Reference Pond Research Articles

Assessment of the Present State and Future Fate of River Saraswati, India: Water Quality Indices and Forecast Models as Diagnostic and Management Tools

AbstractWater quality assessment is key to the conservation and management of rivers. River Saraswati, a distributary of the river Ganga, serves as a lifeline to many villages in the district Hooghly in West Bengal, India. As the river is gradually dying due to diverse man‐made pollution, ten water quality parameters in two sampling spots (PR‐1 and PR‐2) in the river are monitored month‐wise from March 2017 to February 2020, and these are compared with those from a reference pond. The water quality index (WQI) is determined for the two riverine spots and the reference pond based on the Canadian Council of Ministers of Environment WQI (CCMEWQI) and weighted arithmetic WQI, respectively. In addition to actual observations, three different forecasting methods, exponential smoothing, autoregressive integrated moving average, and artificial neural network, are used to predict WQI for the next two years. This study indicates that free CO2, dissolved oxygen, and turbidity are the key parameters to evaluate this river's anthropogenic stress and health. The actual and forecasted results reflect the precipitous degradation of CCMEWQI in PR‐2. Therefore, the immediate intervention of all stakeholders is required to adopt an integrated and comprehensive river management plan to save the river from utter obliteration.

Metabolome adaptation and oxidative stress response of common carp (Cyprinus carpio) to altered water pollution levels

Treated wastewater ponds (TWPs) serve as recipients and passive tertiary treatment mediators for recycled water. These nutrient-rich habitats are increasingly utilised in aquaculture, nevertheless multiple loads of various contaminants with adverse effects on aquatic fauna, including fish, have been recorded. In the present study, we investigated the effects of fish transfer in response to altered levels of pollution on liver metabolic profiles and tissue-specific oxidative stress biomarkers during short- and long-term exposure. In a field experiment, common carp (Cyprinus carpio) originating in severely polluted TWP were restocked after one year to a reference pond with a background pollutant concentration typical of the regional river. In contrast, fish that originated in the reference pond were restocked to TWP. Fish were sampled 0, 7, 14, 60, and 180 days after restocking and fish liver, kidney, intestine, and gill tissues were subjected to biomarker analysis. Pharmaceutically active compounds (PhACs) and metabolic profiles were determined in fish liver using liquid chromatography high-resolution mass spectrometry (LC-HRMS). Fish transferred from reference to polluted pond increased the antioxidant response and absorbed PhACs into metabolism within seven days. Fish liver metabolic profiles were shifted rapidly, but after 180 days to a lesser extent than profiles in fish already adapted in polluted water. Restocked fish from polluted to reference pond eliminated PhACs during the short phase within 14 days, and the highest antioxidant response accompanied the depuration process. Numerous elevated metabolic compounds persisted in such exposed fish for at least 60 days. The period of two weeks was suggested as sufficient for PhACs depuration, but more than two months after restocking is needed for fish to stabilise their metabolism. This study contributed to determining the safe handling with marketed fish commonly restocked to wastewaters and clarified that water pollution irreversibly altered fish metabolic profile.

Effect of initial planting on vegetation establishment in different depth zones of constructed farm ponds

Farm ponds can be constructed and maintained to improve biodiversity and ecosystem functions in agricultural landscapes. Understanding the initial establishment process of vegetation in different water depths and effects of initial planting on this process is important for pond restoration. In the present study, two experimental farm ponds with or without initial planting were monitored for 5 years after their construction. These two ponds maintained high nutrients over 5 years from the beginning. The unplanted pond showed a rapid vegetation establishment and had more species and higher percent vegetation cover in 2–3 years than the reference pond. Planting accelerated this process by 1 year. Most of the early established species appeared to have originated from seed banks and/or seed rains. The species and functional diversity tended to decrease consistently since pond construction in the planted pond but increase initially and then decrease in the unplanted pond. The time when species composition between the unplanted pond and the planted pond became similar was delayed with the increase of water depth. Four years after pond construction, species composition was similar between the two ponds at all water depths. These results suggest that vegetation can establish quickly in farm ponds with fertile conditions and abundant seed sources through natural recolonization. The restoration approach for a farm pond should be decided considering the allowed time to success and the water depth. If the main goal of farm pond restoration is to improve species diversity, management practices may be more important than planting.

