Daphnia Carinata Research Articles

Maternal effects of inducible tolerance against the toxic cyanobacterium Microcystis aeruginosa in the grazer Daphnia carinata

Cyanobacterial blooms are becoming potent agents of natural selection in aquatic ecosystems because of their high production of some toxins and increased frequency in recent decades with eutrophication and climate change. Maternal exposure to the toxic Microcystis aeruginosa significantly increased the intrinsic rates of population increase, average life span, and net reproductive rates of a clone of the planktonic grazer Daphnia carinata in an offspring environment where cyanobacteria were present, but not for two additional clones. Offspring from mothers exposed to M. aeruginosa had lower intrinsic rates of population increase, average life span, and net reproductive rates than individuals from unexposed mothers when fed exclusively a green alga. These results suggest that benefits, costs, and clonal variations of maternal effects of inducible tolerance should be considered when trying to understand ecological consequences of cyanobacterial blooms since they can shape the trophic interactions between cyanobacteria and daphnids.

The response of European Daphnia magna Straus and Australian Daphnia carinata King to changes in geomagnetic field

This study investigates the effects of lifelong exposure to reversed geomagnetic and zero geomagnetic fields (the latter means absence of geomagnetic field) on the life history of Daphnia carinata King from Australia and Daphnia magna Straus from Europe. Considerable deviation in the geomagnetic field from the usual strength, leads to a decrease in daphnia size and life span. Reduced brood sizes and increased body length of neonates are observed in D. magna exposed to unusual magnetic background. The most apparent effects are induced by zero geomagnetic field in both species of Daphnia. A delay in the first reproduction in zero geomagnetic field is observed only in D. magna. No adaptive maternal effects to reversed geomagnetic field are found in a line of D. magna maintained in these magnetic conditions for eight generations. Integrally, the responses of D. magna to unusual geomagnetic conditions are more extensive than that in D. carinata. We suggest that the mechanism of the effects of geomagnetic field reversal on Daphnia may be related to differences in the pattern of distribution of the particles that have a magnetic moment, or to moving charged organic molecules owing to a change in combined outcome and orientation of the geomagnetic field and Earth's gravitational field. The possibility of modulation of self-oscillating processes with changes in geomagnetic field is also discussed.

Individual and Joint Toxicity of Three Chloroacetanilide Herbicides to Freshwater Cladoceran Daphnia carinata

Individual and joint toxicity of three chloroacetanilide herbicides to a freshwater cladoceran were studied. The 48h-LC50 values of alachlor, acetochlor and butachlor to Daphnia carinata Dc42 were 11.1, 11.8 and 3.45mgL(-1), respectively. The toxicity was significantly (p<0.05) related to hydrophobicity. The additive indexes of binary mixtures of three herbicides were less than zero and it showed antagonism. The body length of D. carinata treated with high concentration of herbicides was shorter than that of control group significantly (p<0.05). It suggests that joint actions must be considered when assessing the acute toxicity of chloroacetanilide herbicides to D. carinata.

Fitness benefits and costs of induced defenses in Daphnia carinata (Cladocera: Daphnidae) exposed to cyanobacteria

Induced defenses can shape the trophic interactions between prey and predators, but the presence, benefits, and costs of induced defenses against harmful algae in zooplankton are little known. Here, the hypothesis that a short-time exposure to harmful algae can induce defenses in zooplankton was tested by evaluating the fitness changes in a single clone of Daphnia carinata (Cladocera: Daphnidae) after the exposure to a bloom-forming cyanobacterium Microcystis aeruginosa. Life-table experiments revealed that the 1-day exposure to M. aeruginosa significantly enhanced the average life span, the net reproductive rate, and the intrinsic rate of population increase of D. carinata in the presence of cyanobacteria, compared to nonexposed individuals. Then, we tested the second hypothesis that the induced defense in zooplankton would carry a cost on fitness in the absence of cyanobacteria. The 1-day exposure to M. aeruginosa significantly depressed the average life span, the net reproductive rate, and the intrinsic rate of population increase of D. carinata when exclusively feeding on a green alga, Chlorella pyrenoidosa. The induced defense against M. aeruginosa in D. carinata after a short-time exposure explains some aspects of the interactions between harmful algae and zooplankton, and may provide new general insights into the predator–prey “arms race”.

