In aquatic ecosystems, animals are often exposed to a combination of stressors, including both natural and anthropogenic factors. Combined stressors may have additive or interactive effects on ...animals, either magnifying or reducing the effects caused by each stressor alone. Therefore, standardized bioassays can lead to overestimations or underestimations of the risk of toxicants if natural stressors are not bear in mind. The inclusion of natural stress in laboratory bioassays may help to extrapolate the laboratory results to ecosystems. This study assesses the effects of successive exposure to two sources of stress (high water conductivity and cadmium toxicity) on the behavior and survival of the aquatic snail
Potamopyrgus antipodarum
(Tateidae, Mollusca). I conducted a bioassay consisting on exposure to high conductivity (5000 mg NaCl/L, 7 days), followed by exposure to cadmium (0.03, 0.125, and 0.25 mg Cd/L for 7 days) and by a post-exposure period (7 days). Mortality, inactivity, and the time to start activity of active animals were monitored in each animal. In general, cadmium lethality was higher in animals previously undergoing high conductivity than in non-stressed ones. Previously stressed animals showed longer time to start activity, with a noticeable effect at the two highest cadmium concentrations. Animals submitted to the two highest cadmium concentration both, stressed and non-stressed, showed a moderate recovery during the post-exposure period. It is concluded that previous stress caused a worsening of the cadmium toxicity on the aquatic snail
Potamopyrgus antipodarum
, which is especially noticeable for mortality. However, there was no interactive effect between cadmium and conductivity on snail activity, which may be indicative of recovery after cadmium exposure regardless the previous stress suffered by the snails.
The exposure of animals to pollution in ecosystems is not always chronic. Toxicants can remain in aquatic ecosystems for a short-term. To improve the extrapolation of laboratory results to natural ...scenarios the inclusion of post-exposure periods is a relevant issue. The present study focuses on the assessment of cadmium toxicity on survival and behavior of the aquatic snail
Potamopyrgus antipodarum
(Tateidae, Mollusca) during exposure and post-exposure. Animals were exposed for 48 h to cadmium (0.05, 0.14, 0.44 and 1.34 mg Cd/L) and 168 h of post-exposure. During the post-exposure period an increase in mortality in all concentrations was observed. The effects observed during the post-exposure period on the LC50 and EC50 were significant. During the post-exposure, behavior showed a clear recovery in surviving animals exposed to 0.44 mg Cd/L. Animals exposed to 0.05 mg Cd/L did not show differences with control. Therefore, mortality after exposure should be included in the ecotoxicological bioassays for a more realistic estimation of the cadmium effects. To assess the degree of animal recovery after cadmium exposure, behaviour has been shown as an adequate parameter.
Behavioral endpoints are important parameters to assess the effects of toxicants and other stressors on natural ecosystems. The relevance of these parameters has caused a rise in their use in aquatic ...ecotoxicology. However, abiotic and biotic parameters may interact causing changes in the behavioral responses. Among those parameters, starvation of animals is a factor that is usually applied in ecotoxicological short-term bioassays. This could alter animal behavior, along with the toxicant. Therefore, the study of the effects of starvation on baseline behaviors of invertebrates is a relevant issue. This study assessed the behavior of the aquatic snail
Potamopyrgus antipodarum
under a combination of four treatments: (1) animals normally fed (control treatment), (2) starved animals, (3) animals normally fed and exposed to a high conductivity, and (4) starved animals exposed to a high conductivity. The behavior activity of snails was monitored for 14 days. Results show that animals of the second treatment (starved animals) increased their activity. On the contrary, animals of the third and fourth treatments reduced their activity. Animals from the control treatment showed an activity in between starved animals and animals exposed to high conductivity (both starved and normally fed). These results show that starvation increases the snail activity, but under another environmental stressor (i.e., high conductivity), this trend was reversed. The influence of starvation on behavior should be taken into account in the development of behavioral bioassays.
The origin of the populations used in ecotoxicological bioassays (from nature (wild populations) or from cultures (laboratory populations)) could have a key influence on the sensitivity of the tested ...species to different toxicants. However, the available information on this subject is scarce. To assess the likely influence of the population origin (wild vs. laboratory) of species–genus on the toxicant tolerance, we performed a quantitative review of the ECOTOX database, from which we collected the effective concentrations for a wide range of compounds (metals and organics), endpoints, and exposure times. We found a general trend of lower sensitivity of wild populations to toxicants than laboratory populations, although sensitivity was dependent on species and toxicant groups. This suggests that the results of bioassays with laboratory populations may overestimate the toxicity of most of the compounds. Our study highlights the relevance of the origin of the populations in the determination of the sensitivity of species to toxicants. This study also warns about the biases in the species and toxicants used in ecotoxicology, which may lead to an underrepresentation of the biodiversity and the toxicological context of aquatic ecosystems.