Transfer of elements relevant to radioactive waste into chironomids and fish in boreal freshwater bodies

Information on transfer of elements and their radionuclides is essential for radioecological modeling. In the present study, we investigated the transfer of Cl, Co, Mo, Ni, Se, Sr, U and Zn in a boreal freshwater food chain. These elements were selected on the basis that they have important radionuclides that might be released into the biosphere from various stages of the nuclear fuel cycle. Water, sediment, chironomid larvae (Chironomus sp.), roach (Rutilus rutilus) and perch (Perca fluviatilis) were sampled from two ponds near a former uranium mine and one reference pond located further away from the mining area. Concentrations measured in water, sediment and the three animal species indicated the importance of sediment as a source of uptake for most of the elements (but not Cl). This should be considered in radioecological models, which conventionally predict concentration in aquatic organisms from concentration in water. The results also show that the assumption of linear transfer (constant concentration ratio) may not be valid for elements into fish. The results of this study show that further basic research is needed to understand the fundamental processes involved in transfer of elements into freshwater organisms in order to develop radioecological models.

Enhancing High-concentrated Wastewater Quality on Evaporation Rate from Five-Consecutive Oxidation Ponds as Located in Phetchaburi, Southerly Thailand

This research aimed to examine the environmental factors determining the rates of evaporation, a natural phenomenon contributing to the treatment of wastewater of 5-consecutive oxidation ponds of the King’s Royally Initiated Laem Phak Bia Environmental Research and Development Project. Data collected from the 17th of April to 30th of May 2019 by US Class A Evaporation Pan revealed that the sedimentation pond (Pond 1) has the highest rate, 7.22 mm d-1, the oxidation pond 1 (Pond 2), 5.70 mm d-1, the oxidation pond 3 (Pond 4), 5.56 mm d-1, the stabilization pond (Pond 5), mm d-1, the reference pond at 5.07 mm d-1 and the oxidation pond 2 (Pond 3), 3.59 mm d-1. Concluding the evaporation in domestic wastewater treatment plants is characterized by 1) heat generated from short and long wave radiation emitted by earth and the sun, 2) local wind profiles of the area affected the height differences of the roughness length, and 3) heat generated by the respiration and digestion process of microbial activities and other grey body contaminants. Presenting the day and night variations made for the analysis, the day evaporation was significantly higher resulted by the net radiation were accountable. Wind profile generated from the measurement of speeds and directions at two different sites at 3 and 10 m has explained for the roughness length heights over each pond as lower roughness height have cause the increased in the rates of evaporation in Pond 4 and 5 however, these process were also suppressed by high ionic bonding molecules effected suggested by the high TDS and EC values. The vertical temperature profile has conveyed the movement in the heat flux that dominated an upward flux movement in Pond 1. This is the exothermic reaction from the digestion process have suggested that extra heat has been added.

Is developmental instability in chironomids a sensitive endpoint for testing uranium mine-affected sediments?

There is increasing interest in effects of radionuclides on non-human species, but methods for studying such effects are not well developed. The aims of the current study were to investigate the effects of uranium mine-affected sediments on non-biting midge Chironomus riparius and to compare sensitivity of different endpoints. The midge larvae were exposed in controlled laboratory conditions to sediments from two ponds downstream from an abandoned uranium mine and a reference pond not receiving water from the mining site. Quartz sand was used as an additional control. Developmental effects were assessed by evaluating emergence of adult midges, body mass, and fluctuating asymmetry (FA) in the length of wing upper vein. FA has been suggested to be a sensitive indicator of developmental instability, but the results of previous studies are inconsistent. In the present study, no difference in FA was observed between the treatment groups, but time to emergence was significantly delayed in the contaminated sediments. The approach used in this study (laboratory experiments with sediments from a contaminated site) avoids confounding due to uncontrolled environmental variables and adaptation to long-term contamination, which may mask effects on natural populations. Using this approach, we found no effects on FA of wing length. Time to emergence, in contrast, was found to be a more sensitive endpoint.

