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To better understand zooplankton dynamics in Lake Ontario’s Toronto Harbour and adjacent coastal area (CA), we sampled zooplankton, phytoplankton, nutrients and physical parameters on six dates in 2016. Despite higher levels of nutrients, chlorophyll and primary production in the inner harbor (IH), the areas supported similar May to November zooplankton biomass (IH = 32 ± 7 and CA = 42 ± 10 mg/m3). IH values were much lower than other nutrient-enriched embayments in Lake Ontario, yet CA biomass was twice that of nearshore sites away from Toronto. Small zooplankton such as rotifers and Bosmina dominated IH; and large taxa (Daphnia, calanoids and predatory cladocerans) were more important in the CA. Daphnia, Bosmina, cyclopoids and calanoids were larger in the CA, and adult cyclopoids had higher egg ratios. This led to low annual IH production estimates for both cyclopoid and calanoid copepods. Total phosphorus and chlorophyll did not appear to regulate zooplankton biomass, but positive relationships were found with bacterial biomass in the IH and with temperature in the cool season. Atypically high fish planktivory rates likely suppressed larger IH zooplankton in 2016, allowing small, resilient Bosmina to flourish and contribute 84% of total production in the IH. Comparing 2016 data to previous zooplankton surveys revealed considerable inter-annual variation in proportions of Daphnia, Bosmina and predatory cladocerans over the 1994 to 2016 period, and the strong top-down controls observed in 2016 were not typical. Elevated microbial production may serve as an important alternate trophic pathway supporting cladoceran populations in Toronto Harbour.

In Yellowknife (Northwest Territories, Canada), roaster stack emissions from historic gold mining activities, particularly Giant Mine (1948–2004), have left a legacy of arsenic contamination in lakes. We examined Cladocera (Branchiopoda, Crustacea) subfossil remains in the recent and pre-industrial sediments of 23 lakes (arsenic gradient of 1.5–750 µg/l) within a 40 km radius of Giant Mine to provide a snapshot of regional change in Cladocera since pre-1850. We found that littoral and benthic taxa dominated the recent assemblages in high-[As] lakes (surface water [As] > 100 µg/l), while pelagic Bosmina was dominant in lakes with lower [As]. Cladocera richness and diversity were positively correlated with [As] (P = 0.004, R2 = 0.39; and P = 0.002, R2 = 0.46, respectively), except for four lakes with [As] > 100 µg/l. The lakes that showed the most pronounced changes in Cladocera since pre-1850 were those affected by both metal(loid) pollution and urban development, where complete shifts in the dominant taxa occurred. Lakes that were most heavily impacted by arsenic emissions did not experience notable shifts in Cladocera assemblages. Our study suggests that changes in Cladocera assemblages in mining-impacted subarctic lakes are modulated by local, lake-specific limnological conditions and the interaction of multiple stressors.

Coastal wetlands are essential to the ecosystem health of the Laurentian Great Lakes (North America) watershed. Multiple anthropogenic stressors have been impacting coastal wetlands since European settlement ca. 1850, and remain a concern for wetland health as watershed development intensifies. We used paleolimnological techniques to explore temporal ecosystem dynamics over the last ~ 100 years in two highly degraded Lake Ontario coastal wetlands located in southern Ontario, Canada, using Cladocera (Branchiopoda, Crustacea) subfossil remains as paleoecological indicators. In Cootes Paradise Marsh (Hamilton, Ontario), cladoceran assemblage changes exhibited a shift in dominance from Chydorus to Bosmina, at the turn of the twentieth century. That shift likely reflected the loss of aquatic macrophytes, and corresponds to the postulated timing of the arrival of invasive carp. Despite recent remediation efforts, including attempts to exclude carp from the wetland, little ecological recovery is evident from the subfossil Cladocera assemblage. No Daphnia remains were observed in our sediment core from Cootes Paradise, in contrast to previous studies on extant zooplankton communities, which reported a large Daphnia population in the west end of the marsh in the 1940s. This could indicate that our sediment core recorded ecological changes solely in the east end of Cootes Paradise Marsh. In Jordan Harbour (Lincoln, Ontario), Bosmina were dominant throughout the sediment record, and increases in littoral cladocerans were observed in the most recent sediments, in particular the appearance of periphytic Pleuroxus taxa after ~ 2008. This suggests that some recovery of aquatic macrophyte communities occurred in response to shoreline remediation efforts. Bosmina size structure exhibited only minimal changes in both wetlands, despite known large changes in historic fish community structure. Overall, our study provides perspectives on the benefits and limitations of paleolimnology for documenting ecological change in the Laurentian Great Lakes coastal wetlands.

