Feeding protocol with live feed and inert diet to determine the ideal age/size for weaning mullet Mugil liza (Valenciennes, 1836).

The Lebranche mullet Mugil liza is a marine fish of great importance for artisanal and industrial fishing, as well as aquaculture. The use of live feeds during the larviculture phase of marine fish is a significant component of production costs. The present study evaluated the effects of the feeding transition on different larval stages of M. liza, from the combined supply of live feed (Brachionus rotundiformis + Artemia franciscana) and live + inert feed (Artemia franciscana + inert diet) until the weaning phase to only the inert diet. A total of 3240 M. liza larvae (weight 0.0133 ± 0.0062 g and length 0.793 ± 0.160 cm) were distributed among the 12 experimental units (n = 270), resulting in four groups with three replicates each. Treatment groups consisted of feed transition with A. franciscana (enriched metanauplii) to commercial inert feed starting weaning at four different larval ages: 28, 31, 34, and 37 days post hatching. Zootechnical performance indexes and intestinal histomorphometry were evaluated. Mortality, condition factor, and length variation coefficient did not show significant differences between treatments. Final weight, final length, weight gain, and length gain were significantly greater in larvae that started weaning at 31, 34, and 37 days post hatching. Weight coefficient of variation was significantly higher in larvae that started weaning at 28 days (67.51 ± 11.70) compared to 37 days (34.40 ± 7.30). In intestinal histology, villi height (180.3 ± 4.4) was significantly higher in larvae that started weaning at 37 days post hatching. Considering the evidence found in the present study, it is recommended to start weaning M. liza on the 31st day post-hatching, using a 2-day co-feeding protocol (31st and 32nd days). From the 33rd day after hatching, M. liza larvae can receive only commercial feed.

Resilience of rotifers and cladocerans communities in four reservoirs with eutrophication pollution and lead concentrations in Aguascalientes, Mexico.

Pollution in aquatic ecosystems has been increasing drastically worldwide changing their water quality. Therefore, species must be adapted to these new scenarios. In Aguascalientes City, four representative urban reservoirs contain lead in the water column and extremely high concentrations of sediments. Therefore, an analysis was conducted to evaluate the resilience of zooplankton species to lead exposure in each reservoir using dormant and organisms. Results demonstrated a decrease range from 57.5 to 22.5% in overall diapausing egg hatching rate, while survivorship rate also decreased from 98 to 54% when organisms were exposed to the water of the four reservoirs and increasing lead concentrations. When Pb exposure increased, results showed a global negative effect on both hatching rate (decreasing from 58 to 30% at 0.09 mg L-1) and survivorship levels (decreasing from 100% to 0.07% at 0.09 mg L-1). We provide Species Sensitivity Distribution for both water reservoir dilutions and lead concentration to analyze diapausing eggs hatching and survivorship of offspring in the presence of same polluted conditions or lead of the autochthonous species found in reservoirs. Furthermore, specific analysis with two populations of the cladoceran Moina macrocopa showed clear dissimilar hatching patterns that suggested a different adaptive mechanism. Niagara population shows a hatching rate of approximately 25% in the first two days of reservoir water exposure, while UAA population drastically increased hatching rate to 75% on exposure at day seven. We provide the first record of bioaccumulation in ephippia of M. macrocopa.

Population dynamics of pelagic rotifers in Marala Headworks (Pakistan) / Dinâmica populacional de rotíferos pelágicos em Marala Headworks (Paquistão)

Research work was designed to investigate the density and diversity of pelagic rotifers in a Lake near Marala Headworks. The physico-chemical parameters of water such as pH, dissolved oxygen, temperature, electrical conductivity, transparency and turbidity were evaluated. Correlation between rotifers and these parameters was also studied. Plankton sampling was done on monthly basis in order to check the population density of rotifers. In total, 18 species of rotifers were identified which belonged to 11 genera. The highest number of rotifers and their diversity was shown by genera namely Brachionus, Keratella, and Filinia. The Brachionus calyciflorus was dominant species in all the samples with mean population density (41%). Analysis of variance of physico-chemical parameters presented that the air and water temperature, electrical conductivity, transparency, dissolved oxygen and oxygen saturation were statistically significant in all the months. While pH was statistically non-significant (p≥0.05. Pearson correlation showed that oxygen and transparency were negatively correlated with rotifers density and diversity. Air and water temperature, concentration of hydrogen ions (pH), electrical conductivity and salinity showed positive relationship with density and diversity of rotifers.

