Acute and chronic effects of sodium and potassium on the tropical freshwater cladoceran Pseudosida ramosa

Production Performance of Moina macrocopa (Straus 1820) (Crustacea, Cladocera) Cultured in Different Salinities: The Effect on Growth, Survival, Reproduction, and Fatty Acid Composition of the Neonates

Salinity is a known factor in shaping population dynamics and community structure through direct and indirect effects on aquatic ecosystems. Salinity changes further influence food webs through competition and predation. The responses of Moina macrocopa (Cladocera) collected from Setiu Wetland lagoon (Terengganu) was evaluated through manipulative laboratory experiments to understand the ability of M. macrocopa to tolerate high salinity stress. Specifically, the fatty acid composition, growth, survival, and reproduction of this cladocerans species was examined. Sodium chloride (NaCl) as used in the treatments water with the concentration 0, 4, 6, 8, 12, and 15 salinity. Fatty acid levels were determined using Gas Chromatography and Mass Spectrophotometry (GC-MS). The results indicated that optimal conditions produced the highest fatty acid content, especially the polyunsaturated fatty acid content, such as EPA (eicosapentaenoic acid), ALA (alpha-linoleic acid), ARA (arachidonic acid), and DHA (docosahexaenoic acid). Furthermore, M. macrocopa survival was best at salinity 0, with a percentage of 98%, whereas the opposite occurred at salinity 15, with approximately 20% of viable animals surviving. Besides, M. macrocopa also showed the highest reproduction rate at salinity 0 (e.g., average initial age of reproduction, 4.33 ± 0.58 days) compared with other salinities level. Interestingly, the difference in growth at different salinities was not evident, an unusual finding when considering adverse effects such as osmoregulation pressure on the organism. Based on the results, we conclude that M. macrocopa can only tolerate salinity below salinity 8 and cannot withstand stressful environmental conditions associated with salinities above 8.

Chronic Toxicity of Surface Water from a Canadian Oil Sands End Pit Lake to the Freshwater Invertebrates Chironomus dilutus and Ceriodaphnia dubia

Permanent reclamation of tailings generated by surface mining in the Canadian oil sands may be achieved through the creation of end pit lakes (EPLs) in which tailings are stored in mined-out pits and capped with water. However, these tailings contain high concentrations of dissolved organics, metals, and salts, and thus surface water quality of EPLs is a significant concern. This is the first study to investigate the chronic toxicity of surface water from Base Mine Lake (BML), the Canadian oil sands first large-scale EPL, to aquatic invertebrates that play a vital role in the early development of aquatic ecosystems (Chironomus dilutus and Ceriodaphnia dubia). After exposure of C. dilutus larvae for 23 days and C. dubia neonates for 8 days, no mortality was observed in any treatment with whole BML surface water. However, the emergence of C. dilutus adults was delayed by nearly 1 week, and their survival was significantly reduced (36%) compared with the controls. Reproduction (fecundity) of C. dubia was reduced by 20% after exposure to 2014 BML surface water; however, the effect was not observed after exposure to BML surface water collected a year later in 2015. Despite some adverse effects, the results of this study indicate that BML surface water quality is improving over time and is able to support certain salt-tolerant aquatic organisms. Because salinity within BML will persist for decades without manual intervention, the ecological development of the lake will likely resemble that of a brackish or estuarine ecosystem with reduced diversity.

Multiple riparian-stream connections are predicted to change in response to salinization

Secondary freshwater salinization, a common anthropogenic alteration, has detrimental, lethal and sub-lethal effects on aquatic biota. Ions from secondary salinization can become toxic to terrestrial and aquatic organisms when exposed to salinized runoff that causes periodic high-concentration pulses. Gradual, low-level (less than 1000 ppm salinity) increases in salt concentrations are also commonly documented in regions with urbanization, agriculture, drilling and mining. Despite widespread low-level salt increases, little is known about the biological and ecological consequences in coupled riparian-stream systems. Recent research indicates lethal and even sub-lethal levels of ions can subsidize or stress microbial decomposer and macroinvertebrate detritivores that could lead to alterations of three riparian-stream pathways: (i) salinized runoff that changes microbial decomposer and macroinvertebrate detritivore and algae performance leading to changes in composition and processing of detrital pools; (ii) riparian plant salt uptake and altered litter chemistry, and litterfall for riparian and aquatic detritivores and their subsequent enrichment, stimulating decomposition rates and production of dissolved and fine organic matter; and (iii) salt consumption in salinized soils could increase riparian detritivore growth, decomposition and dissolved organic matter production. Subsidy-stress and reciprocal flows in coupled riparian-stream connections provide frameworks to identify the extent and magnitude of changes in detrital processing from salinization.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