An increase in nutrient levels due to eutrophication has considerable effects on lake ecosystems. Cladocerans are intermediate consumers in lake ecosystems; thus, they are influenced by both the bottom‐up and top‐down effects that occur as eutrophication progresses. The long‐term community succession of cladocerans and the effects cladocerans experience through the various eutrophication stages have rarely been investigated from the perspective of the early‐stage cladoceran community assemblage during lake formation. In our research, long‐term cladoceran community succession was examined via paleolimnological analysis in the currently eutrophic Lake Fukami‐ike, Japan. We measured the concentration of total phosphorus and phytoplankton pigments and counted cladoceran and other invertebrate subfossils in all layers of collected sediment cores, and then assessed changes in the factors controlling the cladoceran community over a 354‐year period from lake formation to the present. The cladoceran community consisted only of benthic taxa at the time of lake formation. When rapid eutrophication occurred and phytoplankton increased, the benthic community was replaced by a pelagic community. After further eutrophication, large Daphnia and high‐order consumers became established. The statistical analysis suggested that bottom‐up effects mainly controlled the cladoceran community in the lake's early stages, and the importance of top‐down effects increased after eutrophication occurred. Total phosphorus and phytoplankton pigments had positive effects on pelagic Bosmina, leading to the replacement of the benthic cladoceran community by the pelagic one. In contrast, the taxa established posteutrophication were affected more by predators than by nutrient levels. A decrease in planktivorous fish possibly allowed large Daphnia to establish, and the subsequent increase in planktivorous fish reduced the body size of the cladoceran community., In this research, we examined the long‐term changes of a cladoceran community from the early stage of lake formation by using paleolimnological methods. Our results suggested that the cladoceran community firstly consisted only of benthic taxa, and subsequent rapid eutrophication caused the replacement of benthic community species to planktonic pelagic ones. In addition, artificial introduction of fish possibly caused the change of predator community, leading to the increase in top‐down effect on the cladoceran community.

Los estudios sobre hábitos alimentarios de comunidades acuáticas ayudan a entender cómo estas interactúan, y considerando que los peces de páramo han sido muy poco investigados, se analizó la dieta y se contribuyó al entendimiento de la ecología trófica de Grundulus quitoensis, especie endémica de los andes del Ecuador. Se estudió el contenido estomacal de 26 ejemplares de la laguna El Voladero. Se identificaron doce categorías de presa, de las cuales, el género Bosmina (Crustacea: Cladocera) (Ni = 2410; Fo = 22) y entidades de la familia Chironomidae (Insecta: Diptera) (Ni = 466; Fo = 46) presentan la mayor abundancia. El factor de condición alométrico (K) obtuvo valores entre 0,11–0,77, significando que los ejemplares se encontraban en condiciones de poca alimentación. Aunque la dieta de esta especie es amplia, consume en gran cantidad insectos y microcrustáceos. Es necesario preservar la laguna El Voladero para conservar su biodiversidad única.

Dormancy is an essential component of the life cycle for populations that disappear from the plankton during winter. The hatching of resting eggs is the main mechanism for restoring active population components. Here, we analyzed the hatching dynamics of zooplankton from sediments of a shallow lake as affected by temperature. Sediment samples collected every other month were incubated at in situ temperatures and at 20°C. The highest number of individual's hatchings was observed for copepod nauplii, the cladoceran Bosmina sp., and the rotifer Brachionus havanaensis. Temperature showed a positive significant effect on the hatchlings of B. havanaensis. Other zooplankton species were less affected by temperature, and there was no relationship between their emergence from the incubated sediments and occurrence in the water column. We also tested the effect of short-term (6 and 12 weeks) and long-term (a year) storage duration on hatching success. The hatching success of B. havanaensis was not affected by the storage time. In contrast, the hatchlings of Bosmina sp. and nauplii increased after short storage time. The evidence collected here suggests that many zooplankters were not affected by temperature, while for B. havanaensis temperature turned out to be a master variable that links planktonic and passive phases.

