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Decreasing toxicity of un-ionized ammonia on the gastropod Bellamya aeruginosa when moving from laboratory to field scale
Abstract
Along with a steady increasing use of artificial nitrogen fertilizer, concerns have been raised about the effects that high nitrogen loading may have on ecosystems. Due to the toxicity of unionized ammonia (NH 3), tolerance criteria have been proposed for ambient water management in many countries; however, these are mainly based on acute or chronic tests carried out under lab conditions run with purified water. Aiming at understanding the responses of organisms to natural exposure to high ammonia concentrations, a Viviparidae gastropod, Bellamya aeruginosa, was tested at three experimental scales: standard 96-h lab test, one-month cage test in 6 experimental ponds with continuous nitrogen inputs, and intensive investigation of the B. aeruginosa from these ponds in spring and winter. The results were: 1) 96-h LC 50 in the standard lab test was 0.56 mg NH 3-N/L and 343.3 mg TAN/L (total ammonia expressed as N, standardized at pH 7 and 20 ℃). 2) In the one-month cage test, the survival rate was 97% when NH 3-N was 0.61 mg/L (i.e., a higher concentration than the lab 96-h LC 50) and the body size of the gastropods actually increased with increasing NH 3-N concentrations. 3) In the winter-spring investigation, little effect of ammonia on the standing crops of gastropods was found, and the body size of the gastropods tended to increase with increasing ammonia concentrations (NH 3-N concentration range of 0.05 ~ 2.06 mg/L). Thus, B. aeruginosa showed higher tolerance to ammonia exposure (NH 3-N concentration < 0.81 mg/L) in the field than under laboratory conditions. Our study points to the necessity of considering the relevant scale when determining criteria for ammonia toxicity in water management.
... Guidance regarding their practical application may, therefore, not be adequate/optimal. Studies comparing lab test and pond experiments, however, suggest a strong scale dependence of ammonia toxicity to aquatic organisms (Wang et al., 2017;Liu et al., 2021). For example, given the same ammonia concentration, higher survival and growth rates of the common gastropod Bellamya aeruginosa were found in a one-month cage test performed in ponds than in 96-h acute test performed under laboratory conditions by Liu et al. (2021). ...
... Studies comparing lab test and pond experiments, however, suggest a strong scale dependence of ammonia toxicity to aquatic organisms (Wang et al., 2017;Liu et al., 2021). For example, given the same ammonia concentration, higher survival and growth rates of the common gastropod Bellamya aeruginosa were found in a one-month cage test performed in ponds than in 96-h acute test performed under laboratory conditions by Liu et al. (2021). Similar findings were obtained for three common fish species, silver carp (Hypophthalmichthys molitrix Val.), bighead carp (Aristichthys nobilis Richardson), and gibel carp (Carassius auratus gibelio Bloch) (Wang et al., 2017), where no dead fish were found in ponds after one year's exposure to ammonia to concentrations as high as 96-h LC 50 of ammonia. ...
... Concentrations of NH 3 -N should also be much lower in sediment than in overlying water, considering the vertical distribution of ammonia, temperature, and pH carefully measured in natural ponds (Liu et al., 2021), where a difference of 2℃ was found for temperature, and 0.2 for pH, and 1.0 mg/L for NH 3 -N between upper and bottom layer of a pond. Besides, sediment provided extra food for gastropods, in form of organic substances or periphyton, as evidenced by the fact that the growth rates of gastropods were obviously higher in treatment Water + Sediment and Water-only of N0(LC 50 ) bioassay (Fig. 4a1, b1, The results of the measured enzymic activities of CAT and SOD were not consistent with that inferred from the growth of gastropods. ...
