Ceratium furcoides
is a freshwater dinoflagellate originally from cold waters of northern Europe that has been expanding its distribution into new areas worldwide. Species distribution modeling (SDM) ...based on maximum entropy algorithm (MaxEnt) showed that
C. furcoides
has a much wider potential range than its current distribution and isothermality as the key environmental variable determining its spatial pattern. The model successfully predicts areas of introduction and the climate matching approach has identified mainly tropical and some subtropical regions as most vulnerable areas at risk of introduction and establishment of
C. furcoides
. Furthermore, the observed shift of the climatic niche occurred between native and non-native ranges, providing, for the first time, a robust evidence that a dinoflagellate can occupy climatically distinct niche spaces following its introduction into new areas. This is probably mirroring the lack of adequate management to deal with various impacts on drainage basins, such as ongoing accelerated cultural eutrophication coupled with river impoundments and water diversion. Thus, this framework provides helpful insights on how to optimize our ability to anticipate invasions and to avoid ecosystem services losses, as well as future studies prospects on adaptive mechanisms of this pervasive invader.
This study evaluated the toxicity of pesticide formulations Kraft® 36 EC (active ingredient—a.i. abamectin) and Score® 250 EC (a.i. difenoconazole), and their mixtures in
Daphnia magna
at different ...biological levels of organization. Survival, reproduction and biochemical markers (cholinesterase (ChE), catalase (CAT) and lipid peroxidation (LPO)) were some of the endpoints evaluated. Total proteins and lipids were also studied together with energy consumption (Ec).
D. magna
neonates were exposed for 96 h to Kraft (2, 4, and 6 ng a.i./L) and Score (12.5, 25, and 50 µg a.i./L) for the biochemical experiments, and for 15 days to abamectin (1–5 ng a.i./L) and to difenoconazole (3.12–50 µg a.i./L) to assess possible changes in reproduction. Exposures of organisms to both single compounds did not cause effects to antioxidant and detoxifying enzymes, except for LPO occurring at the highest concentration of difenoconazole tested. For ChE and CAT there was enzymatic induction in mixture treatments organisms, occurring at minor pesticides concentrations for CAT and at the two highest concentrations for ChE. There were no significant differences for total protein in
D. magna
but lipids showed an increase at the highest concentrations of pesticide mixture combinations. There was a significant increase of Ec in individuals of all treatments tested. In the chronic test, increased fecundity occurred for
D. magna
under difenoconazole exposures and mixtures. This study demonstrated that mixtures of these pesticides caused greater toxicity to
D. magna
than when tested individually, except for Ec. Therefore, effects of mixtures are very hard to predict only based on information from single compounds, which most possibly is the result of biological complexity and redundancy in response pathways, which need further experimentation to become better known.
Aquatic environments are constantly exposed to a cocktail of contaminants mainly due to human activities. As polluted ecosystems may simultaneously present other multiple natural stressors, the ...objective of the present study was to evaluate joint effect of stressors (natural and anthropogenic) on life history traits of the Neotropical cladoceran,
Ceriodaphnia silvestrii
. For this purpose, the effects of water conditioned with predator kairomones (fish) and environmental concentrations (sublethal) of two pesticides widely used in sugarcane monoculture in Brazil, the insecticide Regent
®
800 WG (active ingredient—a.i. fipronil) and the herbicide DMA
®
806 BR (a.i. 2,4-D) were evaluated using chronic toxicity testing, isolated and in mixture, for this cladoceran species. The environmental risks of pesticides for tropical freshwater biota were also estimated from the risk quotient MEC/PNEC. Among the characteristics of the life history of
C. silvestrii
evaluated after 8 days of exposure, compared with the mean value of control, the age of primiparous females was not affected by any evaluated treatment. However, species average survival decreased in the treatment of kairomones mixed with fipronil (FK) and in the treatment with a mixture of fipronil, 2,4-D, and kairomones (MFKD). The body length of maternal females was shorter than in the control after exposure in treatments with only kairomones (K) and FK. Fecundity of this cladoceran was reduced when exposed to FK and MFKD treatments, and the intrinsic rate of population increase significantly decreased for organisms exposed to treatment with fipronil (F) and to mixtures of fipronil and 2,4-D (MFD), MFDK, and FK. The results indicated that the combination of anthropogenic and natural stressors causes changes in
C. silvestrii
life history traits, which can contribute to the decline in populations, and our preliminary risk assessment results are a matter of concern regarding biota conservation.