Fish larvae play an important structuring role for their prey and show ontogenetic shifts in diet. Changes in diet differ between species and habitats and may also be affected by turbidity (eutrophication). We investigated the diet (stomach content) and the food selection (ratio of ingested prey and prey availability) of roach and perch larvae in a clear lake and of roach, perch and pikeperch larvae in a turbid lake multiple times during spring to autumn. The diet of the fish larvae changed with size, and for roach and perch larvae between the lakes. Coexisting species of fish larvae had different diets in the two lakes, pointing to resource partitioning; yet, in the clear lake, medium-sized larvae had a high diet overlap, suggesting a competitive relationship at this developmental stage. In the clear lake, roach larvae showed diel differentiation in diet, while perch demonstrated diet shifts between habitats, which probably aided in reducing competition and also evidenced an effect of light on the larval prey capture and/or predator-fish larvae interactions. In the turbid lake, roach and perch larvae did not reveal differences in diet between habitats or time of the day, owing to homogeneity of food items and poor light conditions. However, the diet of pikeperch larvae differed between day and night following daily variations in the abundance of its preferred prey. The roach larvae were highly selective for Bosmina, Daphnia and benthic cladocerans, perch larvae generally consumed what was available, while pikeperch primarily preyed on cyclopoid copepodites. We conclude that turbidity acted as a cover for fish larvae in the turbid lake. Under eutrophication-induced turbidity scenarios the effects of fish larvae on their prey are stronger (i.e., high selectivity for several resources) than that of larvae in clear waters, creating a negative feedback on the path to restore water clarity. (c) 2021 Elsevier B.V. All rights reserved.

Fish predation can structure zooplankton communities; however, the impacts of other organisms on zooplankton communities, alone or interacting with fish predation, are less known. We used two mesocosm experiments to study the impacts of Bluegill (Lepomis macrochirus) and tadpoles on temperate zooplankton communities, one with American Toad tadpoles (Anaxyrus americanus) and the other with Bullfrog tadpoles (Lithobates catesbeianus). In both experiments Daphnia (a larger bodied cladoceran) were virtually eliminated and rotifers were more abundant with Bluegill. Bluegill slightly reduced cyclopoid copepods in the American Toad experiment but not significantly, whereas cyclopoid copepods were more abundant with Bluegill in the Bullfrog experiment. Bosmina (a smaller bodied cladoceran) in the Bullfrog experiment were more abundant when Bluegill were absent, but there was no significant effect of Bluegill in the American Toad experiment. Tadpoles in general had no effect on our zooplankton communities. Our experiments confirm the influence of Bluegill on zooplankton communities, whereas tadpoles of the two anuran species had no widespread effects on zooplankton.