We provide a global assessment, with detailed multi-scale data, of the ecological and toxicological effects generated by inorganic nitrogen pollution in aquatic ecosystems. Our synthesis of the ...published scientific literature shows three major environmental problems: (1) it can increase the concentration of hydrogen ions in freshwater ecosystems without much acid-neutralizing capacity, resulting in acidification of those systems; (2) it can stimulate or enhance the development, maintenance and proliferation of primary producers, resulting in eutrophication of aquatic ecosystems; (3) it can reach toxic levels that impair the ability of aquatic animals to survive, grow and reproduce. Inorganic nitrogen pollution of ground and surface waters can also induce adverse effects on human health and economy.
Because reductions in SO
2 emissions have reduced the atmospheric deposition of H
2SO
4 across large portions of North America and Europe, while emissions of NO
x
have gone unchecked, HNO
3 is now playing an increasing role in the acidification of freshwater ecosystems. This acidification process has caused several adverse effects on primary and secondary producers, with significant biotic impoverishments, particularly concerning invertebrates and fishes, in many atmospherically acidified lakes and streams. The cultural eutrophication of freshwater, estuarine, and coastal marine ecosystems can cause ecological and toxicological effects that are either directly or indirectly related to the proliferation of primary producers. Extensive kills of both invertebrates and fishes are probably the most dramatic manifestation of hypoxia (or anoxia) in eutrophic and hypereutrophic aquatic ecosystems with low water turnover rates. The decline in dissolved oxygen concentrations can also promote the formation of reduced compounds, such as hydrogen sulphide, resulting in higher adverse (toxic) effects on aquatic animals. Additionally, the occurrence of toxic algae can significantly contribute to the extensive kills of aquatic animals. Cyanobacteria, dinoflagellates and diatoms appear to be major responsible that may be stimulated by inorganic nitrogen pollution. Among the different inorganic nitrogenous compounds (NH
4
+, NH
3, NO
2
−, HNO
2, NO
3
−) that aquatic animals can take up directly from the ambient water, unionized ammonia is the most toxic, while ammonium and nitrate ions are the least toxic. In general, seawater animals seem to be more tolerant to the toxicity of inorganic nitrogenous compounds than freshwater animals, probably because of the ameliorating effect of water salinity (sodium, chloride, calcium and other ions) on the tolerance of aquatic animals.
Ingested nitrites and nitrates from polluted drinking waters can induce methemoglobinemia in humans, particularly in young infants, by blocking the oxygen-carrying capacity of hemoglobin. Ingested nitrites and nitrates also have a potential role in developing cancers of the digestive tract through their contribution to the formation of nitrosamines. In addition, some scientific evidences suggest that ingested nitrites and nitrates might result in mutagenicity, teratogenicity and birth defects, contribute to the risks of non-Hodgkin's lymphoma and bladder and ovarian cancers, play a role in the etiology of insulin-dependent diabetes mellitus and in the development of thyroid hypertrophy, or cause spontaneous abortions and respiratory tract infections. Indirect health hazards can occur as a consequence of algal toxins, causing nausea, vomiting, diarrhoea, pneumonia, gastroenteritis, hepatoenteritis, muscular cramps, and several poisoning syndromes (paralytic shellfish poisoning, neurotoxic shellfish poisoning, amnesic shellfish poisoning). Other indirect health hazards can also come from the potential relationship between inorganic nitrogen pollution and human infectious diseases (malaria, cholera). Human sickness and death, extensive kills of aquatic animals, and other negative effects, can have elevated costs on human economy, with the recreation and tourism industry suffering the most important economic impacts, at least locally.
It is concluded that levels of total nitrogen lower than 0.5–1.0 mg TN/L could prevent aquatic ecosystems (excluding those ecosystems with naturally high N levels) from developing acidification and eutrophication, at least by inorganic nitrogen pollution. Those relatively low TN levels could also protect aquatic animals against the toxicity of inorganic nitrogenous compounds since, in the absence of eutrophication, surface waters usually present relatively high concentrations of dissolved oxygen, most inorganic reactive nitrogen being in the form of nitrate. Additionally, human health and economy would be safer from the adverse effects of inorganic nitrogen pollution.