The toxic effect of unionized ammonia (NH3) on aquatic organisms is receiving increasing attention due to the excessive nitrogen discharge to various surface waters. Researches have suggested the scale-dependence of NH3 toxicity, being lower in field than under lab conditions. Such scale-dependence of toxicity is a big challenge to water quality criteria setting as the results solely from lab tests might not apply to natural ecosystems. Therefore, it is necessary to explore the underlying mechanism to understand the difference of toxicity across various spatial scales. In this study, we used the widely distributed gastropod Bellamya aeruginosa as the test animal and performed two 192-h microcosm experiments. Each experiment included a control and an ammonia addition treatment: N0(LC50) & N+(LC50), N0(LC100) & N+(LC100) (96-h LC50 = 0.8 mg NH3-N/L, 96-h LC100 = 18.1 mg NH3-N/L). Besides water-only, three potential key components (food, sediment, and submersed macrophytes) were included in the various treatments to mimic different complexity levels of aquatic ecosystems (Water, Water + Food, Water + Sediment, Water + Sediment + Macrophytes). The results showed that: 1) food directly improved the survival and growth of gastropods under expected lethal concentration of ammonia (96-h concentration of NH3-N = LC20 of the 96-h acute test); 2) sediment and macrophyte quickly decreased the ammonia concentration, mainly by sediment adsorption and macrophyte uptake, to alleviate the ammonia stress to gastropods and permitted them to survive and grow under expected lethal concentration of ammonia (96-h concentration of NH3-N = LC10∼LC20 of the 96-h acute test); 3) sediment and macrophyte also provided additional food for gastropods; 4) under extremely high ammonia stress (i.e., 96-h LC100, food was left uneaten and macrophyte died, and gastropods could, therefore, not be released from ammonia stress. Our results demonstrate that under moderate ammonia stress, the introduction of extra ecosystem elements (food, sediment, and macrophytes) significantly improved the survival and growth of gastropods, mainly by enhancing their tolerance and by quickly decreasing the NH3 concentration and thus toxicity. However, these introduced elements had little effect at very high concentration of ammonia (i.e., 96-h LC100). Our findings add to the understanding of the reasons behind the previous observed scale-dependent toxicity of NH3 on aquatic organisms and contribute to better decisions on the role of NH3 in relation to water quality management.
... The increases in N production have resulted in large fluxes of N in nature [3]. Unintentional N enrichment has a variety of negative environmental impacts, including soil acidification [4], reduction of global terrestrial biodiversity [5], increased nutrient runoff to aquatic ecosystems, causing eutrophication [6], and potential risk of toxicological stress on aquatic changes [7][8][9][10] can ultimately impact ecosystem services and human well-being [11]. ...
Excessive nitrogen (N) input is an important factor influencing aquatic ecosystems and has received increasing public attention in the past decades. It remains unclear how N input affects the denitrifying bacterial communities that play a key role in regulating N cycles in various ecosystems. To test our hypothesis—that the abundance and biodiversity of denitrifying bacterial communities decrease with increasing N—we compared the abundance and composition of denitrifying bacteria having nitrous oxide reductase gene (nosZ I) from sediments (0–20 cm) in five experimental ponds with different nitrogen fertilization treatment (TN10, TN20, TN30, TN40, TN50) using quantitative PCR and pyrosequencing techniques. We found that (1) N addition significantly decreased nosZ I gene abundance, (2) the Invsimpson and Shannon indices (reflecting biodiversity) first increased significantly along with the increasing N loading in TN10–TN40 followed by a decrease in TN50, (3) the beta diversity of the nosZ I denitrifier was clustered into three groups along the TN concentration levels: Cluster I (TN50), Cluster II (TN40), and Cluster III (TN10–TN30), (4) the proportions of Alphaproteobacteria and Betaproteobacteria in the high-N treatment (TN50) were significantly lower than in the lower N treatments (TN10–TN30). (5) The TN concentration was the most important factor driving the alteration of denitrifying bacteria assemblages. Our findings shed new light on the response of denitrification-related bacteria to long-term N loading at pond scale and on the response of denitrifying microorganisms to N pollution.