Bosmina (Liederobosmina) korineki sp.nov. (Figures 1���4) Etymology. The taxon is named after Professor Vladim��r Koř��nek (1934���2019) (see Fott 2019), who detected this taxon in the Andean samples and send the samples to AAK for their detailed study. Type locality. Laguna Chisaca (N 4.28��, W 74.21��; 3709 m.a.s.l.), Distrito Capital de Bogot��, Colombia. Type material. Holotype. A parthenogenetic female in 96% alcohol, MGU Ml 240 in the Collection of Moscow State University, Moscow, Russia. Label of holotype: ��� Bosmina korineki sp.nov., 1 parth. ♀ from Laguna Chisaca, Colombia, HOLOTYPE ���. Paratypes. 4 parthenogenetic females, MGU Ml 241. 4 parthenogenetic females, AAK 2020-017 in the personal collection of A.A. Kotov, Moscow, Russia. The type series was collected in 10.01.1990 by S. Gaviria. Other material studied. 16 females from Embalse de Neusa (N 5.16��, W 73.95��; 2967 m.a.s.l.), Cundimarca Province, Colombia, collected in 15.03.1999 by P. Alvarez in the personal collection of V. Koř��nek, sent to the collection of the Natural History Museum, London, United Kingdom. Description. Parthenogenetic female. Body short and wide in lateral view in adults (Figs 1A, 2A���B, 3A) and more elongated in juveniles (Figs 1B, 3B); dorsal margin regularly curved from distalmost extremity to posterodorsal angle; posterior margin straight, its height about half of body height; ventral margin almost straight, with a shallow depression anterior to mucro. Sculpture as a strong striation on head and on valves (Fig. 2A���E, I), but not on head shield. Head without ocular dome and without a pre-ocular depression; rostrum very short, rounded. Frontal head pore small, located slightly dorsally to the level of antennae I (Fig. 3C���D: fhp). Median head pore minute (Fig. 3A, D: mhp), located posteriorly to ocular capsule. Fornix well-developed, covering coxal part of antenna II. Lateral head pore small (Figs 2E���G. 3C, E: lhp), with a raised ring-like margin, located at a great distance from ventral margin of head shield (fornix, Fig. 3C: fnx), dorsally to the level of mandibular articulation. Compound eye of moderate size. Labrum as a fleshy appendage lacking significant projections, distal labral plate small. Anterior portion of ventral valve margin with a series of stout setae. Seta kurzi with small setulae, located on internal side of valve anterior to abovementioned depression near mucro, which is strong and long even in large adults; no incisions on ventral side of mucro (Fig. 3F), while some incisions present on dorsal side of mucro in some juveniles (Fig. 3B). On inner side of mucro, there are several relatively strong denticles, as a continuation of a series of setulae at posterior valve margin. Thorax relatively long, with 6 limb pairs, abdomen short, with transverse rows of setulae (Fig. 3G). Postabdomen strongly compressed laterally, with width approximately equal along all its length, with ventral (functionally dorsal!) margin straight. Preanal margin with groups of setulae; sides of postabdomen supplied with series of finer setulae. Distal (anal) margin nearly directly truncated. Postanal portion as a cylindrical projection bearing paired postabdominal claws. Each claw regularly bent, with two pectens on concave (dorsal) margin, distal pecten consists of fine setulae, while proximal pecten consists of 7���9 rather strong, sparsely located teeth. Postabdominal seta shorter than preanal margin; its distal segment about two times shorter than proximal one, supplied with fine, long setulae. Antenna I fused with rostrum; its body relatively short; its length from tip to tip of rostrum about 0.3���0.4 body lengths (Fig. 3A���B). Antennular (frontal) sensory seta located on head surface. Free part of antenna I consists of a pre-aesthetasc portion, fused with head, and post-aesthetasc portion, presence of which is a unique synapomorphy of Bosmina (Kotov et al., 2009). Nine aesthetascs delicate, slightly differing in size. Post-aesthetasc portion directed ventrally and somewhat posteriorly, almost straight. Both portions supplied with crossing series of fine denticles. Antenna II typical for the genus (Figs 2H, 3C). Six pairs of thoracic limbs with morphology indistinguishable from that in other species (Kotov, 1995). Limb I with epipodite bearing a finger-like projection (Fig. 4A: epp). Outer distal lobe (Fig. 4A���B: odl) cylindrical, bearing a long distal seta and a long lateral seta. Subdistal lobe with a single seta of unclear homology; limb corm with six setae of unclear homology and a pair of ejector hooks (Fig. 4A���B: ejh). Distal armature of gnathobase with two setulated setae (Fig. 4A: dag). Limb II with epipodite bearing a long finger-like projection (Fig. 4C: epp). Exopodite fully reduced. Limb corm with an inner-distal lobe bearing a single anterior (1) and single posterior (a) setae; the