination of the best microalgal diet and fermented organic matters (FOM) divided into five treatments with three replication and those were 100% T. chuii (A); 75% T.chuii and 25% FOM (B); 50% T.chuii and 50% FOM (C); 25% T.chuii and 75% FOM (D); and 100% FOM (E). The results showed that T. chuii has significant different (P<0,05) than another algal cells, which as the best algal diet based on its total density (25,875±1,142 ind.mL-1); population growth rate (0,163±0,022 d-1); and egg production (3,446±0,363 eggs.ind-1) was better than N. oculata (P<0,05). The results of the second experiment showed that with 50%:50% combination of T. chuii and FOM was confirmed as the best treatment (P<0,05) based on its total density (38,183±3,595 ind.mL-1); population growth rate (0,82±0,005 d-1); and egg production (2,418±0,031 eggs.ind-1).

Defining Seasonal Functional Traits of a Freshwater Zooplankton Community Using δ13C and δ15N Stable Isotope Analysis

Functional-based approaches are increasingly being used to define the functional diversity of aquatic ecosystems. In this study, we proposed the use of δ13C and δ15N stable isotopes as a proxy of zooplankton functional traits in Lake Maggiore, a large, deep subalpine Italian lake. We analyzed the seasonal pattern of δ13C and δ15N signatures of different crustacean zooplankton taxa to determine food sources, preferred habitats, and trophic positions of species throughout one year. The cladocerans Daphnia longispina galeata gr., Diaphanosoma brachyurum, and Eubosmina longispina were grouped into a primary consumer functional group from their δ13C and δ15N isotopic signatures, but while the former two species shared the same food sources, the latter exhibited a more selective feeding strategy. Cyclopoid copepods occupied a distinct functional group from the other secondary consumers, being the most 15N enriched group in the lake. The δ15N signature of calanoid copepods showed trophic enrichment in comparison to Daphnia and Eubosmina and linear mixing model results confirmed a predator-prey relationship. In our study, we have demonstrated that the use of δ13C and δ15N stable isotopes represented an effective tool to define ecological roles of freshwater zooplankton species and to determine functional diversity in a lake.

Dynamics of small-sized Cladocera and their algal diet in lake with toxic cyanobacterial water blooms

Species composition and quantitative structure of small-sized Cladocera community and their algal diet before, during and after cyanobacterial blooms were studied in highly eutrophic lake. The objective of the study was to investigate, how the mass development of toxin-producing cyanobacteria affect the abundances of small-sized Cladocera and their preferences within consumed algal cells. Cyanobacterial blooms were predominantly constituted by microcystin-producing genera Planktothrix, Dolichospermum, Microcystis. The concentration of intracellular microcystins in lake water ranged 0.0–23.61 μg dm−3. Bosmina longirostris, B. coregonii, Diaphanosoma brachyurum and Daphnia cucullata were dominant in Cladocera community. The highest abundances of B. longirostris occurred in periods without cyanobacterial blooms and B. coregonii during blooms and after them. The maximum abundances of D. cucullata were observed before and after the cyanobacterial blooms, while the abundance of D. brachyurum was the highest at the beginning of blooms. Small Bacillariophyceae, small Chlorophyceae and Cryptophyceae were the most abundant among identified algal cells detected in digestive tracts of the Cladocera dominants. Tracts of D. cucullata, B. longirostris and B. coregonii contained the highest number of Bacillariophyceae always before blooms. During cyanobacterial blooms, cells of small Chlorophyceae predominated in tracts of D. cucullata. After bloom, cells of Cryptomonas spp. were mainly consumed both by D. cucullata and by B. coregonii. Fragments of Dolichospermum spp., besides Bacillariophyceae and Cryptomonas spp. cells, were occasionally found in tracts of D. brachyurum. Our study indicated that blooms constituted by toxin-producing cyanobacteria may influence quantitative and qualitative structure of the small-sized Cladocera community.

Subfossil Cladocera from surface sediment reflect contemporary assemblages and their environmental controls in Iberian flatland ponds

Cladoceran subfossils from surface sediments have been recognized as useful and reliable ecological indicators in freshwater ecosystems. Nevertheless, investigations concerning the relationships between contemporary and sedimentary assemblages are scarce in the Mediterranean region and no studies are available from Iberian flatland ponds. Here, we explore the concordance between present-day Cladocera assemblages and their sedimentary remains from 25 ponds distributed across a vast heterogeneous region in the Iberian Plateau. Overall, this study aims at identifying sediment biological proxies with good capacity to track long-term changes in Iberian flatland ponds. We found a total of 15 and 18 taxa in the contemporary and sedimentary samples, respectively, with daphniids dominating water column samples whereas the majority of the remains recovered from surface sediments were from chydorids. In accordance with previous work, we found that subfossil Cladocera properly reflect the contemporary assemblages from which they are derived. Similarly, our results showed not only analogous environmental controls structuring contemporary and sedimentary assemblages (mainly pH and soluble reactive phosphorous), but also a similar proportion of explained variance in the two. Although there were several taxa occurring only in contemporary samples (Diaphanosoma brachyurum, Moina rosea, Macrothrix hirsuticornis, Scapholeberis sp. and Simocephalus sp.), we found that subfossil assemblages were significantly more rich, diverse, equitable and heterogeneous, indicating that an integrated sample of surface sediment from each pond may supply enough information for assessing cladoceran composition and the numerous drivers controlling their assemblage structure.