Chlorovirus and myovirus diversity in permafrost thaw ponds

Permafrost thaw ponds occur in high abundance across the northern landscape of Canada and are sites of intense microbial activity, resulting in carbon dioxide and methane emissions to the atmosphere. In this study, we focused on viruses as largely unstudied agents of top-down control in these high-latitude microbial ecosystems. Specifically, we compared the diversity of myovirus, chlorovirus and host microbial communities in an organic soil palsa valley pond and a mineral soil lithalsa valley pond. These 2 subarctic permafrost landscapes are both common in northern Quebec, Canada. Sequence analysis of ribosomal small subunit RNA genes showed that the community structure of bacteria and microbial eukaryotes differed significantly between the 2 ponds, which both differed from microbial communities in a rock-basin lake (whose formation was not related to permafrost thawing and which we used as a reference pond) in the same region. The viral assemblages included 439 OTUs in the uncultured Myoviridae category and 41 OTUs in the family Phycodnaviridae. Phylogenetic analysis of the latter based on an amino acid sequence alignment revealed a single large clade related to chloroviruses, consistent with the abundant presence of chlorophytes in these waters. As there was for the bacterial and eukaryotic communities, there were also significant differences in the community structure of these viral groups among the 3 ponds. These results suggest that host community composition is influenced by environmental filtering, which in turn contributes to driving viral diversity across landscape types.

The Influence of Holothuriaatra(Echinodermata: Holothuroidea)on Organic Matter Assimilation, Ammonification and Nitrification Rate of Sediment.Hurghada,Red Sea, Egypt.

This study was undertaken to investigate the effect of sea-cucumber (Holothuriaatra) population density on sea bottom sediment; redox potential, Total organic matter (TOM) assimilation, ammonification and nitrification activity. In protected aquaculture ponds at National Institute of Oceanography and Fisheries (NIOF), Four treatments of high population density (108 individuals/HPDP of 30m2), mediumpopulation density (54 individuals/MPDP of 30m2), low population density (18 individuals/LPDP of 30m2) and reference (RP; Empty ofH.atra). Intestinal (Foregut and hindgut) of H. atra and ambient sediment samples were used. The data showed that presence of Holothuriaatra increase the Redox Potential of sediment and kept its characteristics in the oxidized form which enhanced the biological activities.The TOM decreased by16.04% (22.32% to 6.28%); 5.34% (10.54% to 5.2%); 3.02 % (8.02% to 5.0%) and 3.61% (8.35% to 4.74%) in HPDP, MPDP, LPDP and reference pond respectively. The maximum monthly mean of ammonia was 6.93µgg-1 in HPDP and the lowest mean was 0.09µg g-1 in recorded in LPDP. Ammonia and nitrate concentrations in the ponds of H. atrawereslightly reduced compared with the RP while nitrite concentration followed different pattern. The highest count of ammonifying,ammonium oxidizing and nitrite oxidizing bacteria were 1100 MPN/g, 460 MPN/g and64 MPN/g recorded in foregut contents.Meanwhile the lowest count was31.5 MPN/g, 20 MPN/g and 6.75 in RP, hindgut contents and LPDP respectively.The highest Ammonification and nitrification activity were36.69 µg/g/h and 1.19 µg/g/hrecorded in HPDP meanwhile, the lowest values were 7.38 µg/g/h and0.07 µg/g/h in RP. Ammonification rate and nitrification rate in foregut were higher than in hindgut contents and the ambient sediment. Data analysis showed ammonia–N; nitrate-N and nitrite-N concentration varied non significantly with H. atra population density (p˃0.05) while a highly significant effect recorded with oxidation reduction potential (Eh) and Nitrification activity (p<0.01) and significant effect on TOM matter and Ammonification rate (p<0.05). This study emphasizes the ecological role of the most dominant holothurians species, H. atra, especially in relation to organic matter assimilation, through its associated bacteria that enhance ammonification and nitrification processes in sediment.