rest of inner-distal limb portion with seven anterior (2���8) and five posterior (b���f) setae; seta 8 armed by strong denticles varying in size among specimens from same population (Fig. 4C���D). Gnathobase with distal armature of four setae (Fig. 4E���F: 1���4); seta 1 represents a sensillum. Filter plate with six setae (Fig. 4C: a���f). Limb III with epipodite having a finger-like projection (Fig. 4G: epp). Exopodite subrectangular, with five distal (1���5) and two lateral (6���7) setulated setae. Distal endite (in terms of Kotov 2013) with three anterior setae (Fig. 4G: 1���3); proximal endite with three setae (Fig. 4H: 4���6). Eight setae (a���h) on posterior limb face. Distal armature of gnathobase with four elements (Fig. 4H���I: 1���4), including a sensillum (1). Filter plates with six setae (a���f). Limb IV with ovoid densely setulated preepipodite (Fig. 4J: pep) and epipodite (Fig. 4J: epp) supplied by a finger-like projection. Exopodite (Figure 4J: ext) rounded, bearing two distal (1���2) and six lateral (3���8) setae. Inner distal portion of limb IV with four anterior setae strongly decreasing in size proximally (Figure 4K: 1���4) and four small posterior setae (a���d). Distal armature of gnathobase with four setae (Fig. 4K: 1���4). Filter plate with four setae (a���d). Limb V with densely setulated preepipodite (Fig. 4L: pep) and ovoid epipodite (epp) supplied by a long fingerlike projection. Exopodite with two distal setae (1���2) and three lateral setae (3���5). Inner limb portion as elongated, flat lobe, with setulated margin. Distal armature of gnathobase with three setae (Fig. 4L: 1���3). Limb VI represented by epipodite only (Fig. 4M: epp). Ephippial female, male. Unknown. Size. Total length (without mucro) 0.45���0.62 mm. Differential diagnosis. Our new species belongs to the subgenus B. (Liederobosmina) having: (1) lateral head pore located dorsally to the level of mandibular articulation; (2) incisions on the dorsal side of mucro in juveniles (see Lieder 1983b; Kotov et al. 2009). This taxon is unique among all the taxa of Bosmina (Liederobosmina) having heavily striated valves. Paggi (1979) recognized three species from this subgenus in South America. B. (L.) korineki sp. nov. has no elongated flattened rostrum as B. (L.) huaronensis Delachaux, and has no pre-ocular depression as B. chilense Daday. To date, we can only say that it differs from B. hagmanni Stingelin only in striated valves in the females as the males are unknown, but they possess most diagnostic characters in the bosminids (Kotov et al. 2009). Distribution. To date the taxon is known only from two large, deep high mountain lakes in Colombia. Embalse de Neusa is an artificial reservoir with surface of over 955 ha, maximum depth of 50 m and mean depth of 10 m. Secchi depth ranges from 3.6 m to 1.5 m; the lake is considered as oligo mesotrophic (Carrillo et al. 2006). We did not find in previous literature any descriptions which could be attributed to B. (L.) korineki sp.nov., although different bosminids were noted in many papers on the Neotropical fauna. Most probably, this taxon has a narrow distribution area in the Andean high mountains., Published as part of Garibian, Petr G., Jura��ka, Petr Jan & Kotov, Alexey A., 2021, A new species of Bosmina (Liederobosmina) Brt��k, 1997 (Cladocera: Bosminidae) from high mountain lakes of Colombia, pp. 280-290 in Zootaxa 4990 (2) on pages 281-287, DOI: 10.11646/zootaxa.4990.2.4, http://zenodo.org/record/5026407, {"references":["Fott, J. (2019) Vzpominky na Vladimira Korinka, pana profesora, vazeneho kolegu a mileho pritele. Limnologicke Noviny, 2019, 4 - 6.","Kotov, A. A., Ishisa, S. & Taylor, D. J. (2009) Revision of the genus Bosmina Baird, 1845 (Cladocera: Bosminidae), based on evidence from male morphological characters and molecular phylogenies. Zoological Journal of the Linnean Society, 156, 1 - 51. https: // doi. org / 10.1111 / j. 1096 - 3642.2008.00475. x","Kotov, A. A. (1995) Structure of the thoracic limbs in Bosmina Baird, 1845 (Crustacea Anomopoda). Arthropoda Selecta, 4 (3 - 4), 41 - 50.","Kotov, A. A. (2013) Morphology and phylogeny of the Anomopoda (Crustacea: Cladocera. KMK Press, Moscow, 638 pp.","Lieder, U. (1983 b) Revision of the genus Bosmina Baird, 1845 (Crustacea, Cladocera). Internationale Revue der gesamten Hydrobiologie und Hydrographie, 68, 121 - 139. https: // doi. org / 10.1002 / iroh. 19830680108","Paggi, J. (1979) Revision de las especies argentinas del genero Bosmina Baird agrupadas en el subgenero Neobosmina Lieder (Crustacea: Cladocera). Acta Zoologica Lilloana, 35, 137 - 162.","Carrillo, Y., Guarin, A., & Guillot, G. (2006) Biomass distribution, growth and decay of Egeria densa in a tropical high-mountain reservoir (NEUSA, Colombia). Aquatic Botany, 85 (1), 7 - 15. https: // doi. org / 10.1016 / j. aquabot. 2006.01.006"]}