O trabalho de pesquisa foi projetado para investigar a densidade e diversidade de rotíferos pelágicos em um lago perto de Marala Headworks. Foram avaliados os parâmetros físico-químicos da água como pH, oxigênio dissolvido, temperatura, condutividade elétrica, transparência e turbidez. A correlação entre rotíferos e esses parâmetros também foi estudada. A amostragem do plâncton foi realizada mensalmente para verificar a densidade populacional dos rotíferos. No total, foram identificadas 18 espécies de rotíferos pertencentes a 11 gêneros. O maior número de rotíferos e sua diversidade foi demonstrado pelos gêneros Brachionus, Keratella e Filinia. O Brachionus calyciflorus foi a espécie dominante em todas as amostras, com densidade populacional média (41%). A análise de variância dos parâmetros físico-químicos mostrou que a temperatura do ar e da água, condutividade elétrica, transparência, oxigênio dissolvido e saturação de oxigênio foram estatisticamente significantes em todos os meses. Enquanto o pH foi estatisticamente não significativo (p≥0,05), a correlação de Pearson mostrou que o oxigênio e a transparência foram negativamente correlacionados com a densidade e diversidade dos rotíferos. A temperatura do ar e da água, a concentração de íons de hidrogênio (pH), a condutividade elétrica e a salinidade mostraram relação positiva com a densidade e diversidade de rotíferos.

How are zooplankton's functional guilds influenced by land use in Amazon streams?

Amazon streams present great biodiversity and offer several ecosystem services, but these systems are threatened by multiple land uses. The changes created by land use are expected to drive the composition of species, ultimately changing the trophic relationships of several biological groups, including zooplankton. We investigated if land use changes the composition of zooplankton functional guilds in Amazon streams and which are the local (physical-chemical) variables driving the zooplankton functional guilds in the land-use gradient. Zooplankton and physical-chemical variables were sampled in 17 water bodies in the municipality of Barcarena, Pará, Brazil in 2018 and 2019, five sampling sites were in the Pará River and 12 in streams. Forest cover (a proxy for land use) was determined through digital image processing and converted in percentage. Zooplankton species were classified into five functional guilds (filter, raptorial, scraper, suctor, and predator feeders). We recorded 98 zooplankton taxa and filters were the most abundant functional guild. The composition of zooplankton functional guilds did not change in the land use gradient. However, the distribution of zooplankton functional guilds in Amazon streams was determined by local environmental variables related to the feeding strategies. Scraper-feeders (cladocerans) were positively related to greater canopy cover, suctor-feeders and predator-feeders (both rotifers) were related to greater total phosphorus, whereas filter-feeders (rotifers, cladocerans, and copepods) and raptorial (copepods) were related to total suspended solids. This study brings new information about zooplankton in Amazon streams that are under-studied. The functional approach clarifies the patterns observed and reflects the trophic relationships in which the zooplankton community is involved in streams under a degree of land use, i.e., scraper-cladocerans can represent more preserved streams under greater canopy cover, whereas the other functional guilds were related to variables that can represent more altered streams.

Integral Study of Paramecium caudatum Acute and Chronic Toxicity, Sites of Entry and Distribution, Bioconcentration and Body Burdens of Five Metals.

An integral analysis of the acute and chronic toxicity, bioaccumulation, sites of entry, and distribution of four trace metals: copper, iron, lead, and nickel, and the non-trace metal mercury were performed in the ciliate Paramecium caudatum. Mercury was the fastest metal accumulated, and the most toxic. The sensitivity of Paramecium caudatum to the five metals tested (Cu, Fe, Hg, Ni, and Zn) falls in the range of other ciliate species. We observed similarities between the toxicity of the five metals to the ciliate P. caudatum with the rotifer Euchlanis dilatata: (a) Mercury was the most toxic metal in terms of acute and body burdens. (b) Acute values were very similar in both species, Hg as the most toxic and Fe as the less toxic, (c) the vacuole/ingestion chronic tests were more sensitive than growth inhibition chronic tests. These analyses would ideally help generate safer guidelines for protecting aquatic biota.

High taxonomic turnover and functional homogenization of rotifer communities in an amazonian river.