Hypoxic conditions in stormwater retention ponds: potential for hydrogen sulfide emission

ABSTRACTImproper design and maintenance of stormwater ponds (SWPs) may lead to hypoxic conditions, poor water quality and the production of hydrogen sulfide (H2S). The objective of this study is to develop a comprehensive understanding of hypoxic conditions of SWPs, with a focus on the potential for H2S production and emission. This study was conducted at two retention SWPs in Ottawa, Canada; a problematic pond with the propensity for H2S emission and a reference pond that did not demonstrate H2S emission. The investigation illustrated a significant impact of low dissolved oxygen (DO) concentrations, hypoxic conditions, on the concentration of total sulfides in the water column. Both ponds were shown to periodically experience hypoxic conditions at depth, especially during summer periods with less precipitation and across longer periods of winter, ice-covered conditions. The problem pond, however, was shown to experience lower DO and longer hypoxic conditions than the reference pond in both non-ice-covered and ice-covered conditions due to greater depth and a longer hydraulic retention time. Hypoxic conditions were initiated at the deepest locations in the problem pond and subsequently were spread across the entirety of the pond under winter, ice-covered conditions. Algal biomass (Chlorophyll-a) and soluble biochemical oxygen demand concentrations were shown to not likely be significant factors in the development of hypoxia in the H2S-generating pond. Algal blooms of colonial Chrysophyceae, Synura, a known mixotroph, were observed during ice-covered conditions in the problem pond possibly due to stress-coping mechanisms of algae.

Multibiomarker toxicity characterization of uranium mine drainages to the fish Carassius auratus.

The release of acidic effluents, naturally enriched in metals and radionuclides, is the main legacy of uranium mines. Generally, metals dissolved by these acidic effluents can cause significant alterations in exposed organisms, with distinct toxicological outcomes. In this study, 72 individuals of the freshwater fish species Carassius auratus were exposed in situ for different periods (8, 16, 24, and 48h) to water from a pond (treatment pond (TP)) with a chemically treated effluent and a reference pond (PRP), in the vicinity of the Cunha Baixa uranium mine (Portugal). Comparing the water of the two ponds, the PRP pond was characterized by higher pH and oxygen values and lower conductivity and hardness values. Regarding total metal concentrations, among others, magnesium (56,000μg/L), sodium (17,400μg/L), zinc (86μg/L), manganese (6340μg/L), and uranium (1380μg/L) concentrations in the TP pond were above the values obtained for the PRP pond. The values of manganese and uranium exceeded the values of quality criteria established for surface waters for cyprinids and for irrigation purposes. After exposure to pond water, significant differences were recorded for several biomarkers: (i) between ponds for acetylcholinesterase (AChE) with higher activities for animals from the PRP and glutathione-S-transferase (GST) activities that were particularly enhanced in animals from the TP pond; (ii) between ponds and exposure periods for lactate dehydrogenase (LDH) activity, since organisms from PRP pond presented always higher values than those from the TP pond, and among these, organisms exposed for the longer period presented a further depression in LDH activity; and (iii) between exposure periods for erythrocyte micronucleus. GSTs and LDH were the most sensitive biomarkers within the timeframe of the in situ assay performed. Despite the alleged efficacy of the chemical treatment (evidenced by a significantly lower pH), some metals persisted in the treated effluent (TP pond), potentially contributing to the induction of oxidative stress or increased conjugation metabolic activity in fish.

