Littoral zooplankton responses to acid and aluminum stress during short-term laboratory bioassays

During autumn 1990, littoral zooplankton were collected from three alkaline lakes in Ohio, USA. Toxicity tests were performed, in which animals were placed into treatments of pH 4.5, with or without 500 microg litre(-1) Al added. Percentage survival after 24 h was determined for each test species, and compared to survival in controls (pH roughly 8.0). Three distinct responses were observed: (1) Four cladocerans, Simocephalus serrulatus, Diaphanosoma birgii, Acantholeberis curvirostris and Chydorus sphaericus, were tolerant of both acid and Al, with no significant reductions in survival in the treatments. (2) The cladoceran Eurycercus lamellatus and the capepod Acanthocyclops vernalis were sensitive to both acid and Al, and suffered 100% mortality in both treatments. (3) The cladocerans Camptocercus rectirostris, Alona costata and Pleuroxus denticulatus, and the copopod Mesocyclops edax showed decreased survival in the acid treatment, and a significantly greater decrease in the acid plus Al treatment. For nine of the ten test species, the results were consistent with previous survey and paleolimnological studies. The results indicate that direct toxic effects of H+ and Al ions largely determine the responses of these common littoral species to acidification.     

Acid and aluminum effects on freshwater zooplankton: an in situ Mesocosm study

An in situ mesocosm experiment was performed to evaluate the role of aluminum toxicity in determining zooplankton community responses to take acidification. Large plastic enclosures were suspended in East Twin Lake, Ohio, USA, and duplicates were either untreated controls (pH 8.8), acidified to pH 4.5 over a 23 day period, or acidified and also spiked with incremental additions of Al, to produce a final inorganic monomeric Al level of 180 microg/liter at pH 4.5. Zooplankton abundance and species richness declined in both acid treatments, relative to the control, as numerous acid-sensitive species were eliminated. All of the acid-sensitive species were also Al-sensitive, declining in abundance more rapidly in the acid plus Al treatment than in the acid-alone treatment. Only two small cladocerans (Bosmina longirostris and Chydorus sphaericus) were acid tolerant. Both were also tolerant of elevated Al levels.     

Combined effects of copper and food on the midge Chironomus riparius in whole-sediment bioassays

Effects observed in whole-sediment bioassays must be seen as the joint effect of all sediment characteristics. In whole-sediment bioassays, however, adverse effects on test organisms are usually attributed to the presence of contaminants and effects of food are often ignored. The aim of this study was to analyze the response of the midge Chironomus riparius to sediment spiked with different combinations of food and copper. The responses of C. riparius to these spiked sediments were assessed in 10-day whole-sediment bioassays. Decreases in survival, dry weight, and length of C. riparius were observed with increasing copper concentrations. However, an increase in the amount of food resulted in an increase of larval dry weight and length until copper concentrations reached a critical threshold of 200 mg/kg. In addition, an increase in the amount of food resulted in a decrease of accumulated copper in the larvae. The present study demonstrated that the combination of copper and food in the sediment determines the performance of C. riparius in whole-sediment bioassays. The dependency of C. riparius on high feeding levels, which mask toxic effects, questions its suitability as a test organism for whole-sediment bioassays. Because benthic communities in polluted ecosystems are often exposed to varying levels of both food and toxicants it is concluded that the trophic state of the ecosystem may alter the ecological risk of sediment-bound toxicants to opportunistic benthic invertebrates such as C. riparius.     

The effects of aluminum and other metals on amphibians

This review discusses the effects of aluminum and other metals associated with acidification on amphibians. The majority of research has centered around aluminum although some information is available regarding copper, cadmium, iron, zinc and lead. The major habitat types in which amphibians live and breed are listed and the mechanisms by which these habitats may become acidified and contaminated with metals are discussed. Three lines of investigation into acid and metal toxicity are reviewed in detail: (1) field surveys of water chemistry, (2) laboratory toxicity tests, (3) field studies which include in situ toxicity tests, and surveys of amphibian distribution and survival relative to water chemistry. As a result of recent information from each of these three lines of research, it appears that aluminum toxicity is an extremely complex phenomenon which is influenced by the hardness, pH, DOC of the water, and the developmental stage and species of amphibian.     