Patterns of beta diversity of plankton communities in rivers have been mainly determined by hydrological factors that alter the dispersion and composition of species and traits. Rotifers in the Guamá River (eastern Amazonian River) were sampled (monthly between October 2017 and June 2019) to analyze the temporal variation of taxonomic and functional beta diversity and its partitions (turnover and nestedness) as well as the effects of temporal, environmental, and seasonal dissimilarities. Taxonomic turnover and functional nestedness over time were observed as well as functional homogenization, which was arguably due to the hypereutrophic condition of the river. There were no seasonal differences in taxonomic and functional beta diversity probably due the low environmental dissimilarity. This study demonstrated that this Guamá River stretch presented low environmental dissimilarity and hypereutrophic waters, which benefited the establishment of a community of species with high taxonomic turnover over time, but with low functional dissimilarity and loss of some functions related to the functional traits evaluated in the ecosystem. It is important to point out that temporal studies should evaluate both taxonomic and functional aspects of communities, mainly because the effect of environmental changes may be more noticeable at the functional level of communities.

Multi-and transgenerational synergistic effects of glyphosate and chlorpyrifos at environmentally relevant concentrations in the estuarine rotifer Proales similis.

We evaluated the multi-and transgenerational effects of single and combined environmentally relevant concentrations of glyphosate (GLY) and chlorpyrifos (CPF) in the estuarine rotifer Proales similis. The acute and chronic toxicities of GLY and CPF were determined as individual compounds and as a mixture. Rotifers were exposed to environmental concentrations of GLY (1, 10, 100, and 1000 µg/L) and CPF (0.1, 1, 5, and 10 µg/L). The main findings were as follows: (i) the LC50 values were 33.91 mg/L (GLY) and 280 µg/L (CPF); (ii) the toxic unit (TU50) of the mixture was 0.30, corresponding to 10.17 mg/L GLY and 83 µg/L CPF; (iii) the multigenerational study indicated that the tested concentrations of GLY and CPF, both single and combined, significantly and consistently decreased the growth rates of P. similis from the F0 to F6 generations; (iv) in most cases, GLY and CPF mixtures induced a strong synergistic effect; and (v) transgenerational effects were detected in the F4 generation, especially GLY and CPF in higher equitoxic proportions. These effects seem to dissipate in F5. Across multigeneration, a slight recovery could indicate population resilience to pollution. Our findings suggest that a mixture of GLY and CPF at environmental concentrations is likely to occur under real field conditions, increasing the risk to marine and estuarine invertebrates such as rotifers.

Synergistic effect of chloroquine and copper to the euryhaline rotifer Proales similis.

Chloroquine (CQ) has been widely used for many years against malaria and various viral diseases. Its important use and high potential to being persistent make it of particular concern for ecotoxicological studies. Here, we evaluated the toxicity of CQ alone and in combination with copper (Cu) to the euryhaline rotifer Proales similis. All experiments were carried out using chronic toxicity reproductive five-day tests and an application factor (AF) of 0.05, 0.1, 0.3, and 0.5 by multiplying the 24-h LC50 values of CQ (4250 µg/L) and Cu (68 µg/L), which were administered in solution. The rate of population increase (r, d-1) ranged from 0.50 to 52 (controls); 0.20 to 0.40 (CQ); 0.09 to 0.43 (Cu); and -0.03 to 0.30 (CQ-Cu) and showed significant decrease as the concentration of both chemicals in the medium increased. Almost all tested mixtures induced synergistic effects, mainly as the AF increased. We found that the presence of Cu intensifies the vulnerability of organisms to CQ and vice versa. These results stress the potential hazard that these combined chemicals may have on the aquatic systems. This research suggests that P. similis is sensitive to CQ as other standardized zooplankton species and may serve as a potential test species in the risk assessment of emerging pollutants in marine environments.

Feeding behavior of early life stages of the zebrafish Danio rerio is altered by exposure to glyphosate.