Aquatic ecotoxicity of ashes from Brazilian savanna wildfires

In a global scenario of climate change, several studies have predicted an increase in fires in different parts of the world. With the occurrence of rains following the fires in the Brazilian savanna (Cerrado biome), the compounds present in ashes may enter aquatic environments and cause adverse effects to these ecosystems. In this context, this study evaluated the potential toxicity of ashes from two areas of Cerrado and an area of pasture, through ecotoxicological bioassays and using three aquatic species from distinct trophic levels, which were exposed to different dilutions of ashes: the microcrustacean Ceriodaphnia dubia, the fish Danio rerio and the mollusc Biomphalaria glabrata. The ashes from the three sampled areas showed higher concentrations of some elements in relation to the soil samples (B, Ca, K, Mg, Mn, P, S, Si, Sr, Zn), but only a small quantity of these compounds was solubilised. Our data showed that all ash samples caused acute toxicity to C. dubia (48hs-LC₅₀ = 13.4 g L^-1; 48hs-LC₅₀ = 6.33 g L^-1; 48hs-LC₅₀ = 9.73 g L^-1 respectively for transition area, pasture, typical cerrado areas), while in relation to D. rerio and B. glabrata, no acute toxicity was observed when they were exposed to ashes from native Cerrado vegetation and pasture areas. Ashes from a transition area showed toxicity for D. rerio (48hs-LC₅₀ = 25.0 g L^-1); possibly, this was due to the combination of multiple preponderant inorganic elements of ashes with other organic compounds not analysed, such as polycyclic aromatic hydrocarbons (PAHs). In summary, these results suggest that wildfires may pose risks to zooplankton communities and emphasize the need for more studies to better understand the complexity of the ecological effects of fire on aquatic ecosystems.

Soil ecotoxicology in Latin America: Current research and perspectives

Soils from some Latin American countries support the highest biodiversity levels on the planet and simultaneously have some of the most serious environmental impacts attributed to both historical and current agricultural practices and industrial activities. Soil contamination has resulted from intensive use of pesticides, extensive mining and other industrial activities, and uncontrolled management of waste within inappropriate regulatory frameworks. The present study presents an overview of the scientific research on soil ecotoxicology conducted in Latin America, summarizing the recent advances and highlighting the needs for further refinements in this research field. Most of the contributions to the scientific literature have been from Brazil. The most investigated issue is the ecotoxicity of pesticides and earthworms, which were the organisms most frequently used as test species. Needs identified by Latin American researchers include methods and procedures for: 1) identifying and collecting natural soils to be used as reference test-substrates in tests, 2) identifying and discerning the range of sensitivities of native test species to soil contaminants, 3) developing environmental guidelines applicable to tropical/subtropical conditions, and 4) developing methods and procedures for higher tier testing for full development and implementation of environmental risk assessment schemes. The protection of Latin American soils, including provision of goods and services, is currently framed in legislation and other regulations, but implementation requires significant improvement and additional training programs. Environ Toxicol Chem 2017;36:1795-1810. © 2017 SETAC.

Comparative Analysis between Ecotoxicity of Nitrogen-, Phosphorus-, and Potassium-Based Fertilizers and Their Active Ingredients

This study aimed to analyze the ecotoxicity of nitrogen-, phosphorus-, and potassium-based compounds to organisms of two different trophic levels in order to compare the toxic effect between high-purity substances and these substances as components of fertilizers. Dilutions were made with the fertilizers' potassium chloride, potassium nitrate, superphosphate, urea, and their equivalent reagents, to conduct assays to establish the acute lethal concentration for half of the population (LC50). Ten individuals of the benthic snail Biomphalaria glabrata and the fish Danio rerio were exposed to each concentration of tested compounds. As a result, the toxicity levels of potassium chloride, potassium nitrate, and urea were obtained for B. glabrata and D. rerio, with the fish being more susceptible to potassium chloride in the fertilizer and the snail to potassium nitrate and urea, in both commercial and reagent forms. Regarding superphosphate, no significant toxicity was found. This study concluded that among the tested substances, KNO₃ and KCl were the most toxic substances and urea the least toxic. It was not possible to establish the most sensitive species since, for KCl, the fish were more susceptible to the fertilizer and the snail to the reagent, while for KNO₃ the opposite was observed.