Melanomacrophage proliferation in the spleen of Nile tilapia (Oreochromis niloticus L.) as biomarker of insecticides loading from the waters of Laguna de Bay, Municipality of Bay, Laguna, Philippines

Massive use of insecticides along Laguna de Bay exacerbates the poor condition of the lake waters. Hence, this study was done to evaluate the size and number of Melanomacrophage (MMCs) of ten freshly caught sampled O. niloticus L. (April 2010-May 2010, dry season; October 2010-November 2010, wet season) collected from bay fish cages with no sexual preferences and from a reference pond per season for five consecutive weeks. The spleen was obtained and stained by Perl's technique. The study revealed that there were significant (P < 0.05) differences in the number of splenic MMCs during the dry season while there were no significant differences (P > 0.05) during the wet season. Also, there were no significant differences (P > 0.05) in the sizes of MMCs for both seasons. The results, suggest that MMCs are reliable biomarkers for water quality in terms of environmental stress because of insecticides loading.

Вплив побутових забруднювачів на стан металотіонеїнів у тканинах двостулкового молюска Unio tumidus

Personal care products and pharmaceuticals are the most common novel water pollutants, and it is difficult to predict the effects. It is expected that they can modulate the activity of molecular detoxification systems. Since the production of the metal-binding proteins, metallothioneins (MTs) are activated by a wide range of stress factors, the aim of the study was to compare the functional characteristics of the MTs from digestive gland (DG) of male bivalve mollusc Unio tumidus from reference pond, polluted by sewage effluents pond and after the exposure to widespread water personal care pollutants ibuprofen (I, 250 ng / L), triclosan (T, 500 ng / L) or estrone (E1, 100 ng / L) for 14 days (overall term of staying in the laboratory aquaria – 21 days). The elevation of the content of zinc, copper and cadmium in bivalves’ tissues of DG, gonads and MTs as well as total level of MTs was noted in polluted pond compared to the reference one. Exposure factors and chronic pollution caused an increase of level of Zn-binding MT form on a background of reduced (I-, T-group) or increased (E1 group) total protein content of MTs and constant total level of zinc and copper in tissue. Under the effect of I, T and E1, marked decreasing in copper level and increasing (in 2.2–3 times) in zinc level were observed in the gonads. Thus, we should assume that the elevation of the content of zinc-MT in the bivalves DG can be considerded as the compound of the unspecific supporting strategy of the signa­ling function of these ions under the harmful efects. Keywords : bivalve mollusc, ibuprofen, triclosan, estron, metallothioneins, zinc.

Application of Biological Activated Carbon Process for Water Quality Improvement of Stagnant Stream Channels

The water quality improvement of golf course ponds, as representative stagnant stream channels, was evaluated by applying a biological activated carbon (BAC) process composed of four consecutive activated carbon reactors. The study was performed from autumn to winter in order to evaluate the feasibility of the BAC process under low temperature conditions. In the study, water quality of pond A (target pond) and pond B (reference pond) were monitored. Pond water was pumped into the BAC process, and was then returned to the pond after treatment. The optimal conditions were determined to be 2 hr of empty bed contact time (EBCT) at a temperature above 4˚C, in which improvements of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) of pond A compared to pond B were 3.62%, 3.48% and 1.81%, respectively. On the other hand, as the temperature was below 4˚C, some degree of water quality improvement was achieved even when EBCT were 1 or 0.5 hr, suggesting that the BAC process can be successfully applied for the improvement of pond water quality in winter months. The values of biomass concentration and microorganism activity in each condition were highest where 2 hr of EBCT was applied at a temperature above 4˚C, but values were similar throughout all treatment conditions, and thus, adsorption is considered to be the dominant factor affecting process efficiency. From the denaturing gel gradient electrophoresis (DGGE) results, no significant differences were observed among the activated carbon reactors, suggesting that the number of reactors in the system could be decreased for a more compact application of the system.