Aim In the present study has analyzed several aspects of the life history traits of Melanoides tuberculata, an exotic species, under laboratory conditions, and its response to some stressors has also ...been applied. Methods Sensitivity to two toxic substances was tested. The mollusks were collected and cultured in the laboratory under controlled conditions of temperature of 25 ± 1 °C and ad libitum food regime. Growth rates and biomass were experimentally obtained and the individual growth curve obtained. Results The experiment lasted 287 days and the maximum shell lengths registered was 11.67 mm. The growth curve indicated a rate of 3.98 year-1 and a maximum theoretical length of 10.61 mm. The mean post-embrionary development time until first reproduction was 275 days and the size of the primipara was 10.13 mm. An accelerated growth of juveniles was observed with fast increase in the shell length until sexual maturity, but growth rate decreased afterwards as more energy was devoted to reproduction. Under the combination of 25 °C and fed on alternate days, M. tuberculata had a slow growth and a long-life expectancy under laboratory conditions. The tolerance of this mollusk to temperature as a stressor ranged between 16 °C and 37 °C, being the optimum temperature situated between 29 °C and 34 °C. The LC(I)50-24h for reference substances were: 0.70 g L-1 for KCl and 9.05 g L-1 for NaCl. Conclusion Based on these results, we can conclude that M. tuberculata is a species tolerant to temperature and salinity, what partially explains to accordance to its wide and rapid dispersion throughout tropical waters.
Resumo: Objetivo No presente estudo foram analisados diversos aspectos do ciclo de vida de Melanoides tuberculata, um gastrópode exótico, sob condições controladas em laboratório, e, também foram avaliados a sua resposta a alguns estressores. Métodos Foram testadas a sensibilidade a duas substâncias tóxicas. Os moluscos foram coletados e cultivados em laboratório sobre condições controladas de temperatura de 25 ± 1 °C e alimentação ad libitum. A taxa de crescimento e as relações peso-comprimento foram determinadas, além da curva de crescimento individual. Resultados A duração do experimento foi de 287 dias, os valores de comprimentos máximo da concha foi de 11,67 mm. Os parâmetros da curva de crescimento revelaram taxa de crescimento de 3,98 ano-1 e comprimento máximo teórico de 10,61 mm. Em média M. tuberculata apresentou a primípara em 275 dias com comprimento de 10,13 mm. O crescimento foi mais acentuado na fase juvenil decorrente do maior investimento nesta fase para a formação da concha até a maturidade sexual, após isso houve redução nas taxas de crescimento para maior investimento de energia na reprodução. Assim, M. tuberculata apresentou crescimento lento e uma longa expectativa de vida em condições laboratoriais. A faixa de tolerância à temperatura de M. tuberculata situa-se entre 16 °C e 37 °C, sendo a faixa ótima de temperatura entre 29 °C e 34 °C. A CL(I)50-24h foram: 0,70 g.L-1 para KCl e 9,05 g.L-1 para NaCl. Conclusões Baseados nestes resultados podemos concluir que M. tuberculata é uma espécie tolerante a temperatura e salinidade, o que explicaria parcialmente sua ampla e rápida dispersão em águas tropicais.
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•Combined pressures in the invasion success of Ceratium furcoides were investigated.•Niche modelling and habitat-relatedness were used to predict future areas at risk.•Model show an ...overlap between future suitable areas and dam construction projections.•Dams and climate change will interplay in the outcomes of invasion success.