Acute toxicity of butachlor and atrazine to freshwater green alga Scenedesmus obliquus and cladoceran Daphnia carinata

Both single and joint toxicity of atrazine and butachlor to freshwater green alga Scenedesmus obliquus and cladoceran Daphnia carinata isolated from South China were investigated in the present study. The 96h-EC50 values of atrazine and butachlor to S. obliquus were 0.0147 and 2.31mgL−1, while the 48h-LC50 values to D. carinata were 60.6 and 3.40mgL−1, respectively. These results suggest that atrazine could be highly toxic to S. obliquus and slightly toxic to D. carinata, while butachlor exhibits moderate toxicity to both organisms. The additive indexes of atrazine and butachlor mixtures were −2.68 (−3.02 to −2.32) to S. obliquus and 0.054 (−0.025 to 0.238) to D. carinata, respectively. Therefore, the joint action of two herbicides was significant antagonism to S. obliquus, while significant synergism was not shown to D. carinata. Moreover, significant linear correlation between the natural logarithm of herbicide concentrations and growth rates of alga S. obliquus was observed. Taken together, it is the first study reporting the toxicity endpoints for mixture of atrazine and butachlor against S. obliquus and D. carinata isolated from south China. The present results would be helpful to provide data to assess the ecological risk of both herbicides to aquatic organisms.

Use Inhibition Rate of Vertical Movement Ability of Daphnia Carinata as an Indicator of Chromium Acute Bio-Toxicity

In order to develop a sensitive bio-monitor and a quick method for detecting water pollution, this research used a specific Daphnia Carinata clone (Dc42) to study its reaction or behavior to water pollutant, such as the ability of vertical movement, EC50 and LC50 in chromium solution. The results showed that the numbers of Daphnia Carinata population decreases with the rise of Cr6+ concentration in the upper of the tuber. Compared to the standard EC50 and LC50 bioassay, the detection limit of 8h-Ri (inhibition rate of vertical movement ability) was 76.40%, 61.00%, 68.20% and 53.87% lower than that of 24h-LC50, 48h-LC50, 24h-EC50 and 48h-EC50, respectively; similar to 96h- LC50 and 96h-LC50. The sensitivity of Daphnia Carinata clone (Dc42) in response to pollutants showed a good and attractive prospect to use its population behavior as a biomonitoring approach for water quality. It has the potential to be a sensitive, quick and efficient method for detecting pollutants in water.

Acute Toxicological Response ofDaphniaandMoinato Hydrogen Peroxide

AbstractHydrogen peroxide (H2O2) is suggested to be an environmentally benign chemical that may be used for wastewater purification. A recent study on the application of H2O2 in a wastewater stabilization pond (WSP) showed that H2O2 is a promising method to decrease high amounts of potentially toxic cyanobacteria. However, WSPs are complex biological systems that require healthy bacterial, phytoplankton, and zooplankton communities for optimal performance. Therefore, if H2O2 is to be regularly used in WSPs, its effect on all components of a healthy WSP food web, including zooplankton, must be assessed. This study quantifies the acute toxicity of H2O2 to Moina and Daphnia, two zooplankton genera that are common in WSPs in Western Australia’s Mediterranean climate. The results indicate that Daphnia carinata is less susceptible to H2O2 than Moina sp., as mean survival time was significantly higher at concentrations ≥2 mg H2O2/L. Additionally, the LC50 was 5.6 mg H2O2/L in Daphnia and 2 mg H2O2/L in Moina...

Impacts of un-ionized ammonia in digested piggery effluent on reproductive performance and longevity of Daphnia carinata and Moina australiensis

In effluent treatment systems, a major concern is how to maintain culture of local zooplankton species ( Daphnia carinata and Moina australiensis), particularly with the impact of un-ionized ammonia on their life cycle response. Hence the impact of un-ionized ammonia present in digested piggery effluent on the reproductive physiology and survival of D. carinata and M. australiensis was evaluated in this study. Both species were cultured in diluted digested piggery effluent and supplied with algae, Chlorella vulgaris as food. The effects of different un-ionized ammonia concentrations on total fertility, number of clutches, clutch size and survival were recorded every 24 h. The lethal concentration of unionized ammonia, with 50% survival after 24 h exposure to (24 hr LC50 values) un-ionized ammonia was determined for each species relative to total ammonia nitrogen, pH and temperature. M. australiensis had greater tolerance at higher levels of un-ionized ammonia than D. carinata. However, older neonates (< 48 h old) could survive at a higher concentration of un-ionized ammonia nitrogen (up to 2.8 mg/l D. carinata and 8.8 mg/l M. australiensis) than younger neonates (2.2 mg/l D. carinata and 7.5 mg/l M. australiensis). The net reproduction rates ( R 0) were derived from fertility and survival while the intrinsic rates of increases ( r) were calculated with net reproduction rate and generation time. M. australiensis has a maximum R 0 (189.84) and r (0.54) at 4.5 and 6.5 mg/l NH 3–N, respectively, while D. carinata has a maximum R 0 (100.46) and r (0.39) at 0.5 and 1.0 mg/l NH 3–N. Hence, M. australiensis is a faster growing species than D. carinata when cultured in digested piggery effluent.