Behavioral endpoints are important parameters to assess the effects of toxicants on aquatic animals. These endpoints are useful in ecotoxicology because several toxicants modify the animal behavior, which may cause adverse effects at higher levels of ecological organization. However, for the development of new bioassays and for including the behavior in ecotoxicological risk assessment, the comparison of sensitivity between different behavioral endpoints is necessary. Additionally, some toxicants remain in aquatic environments for a few hours or days, which may lead to animal recovery after toxicant exposure. Our study aimed to assess the effect of unionized ammonia on the movement and feeding behaviors of the aquatic gastropod Potamopyrgus antipodarum (Tateidae, Mollusca) and its recovery after exposure. Four treatments were used: a control and three nominal concentrations of unionized ammonia (0.25, 0.5 and 1 mg N-NH3/L). Each treatment was replicated eight times, with six animals in each replicate. Animals were exposed to unionized ammonia for 48 h (exposure period) and, subsequently, to control water for 144 h (post-exposure period). Two movement variables were monitored without food and five feeding behavioral variables were monitored in the presence of food. Some of the feeding behavioral variables showed higher sensitivity (LOEC = 0.25–0.5 mg N-NH3/L) than the movement behavior variables monitored without food (LOEC = 1 mg N-NH3/L). After exposure to unionized ammonia, animals showed a recovery of most behavioral endpoints. The inclusion of post-exposure period and feeding behaviors in bioassays may make studies more realistic, which is crucial for a proper ecotoxicological risk assessment.
The recent mass mortality event of more than 330 African elephants in Botswana has been attributed to biotoxins produced by cyanobacteria; however, scientific evidence of this is lacking. Here, by synthesizing multiple sources of data, we show that, during the past decades, the widespread hypertrophic waters in southern Africa have entailed an extremely high risk and frequent exposure of cyanotoxins to the wildlife within this area, which functions as a hotspot of mammal species richness. The hot and dry climatic extremes have most likely acted as the primary trigger of the recent and perhaps also of prehistoric mass mortality events. As such climate extremes are projected to become more frequent in southern Africa in the near future, there is a risk that similar tragedies may take place, rendering African megafauna species, especially those that are already endangered, in risk of extinction. Moreover, cyanotoxin poisoning amplified by climate change may have unexpected cascading effects on human societies. Seen within this perspective, the tragic mass death of the world’s largest terrestrial mammal species serves as an alarming early warning signal of future environmental catastrophes in southern Africa. We suggest that systematic, quantitative cyanotoxin risk assessments are made and precautionary actions to mitigate the risks are taken without hesitation to ensure the health and sustainability of the megafauna and human societies within the region.
Fertilizers increase yield of crops but may have unintended negative effects on fish as a byproduct of runoff into bodies of freshwater. The objective of this study was to determine if environmentally relevant concentrations of an ammonium fertilizer impacts stress and innate immunity in Western mosquitofish (Gambusia affinis). The mosquitofish were exposed to different concentrations of ammonium sulfate fertilizer: 0 ppm, 40 ppm, and 80 ppm. To test the effects of ammonium sulfate on stress physiology, cortisol released into water by individual fish was collected after 1 week of exposure and again after 2 weeks of exposure and quantified with an enzyme immunoassay. Cortisol levels in the 0-ppm group were not significantly different over the course of the study, but we found a significant increase in cortisol levels in the fish exposed to 40 ppm and 80 ppm. We found reduced survival in fish from the 40 ppm and 80 ppm of ammonium sulfate groups compared with the 0-ppm group. We also used blood samples to complete a lysozyme assay as a measure of innate immune defense. Higher concentrations of ammonium sulfate correlated with significantly lower lysozyme activity in the fish. Overall, our results suggest that relatively low amounts of ammonium sulfate runoff into bodies of water are likely to have negative sublethal and lethal effects on small fishes.