Glyphosate levels and the transfer of glyphosate across trophic levels have rarely been studied in zooplankton. The food preferences of zebrafish during the first-feeding stage (which is critical for the survival of organisms), were analyzed because of the requirement for live food. Larval survival begins to be affected when glyphosate intake exceeds 0.3666 µg/larvae/day, in the case that only the food is contaminated; if the medium is also contaminated, the effects on survival start from 0.2456 µg/larvae/day. It was shown that glyphosate was more likely to be incorporated through the medium than through the food (zooplankton), which supports the results of previous studies that have ruled out the potential for biomagnification. The bioconcentration factor (BCF) of glyphosate was determined using an ELISA tests specific to measure glyphosate in the fish D. rerio, the rotifers Brachionus calyciflorus and Lecane papuana, and the cladoceran Ceriodaphnia dubia. The experimental design consisted in exposing seven zebrafish adults per replica (four replicates) in three treatments 1, 5, and 10 mg/L of glyphosate for 96 h to obtain bioconcentration factors in the gills, liver, and muscle. These concentrations were selected as potential glyphosate concentrations right after application as double highest reported concentration. Glyphosate levels in zooplankton can represent up to 6.26% of the total weight of rotifers (BFC = 60.35) and in zebrafish adult organs were less than 8 µg/mg of tissue (BCF values < 6). Although glyphosate does not biomagnify, our results suggest that glyphosate affected the dynamics between zooplankton and zebrafish larvae, diminishing survival and feeding rates, given that zooplankton species bioconcentrate glyphosate in large quantities. The BCF values found in this contribution are higher than expected. Glyphosate exposure affected energy metabolism and feeding behavior of zebrafish larvae, which presented high mortality rates at environmentally relevant concentrations.

Population dynamics of pelagic rotifers in Marala Headworks (Pakistan).

Research work was designed to investigate the density and diversity of pelagic rotifers in a Lake near Marala Headworks. The physico-chemical parameters of water such as pH, dissolved oxygen, temperature, electrical conductivity, transparency and turbidity were evaluated. Correlation between rotifers and these parameters was also studied. Plankton sampling was done on monthly basis in order to check the population density of rotifers. In total, 18 species of rotifers were identified which belonged to 11 genera. The highest number of rotifers and their diversity was shown by genera namely Brachionus, Keratella, and Filinia. The Brachionus calyciflorus was dominant species in all the samples with mean population density (41%). Analysis of variance of physico-chemical parameters presented that the air and water temperature, electrical conductivity, transparency, dissolved oxygen and oxygen saturation were statistically significant in all the months. While pH was statistically non-significant (p≥0.05. Pearson correlation showed that oxygen and transparency were negatively correlated with rotifers density and diversity. Air and water temperature, concentration of hydrogen ions (pH), electrical conductivity and salinity showed positive relationship with density and diversity of rotifers.

Rotifers of Bahia State, Brazil: news records and limitations to studies / Rotíferos do Estado da Bahia, Brasil: novos registros e limitações dos estudos

A first checklist of Rotifera species in freshwater environments in Bahia State, in northeastern Brazil, is provided. The list includes sampling data from 26 aquatic environments (lotic and lentic) undertaken from 2010 to 2016. One hundred and fifty-five species were recorded, with 68 new records for the state. The family Brachionidae and Lecanidae were the most representative (54.8%). The greatest richness was recorded in the Colônia River (57 species). Those results reflect the low numbers of studies previously undertaken in the region, indicating more research needs to be focused on Rotifera biodiversity in Bahia, the fifth largest state in Brazil (567,295 km2) with large numbers of freshwater bodies.(AU)

É fornecida uma primeira lista de verificação das espécies de Rotifera em ambientes de água doce no Estado da Bahia, nordeste do Brasil. A lista de espécies inclui dados de amostragem de 26 ambientes aquáticos (lóticos e lênticos) de 2010 a 2016. Cento e cinquenta e cinco espécies foram registradas, com 68 novos registros para o estado. As famílias Brachionidae e Lecanidae foram as mais representativas (54,8%). A maior riqueza foi registrada no rio Colônia (57 espécies). Esses resultados provavelmente refletem o número de estudos na região, sugerindo mais pesquisas sobre a biodiversidade de Rotifera na Bahia, o quinto maior estado do Brasil (567.295 km2) com grande número de corpos aquáticos de água doce.(AU)

Rotifers of Bahia State, Brazil: news records and limitations to studies / Rotíferos do Estado da Bahia, Brasil: novos registros e limitações dos estudos

A first checklist of Rotifera species in freshwater environments in Bahia State, in northeastern Brazil, is provided. The list includes sampling data from 26 aquatic environments (lotic and lentic) undertaken from 2010 to 2016. One hundred and fifty-five species were recorded, with 68 new records for the state. The family Brachionidae and Lecanidae were the most representative (54.8%). The greatest richness was recorded in the Colônia River (57 species). Those results reflect the low numbers of studies previously undertaken in the region, indicating more research needs to be focused on Rotifera biodiversity in Bahia, the fifth largest state in Brazil (567,295 km2) with large numbers of freshwater bodies.