Exposure and effects of sediment-spiked fludioxonil on macroinvertebrates and zooplankton in outdoor aquatic microcosms

Information from effects of pesticides in sediments at an ecosystem level, to validate current and proposed risk assessment procedures, is scarce. A sediment-spiked outdoor freshwater microcosm experiment was conducted with fludioxonil (lipophilic, non-systemic fungicide) to study exposure dynamics and treatment-related responses of benthic and pelagic macroinvertebrates and zooplankton. Besides blank control and solvent control systems the experiment had six different treatment levels (1.7–614mga.s./kg dry sediment) based around the reported 28-d No Observed Effect Concentration (NOEC) for Chironomus riparius (40mga.s./kg dry sediment). Twelve systems were available per treatment of which four were sacrificed on each of days 28, 56 and 84 after microcosm construction.Fludioxonil persisted in the sediment and mean measured concentrations were 53–82% of the initial concentration after 84days. The dissipation rate increased with the treatment level. Also exposure concentrations in overlying water were long-term, with highest concentrations 28days after initiation of the experiment. Sediment-dwelling Oligochaeta and pelagic Rotifera and Cladocera showed the most pronounced treatment-related declines. The most sensitive sediment-dwelling oligochaete was Dero digitata (population NOEC 14.2mga.s./kg dry sediment). The same NOEC was calculated for the sediment-dwelling macroinvertebrate community. The most sensitive zooplankton species was the cladoceran Diaphanosoma brachyurum (NOEC of 1.6μga.s./L in overlying water corresponding to 5.0mga.s./kg dry sediment). At the two highest treatments several rotifer taxa showed a pronounced decrease, while the zooplankton community-level NOEC was 5.6μga.s./L (corresponding to 14.2mga.s./kg dry sediment). Zooplankton taxa calanoid Copepoda and Daphnia gr. longispina showed a pronounced treatment-related increase (indirect effects). Consequently, an assessment factor of 10 to the chronic laboratory NOECs of Chironomus riparius (sediment) and Daphnia magna (water) results in a regulatory acceptable concentration that is sufficiently protective for both the sediment-dwelling and pelagic organisms in the microcosms.

Struktur Komunitas Zooplankton di Bendungan Telaga Tunjung, Kabupaten Tabanan-Bali

Zooplankton are the heterotroph aquatic organisms and has a week swimming. Zooplankton acts as the first consumer in the waters, which utilize phytoplankton as their food. This research located in Telaga Tunjung reservoir, Timpag Village, Kerambitan Subdistrict, Tabanan Regency. The reservoir is used for industry, irrigation and tourism development. The aim of the research was to determine the community structure of zooplankton in Telaga Tunjung reservoir. This research was conducted from January to February 2016. Water sampling was conducted twice with a sampling interval of 2 weeks in 4 stations. There was a total of 23 species of zooplankton found, consisting of 6 classes: Eurotatoria (8 genera), Ciliatea (1 genera), Branchiopoda (4 genera), Monogononta (1 genera), Tubulinea (1 genera) and Maxillopoda (3 genera). The most common species of zooplankton found in the sampling station were Polyarthra vulgaris (3.04 ind/l), Anuraeopsis coelata (1.28 ind/l), Keratella valga (0.43 ind/l), Vorticella sp. (0.49 ind/l), Diaphanosoma brachyurum (0.28 ind/l), Nauplius sp. (0.16 ind/l) and Megacyclops viridis (1.16 ind/l). The average abundance of zooplankton was 9.38 ind/l. Based on the abundance of zooplankton, the trophic status of Telaga Tunjung reservoir is mesotrophic.

Effects of common carp (Cyprinus carpio) and bream (Abramis brama) on the structure of the littoral community in a mesotrophic lake (Mesocosm Experiments)

The effect of common carp and bream on hydrochemical parameters, abundance, and structure of phyto-, zooplankton, and macrozoobenthos has been studied in semienclosed mesocosms installed in the littoral zone of a mesotrophic lake. Significant differences in the biomass of different algal groups in mesocosms with fish in respect to the control were established only for diatoms and were not found for other phytoplankton groups. Common carp had a greater effect on the abundance of large zooplankton species (Diaphanosoma brachyurum) compared to bream. The abundance of the small Bosmina longirostris increased in mesocosms both with bream and common carp. The macrozoobenthos biomass reduced at higher rates in mesocosms with common carp than in those with bream, with the strongest effect of common carp on mayfly larvae. The differences between the consumption of chironomid and oligochaete larvae were not established in mesocosms with common carp. Bream mainly affected the larvae of mayflies and oligochaetes and, to a lesser degree, the chironomid larvae.