There is concern about the deteriorating nutrient status of aquatic receiving environments in New Zealand. We estimated the amount by which current nitrogen (N) concentrations and loads exceed criteria in rivers, lakes and estuaries nationally. Criteria corresponded to national ‘bottom-line’ (i.e. minimal) environmental objectives set by government policy. Three metrics were evaluated: (1) degree of compliance describes the current TN loads in receiving environments relative to criteria; (2) catchment N status describes the acceptability of catchment N loads compared to criteria; and (3) excess load indicates the amount by which the N load exceeds the maximum allowable load (kg yr⁻¹). Non-compliance with N criteria was broadly distributed nationally particularly in low-elevation catchments. Catchments with unacceptable N status constituted at least 31% of New Zealand’s land area, which corresponds to at least 43% of the country’s agricultural land. The national excess load was estimated to be at least 19.1 Gg yr⁻¹. We are 97.5% confident that estimated excess loads exceed zero for nine of 15 regions and for the nation as a whole. The analyses provide a strategic assessment of where reductions in N emissions are required to achieve the minimal national objectives.
Nitrogen is a critical component of the economy, food security, and planetary health. Many of the world's sustainability targets hinge on global nitrogen solutions, which, in turn, contribute lasting benefits for (i) world hunger; (ii) soil, air, and water quality; (iii) climate change mitigation; and (iv) biodiversity conservation. Balancing the projected rise in agricultural nitrogen demands while achieving these 21st century ideals will require policies to coordinate solutions among technologies, consumer choice, and socioeconomic transformation.
Concentrations of heavy metals (Cd, Ni and Pb) were determined in soft and hard tissues (three separated shell sections) of gastropod Bufonaria echinata as well as surficial sediments collected in October 2015 from two sampling sites located in the sub-littoral zone of Qeshm Island, Persian Gulf. There were significant differences between the sampling sites for concentrations of all the three elements in the shells and sediments. But in terms of the soft tissues, in the case of Ni and Pb significant differences between the sites could be observed. In all the cases, higher levels were observed in the samples from Suza site, which may be mainly due to the proximity of this site to the relevant anthropogenic sources. Comparison of the gained data from this study with the other relevant researches shows that in most cases the levels of the elements in the soft tissues and shells either fell within the range for other world areas or were lower. The observed increasing trends of metals accumulation in the shell sections (from older to younger sections) could be mainly attributed to the gradual increase of relevant anthropogenic pollutants in the study area, especially in Suza pier, during the recent years. Generally, it can be concluded that the shells of B.echinata could be possibly employed as a biomonitoring tool for historic metals contamination in northeastern part of the Persian Gulf. © 2019 Iranian Fisheries Research Organization. All rights reserved.
We performed toxicity tests with two species of pulmonate snails (Lymnaea stagnalis and Physa gyrina) and four taxa of nonpulmonate snails in the family Hydrobiidae (Pyrgulopsis robusta, Taylorconcha serpenticola, Fluminicola sp., and Fontigens aldrichi). Snails were maintained in static-renewal or recirculating culture systems with adults removed periodically to isolate cohorts of offspring for toxicity testing. This method successfully produced offspring for both species of pulmonate snails and for two hydrobiid species, P. robusta and Fluminicola sp. Toxicity tests were performed for 28 days with copper, ammonia, and pentachlorophenol in hard reconstituted water with endpoints of survival and growth. Tests were started with 1-week-old L. stagnalis, 2-week-old P. gyrina, 5- to 13-week-old P. robusta and Fluminicola sp., and older juveniles and adults of several hydrobiid species. For all three chemicals, chronic toxicity values for pulmonate snails were consistently greater than those for hydrobiid snails, and hydrobiids were among the most sensitive taxa in species sensitivity distributions for all three chemicals. These results suggest that the toxicant sensitivity of nonpulmonate snails in the family Hydrobiidae would not be adequately represented by results of toxicity testing with pulmonate snails.