Predation Risk Perception in Daphnia carinata Induced by the Milt of Common Carp (Cyprinus carpio)

ABSTRACT Numerous experimental studies suggest that many organisms can sense predation risk and subsequently adjust their life history, behavior, and morphology as adaptations to predators. The aim of the present study was to test if fish milt would induce changes in Daphnia carinata. We exposed D. carinata to the milt of fish and then measured parameters of growth and reproduction until the offspring of the third clutch were released. Individual growth rate was higher in the treatment with fish milt than in the control. Size at the first three clutches was greater in the milt treatment than in the control. Age at the first three clutches was significantly younger in the high milt treatment than in the control. Moreover, D. carinata produced more offspring in the presence offish milt. The degree of response by D. carinata was dose-dependent, correlating with the concentration of milt. D. carinata can use some substance originating from fish milt to sense risk of predation risk and change its life history to increase its fitness.

A study on the effects of food quantity and quality on glutathione S-transferase (GST) activity and growth rate parameters of Daphnia carinata varying in age

The adverse influences of insufficient food and toxins on Daphnia carinata's body growth, reproduction and tolerance were investigated in the laboratory. Different concentrations of Scendesmus obliquus and a mixture of S. obliquus and microcystin (MC)-containing Microcystis aeruginosa PCC7820 were used to feed D. carinata. Glutathione S-transferase (GST) activity towards five chemical compounds (substrates) was measured and used as an indicator of their tolerance. Body growth rate and clutch size of D. carinata decreased with declined concentration or decreased proportion of S. obliquus in the diet. GST activity decreased with ageing in D. carinata. However, GST activity to several chemical compounds increased when food quantity or food quality decreased. Adult D. carinata had a lower GST activity towards p-nitrophenenzyl chloride (PNBC) than juveniles and exhibited a sharp decline (P < 0.001) in GST activity towards PNBC as the animals aged. It is suggested that the age-specific decrease in GST activity is a possible mechanism for the high morality of adult D. carinata in the summer of eutrophic lakes.

Bioinformatic analyses of the publicly accessible crustacean expressed sequence tags (ESTs) reveal numerous novel neuropeptide-encoding precursor proteins, including ones from members of several little studied taxa

ESTs have been generated for many crustacean species, providing an invaluable resource for peptide discovery in members of this arthropod subphylum. Here, these data were mined for novel peptide-encoding transcripts, with the mature peptides encoded by them predicted using a combination of online peptide prediction programs and homology to known arthropod sequences. In total, 70 mature full-length/partial peptides representing members of 16 families/subfamilies were predicted, the vast majority being novel; the species from which the peptides were identified included members of the Branchiopoda ( Daphnia carinata and Triops cancriformis), Maxillopoda ( Caligus clemensi, Caligus rogercresseyi, Lepeophtheirus salmonis and Lernaeocera branchialis) and Malacostraca ( Euphausia superba, Marsupenaeus japonicus, Penaeus monodon, Homarus americanus, Petrolisthes cinctipes, Callinectes sapidus and Portunus trituberculatus). Of particular note were the identifications of an intermediate between the insect adipokinetic hormones and crustacean red pigment concentrating hormone and a modified crustacean cardioactive peptide from the daphnid D. carinata; Arg 7-corazonin was also deduced from this species, the first identification of a corazonin from a non-decapod crustacean. Our data also include the first reports of members of the calcitonin-like diuretic hormone, FMRFamide-related peptide (neuropeptide F subfamily) and orcokinin families from members of the Copepoda. Moreover, the prediction of a bursicon α from the euphausid E. superba represents the first peptide identified from any member of the basal eucaridean order Euphausiacea. In addition, large collections of insect eclosion hormone- and neuroparsin-like peptides were identified from a variety of species, greatly expanding the number of known members of these families in crustaceans.