First evidence of fish genotoxicity induced by heavy metals from landfill leachates: The advantage of using the RAPD-PCR technique

Municipal leachates are loaded with heavy metals that can contaminate surface water before discharge into a receiving body of water. The aim of this study is to evaluate the genotoxic effects of heavy metals generated by domestic waste on the common roach Rutilus rutilus in the last of the four interconnected ponds at the Etueffont landfill. We used random amplified polymorphic DNA (RAPD) since it has been shown to be a powerful means of detecting a broad range of DNA damage due to environmental contaminants. Our results show the ability of RAPD analysis to detect significant genetic alterations in roach DNA, after contamination with a set of metals contained in the landfill leachates in comparison to a roach from a non-polluted reference pond. Analysis of electrophoresis profiles indicates apparent changes such as the appearance of new bands or disappearance of bands as compared to the control. In fact, mixed smearing and laddering of DNA fragments in muscle samples support the genotoxic effects of metal deposits in the roach. This study is the first evidence found via the RAPD-PCR technique in the detection of pollutant impacts on fish exposed to landfill leachates.

Using nekton growth as a metric for assessing habitat restoration by marsh terracing

We conducted field growth experiments to evaluate marsh-terracing restoration in Galveston Bay, Texas (USA). Growth rates were compared for selected species held in mesocosms for ~7 d within 4 habitat type treatments: terrace marsh edge (TerM), terrace pond (TerP), reference marsh edge (RefM), and reference pond (RefP). Environmental variables were measured during each experiment, and values measured inside the experimental mesocosms generally tracked outside values. Mean daily growth rates were 0.7 to 1.9 mm (30 to 143 mg) for brown shrimp Farfantepenaeus aztecus, 0.4 to 1.2 mm (8 to 67 mg) for white shrimp Litopenaeus setiferus, 0.3 to 0.6 mm (15 to 194 mg) for blue crab Callinectes sapidus, and 0.1 to 0.4 mm (0.3 to 3 mg) for daggerblade grass shrimp Palaemonetes pugio. No difference was detected in growth rates among treatments for blue crab and daggerblade grass shrimp. White shrimp growth rates in August 2002 were higher in TerP than RefP, and in October 2002, were higher in RefP than TerM. Brown shrimp grew more rapidly in RefM than TerM in early May 2003, but mean growth rates were similar in both habitat types later in May 2003, and significantly lower than growth rates in RefP and TerP. Even though growth rates were not consistently higher in terrace habitat types, production rates may be higher in terrace fields than over shallow non-vegetated bottom (the habitat type replaced by marsh terracing); much higher densities of fishery species in terrace habitats more than compensate for occasionally lower growth rates there. However, our production rates should be used cautiously, because we did not include mortality rates in these estimates. We recommend using a combination of different metrics, including mortality rate, to assess secondary productivity of marsh terracing or other restoration projects.

Effect of cadmium on gonadal development in freshwater turtle (Trachemys scripta, Chrysemys picta) embryos

Prior studies on painted turtle (Chrysemys picta) sub-populations near the Massachusetts Military Reservation (MMR), a Superfund site on Cape Cod, Massachusetts, USA, suggest several reproductive deficits which may be related to xenobiotics. Several heavy metals, including cadmium, have been detected in Cape Cod surface water and sediments. The present study was carried out to investigate the effect of an environmentally relevant dose of cadmium on gonadal development during the end of the germ cell migration phase and post-natal gonadal maturation in freshwater turtles. Comparison of cadmium concentration in eggs of C. picta from Cape Cod showed that eggs from the impacted site animals had significantly higher cadmium in yolk than eggs from the reference site animals (7.23 ± 1.95 ng/g vs. 1.31 ± 0.50 ng/g). Gonadal structure and the number of proliferating germ cells of neonates derived from eggs of adult females from these sites showed no marked difference between sites. However, apoptosis of oocytes was significantly increased in neonate C. picta from the impacted pond compared to the reference pond. The effect of an administered environmentally relevant dose of cadmium on germ cell number and oocyte apoptosis was subsequently assessed in lab-reared Trachemys scripta, a closely related freshwater turtle species. Assessment of isotopic cadmium transmission showed that 6.29% of cadmium applied to the eggshell was transmitted through the eggshell to the yolk. The results showed that the total number of germ cells in cadmium-treated (1 μg/g) embryos was less than half that found in control embryos. The reduced germ cell number in Cd-treated embryos suggests that cadmium may reduce proliferation and/or delay migration of germ cells to the genital ridge. The effects of cadmium on turtle gonadal development were found to extend into 3 months post hatch. Proliferation of oocytes was not influenced by exposure to cadmium in ovo. In contrast, apoptosis of oocytes was significantly increased in cadmium exposed T. scripta. Since a lesion at the gonial stages will lead eventually to the depletion of more mature germ cells, the results for neonate turtles suggest that an environmental impact due to a xenobiotic mixture may enhance the rate of apoptosis, thus resulting in the reduction in follicle number seen in adult turtles from the impacted site. Overall, the data provide evidence that environmentally relevant doses of cadmium may affect gonadal developmental processes of freshwater turtles during embryonic and post-natal stages that may result in disruption of reproductive processes later in life.