Insufficient attention has been recently paid by the taxonomists to the family Bosminidae Baird (Crustacea: Cladocera). Here we describe a new species of Bosmina (Liederobosmina) Brték from high mountain water bodies of Colombia which is unique among all bosminids having heavily striated valves. Most probably, this taxon has a narrow distribution area in the Andean high mountains. It is obvious that the Andean highlands must be studied in detail, i.e. using molecular methods, and more new taxa might be detected in the future.

Multiple biogeochemical variables in a sediment core from Lake Lugu in southwest China were studied to investigate the effects of regional environmental changes on the ecosystem. Subfossil Cladocera, together with diatom, pollen and geochemical records, were used to examine climate-induced changes in lake ecosystem since the Last Glacial Maximum (30 000–0 cal year BP). Consistency among these biological records indicates that the succession of zooplankton, algae and vegetation changed in response to direct and indirect climatic factors. Alterations in the nutrient supply mediated by climate-induced changes in vegetation and soil processes are likely responsible for the variability of cladocerans. During the Last Glacial Maximum, cladocerans were dominated by littoral taxa (e.g. Alona), indicating an unproductive and oligotrophic lake system. A peak distribution in the pelagic Bosmina highlights the period of increased nutrient availability at 11 500 cal year BP. The ecological changes in Cladocera at 19 000 cal year BP and diatom communities at 18 000 cal year BP reveal independent and indirect responses to nutrient and light conditions induced by solar radiation and increased monsoon intensity across the study region. The palaeoecological archives from Lake Lugu sediments highlight a complex lake ecosystem influenced by both direct and indirect changes corresponding to climate changes and shifts in regional anthropogenic pressure over the last 30 000 years.

Density estimation of pelagic fish was performed by means of single beam echosounding in 17 lakes within a period of 34 years, from 1985 to 2018. Surveys were performed repeatedly (two to fourteen times) in five lakes. The density estimates ranged from 34 to 4720 fish/ha and were significantly correlated with total phosphorus concentration. The high density in relatively phosphorus rich lakes (TP &gt, 10 µg/L) was comprised of small fish (&lt, 20 cm) and was partly due to the higher number of pelagic fish species. The number of pelagic species varied from one, Arctic charr, in the most elevated and oligotrophic lakes, and whitefish dominated in less elevated oligotrophic lakes. In lowland lakes characterized as mesotrophic or tending to mesotrophy, smelt, vendace, and two to three cyprinids comprised the pelagic fish stock. These fish species predate zooplankton effectively, and species composition and body size of planktonic cladocerans was affected by fish density. Large species of Daphnia were lacking in lakes with high fish density, and body size of present species, D. galeata, D. cristata, and Bosmina spp. were negatively correlated with pelagic fish density.

Water fleas (Crustacea: Cladocera) of the Family Bosminidae have been studied since the founding of paleolimnology and freshwater ecology. However, one species,Bosminopsis deitersi, stands out for its exceptional multicontinental range and broad ecological requirements. Here we use an integrated morphological and multilocus genetic approach to address the species problem inB. deitersi. We analyzed 32 populations ofB. deitersis. lat. Two nuclear and two mitochondrial loci were used to carry out the bGMYC, mPTP and STACEY algorithms for species delimitation. Detailed morphological study was also carried out across continents. The evidence indicated a widely distributed cryptic species in the Old World (Bosminopsis zernowi) that is genetically divergent fromB. deitersis.str. We revised the taxonomy and redescribed the species in this complex. Our sampling indicated thatB. zernowihad weak genetic differentiation across its range. A molecular clock and biogeographic analysis with fossil calibrations suggested a Mesozoic origin for theBosminopsis deitersigroup. Our evidence rejects the single species hypothesis forB. deitersiand is consistent with an ancient species group (potentially Mesozoic) that shows marked morphological conservation. The family Bosminidae, then, has examples of both rapid morphological evolution (HoloceneBosmina), and morphological stasis (Bosminopsis).

In aquatic systems, an interplay between bottom-up and top-down processes determines the dynamic of picocyanobacteria (Pcy) abundance and community structure. Here, we analyzed a 10-year time series (sampled fortnightly) from a hypereutrophic turbid shallow lake located within the Pampa Region of South America, generating the first long-term record of freshwater Pcy from the Southern Hemisphere. We used a cytometric approach to study Pcy community, and focused on its relations with nutrient and light conditions (bottom-up) and potential grazers (top-down). A novel Pcy abundance seasonality with winter maximums was observed for years with relatively stable hydrological levels, related with decreased abundance of seasonal rotifers during colder seasons. Pcy showed lower abundance and higher cytometric alpha diversity during summer, probably due to a strong predation exerted by rotifers. In turn, a direct effect of the non-seasonal small cladocerans Bosmina spp. decreased Pcy abundance and induced a shift from single-cell Pcy into aggregated forms. This structuring effect of Bosmina spp. was further confirmed by Pcy cytometric (dis)similarity analyses from the time series and in situ experimental data. Remarkably, Pcy showed acclimatization to underwater light variations, resembling the relevance of light in this turbid system.