Global inland water biodiversity is under mounting stress facing future scenarios of climate change, biological invasions, pollution, diversion, damming of rivers, and increase of water abstractions. Apart from having isolated effects, all these stressors threats act synergistically and thus pose additional emerging threats to biodiversity and ecosystem services. Native to Northern Europe, the nuisance and potential toxic dinoflagellate Ceratium furcoides (Levander) Langhans 1925 is a silent invader that blooms in freshwater systems; it has one of the most rapid spread rates globally. We propose a framework to determine the worldwide most vulnerable areas for the invasion by C. furcoides shortly (2041–2060) by combining future scenarios of climate change (a proxy for invasiveness) derived from ecological niche models with future dam construction data (a proxy for invasibility). The nine models applied in four future scenarios of greenhouse gas emission from Coupled Model Intercomparison Project Phase 6 showed a general increase in areas suitable for the invasion success of C. furcoides. High susceptibility overlapped with areas densely occupied by large and medium-size dams and future dam construction projects. Considering that C. furcoides can reproduce from a single cell, produces resistant stages, and has several strategies to cope with local environmental constraints, early detection protocols, and mitigation actions are urgently needed to avoid biodiversity declines related to this invader.
•Toxicity of abamectin and difenoconazole was determined to a tropical cladoceran.•Mixture toxicity of the two pesticides was also evaluated.•Risks of realistic runoff and spray drift exposure were ...assessed.•Synergistic interactions occurred in mixtures of both commercial products.•Realistic exposure to pesticide mixture is likely to impose risks to aquatic biota.
Aquatic risk assessments of pesticides in tropical countries have often been disputed for being largely based on risk evaluations conducted in temperate regions. Although pesticide sensitivity comparisons between temperate and tropical freshwater organisms have indeed not revealed consistent differences, risk assessments are currently still based on a relatively small tropical toxicity dataset. In addition, greater levels of runoff and spray drift may be expected in tropical than in temperate agroecosystems, indicating that aquatic life in edge-of-field water bodies is likely to be subjected to higher concentrations of pesticides and their mixtures. The aim of the present study was to evaluate the toxicity of Kraft® 36 EC (a.i. abamectin), Score® 250 EC (a.i. difenoconazole) and their mixture to the Neotropical cladoceran Macrothrix flabelligera. Laboratory toxicity tests with the individual formulated products indicated EC50–48h values of 3.1 and 659μg a.i./L given as nominal test concentrations, respectively. Mixtures of the two pesticides revealed a concentration-dependent deviation of the independent action model, with antagonism at low and synergism at high pesticide mixture concentrations. Laboratory toxicity tests were also conducted with microcosm water that was treated with the individual or mixtures through runoff or direct overspray. Microcosm tanks receiving runoff water from experimental soil plots applied with recommended doses of the individual pesticides did not show toxicity to the test organism. Microcosms that received runoff water containing the pesticide mixture, however, did cause a short-term effect on immobility. The microcosms that were treated by direct overspray of both pesticide formulations showed the most pronounced toxic effects. Study findings suggest a potential risk of these pesticides at environmentally relevant concentrations, especially when they are both present.
The freshwater rotifer
Kellicottia bostoniensis
(Rousselet, 1908), native from North America, has been considered invasive in European, Russian and South American waterbodies. More than reporting its ...presence, for the first time, in Araguaia River, which plays critical role in a set of floodplain systems in the Brazilian savanna, we aim to understand how this invader react to new physical, chemical and hydrodynamics conditions, which can be helpful for predicting its invasiveness and colonization success in other similar non-native ranges. We use population data of
K. bostoniensis
and environmental variables surveyed across the meandering middle-stretch of the Araguaia River. The highest frequencies of
K. bostoniensis
were registered in sites of lower mean temperatures, higher pH and dissolved oxygen at sites with higher hydrodynamics. However, the highest abundance was found in a backwater site, a more lentic habitat in which total body size was slightly higher than those with lotic conditions. Both the abundance values and body length were the lowest registered in non-native areas, suggesting the initial phase of the invasion process. Also, the trade-off between abundance and body size may allow population to persist in flowing water conditions, thus playing fundamental role in population recruitment and dispersal, favoring the propagation of this organism in the river curse and adjacent environments. Specifically, stepping stones created by the river meanders would increase population growth and the rapid spread of
K. bostoniensis
through Araguaia River. Due to its wide environmental tolerance, morphological plasticity and high dispersal ability, we further anticipate continued dispersion of
K. bostoniensis
to other Brazilian basins highlighting the need for persistent monitoring upstream and downstream of this freshwater ecotone.