Evaluation of the potential toxicity (acute and chronic) of sediments from abandoned uranium mine ponds

The superficial aquatic system of the Cunha Baixa uranium mine area is comprised by the flooded mine pit (M), which receives the acidic mine effluent resultant from in situ leaching of pore ore, a pond where this effluent is neutralised (T), and a potential reference pond (Ref). As part of the first tiers of an ecological risk assessment that is being performed in this area, the aim of this work was to evaluate the potential sediment toxicity of these ponds. To perform this work, elutriates were produced from sediments collected at the three ponds in two distinct seasons (Spring and Winter). Acute and chronic toxicity of elutriates was evaluated by standard assay protocols, using Daphnia spp. as test species (D. magna-standard species and D. longispina-native species). In opposition to what could be previewed based on total metal concentrations, results showed acute toxicity only in M site (low pH, high metal levels) in spring for both species with EC50=94.7% and 96.3% (D. longispina and D. magna respectively). A stimulatory effect (in growth and fecundity) was observed in the chronic assays, for almost all of the tested concentrations of the three elutriates tested-except for the highest concentrations of the M elutriate. Some differences were observed in the responses of Daphnia, both between test species and seasons. Differences between the two sampling periods were also found for pH. Although some toxicity was observed in M, overall no toxicity was found for sediments of the aquatic system, corroborating previous results from our team (including whole-sediment tests). Differences in pH may explain the observed toxicity, acting both as a stressor and mobilizing contaminants. Stimulatory phenomena, typical when dealing with natural samples, worked as confounding factors. Several explanations should be considered for these stimulatory effects, however the role of radionuclides (not measured in this work) cannot be ignored. Supported by the results gathered in this study and in previous evaluations already performed, it is possible to state that in the present situation sediments plays a secondary role in the toxicity of the Cunha Baixa uranium mine, probably working more as a barrier than as a source of contaminants to the water column. However, future reclamation works in this area should carefully consider the remobilisation of sediments, especially from pond M. Radiochemical contamination is expected to be higher in field situations where radiation emitter isotopes are present in all the sediment compartment and overlying water, emitting radiations in all the directions. Thus whole-sediment and elutriate laboratory bioassays are not representative of long-term field exposures to radiation. Based on this supposition, these laboratory responses should be validated by field surveys of the benthic and planktonic freshwater communities of these ponds and freshwater receiving resources, at the higher tiers of the local ecological risk assessment.