Bosmina is a globally distributed zooplankton that adapts to a eutrophic environment. In this study, we cultivated monoclonal Bosmina fatalis and determined its complete mitochondrial gene sequence using the Illumina HiSeq 4000 platform. It was 15,209 bp in length, including 13 protein-coding genes, 22 tRNA genes, and 2 rRNA genes, with the A + T content (69.2%) significantly higher than the G + C content (30.9%). All 22 typical tRNA genes had a classical cloverleaf structure, except for tRNAIle. The complete mitochondrial genome of nine other cladoceran species was used to reconstruct a phylogenetic tree, showing that B. fatalis has a closer relationship with Daphnia than other cladocerans.

An intensive study of cladoceran diversity in Lake Kud-Thing, a Ramsar site of Bueng Kan Province, Thailand, was conducted. One hundred and twenty-five qualitative samples were collected from 15 localities during the period from June 2012 to November 2014. A total of 58 species belonging to 38 genera was recorded. Three species, Chydorus idrisi Sinev 2014, Karualona kwangsiensis (Chiang 1963) and Streblocerus cf. serricaudatus (Fisher 1849) are new records for Thailand. The most species rich family was Chydoridae (32 species, 55% of the encountered species in the lake) followed by Sididae (8 species, 14%) and Macrothricidae (8 species, 14%) while only a single species of Ilyocryptidae was observed. The most frequently encountered planktonic species were Ceriodaphnia cornuta Sars 1885, Bosmina cf. meridionalis Sars 1904 and Ephemeroporus barroisi (Richard 1894). A newly described chydorid, Anthalona spinifera Tiang-nga, Sinev & Sanoamuang 2016, was also recorded from this lake. The number of cladocerans recorded in this study is remarkably higher than that of previous studies in other natural lakes (17–40 species) within Thailand. In addition to earlier records, the number of cladocerans of Lake Kud-Thing has been updated to 62 species, about two times higher than that of other lakes in this region. Thus, our results suggest that Lake Kud-Thing is one of the biodiversity hotspots for Cladocera of Southeast Asia.

The Bełchatów Lignite Mine of Poland is a treasure-cove for mid-to late Miocene plant and animal fossils, deposited in a slow-flowing river valley with swamps and oxbow lakes. Here, we report the finding of abundant fossil anomopod cladocerans. Some are three-dimensionally preserved, including the taxonomically important trunk limbs. They pertain to the families Chydoridae and Bosminidae, with species similar to but distinct from modern ones. All are members of the zooplankton, though some are littoral while others are pelagic in nature. Morphological stasis in these families is not outspoken as in the Daphniidae and the stasis hypothesis, based on ephippia only, is challenged. The absence of Daphnia is conspicuous and ascribed to a combination of fish predation and local water chemistry. Its place in the oxbow lakes is taken by at least two Bosmina species, one of which is undescribed. We consider this a case of paleo-competitive release. For Bosminidae, these are the first certified fossils predating the Pleistocene.

Mine-fed waters have been rigorously studied, but most of the ecological research on mine water has been conducted in riverine systems. Lakes, however, are known to recover from pollution more slowly than riverine systems and, thus, the impacts of mine water on lakes are equally interesting. One of the most important biological components in lakes are the Cladocera, an order of crustacean zooplankton. Cladocerans are regarded as excellent indicators of environmental change and, for example, genus Daphnia is one of the most used test organisms in ecotoxicology. While in vitro tests regarding pollutants and cladocerans have been reviewed multiple times, the literature regarding the community level responses to mine pollution in natural settings is still to be better explored. The main aim of this paper is to screen and compile the current literature related to cladoceran communities and mine-induced water pollution. In addition, the applicability of cladocerans as a bioindicators group in mine water studies will be explored. This review shows that cladocerans have been studied in many cases of mining related pollution and most of the research has been conducted in North America, central Europe and Brazil. Acidity, turbidity and metals pollution are nearly equally important in shaping cladoceran communities in mining impacted lakes. The most tolerant taxa to mining pollution are Bosmina spp. and Chydorus sphaericus. The group clearly has potential as community level bioindicator/biomonitor in mining pollution studies, but challenges remain. Namely, the lack of data regarding the most sensitive taxa is a major problem when indicator value of any single species is assessed.