Impact of the fish Garra on the ecology of reservoirs and the occurrence of Microcystis blooms in semi‐arid tropical highlands: an experimental assessment using enclosures

Summary1. Many man‐made reservoirs in the semi‐arid highlands of Northern Ethiopia (Tigray) are characterised by the occurrence of intensive blooms of cyanobacteria and a dominance of small riverine fishes belonging to the genus Garra.2. We carried out enclosure experiments to test for the effect of these small fish on abiotic characteristics, phytoplankton biomass and zooplankton community structure in the pelagic of two reservoirs (Gereb Awso and Tsinkanet). Two experiments were carried out in each of the reservoirs, one at the end of the rainy season (highest water level) and one at the end of the dry season (lowest water level).3. The presence of Garra in general increased the amount of suspended matter, nutrient concentrations (total nitrogen and total phosphorus), phytoplankton and Microcystis biomass (including the proportion of Microcystis in the phytoplankton community), and reduced water transparency. The positive effect of the presence of Garra on nutrient concentrations and phytoplankton productivity indicate that Garra has the potential to affect food web functioning indirectly through bottom‐up effects, by enhancing nutrient concentrations through sediment resuspension and excretion of nutrients. Indeed, population densities of the cladoceran zooplankton taxa Ceriodaphnia and Diaphanosoma also showed an overall increase in enclosures with Garra.4. However, our data also provide some evidence for a potential of Garra to exert top‐down control on large bodied daphnids (Daphnia carinata, D. barbata), although such effect varied among experiments. The limited capability of Garra to control zooplankton communities mainly reflects the low efficiency of these small, riverine and benthos‐oriented fish in foraging on zooplankton and suggests the existence of an unoccupied niche for zooplanktivorous fish in the majority of the reservoirs.5. Although the main effects of Garra on the pelagic food web seemed to be mediated by bottom‐up mechanisms, our results also indicate that one of the key variables, the relative abundance of Microcystis, was impacted by Daphnia‐mediated trophic cascade effects.

THE TOXIC EFFECTS OF BPA AND NP ON &lt;I&gt;D.CARINATA&lt;/I&gt; AND &lt;I&gt;M.MICRURA&lt;/I&gt;

In our experiments, Daphnia carinata and Moina micura were used as material to evaluate the toxicity of BPA and NP. From acute experiments, the 24h and 48 h LC50 of D. carinata to BPA were 12.02 mg/L and 11.64 mg/L, the 24h and 48h LC50 of M. micura to BPA were 13.70mg/L and 9.63mg/L, respectively. The 24h and 48h LC50 of D. carinata to NP were 0.221 mg/L and 0.159 mg/L, the 24 h and 48 h LC50 of M. micara to NP were 0.334mg/L and 0.126mg/L, respectively. It indicated that M. micura was more sensitive to the toxicity of BPA and NP than D. carinata, which offers a good tool to evaluate the Pollution of water environment. In chronic experiments, there is a significant relationship between the ratio of male offspring in total offspring and the exposed concentration of BPA and the effects looks like a hormesis phenomenon. The life history and the survive rate of offspring exhibited a negative correlation to the exposed concentration of NP, our results suggested that the chronic toxicity of BPA and the acute toxicity of NP were very important to evaluate the pollution of water environment by the two compounds.

Analysis and comparison of a set of expressed sequence tags of the parthenogenetic water flea Daphnia carinata

The water flea Daphnia carinata (D. carinata) reproduces both sexually and parthenogenetically, yet little is known about the genes involved in these processes. To further clarify the reproductive biology of Daphnia and elucidate their unique mechanism of reproductive transformation, we have generated and characterized an expressed sequence tag (EST) data set from D. carinata. A set of 1,495 clusters were generated from sequencing 3,072 randomly chosen clones from a parthenogenetic, juvenile water flea cDNA library. The nucleic acid and deduced amino acid sequences were compared with known GenBank sequences. Functional annotation found that 959 clusters showed significant homology with known genes involved in a broad range of activities, including metabolism, translation, development and reproduction, as well as genes involved in sensing environmental factors. We speculate that genes involved in development and reproduction, along with genes that allow the organism to sense changes in the environment, play important roles in the process of parthenogenetic reproduction and could be markers of the early steps of sexual differentiation. Additionally, 86% of the D. Carinata unique sequences could be stringently mapped to the D. pulex genome, of which 125 mapped to intergenic and intronic regions on the current assembly. Our results provide practical insight into crustacean reproductive biology, in addition to establishing a new animal model for reproductive and developmental biology.