Ecotoxicological effects of metal pollution in two mollusc species from the Spanish South Atlantic littoral

Metal accumulation and some of their biochemical effects have been studied in oysters (Crassostrea angulata) and mussels (Mytilus galloprovincialis) of the South Atlantic Spanish littoral. Especial attention has been paid to antioxidant defences and oxidative damage to biomolecules. Deep differences in the response of oysters and mussels to metal pollution were found. Oysters, with the higher metal loads of both species, showed increased antioxidant defences, and less extensive oxidative damage. In contrast, mussels, which accumulated much lower metal concentrations, showed clear increases in oxidized biomolecules, in agreement with their low increases in the antioxidant defence mechanisms. Our results suggest that mussels are more sensitive and less well adapted to metal pollution, probably explaining their absence in the most contaminated studied site, Mazagón. We conclude that oysters can be used as more sensitive bioindicator of pollution in the South Spanish littoral, and as a suitable model to study the adaptation to metal pollution.     

The effects of bayluscide and malathion on the survival of Schistosoma mansoni miracidia

Laboratory experiments were conducted to assess the toxic effects of bayluscide and malathion against Schistosoma mansoni miracidia. The results indicate that survival of miracidia varied with times of exposure and concentrations of tested chemicals. Statistical analyses reveal that LC5, LC50 and LC95 for bayluscide were 0.04 ppm, 0.06 ppm and 0.12 ppm after 2 hours of exposure; 0.02 ppm, 0.03 ppm and 0.06 ppm after 4 hours of exposure; and 0.01 ppm, 0.02 ppm and 0.04 ppm after 6 hours of exposure respectively. These data indicate that bayluscide is much more toxic to the first stage larvae of schistosomes than to snail intermediate hosts cited in the literature. Application of lower concentrations of molluscicide in the transmission sites is thus expected to curtail the survival of miracidia; therefore controlling schistosomiasis at relatively low costs. Such applications also reduce the risk of toxicity to non target organisms present in the aquatic environment. Statistical analysis of the results of tests using malathion gave LC5, LC50 and LC95 values of 83.38 ppm, 153.11 ppm and 245.85 ppm after 2 hours of exposure; and 76.86 ppm, 116.48 ppm and 172.04 ppm after 4 hours of exposure respectively. These data indicate that the use of malathion as an insecticide in tropical ecosystems may also affect the survival and viability of schistosome miracidia. Such uses could help reducing the risk of schistosomiasis transmission in these particular locations.     

An assessment of endocrine disrupting activity changes during wastewater treatment through the use of bioassays and chemical measurements.

The objective of this study was to assess the removal efficiencies of secondary wastewater treatment processes for compounds causing endocrine disrupting activity. The study used bioassays and chemical measurements, such as gas chromatography with mass spectrometry and enzyme immunosorbent assays. A total of seven full-scale water reclamation facilities using different unit operations and two pilot-scale membrane bioreactors were examined. Findings of this study imply that estrogenic disrupting activity in primary effluent is mainly caused by two steroidal hormones (17beta-estradiol and estriol) and, to a lesser extent, by synthetic chemicals, such as bisphenol A, 4-nonylphenol, and 4-tert-octylphenol. During secondary treatment, steroidal hormones were removed to a higher degree than nonylphenol and bisphenol A. The total estrogenic activity was removed by an average of 96%. The remaining concentrations of targeted steroids in secondary effluents, except for estriol, still had the potential to elicit a positive response in the human breast cell cancer assay. For the majority of facilities, the remaining activity was likely attributed to residual concentrations of two steroidal hormones (17beta-estradiol and estriol).     

Transport and acclimation conditions for the use of an estuarine fish (Pomatoschistus microps) in ecotoxicity bioassays: effects on enzymatic biomarkers

Acclimation of organisms for ecotoxicity testing is in general processed according to Organisation for Economic Co-operation and Development (OECD) and/or Environmental Protection Agency (EPA) guidelines, under controlled conditions. However, when organisms are collected in the field, their capture, transport and adaptation to laboratory conditions are factors of stress. In their natural habitat, estuarine fish are exposed to considerable fluctuations of environmental variables, while in laboratory they are acclimated to constant conditions and this can be per se a factor of stress that may influence biomarker responses. Therefore, it is important to investigate the effects of these procedures on estuarine fish performance before using them as test organisms in ecotoxicity bioassays. The goal of the present study was to investigate the effects of transporting the common goby, Pomatoschistus microps from the field (natural populations) to the laboratory and of its acclimation to laboratory conditions on the enzymes acetylcholinesterase (AChE), lactate dehydrogenase (LDH) and glutathione S-transferases (GSTs). Fish were collected in a reference site of the Minho River estuary (NW of Portugal) and the activities of the biomarkers were monitored before and after the transport of organisms to the laboratory and during the acclimation period (at 5, 10 and 15 days). The activities of all the enzymes indicated that capture and transport conditions had no effects on enzymatic activities. Furthermore, AChE, LDH and GST presented higher activities at the end of the acclimation period than at beginning, suggesting a physiological adaptation to laboratory conditions. This adaptation should be taken into consideration in the experimental design to avoid bias in the interpretation of effects of xenobiotics on biomarkers.     