A paleolimnological approach was used at 45 mostly remote, low-nutrient lakes in New Brunswick (NB), Canada, to determine bioindicator responses and lake sensitivity to post twentieth century environmental change. From each undated core we assessed zooplankton (Cladocera) change between discrete time periods using related assemblage metrics, including the rise of Bosmina sp., cladoceran richness, and average assemblage body size. Cladocerans from a pre-industrial interval (20–20.5 cm) were compared to those from a present-day interval (0–0.5 cm). Lakes were then classified as either high- or low-sensitivity based on assemblage metrics, and sensitivity group differences in physical–chemical measures were tested for significance. Compared to pre-industrial times, Bosmina sp. relative abundance increased in 33 of 43 lakes (75% of lakes surveyed) by on average 20%. Body size and rarefied species richness of assemblages decreased significantly. These ecological shifts detected at an important intermediate trophic level are attributable to indirect effects of climate change, although we cannot rule out shifts in fish predation and littoral habitat as additional structuring factors. Eighteen lakes were classified as high-sensitivity lakes and showed significant differences in latitude, surface area, elevation, dissolved calcium and magnesium concentrations, and conductivity compared to 25 low-sensitivity lakes. In high-sensitivity lakes, richness decreased on average by 6 species and body size decreased by 0.2 mm. This study presents a historical context for constructing effective conservation and management efforts at a time of substantial environmental change in low-nutrient NB lakes.

Hemimysis anomala is a recent invader to North American aquatic ecosystems and is spreading rapidly throughout the Great Lakes region. This is the first littoral mysid in the North American Great Lakes; and, as such, the ecosystem effects are unknown and could be substantial. These effects depend on the role of Hemimysis in the food web and, therefore, on its diet. We examined the stomach contents of two life stages of Hemimysis from two sites in Lake Ontario during the growing season (May–November 2010). We also report the relationship between zooplankton hard parts and size for a number of potential prey species to allow the back-calculation of prey lengths from stomach contents. Both juvenile (2–5 mm) and adult Hemimysis (5–11 mm) were omnivorous, consuming phytoplankton, zooplankton, and benthos when available. However, adults appeared slightly more carnivorous and incorporated larger prey in their diets. Hemimysis were able to consume zooplankton prey up to 30% of their own length, including Bythotrephes longimanus and Cercopagis pengoi. Daphnia and Bosmina were selected over other prey by both juvenile and adult Hemimysis and were most common in stomachs during July and September when their abundances in the zooplankton were highest. Measurements of δ13C and δ15N corroborated stomach content materials, indicating an omnivorous diet which included benthic and pelagic sources. Omnivory by Hemimysis is typical of mysids in general and makes them less sensitive to seasonal dynamics of preferred prey items.

The vertical distribution of Bomina, Daphnia, Ceriodaphnia, Diaptomus and cyclopoids was studied for a 48 hours period in Arenal Reservoir, Costa Rica. In general the zooplankton decreased during day time across the water colurnn. Daphnia, Diaptomus and the cyclopoids had a constant depth distribution with time, whereas Bosmina, and Ceriodaphnia showed slight evidence of vertical migration. Due to the scarcity of planktivorous fishes in the lirnnetic zone of the reservoir, the migration of small-sized cladocerans is purpoudtely explained by invertebrate predation pressure (e.g. cyclopoids).

Introductions of Bythotrephes longimanus have resulted in reduced cladoceran species richness and biomass in the Laurentian Great Lakes and many inland lakes. Bythotrephes was first observed in Lake Superior in 1987 but its effect on the cladoceran community has been unknown. We compared the composition of the offshore cladoceran community of Western Lake Superior during 2014 and 2015 to zooplankton surveys from 1971–2001 to determine whether changes in the cladoceran community have occurred. Monthly comparisons show that the contribution of Bosmina longirostris to offshore cladoceran numbers was generally twice as much in the 1970s than during 2014–2015 while the relative contribution of Daphnia mendotae increased after the 1970s. These community changes are consistent with changes due to Bythotrephes observed in other lakes. To evaluate evidence for the role of Bythotrephes in these community changes, we used data from 2014–2015 to analyze patterns in spatial and vertical overlap between Bythotrephes and its cladoceran prey species (Bosmina, Daphnia, and Holopedium) and compared estimates of consumption by Bythotrephes to production of these potential prey. Bosmina was the species whose vertical position and rate of production made it most vulnerable to suppression by Bythotrephes. Of the potential cladoceran prey species, Bosmina densities were also the most negatively correlated with Bythotrephes densities. These findings support a hypothesis of top-down effects on Bosmina by Bythotrephes in Lake Superior. This work informs future zooplankton research in Lake Superior and furthers our understanding of the effects of Bythotrephes on the Lake Superior food web.