Toxicity of copper, lead, and zinc mixtures to Ceriodaphnia dubia and Daphnia carinata

Acute and chronic bioassays were conducted to determine the effects of copper, lead, and zinc mixtures on Ceriodaphnia dubia and Daphnia carinata. Copper, lead, and zinc combined at up to 5.2, 4.5, and 51.8 μg/L, respectively, did not cause significant mortality during acute exposures, although mixtures of 10.6, 9, and 101.1 μg/L and higher resulted in 65–100% mortality. Binary combinations of Cu+Zn (1.3+13.0 μg/L) and Cu+Pb (1.3+1.1 μg/L) and ternary combinations of Cu+Pb+Zn (1.3+1.1+13.0 μg/L) had a significant effect on reproduction of C. dubia. Toxic units and associated confidence intervals were calculated to characterize the nature of metal interactions. In most cases, and based on confidence intervals encompassing a value of 1, most of the metal interactions would be classified as additive. However, a more than additive effect was indicated by the acute tests for both species exposed to Cu+Pb, for D. carinata exposed to Cu+Zn, and for C. dubia exposed to all three metals.

Effects of &lt;i&gt;Daphnia carinata&lt;/i&gt; grazing on the phytoplankton of Lake Xuanwu, Nanjing

隆腺溞(Daphnia carinata)是许多湖泊的常见大型浮游动物,习居于富营养的水域中,以浮游植物为食,且滤食效率较高.通过浮游动物添加实验,研究了隆腺溞对南京玄武湖叶绿素和浮游植物群落结构的影响.结果表明,在隆腺溞组,浮游植物密度较对照组降低了83%,叶绿素较对照组下降了81%,氮、磷营养盐与叶绿素的相关性不显著.浮游植物的群落结构较对照组也发生了很大变化,蓝藻、绿藻和硅藻的比例有显著上升,隐藻呈显著下降趋势,金藻、甲藻和裸藻在实验结束时已没有检出.说明隆腺溞的摄食能有效控制浮游植物的生物量,可对浮游植物的群落结构产生显著影响.;Daphnia carinata is a large zooplankter in many eutrophic lakes and has a high efficiency to graze phytoplankton. The effects of Daphnia carinata on chlorophyll-a and the community structure of phytoplankton of Lake Xuanwu in Nanjing was studied experimentally. The results showed that the density of phytoplankton decreased 83% and the chlorophyll-a decreased 81% in the Daphnia carinata treatment comparing with the control. There is no significant relationship between nitrogen, phosphorus and chlorophyll-a in the Daphnia treatment. When Daphnia presented, the community structure of phytoplankton had changed. The proportion of Cyanophyta, Chlorophyta and Bacillariophyta obviously increased and the proportion of Cryptophyta obviously decreased. The Chrysophyta, Pyrrophyta, and Euglenophyta were not found at the end of the experimentation. Our experiments showed that Daphnia carinata can efficiently control the biomass of phytoplankton and change the community structure of phytoplankton.

Effect of natural food from three levels of eutrophic lakes on the growth and reproduction of &lt;i&gt;Daphnia carinata&lt;/i&gt;

用花神湖、玄武湖、南湖的湖水培养隆腺溞,探讨不同营养水体的自然食物对隆腺溞生长、繁殖的影响.花神湖氮、磷营养盐浓度和浮游植物生物量均很低,用花神湖湖水培养的隆腺溞生长缓慢,个体在没有繁殖前就全部死亡.玄武湖氮、磷营养盐浓度和浮游植物生物量均低于南湖,但用玄武湖湖水培养的隆腺溞在生长速率、平均体长、生殖量上均高于用南湖湖水培养的隆腺溞.实验结果表明:不同营养盐条件下,湖泊中浮游植物的组成有较大的差别,这种差别会对浮游动物生长、繁殖产生影响;在浮游植物种类和生物量适宜时,隆腺溞有较大的生殖量.浮游植物种类组成、浮游植物生物量的过低或过高都会抑制隆腺溞的生长、生殖.;A laboratory experiment was conducted to evaluate the effect of different natural food on the growth and reproduction ofDaphnia carinata. The natural food came from the three lakes: Lake Huashen, Lake Xuanwu and Lake Nanhu with differentconcentrations of nitrogen and phosphorus. D. carinata had the lowest growth rate and all died before starting reproduction with thefood from Lake Huashen. Both nutrient concentrations and phytoplankton biomass in Lake Xuanwu were lower than that in LakeNanhu. However, the growth rate, the average body length and the reproductive capacity of D. Carinatacultured with the food from LakeXuanwu were higher than that in Lake Nanhu. The experiment showed that the nutrition level of nitrogen and phosphorus and the foodconcentration had an evident influence on the growth and reproduction of D. Carinata. When the nutrition level of nitrogen andphosphorus and the food concentration in the lakes were too high or low, the growth and reproduction of D. Carinatawould be restrained.