抗生素类污染物对活性污泥生物毒性测定方法的筛选与评价

尽管衡量化学物质生物毒性的标准方法很多,但关于环境中抗生素类污染物的生物毒性及其对污泥活性影响的科学数据较少。以磺胺和四环素两类作用机理和作用谱带不同的抗生素为研究对象,分别用发光细菌法、脱氢酶活性法、生长抑制法及呼吸速率法进行了抗生素类污染物生物毒性测定方法的筛选与评价。结果表明,发光细菌标准方法中30min的作用时间太短,延长作用时间不仅导致各种抗生素的EC50值大幅度降低,同时毒性排列顺序也发生了改变;以活性污泥为对象的脱氢酶活性和呼吸速率抑制实验的EC50值与抗生素类物质对敏感致病菌的MICs相比异常高,不适宜于作为单独方法准确评估抗生素类污染物的生物毒性。生长抑制实验中,活性污泥混合菌种增殖生长对磺胺类抗生素敏感,而假单胞杆菌对四环素类抗生素敏感。不同方法测定抗生素毒性的灵敏度顺序是发光细菌(24 h)>生长抑制(7 h)>呼吸速率(24 h)>脱氢酶活性(24 h)。用标准方法评价抗生素类污染物的生物毒性,可能导致对抗生素排放到水环境中所带来的风险估计不足。     

Acid mist and ozone effects on the leaf chemistry of two western conifer species

Seedlings of Jeffrey pine (Pinus jeffreyi) and giant sequoia (Sequoiadendron gigantea) were more susceptible to leaf chemical changes following exposure to acid mist (pH 3.4-2.0) or acid mist/ozone combinations, than to ozone alone (0.1-0.2 microl/litre), when plants were exposed to alternating doses of these pollutants for 6-9 weeks. Under acid mist treatment, leaves exhibited higher levels of nitrogen and sulfur, two elements applied in acid mist. In addition, levels of foliar sodium, and, in the case of giant sequia, potassium, as well, increased under acid mist treatment. Iron and manganese were also mobilized, resulting in significant increases in these elements in pine, and decreases in manganese in giant sequoia foliage. The acid treatment also reduced chlorophyll b concentrations in pine, and, to a less significant extent, in giant sequoia. Calcium, magnesium, barium and strontium were differentially accumulated in giant sequoia compared to Jeffrey pine. Under acid mist treatment, all of these elements (except strontium) declined in concentration in giant sequoia, with calcium showing the most significant trend. The more extensive changes in leaf chemistry induced by acid mist are consistent with earlier observations of significant changes in spectral reflectance of these seedlings after 3 weeks of fumigation. Limited foliage samples collected from these two species in 1985 and 1986 in Sequoia/Kings Canyon National Parks in the southern Sierra Nevada do not in themselves indicate any clearcut or severe effects of ozone alone on leaf chemistry of these species, but a mild influence of nitrate-laden acid deposition, possibly in combination with ozone, is consistent with the rise in nitrogen and lignin levels in Jeffrey pine on sites observed to have moderate visible injury symptoms. No firm conclusions about effects of pollutants on leaf chemistry in these field sites is possible without further study.     