Effects of Bacillus thuringiensis var. israelensis on nonstandard microcrustacean species isolated from field zooplankton communities

The toxicity of Bacillus thuringiensis var. israelensis on zooplanktonic microcrustaceans was evaluated using individuals collected in coastal wetlands where this larvicide has been used for mosquito control over the last decades. We tested five zooplankton species that coexist with mosquito larvae: two copepods (both nauplii and adults of Tropocyclops prasinus and Acantocyclops americanus), and three cladocerans (Ceriodaphnia reticulata, Chydorus sphaericus, and Daphnia cf. pulex). Our experiments included seven replicates of six concentrations (Bti Vectobac12AS 1200 Bti ITU/mg): 0, 5, 25, 50, 250, and 500 mg L^-1. We analyzed acute and sub-chronic effects after a single inoculation. Despite the high variability of responses among our tested organisms, we found a general pattern of increasing mortality with concentration and time. We conclude that negative effects at the community level are not unlikely as some species were affected at doses close to those used in field applications.

Ecotoxicological characterization of sugarcane vinasses when applied to tropical soils

The impact of sugarcane vinasse on soil invertebrates was assessed through ecotoxicological assays. Increasing concentrations of two vinasses from different distillery plants (VA and VB), and a vinasse from a laboratory production (VC), were amended on two natural tropical Oxisols (LV and LVA) and a tropical artificial soil (TAS) to characterize the effects of the vinasses on earthworms (Eisenia andrei), enchytraeids (Enchytraeus crypticus), mites (Hypoaspis aculeifer) and collembolans (Folsomia candida). The highest concentrations of VA and VB were avoided by earthworms in all soils and by collembolans especially in the natural soils. The presence of VC in all of the tested soils did not cause avoidance behavior in these species. The reproduction of earthworms, enchytraeids and collembolans was decreased in the highest concentrations of VA and VB in the natural soils. In TAS, VB reduced the reproduction of all test species, whereas VA was toxic exclusively to E. andrei and E. crypticus. The vinasse VC only reduced the number of earthworms in TAS and enchytraeids in LVA. The reproduction of mites was reduced by VB in TAS. Vinasses from distillery plants were more toxic than the vinasse produced in laboratory. The vinasse toxicities were influenced by soil type, although this result was most likely because of the way the organisms are exposed to the contaminants in the soils. Toxicity was attributed to the vinasses' high salt content and especially the high potassium concentrations. Data obtained in this study highlights the potential risk of vinasse disposal on tropical soils to soil biota. The toxic values estimated are even more relevant when considering the usual continuous use of vinasses in crop productions.

Measurements of cholinesterase activity in the tropical freshwater cladoceran Pseudosida ramosa and its standardization as a biomarker

The activity of cholinesterases (ChE) has been recognized as a useful tool for assessing the toxicity in the environmental assessment programs. Nevertheless, the prior optimization of the experimental conditions for the appropriate measuring of the ChE activity enables us to get reliable results. Thus, the main objective of this study was to adapt and optimize a microplate assay for measuring the activity of ChE in the tropical cladoceran Pseudosida ramosa. The best readings for the reaction rates were obtained with buffers of pH 8.0 and molarity of 0.02M. The measurements of the reaction rates for the different substrate concentrations showed that the maximum reaction rate (32mODmin(-1)) was achieved by the final concentration of 2mM of substrate. In relation to the enzyme concentration, reaction rates were directly proportional to the protein concentration, which confirmed the linear kinetics for a maximum reaction rate. On the basis of the results of the assays for the effect of the number of individuals and homogenate dilution on the reaction rate of substrate hydrolysis and ChE activity, we recommend using of 30 individuals (3 days-old) in 250μL of buffer, 20 individuals (7 days-old) in 250μL of buffer and 15 individuals (both 14 and 21 days-old) in 300μL of buffer. The limits of quantitation obtained were 1.419mODmin(-1) (≤72h-old), 1.670mODmin(-1) (7 days-old), 0.943mODmin(-1) (14 days-old) and 0.797mODmin(-1) (21 days-old). In conclusion, it was possible to measure the ChE activity in P. ramosa with the methodology adapted, thus contributing to the implementation of a biochemical biomarker in freshwater toxicity assessments in tropical regions.