Toxicity of tri- and penta-valent arsenic, alone and in combination, to the cladoceran Daphnia carinata: the influence of microbial transformation in natural waters

The acute toxicity of arsenic(III) and arsenic(V) alone and in combination to a cladoceran, Daphnia carinata, was studied in both cladoceran culture medium and natural water collected from a local suburban stream. As(III) was found to be more toxic than As(V) to Daphnia survival. The LC(50) values for As(III), As(V), and As(III) + As(V) were 0.554, 1.499, and 0.692 mg l(-1), respectively. Although various species of As, particularly As(III) and As(V) co-exist together in natural waters, the existing guidelines for water quality are based on individual As species. The results of this investigation suggest that As(III) and As(V) can interact either synergistically or additively resulting in an increase in the overall toxicity of the mixture compared to individual As species. Also, indigenous microorganisms in natural water may play a significant role in the transformation of As, thereby influencing the toxicity of As in receiving waters. This study clearly suggests that the joint action of As species should be considered in the development of water quality guidelines. To our knowledge this is the first study on the interactive effect of As(III) and As(V) to a cladoceran. Thus, this study suggests that these two species of As, when present together above 0.1 mg l(-1) concentration, are toxic to fresh water invertebrates; therefore, pollution with these compounds may adversely affect natural ecosystems.

Toxicity of mercury on in vitro development of parthenogenetic eggs of a freshwater cladoceran Daphnia carinata

Chronic toxicity test duration of 21 days for daphnid is time consuming and expensive. Therefore, the developmental stages of Daphnia carinata eggs that could be used as potential endpoints for sublethal and chronic toxicity tests have been investigated and defined. Daphnid egg test is simple, easy to conduct and handle in the laboratory, and cost-effective. The 72 h ‘egg arrest’ bioassay system could be an alternative to the classic 21-day chronic test with neonates of daphnid. The main aims of the study were to establish easy to identify stages of D. carinata egg that could be used as potential endpoints for toxicity tests with in vitro cultures of daphnid parthenogenetic eggs. Commonly available Indian freshwater cladoceran Daphnia carinata parthenogenetic eggs in vitro were exposed to water borne mercury concentrations, ranging from 0.1 to 32 μg l −1. Adult female cladoceran D. carinata have eight main developmental stages of parthenogenetic reproduction based on the release of external and internal membranes, formation of cephalic and body regions, appearance of secondary antennae, presence of two pink eyes, than a single black eye, and finally caudal or shell spine separation and finally free-swimming neonate within 65–72 h. At 1, 3.2 and 10 μg l −1 of Hg concentrations; the 25, 50 and 70% embryonic developmental arrests were observed. The lower concentrations of Hg (0.32, 1, and 3.2 μg l −1) tested in the present study are not generally harmful to the neonates and adults daphnid species, but the same are highly toxic to the embryos of D. carinata. The 48 h and 72 h EC 50s and their 95% confidence limits for survival and hatchability were lower than previously reported 48 h EC 50s for Daphnia magna immobilization assay. The egg of D. carinata turned out to be a suitable alternative model for ecotoxicological and water quality assessment studies.

Well water contaminated by acidic mine water from the Dabaoshan Mine, South China: Chemistry and toxicity

An investigation into well water quality was carried out in a rural area subject to irrigation with acidic mine water from the Guangdong Dabaoshan Mine, southern China. The results of water pH measurements from 112 wells in two different seasons suggest that the well water has been contaminated to varying degrees in the investigated Shangba floodplain (approximately 11 km south of the Guangdong Dabaoshan Mine). There is a trend that well water pH increased southwards, suggesting that the impacts of acidic irrigation water on groundwater decreased with increasing distance to the entry point of acidic irrigation water. Water quality monitoring results of the selected wells show that Cu and Cd in the water exceeded the limits set in the Chinese National Standards for Drinking Water (GB 5749-85) for the wells close to the irrigation water source. If the World Health Organization (WHO) standard was considered, Cd in some wells was almost 10 times as high as the WHO guideline value (0.003 mg l −1). Water collected from the location closest to the acidic irrigation water source was acutely toxic to the test organism ( Daphnia carinata) even after 51 time dilution. It is likely that the extremely high mortality rate of the local population reported for the study area is at least partly related to the high levels of heavy metals, particularly Cd in the drinking well water.