É fornecida uma primeira lista de verificação das espécies de Rotifera em ambientes de água doce no Estado da Bahia, nordeste do Brasil. A lista de espécies inclui dados de amostragem de 26 ambientes aquáticos (lóticos e lênticos) de 2010 a 2016. Cento e cinquenta e cinco espécies foram registradas, com 68 novos registros para o estado. As famílias Brachionidae e Lecanidae foram as mais representativas (54,8%). A maior riqueza foi registrada no rio Colônia (57 espécies). Esses resultados provavelmente refletem o número de estudos na região, sugerindo mais pesquisas sobre a biodiversidade de Rotifera na Bahia, o quinto maior estado do Brasil (567.295 km2) com grande número de corpos aquáticos de água doce.

Rotifers of Bahia State, Brazil: News records and limitations to studies / Rotíferos do Estado da Bahia, Brasil: Novos registros e limitações dos estudos

A first checklist of Rotifera species in freshwater environments in Bahia State, in northeastern Brazil, is provided. The list includes sampling data from 26 aquatic environments (lotic and lentic) undertaken from 2010 to 2016. One hundred and fifty-five species were recorded, with 68 new records for the state. The family Brachionidae and Lecanidae were the most representative (54.8%). The greatest richness was recorded in the Colônia River (57 species). Those results reflect the low numbers of studies previously undertaken in the region, indicating more research needs to be focused on Rotifera biodiversity in Bahia, the fifth largest state in Brazil (567,295 km2) with large numbers of freshwater bodies.

É fornecida uma primeira lista de verificação das espécies de Rotifera em ambientes de água doce no Estado da Bahia, nordeste do Brasil. A lista de espécies inclui dados de amostragem de 26 ambientes aquáticos (lóticos e lênticos) de 2010 a 2016. Cento e cinquenta e cinco espécies foram registradas, com 68 novos registros para o estado. As famílias Brachionidae e Lecanidae foram as mais representativas (54,8%). A maior riqueza foi registrada no rio Colônia (57 espécies). Esses resultados provavelmente refletem o número de estudos na região, sugerindo mais pesquisas sobre a biodiversidade de Rotifera na Bahia, o quinto maior estado do Brasil (567.295 km2) com grande número de corpos aquáticos de água doce.

Effects of the endocrine disruptor 4-nonylphenol on the demography of rotifers Plationus patulus and Brachionus havanaensis: a multigenerational study.

The emerging contaminant 4-nonylphenol is an active ingredient in many surfactants. Though 4-nonylphenol has been reported in Mexican waterbodies, no stringent law is available to establish its permissible limits. Most ecotoxicological assays using zooplankton species are based on previously unexposed populations, and multigenerational experiments are rare. Plationus patulus and Brachionus havanaensis are widely distributed species in Mexico and have been used in ecotoxicological assessments. In this work, the median lethal concentration of 4-nonylphenol (LC50, 24 h) for both rotifer species was derived. Based on our acute toxicity data (24 h LC50 of 4-nonylphenol for P. patulus and B. havanaensis were 500 and 250 µg L-1, respectively), three sublethal concentrations (µg L-1) (7.81, 15.82 and 31.25 for B. havanaensis and 15.62, 31.25 and 62.5 for P. patulus) were used in the life table demography tests for two successive generations (F0 and F1) of either rotifer species. Regardless of the concentrations used, 4-nonylphenol had an adverse effect on both rotifer species over two successive generations. P. patulus was more sensitive than B. havanaensis in chronic toxicity tests. F1 generation of both rotifer species was far more adversely affected than the F0 in all toxicant treatments.

Rotifers of Bahia State, Brazil: News records and limitations to studies.

A first checklist of Rotifera species in freshwater environments in Bahia State, in northeastern Brazil, is provided. The list includes sampling data from 26 aquatic environments (lotic and lentic) undertaken from 2010 to 2016. One hundred and fifty-five species were recorded, with 68 new records for the state. The family Brachionidae and Lecanidae were the most representative (54.8%). The greatest richness was recorded in the Colônia River (57 species). Those results reflect the low numbers of studies previously undertaken in the region, indicating more research needs to be focused on Rotifera biodiversity in Bahia, the fifth largest state in Brazil (567,295 km2) with large numbers of freshwater bodies.