High methane emissions from a littoral zone on the Qinghai-Tibetan Plateau

The littoral zones of lakes have been regarded as hotspots of methane (CH₄) fluxes through several studies. In the present study, we measured CH₄ fluxes in six kinds of littoral zones of Huahu Lake on the Qinghai-Tibetan Plateau in the peak growing season of 2006 and 2007. We found that CH₄ efflux (ranging from −0.1 to 90 mg CH₄ m⁻² h⁻¹) from the littoral zones of this lake was relatively high among those of boreal and temperate lakes. Our results also showed that emergent plant zones (Hippuris vulgaris and Glyceria maxima stands) recorded the highest CH₄ flux rate. The CH₄ flux in the floating mat zone of Carex muliensis was significantly lower than those of the emergent plant zones. CH₄ fluxes in the floating-leaved zone of Polygonum amphibium and bare lakeshore showed no significant difference and ranked last but one, only higher than that of the littoral meadow (Kobresia tibetica). Plant biomass and standing water depths were important factors to explain such spatial variations in CH₄ fluxes. No significant temporal variations in CH₄ fluxes were found due to the insignificant variations of physical factors in the peak growing season. These results may help in our understanding of the importance of the littoral zone of lakes, especially the emergent plant zone, as a hotspot of CH₄ emission.     

Influence of reduced dietary calcium on the accumulation and effects of lead, cadmium, and aluminum in birds

The influence of low dietary calcium on the accumulation and effects of dietary lead, cadmium and aluminum was examined in zebra finches and ring doves. In zebra finches fed a diet containing 0.3% Ca, the hepatic and renal accumulation of lead was enhanced approximately 400% and of cadmium about 150-200%, compared to birds fed a 3.0% Ca diet. Low dietary Ca also caused bones of female finches to lose an average of about 60% of their normal Ca content. Loss of bone-Ca was also observed in male finches, but was less than in females. In reproductively active ring doves, low (0.4%) dietary Ca enhanced the accumulation of lead and cadmium, but not of aluminum, compared with accumulation in doves consuming a 2.0% Ca diet. Enhanced accumulation of lead and cadmium was accompanied by increased synthesis of the metal-binding protein metallothionein and by greater inhibition of delta-aminolevulinic acid dehydratase activity. These results indicate that, under conditions of reduced dietary Ca availability, such as can occur in acid-impacted environments, wild birds risk increased uptake of certain toxic metals and may accumulate toxic concentrations of these metals more rapidly. Researchers should take account of dietary Ca levels when interpreting results of dosing studies in which metals such as lead and cadmium are administered to birds.     

Phytoplankton succession during acidification with and without increasing aluminum levels

An in situ mesocosm experiment was performed to investigate the role of aluminum in controlling phytoplankton community succession during lake acidification. Large (2000 liter) mesocosms were suspended in mesotrophic East Twin Lake, Ohio, USA. Duplicates were either untreated controls (pH 8.8), acidified to pH 4.5 over 23 days, or acidified and spiked with 200 microg/liter Al in incremental additions. Filamentous blue greens, diatoms and other chrysophytes became extinct in both acid treatments, but declined most rapidly where Al levels were also increased. The large desmid Closterium and the filamentous chlorophyte Mougoetia became dominant in the Acid treatment. In the Acid + Al treatment, these algae also became dominant, but the species with greatest biomass was the dinoflagellate Peridinium inconspicuum. Acidification (with or without added Al) also resulted in a significant shift in the algal size spectrum to larger (> 20 microm) cells.     

Effects of colliery waste on littoral communities in north-east England

Colliery waste input has a detrimental effect on the species richness and alpha diversity of sandy and rocky shore communities in north-east England. On sandy shores at the shore levels Chart Datum (CD) + 1.2 to 1.5 m (low shore) and CD + 2.7 to 3.0 m (mid-shore), a maximum of two species of macroinvertebrates per shore level was found at sites heavily contaminated by colliery waste input. In contrast, typically about eight species were found at uncontaminated shores. At the shore level CD + 4.2 to 4.5 m (high shore), the species richness and diversity of fauna were not detectably affected by colliery waste input. On rocky shores that were uncontaminated, 12-15 species of macroalgae were found, whereas only five to eight species were found at contaminated shores. The absentees were usually ephemeral, early successional species. Macroalgal biomass, although less at contaminated shores, showed no significant relationship with colliery waste input. However, the alpha diversity of animal communities on rocky shores was, on occasions, significantly increased where colliery waste inputs occurred. The physical properties of colliery waste are likely to be the reason for the effects observed on both sandy and rocky shores, since many of the leachable chemicals in colliery waste are leached during the period that it spends on the sea bed before accumulating in the intertidal zone.     