Acute and Chronic Toxicity of Effluent Water from an Abandoned Uranium Mine

Inactive or abandoned mines represent a significant source of environmental, chemical, physical, and aesthetic impact. Among concerning situations, the occurrence of abandoned or semi-abandoned mine-associated ponds (for sedimentation of solids, for effluent neutralization, or for washing the ore) is a common feature in this type of system. These ponds are a source of contamination for the groundwater resources and adjacent soils, because they lack appropriate impermeabilization. The use of this water for agriculture may also pose chronic risks to humans. In Portugal, these problems have been diagnosed and some remediation projects have been developed. The purpose of our study was to evaluate the acute and chronic toxicity of water samples collected from the aquatic system surrounding an abandoned uranium mine (Cunha Baixa, Mangualde, Central Portugal). The present study focuses on the water compartment, whose toxicity was evaluated by means of standard toxicity assays using two Daphnia species (D. longispina and D. magna). Three different ponds were used in the characterization of the aquatic system from Cunha Baixa mine: a reference pond (Ref), a mine effluent treatment pond (T), and a mine pit pond (M). Metal analyses performed in the water samples from these ponds showed values that, in some cases, were much higher than maximum recommendable values established (especially Al, Mn) by Portuguese legislation for waters for crop irrigation. Acute toxicity was only observed in the mine pit pond, with EC(50) values of 28.4% and 50.4% for D. longispina and D. magna, respectively. The significant impairment of chronic endpoints, translated in reductions in the population growth rate for both species, gives rise to concerns regarding the potential risks for aquatic zooplanktonic communities, from local receiving waters, potentially exposed to point source discharges of the treated and nontreated effluent from Cunha Baixa uranium mine.

Deformities in cane toad (Bufo marinus) populations in Bermuda: Part II. Progress towards characterization of chemical stressors

An alarming high incidence of deformities in mature and newly metamorphosed Bufo marinus was identified in 2002 (29% in adults and 21% in metamorph specimens) in Bermuda. Suspicion of multiple chemical stressors in many of the effected ponds warranted identification of potential causative agents. Short-term embryo-larval, chronic exposure studies through hind limb development, and a battery of toxicity identification studies were performed with B. marinus and the surrogate species, Xenopus laevis, using sediment and water collected from four target ponds and one reference pond in Bermuda. Short-term embryo larval developmental toxicity studies based on a modified FETAX method indicated that samples from each of the target sites were capable of inducing abnormal development. Malformations induced in the early developmental tests were consistent amongst the species and included abnormal development of the craniofacial region, eye, mouth, and gut. Limb reduction deficit defects were identified in the chronic exposure studies with B. marinus and X. laevis. Toxicity characterization studies found that the toxicity of sediment extracts was variably filterable and reduced by C18-SPE, cation exchange, and zeolite treatments. Developmentally toxic samples contained elevated levels of petroleum hydrocarbons, metals (Al, As, Sn, Cd, Cr, Cu, Fe, Pb, Hg, Mn, Ni, and Zn), and ammonia. Sediment spiking studies with reference sediment confirmed that the levels of petroleum hydrocarbons and metals were capable of inducing developmental toxicity individually. Joint mixture interaction studies with sediment extracts prepared from the individually spiked reference sediment suggested however, that these extracts were potentially capable of acting synergistically, producing a greater level of toxicity than would normally be predicted based on the response to the individual spiked samples.

Exposure and effects of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin in tree swallows (Tachycineta bicolor) nesting along the Woonasquatucket River, Rhode Island, USA

Concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in tree swallows (Tachycineta bicolor) nesting along the Woonasquatucket River northwest of Providence (RI, USA) in 2000 and 2001 were some of the highest ever reported in avian tissues. Mean concentrations in eggs ranged from 300 to >1,000 pg/g wet weight at the two most contaminated ponds, Allendale and Lyman. Mean egg concentrations at Greystone, the upstream reference pond, were 12 and 29 pg/g. Positive accumulation rates and concentrations in diet samples from 12-day-old nestlings indicated that the contamination was accumulated locally. Concentrations in diet of between 71 and 219 pg/g wet weight were more than 6 and 18 times higher than concentrations considered safe for birds (10-12 pg/g). Hatching success was negatively associated with concentration of TCDD in eggs. Only about half the eggs hatched at Allendale compared with >77% at Greystone. The national average for hatching success in successful nests is 85%. No other contaminants, such as polychlorinated biphenyls and mercury, were present in any sample at concentrations known to affect avian reproduction. Three bioindicators, half-peak coefficient of geometric variation, ethoxyresorufin-O-dealkylase activity, and brain asymmetry were assessed relative to TCDD contamination.