Comparative Study of Present and Past Cladoceran Diversity in Manasbal Lake of Kashmir (India)

Present research was carried out to study the diversity of Cladocera in Manasbal Lake and compare it with previous studies. In present study, 21 species of cladocerans were recorded belonging to 5 families: Chydoridae, Daphnidae, Bosminidae, Macrothricidae and Sididae. Chydorids were responsible for major cladoceran diversity followed by daphnids. The frequently species found were Chydorus sphaericus, Graptoleberis testudinaria, Daphnia pulex, Ceriodaphnia reticulata and Bosmina longirostris. While comparing the cladoceran diversity of present study with earlier studies, many species present earlier were not found in present study due to increasing pollution of the lake. However, five species (Chydorus sphaericus, Graptoleberis testudinaria, Bosmina longirostris, Sida crystallina and Diaphanosoma brachyurum) recorded earlier were still present and were reported by all authors. This depicted that these species can tolerate wide range of fluctuations in environmental changes. Further, Daphnia pulex was not recorded in earlier studies but was recorded latter which also showed increased pollution in the lake as this species prefers polluted water. Environmental changes have great influence on distribution of cladocerans and therefore, they act as excellent indicators of pollution.

Effect of hydrophyte thickets density on zooplankton

An experimental study on the zooplankton community in the thickets of elodea Elodea canadensis Michx. of different densities (2, 4, and 8 g/L, wet weight/L) has been conducted. It is revealed that specific cationic composition and pH and sharp daily fluctuation of oxygen concentrations is a characteristic of the water in dense thickets of plants. Changes in water chemistry and in spatial organization of the environment influence zooplankton diversity and population dynamics of some species. With an increase in density of thickets, the number of Daphnia longispina O.F. Muller decreases, while the share of predators (Cyclopidae and Polyphemus pediculus O.F. Muller) increases. The abundance of Ceriodaphnia quadrangula (O.F. Muller) increases in the presence of plants, but does not depend on the density of the thickets. The correlation between the development of Simocephalus vetulus (O.F. Muller) and Diaphanosoma brachyurum (Lievin) and water cationic composition, changing in the process of growth and senescence of plants, is revealed.

Microcrustacean (Cladocera, Copepoda) source-sink dynamics in a lowland river ecosystem with a dam reservoir

Abstract Dispersal of crustacean zooplankton from a reservoir in a lowland river was observed over a relatively long distance. Zooplankton samples were collected by a unique technique from “the same water”. Large Cladocera (Daphnia cucullata and Diaphanosoma brachyurum) showed the greatest reduction in a river, but they were common over a distance of up to 130 km below a dam. These two planktonic species revealed a low potential for colonizing oxbow lakes. Eurytopic Chydorus sphaericus and Mesocyclops leuckarti transferred from the Siemianówka Reservoir had a great dispersal capacity in the Narew River and could effectively support local populations in oxbow lakes over a distance of 180 km. Similarity between the crustacean communities in the river and the reservoir significantly decreased with the increasing distance from the dam. At the same time, crustacean communities in oxbow lakes were not affected by the distance from the source. Dispersal from the large source of zooplankton to local communities is a very important process but the local environmental factors such as habitat heterogeneity, aquatic vegetation and the hydrological connectivity can be strong enough to affect the structure of local crustacean communities in oxbow lakes.

Succession of Phytoplankton and Zooplankton Communities Coupled to Environmental Factors in the Oligo-mesotrophic Nabhana Reservoir (Semi Arid Mediterranean Area, Central Tunisia).

Ikbel Sellami, Asma Hamza, Monia El Bour, Mohammed Alaoui Mhamdi, Bernadette Pinel-alloul, and Habib Ayadi (2016) The occurrence of plankton seasonal dynamics in Mediterranean shallow lakes is characterised by a marked interannual variability, which makes it difficult to establish reliable predictions on the dynamics and functioning of plankton in these ecosystems based on the Plankton Ecology Group (PEG) model. In the present paper we study the succession of the phytoplankton and zooplankton communities in the semi-arid Mediterranean Nabhana reservoir (Central Tunisia) and its relationships with environmental factors during the period from May 2005 to January 2006 in the deepest area of this oligo-mesotrophic reservoir. Water temperature was a keystone factors in the seasonal dynamics of zooplankton. Cyanobacteria dominated the phytoplankton community throughout the study year 2005-2006 (94-99%) and Microcystis aeruginosa contributed for 93% of the total cyanobacteria abundance. The zooplankton community was dominated by copepods (66%) and cladocerans (28%). The dominant species was Copidodiaptomus numidicus (66% of total zooplankton) followed by Diaphanosoma brachyurum (22% of the total zooplankton). In addition, our results showed that the peak of phytoplankton abundance (5.6 ×106 cells l-1, June) coincided with that of zooplankton abundance (2.1 ×102 ind l-1, June) contrary to the clear-water phase model. The cyanobacteria and copepods were responsible for these exceptional peaks that occurred in June, accounting respectively for 99% of the total phytoplankton and 82% of the total zooplankton. In the Nabhana reservoir, the trophic relationship between phytoplankton and zooplankton were implicated in the phytoplankton abundance and dynamics. The occurrence of cyanobacterial blooms is determined by biotic and abiotic factors. The dynamics between cyanobacteria and their grazers may emerge as a regulator of blooms.