Acute effects of Anabaena spiroides extract and paraoxon-methyl on freshwater cladocerans from tropical and temperate regions: links between the ChE activity and survival and its implications for tropical ecotoxicological studies

Cholinesterase (ChE) activity was measured in Pseudosida ramosa and Daphnia magna, which had previously been exposed to Anabaena spiroides extract or to paraoxon-methyl for 48 h. These activities were then related to survival at 48 h. For A. spiroides extract, the observed 48-h LC50 was 2.27 and 2.70 × 10(6)cells mL(-1), while for paraoxon-methyl it was 0.60 and 2.17 μg L(-1), respectively, for P. ramosa and D. magna. Dose-response relationships were obtained for both P. ramosa and D. magna, when exposed to A. spiroides extract or paraoxon-methyl. Thus, when the tested concentrations of the toxicants increased, ChE activity and survival decreased. The ratio between 48-h IC50 for ChE and 48-h LC50 ranged from 75% to 81% for P. ramosa and from 77% to 81% for D. magna. This indicated that the concentrations of both A. spiroides extract and paraoxon-methyl that cause 50% mortality also inhibit ChE activity by 50%. Also, it was found that, for P. ramosa, a 50% inhibition of ChE activity was associated with a survival of 59.5% and 60.9%, respectively, for A. spiroides extract and paraoxon-methyl. However, for D. magna, at high levels of inhibition of ChE activity, almost no mortality was detected. In this specific case, 50% inhibition of the ChE activity was associated with 90.4 and 95.4% survival for A. spiroides extract and paraoxon-methyl, respectively. In contrast, enzyme inhibition slightly above 60% had a strong detrimental effect on survival in D. magna. These different patterns found in the relationship between ChE inhibition and survival may be due to species-specific differences in the affinities of both acetylcholinesterase and pseudocholinesterases, since the cladoceran ChE assays were performed with whole-body homogenates. In conclusion, when using ChE as a biochemical biomarker in risk assessment of cyanobacterial neurotoxic blooms in tropical regions, it is strongly recommended that native species are used, since our results revealed that P. ramosa was more sensitive than D. magna for both assay endpoints and both toxicants. Furthermore, the relationship between ChE activity and survival had a species-specific response. Therefore, the use of the model species D. magna in acute toxicity tests and ChE assays in tropical regions may lead to errors in the estimation of risks to the local species.

Evolutionary and plastic responses of freshwater invertebrates to climate change: realized patterns and future potential

We integrated the evidence for evolutionary and plastic trait changes in situ in response to climate change in freshwater invertebrates (aquatic insects and zooplankton). The synthesis on the trait changes in response to the expected reductions in hydroperiod and increases in salinity indicated little evidence for adaptive, plastic, and genetic trait changes and for local adaptation. With respect to responses to temperature, there are many studies on temporal trait changes in phenology and body size in the wild that are believed to be driven by temperature increases, but there is a general lack of rigorous demonstration whether these trait changes are genetically based, adaptive, and causally driven by climate change. Current proof for genetic trait changes under climate change in freshwater invertebrates stems from a limited set of common garden experiments replicated in time. Experimental thermal evolution experiments and common garden warming experiments associated with space-for-time substitutions along latitudinal gradients indicate that besides genetic changes, also phenotypic plasticity and evolution of plasticity are likely to contribute to the observed phenotypic changes under climate change in aquatic invertebrates. Apart from plastic and genetic thermal adjustments, also genetic photoperiod adjustments are widespread and may even dominate the observed phenological shifts.

Distribution and biological aspects of the introduced speciesMoina macrocopa (Straus, 1820) (Crustacea, Cladocera) in the semi-arid central region of Argentina

Moina macrocopa is common in eutrophic water bodies. Two subspecies have been described: M. macrocopa macrocopa (Straus, 1820), whose original distribution was restricted to the Old World, and M. macrocopa americanaGoulden, 1968, recorded only in North America. In 1994, the species was found in Bolivia, and in 1997 it was found in the northeast of Argentina. As the specimens belonged to M. macrocopa macrocopa in both cases, the authors suggested that it may have been introduced from the Old World by anthropogenic means. The aim of this study was to assess the distribution of M. macrocopa in La Pampa (Argentina), and provide information on its population characteristics under natural conditions. The species was recorded in six out of more than 100 water bodies surveyed; the specimens belong to M. macrocopa macrocopa. Although this species is not considered halophilic, the water bodies where it was found present high salinity (5.7 to 21.8 g.L–1). All are shallow, temporary and hypertrophic due to the agricultural activities carried out in their basins. Densities were between 1 and 312.6 ind.L–1. Size varied between 0.6 and 1.8 mm and some specimens were larger than those of other places. The parthenogenetic fraction predominated and the number of eggs ranged between 2 and 23. No correlations were found between density, size, or number of eggs and the environmental parameters studied. The presence of M. macrocopa in Pampean lakes could be due to the introduction of fish from hatcheries in the province of Buenos Aires, where it is used as food. Considering that the invasive character ofM. macrocopa has been recognized and that this study found that it is tolerant to a wide range of environmental conditions, attention should be paid to a possible displacement of its native congeneric species, typical of saline and temporary water bodies in central Argentina.