Structure and spatial distribution of the rotifer assemblages along a tropical reservoir / Estrutura e distribuição espacial da comunidade de rotíferos em um reservatório tropical

The construction of reservoirs is a common practice in the world. These systems modify the hydric landscape and alter the flow of rivers, becoming lotic environments in lentic. Here we investigated the structure and spatial distribution of rotifers along a tropical reservoir. We sampled four points in the Pedra do Cavalo Reservoir, Bahia, Brazil, bimonthly, between August 2014 and June 2015. We registered more than 70 taxa distributed in 17 families, with the majority of species belonging to the Lecanidae, Brachionidae and Trichocercidae families. The species rarefaction curve did not achieve a total asymptote, indicating that species richness in the reservoir is higher than what was registered. Based in the species frequency of occurrence, we identified 48 rare species, 16 common species, five constant species and one frequent species. The highest beta diversity values were registered in riverine P1 (0.513) and intermediate P2 (0.503), although there were no significant differences between the sampling points. Despite the high abundance values in P1, P2 and P3 no significant differences were found between the studied points. Thus, this study substantially increases the knowledge on the rotifer community in the Paraguaçu River and contributes to future studies that focus on biodiversity, ecology and conservation in the Brazilian reservoir ecosystems.(AU)

A construção de reservatórios é uma prática comum no mundo. Esses sistemas modificam a paisagem hídrica e alteram o fluxo dos rios, tornando-se ambientes lóticos em lênticos. Aqui investigamos a estrutura e distribuição espacial de rotíferos ao longo de um reservatório tropical. Foram amostrados quatro pontos no Reservatório da Pedra do Cavalo, Bahia, Brasil, bimestralmente, entre agosto de 2014 e junho de 2015. Registramos mais de 70 táxons distribuídos em 17 famílias, com a maioria das espécies pertencentes às famílias Lecanidae, Brachionidae e Trichocercidae. A curva de rarefação das espécies não alcançou uma assíntota total, indicando que a riqueza de espécies no reservatório é superior à registrada. Com base na frequência de ocorrência das espécies, identificamos 48 espécies raras, 16 espécies comuns, cinco espécies constantes e uma espécie frequente. Os maiores valores de diversidade beta foram registrados no ribeirinho P1 (0,513) e no intermediário P2 (0,503), embora não houvesse diferenças significativas entre os pontos de amostragem. Apesar dos altos valores de abundância em P1, P2 e P3, não foram encontradas diferenças significativas entre os pontos estudados. Assim, este estudo aumenta substancialmente o conhecimento sobre a comunidade de rotíferos no rio Paraguaçu e contribui para estudos futuros que enfocam biodiversidade, ecologia e conservação nos ecossistemas de reservatórios brasileiros.(AU)

Resting egg banks can facilitate recovery of zooplankton communities after short exposure to glyphosate.

We assessed the short-term viability and recovery of zooplankton communities after exposure to glyphosate (active ingredient-a.i.). We conducted a hatching experiment in two steps: Step 1-natural lake sediments containing resting egg banks were placed into individual trays and exposed to a solution medium of glyphosate at three different treatments (LD = Values below the detection limits, LD < 0.05, 0.44, and 0.89 mg a.i./L) for 14 days; and Step 2-we replaced the exposure solution of glyphosate with distilled freshwater, keeping them all trays under freshwater conditions for another 14 day. The results from Step 1 showed significant effects of glyphosate on the emergence patterns of resting eggs, with a reduction in hatching of rotifers, mainly at concentrations of 0.44 and 0.89 mg a.i./L. On the other hand, the results from Step 2 showed an increase in the emergence of viable eggs for rotifers after restoration of freshwater conditions in all treatments; there was no effect for total zooplankton and microcrustaceans. These findings suggest that (i) glyphosate may, effectively, impair zooplankton hatching from resting egg banks; (ii) the magnitude of the negative effects depends on the the zooplanktonic group considered; and (iii) the restoration of freshwater conditions may, in some way, allow the recovery of the zooplankton community from viable egg banks. Our results can be useful in predicting the influence of glyphosate on the distribution patterns of freshwater zooplankton, which can represent vital information for environmental managers.

The dynamics of picocyanobacteria from a hypereutrophic shallow lake is affected by light-climate and small-bodied zooplankton: a 10-year cytometric time-series analysis.

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.