Predation is known to play a prominent role in maintaining ecosystem structure and functioning. Despite metals being known to potentially affect predation in aquatic ecosystems, few studies have been ...conducted, so far, with the aim of evaluating this interplay. In the present study, the effects of four metal salts (copper, cadmium, mercury, and manganese) on the feeding rates and food preference of the dragonfly
Tramea cophisa
and of the ostracod
Chlamydotheca
sp. were studied by performing laboratory ecotoxicity tests. Food preference was evaluated by offering four prey species to dragonfly nymphs and three to adult large ostracods. In general, the food preference of both predator species after being exposed to metal salts was not altered, compared with controls, but the feeding rate of
T. cophisa
decreased in comparison with controls, after exposure to each metal salt, except manganese. Contrastingly, predation rates of
Chlamydotheca
sp. increased after metal salt exposure. This difference in response can be explained by differences in life-history traits of these two organisms. Both species individuals preferred soft-bodied prey (Oligochaeta, Chironomidae) over water-dwelling crustaceans that are likely to be more difficult to prey upon. Tests evaluating the effects of metals and other chemicals on predation behavior may lead to a better understanding of biotic interactions that can be restricted by chemical stress, improving our understanding of possible food web disruptions underlying chemical stress.
In conventional agriculture, several pesticides can be applied at the same stage of plant development, either individually or in mixtures and these compounds also reach aquatic ecosystems. The aim of ...the present study was to investigate the short-term effects of the insecticide Kraft® 36 EC (active ingredient — a.i. abamectin) and the fungicide Score® 250 EC (a.i. difenoconazole) on the zooplankton community in outdoor freshwater microcosms. The potential risks related to the exposure to both compounds, isolated and in mixture, likely to occur in the field after runoff and spray drift events of their recommended doses were assessed in these microcosms through integrative analyses of the effects on the composition, density, and functional diversity of zooplankton. Namely, these endpoints were evaluated for eight different exposures, which were (1) Runoff control — RC; (2) Kraft-contaminated runoff — RK; (3) Score-contaminated runoff — RS; (4) Kraft and Score-contaminated runoff — RKS; (5) Spray drift Control — SC; (6) Kraft spray drift — SK; (7) Score spray drift — SS; and (8) Kraft and Score spray drift — SKS. Zooplankton taxa responded quickly to physical, chemical, and biological changes in the aquatic ecosystems. The principal response curves (PRC) analyses of the zooplankton community in the microcosms indicated significant effects after all insecticide treatments, both when applied individually and in a mixture with the fungicide. The insecticide treatment (RK and SK) demonstrated a decrease in the number of unique species (sing.sp) of zooplankton in the microcosms, and RK also decreased the functional divergence (FDiv). However, it was the treatment of mixtures (SKS) that caused a decrease in functional diversity (FD) and in the functional diversity indexes (divergence and richness) and sing.sp. Thus, the results showed the risk of the insecticide and their mixture to aquatic ecosystems.
We investigated feeding and reproductive performance of coexisting pelagic turbellarians from experiments on predation rates of Mesostoma ehrenbergii and M. craci as a function of food (Daphnia ...similis, three levels) and temperature (4 levels) during 10 days. Flatworms were collected from the pelagic of a subtropical lake in Brazil. Growth was more rapid at higher temperatures: more prey were consumed, and more eggs produced. M. craci and particularly M. ehrenbergii fitted a linear mixed-effects model and showed a type II functional response. M. craci was the more stenothermic of the two. Intrageneric predation also occurred: M. ehrenbergii fed on M. craci, but not vice versa. After a first clutch of subitaneous eggs, M. ehrenbergii produced resting eggs only. In M. craci an intermediate type of eggs hatched some time after release, survived passage through the gut of M. ehrenbergii, but did not resist drying. By primarily selecting cladoceran prey, M. ehrenbergii can make coexistence of both flatworms possible. As population density of M. ehrenbergii increases, it turns to producing resting and non-viable subitaneous eggs, thus limiting its population size. In nature, these processes structure the zooplankton community, while avoiding extinction of prey and predator.
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