The ability of ensemble models to retain the bias of their learners while decreasing their individual variance has long made them quite attractive in a number of classification and regression ...problems. In this work we will study the application of Random Forest Regression (RFR), Gradient Boosted Regression (GBR) and Extreme Gradient Boosting (XGB) to global and local wind energy prediction as well as to a solar radiation problem. Besides a complete exploration of the fundamentals of RFR, GBR and XGB, we will show experimentally that ensemble methods can improve on Support Vector Regression (SVR) for individual wind farm energy prediction, that GBR and XGB are competitive when the interest lies in predicting wind energy in a much larger geographical scale and, finally, that both gradient-based ensemble methods can improve on SVR in the solar radiation problem.
The exposure of animals to toxicants may cause a depletion in the energy uptake, which compromises reproduction and growth. Although both parameters are ecologically relevant, they usually need ...long-term bioassays. This is a handicap for the availability of toxicological data for environmental risk assessment. Short-term bioassays conducted with environmental concentrations, and using relevant ecological parameters sensitive to short-term exposures, such as behavior, could be a good alternative. Therefore, to include this parameter in the risk assessment procedures, it is relevant the comparison of its sensitivity with that of growth and reproduction bioassays. The study aim was the assessment of differences between endpoints based on mortality, behaviour, reproduction, and growth for the toxicity of metals on aquatic animals. We used the ECOTOX database to gather data to construct chemical toxicity distribution (CTD) curves. The mean concentrations, the mean exposure time, and the ratio between the mean concentration and the exposure time were compared among endpoints. Our results showed that behavioral, growth, and reproduction bioassays presented similar sensitivity. The shortest exposure was found in behavioral and reproduction bioassays. In general, the amount of toxicant used per time was lower in growth and reproduction bioassays than in behavioral and mortality bioassays. We can conclude that, for metal toxicity, behavioral bioassays are less time-consuming than growth bioassays. As the sensitivity of behavior was similar to that of growth and reproduction, this endpoint could be a better alternative to longer bioassays.
Atrial fibrillation (AF) is 1 of the most clinically diagnosed cardiac disturbances but little is known about its risk factors. Previous epidemiologic studies have reported on the association between ...diabetes mellitus (DM) and subsequent risk of AF, with inconsistent results. The aim of this study was to conduct a meta-analysis of published studies to reliably determine the direction and magnitude of any association between DM and AF. A systematic review and meta-analysis was conducted. PubMed and EMBASE were searched to identify prospective cohort and case–control studies that had reported on the association between DM and other measurements of glucose homeostasis with incident AF by April 2010. Studies conducted in primarily high-risk populations and participants in randomized controlled trials were excluded. Seven prospective cohort studies and 4 case–control studies with information on 108,703 cases of AF in 1,686,097 subjects contributed to this analysis. The summary estimate indicated that patients with DM had an approximate 40% greater risk of AF compared to unaffected patients (relative risk RR 1.39, 95% confidence interval CI 1.10 to 1.75, p for heterogeneity <0.001). After correcting for publication bias, the RR was 1.34 (1.07 to 1.68). Studies that had adjusted for multiple risk factors reported a smaller effect estimate compared to age-adjusted studies (RR 1.24, 95% CI 1.06 to 1.44, vs 1.70, 1.29 to 2.22, p for heterogeneity = 0.053). The population-attributable fraction of AF owing to DM was 2.5% (95% CI 0.1 to 3.9). In conclusion, DM is associated with an increased risk of subsequent AF but the mechanisms that may underpin the relation between DM and AF remain speculative.
Atrial fibrillation (AF) is a common cardiac arrhythmia associated with an increased risk of stroke and other complications. Identifying individuals at higher risk of developing AF in the community ...is now possible using validated predictive models that take into account clinical variables and circulating biomarkers. These models have shown adequate performance in racially and ethnically diverse populations. Similarly, risk stratification schemes predict incidence of ischemic stroke in persons with AF, assisting clinicians and patients in decisions regarding oral anticoagulation use. Complementary schemes have been developed to predict the risk of bleeding in AF patients taking vitamin K antagonists. However, major gaps exist in our ability to predict AF and its complications. Additional research should refine models for AF prediction and determine their value to improve population health and clinical outcomes, advance our ability to predict stroke and other complications in AF patients, and develop predictive models for bleeding events and other adverse effects in patients using non-vitamin K oral anticoagulants. (Circ J 2016; 80: 1061–1066)
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