Sulfur dioxide effects on plants exhibiting Crassulacean Acid Metabolism

The effects of SO(2) on species exhibiting Crassulacean Acid Metabolism (CAM) were determined with short term-high concentration 'acute' greenhouse exposures (0.6 to 3.0 microl liter(-1) (ppm) SO(2) for 2 and 8 h), and long term-low concentration 'chronic' field exposures (0.35 to 0.90 microl liter(-1) SO(2) for 32 to 79 h periodically over 7 to 13 days). In the acute greenhouse exposures, visible injury was observed on Opuntia basilaris Engelm. & Bigel., exposed to 2.0 microl liter(-1) SO(2), but no injury was observed on Ananas comosus (L.) Merr., Bryophyllum blossfeldiana Poelln., Bryophyllum pinnata (Lam.) Pers., or Bryophyllum tubiflora (Harv.) Hamet, exposed to up to 2.8 microl liter(-1) SO(2) for 8 h. Stomatal conductance during the exposures averaged 0.067+/-0.021mol(-2)s(-1) for Opuntia basilaris, 0.029+/-0.008mol(-2)s(-1) for Ananas comosus, and 0.029+/-0.008mol m(-2)s(-1) for Bryophyllum pinnata. Opuntia basilaris was injured early during the day, but not at night; with the injury appearing as a white necrotic banding across just fully expanded pads. Moderately injured pads would regreen beginning 1 to 2 weeks after exposure. In chronic field exposures, no visible injury from SO(2) was observed on Opuntia basilaris, Dudleya arizonica Rose or Agave deserti Engelm. plants, grown either with supplemental irrigation or natural rainfall. In addition, in the field SO(2) had no effect on CO(2) uptake, total sulfur content, transpiration, or tissue acidity in either the light or the dark, or in irrigated vs natural rainfall plots.     

Herbicide impact on Hormosira banksii gametes measured by fluorescence and germination bioassays

The innovative bioassay described here involves chlorophyll a fluorescence measurements of gametes from the macroalgae, Hormosira banksii, where gametes (eggs) were exposed to Diuron, Irgarol and Bromacil. Response was assessed as percent inhibition from control of effective quantum yield (DeltaF/Fm') of photosystem II, herein referred to as % PSII Inhibition. This was measured with the dual-channelled pulse amplitude modulated (PAM) fluorometer, ToxY-PAM. The fluorescence bioassay was run simultaneously with an established H. banksii germination bioassay to compare sensitivity, precision, and time-to-result. The fluorescence bioassay gave highly sensitive results evidenced by EC(50)s (% PSII Inhibition) for Diuron, Irgarol and Bromacil being three, four and three orders of magnitude (respectively) lower than EC50s generated from the germination bioassays. Precision of the fluorescence bioassay was demonstrated with low coefficient of variations (<30%) for all three toxicants. With regard to time, the fluorescence bioassay gave results within 6h, as opposed to more than 50h for the germination bioassay.     

In situ and laboratory bioassays to evaluate the impact of effluent discharges on receiving aquatic ecosystems

Effluents are a main source of direct and often continuous input of pollutants into aquatic ecosystems with long-term implications on ecosystem functioning. Therefore, the study of the effects of effluent exposure on organisms, populations or communities within the framework of impact assessment has a high ecological relevance. The aim of this study was to assess the toxicological impact of two effluents, one household wastewater treatment effluent (Effluent 1) and one industrial effluent (Effluent 2), on the receiving aquatic ecosystem using two test species under both in situ and laboratory conditions. Zebra mussel (Dreissena polymorpha) and common carp (Cyprinus carpio) were exposed under laboratory conditions in an online monitoring flow-through system (receiving different concentrations of Effluent 2) and under in situ conditions along the pollution gradient established by these two effluent discharges. Bioassays focussed on growth and condition related endpoints (i.e. condition, growth, lipid budget), since these are key functional processes within organisms and populations. Under laboratory conditions, increasing concentrations of the industrial effluent (Effluent 2) had a negative effect on both zebra mussel and carp energy reserves and condition. Under in situ conditions, the same negative impact of Effluent 2 was observed for zebra mussels, while Effluent 1 had no apparent effect on exposed zebra mussels. Carp growth and condition, on the other hand, were significantly increased at the discharge sites of both effluents when compared to the reference site, probably due to differences in food availability. The results indicate that a combination of in situ and laboratory exposures can illustrate how ecological processes influence bioassay studies. The incorporation of indirect, ecological effects, like changes in food availability, provides considerable benefit in understanding and predicting effects of effluents on selected species under realistic exposure conditions.