The kinetics of nitrogen removal was studied in upflow submerged nitrification and denitrification filters in series. Nitrification followed first-, half-, and zero-order kinetics. For the half-order range the half-order rate constant was about 0.9 g NH4-N(1/2)m(-1/2)d-1. The zero-order rate constants for the DO ranges of 2-3 mg/L and 4-5 mg/L were found as 0.47 gNH4-Nm-2d-1 and 1.82 gNH4-Nm-2d-1, respectively. In the zero-order region ammonia removal proceeded as a half-order reaction in oxygen concentration and the half-order rate constants were about 1.4-2.7 g O2(1/2)m(-1/2)d-1. Nitrite accumulation reached a considerable degree at bulk oxygen to bulk ammonia ratios lower than 5 since the formation of nitrate was inhibited. Similar to nitrification half- and zero-order kinetic regions were also observed in denitrification. The half- and zero-order rate constants for carbon unlimited cases (influent COD/NO(X)-N > 5) were about 0.23 gNO(X)-N(1/2)m(-1/2)d-1 and 1.9 gNO(X)-Nm-2d-1, respectively. The nitrite produced in the nitrification stage could be reduced in denitrification. The removal kinetics in the presence of nitrite was found to be similar to the kinetics when the influent consisted of nitrate only.
Parasitoids exposed to low temperatures may suffer from extreme physiological conditions inducing direct or indirect chill injuries. Under long cold exposure (which also includes starvation), individuals face a great challenge in maintaining both water balance and energy reserves. Key parameters associated with individual Þtness and physiological parameters related to cold-hardiness were analyzed. One-day-old mummies of the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Aphidiinae) were exposed to cold (2 and 4°�C) for various periods (1-3 wk) under a high relative humidity (75 +- 5% RH) and darkness. High mortality and shortened adult longevity occurred with increasing duration of exposure at low temperatures. Individual parasitoid mass loss increased with cold storage duration and was associated to a marked decrease in dry mass caused by lipid reserve depletion. Water content (water mass/dry mass) slightly increased with cold exposure duration because of starvation. Similar patterns were observed for both temperatures tested. This study emphasizes (1) how energetic reserves may be critical to survive at low temperatures and (2) that the survival and longevity are related, at least in part, to the depletion of energy reserves during starvation.
Nitrogenous wastes including ammonia-N, nitrite-N, and nitrate-N are increasingly becoming a global issue in aquatic ecosystems due to escalating anthropogenic activities and are a ubiquitous concern in aquaculture. These pollutants are interrelated via the nitrification cycle, with the direct metabolic product ammonia-N generally being the most toxic with high species specificity. Furthermore, while environmental factors influencing nitrogenous waste toxicity are similar, the causative underlying mechanisms are often substantially different. In this review, we focus on decapod crustaceans due to their high commercial value and likelihood of encountering these pollutants in their benthic or near-benthic habitat. While a large body of publications exists in this area, to date a comprehensive literature review on relative toxicities of all three nitrogenous wastes, physiological consequences, and adaptive mechanisms of crustaceans is lacking. Understanding these processes will likely have implications for environmental/fisheries management and the aquaculture industry. Additionally, there are strong indications that theoretical "safe" values, traditionally used for predicting toxicity thresholds, substantially underestimate the impact of nitrogenous waste on the growth and physiological condition of crustaceans. These consequences will be emphasized along with various methods of uptake, elimination, and detoxification that ultimately explain differences in nitrogenous waste toxicity to decapod crustaceans.
The present study aimed at analyzing the imposex incidence and the presence of butyltins namely tributyltin (TBT) with its di- and mono-substituted metabolites in Bolinus brandaris whole tissues and in surface sediments at seven sites from the Tunisian coast during one campaign in May 2010. Butyltin levels were evaluated using isotope dilution GC–MS. Except the population collected from Zarat site, imposex was found in snails from the remained six sites with a maximal incidence and sterility (closure of the vaginal opening) registered in Carrier bay. Both imposex indices VDSI and RPLI showed a positive correlation with tissue concentrations of TBT. Total butyltin concentrations in sediments were higher in sites located in the vicinity of shipping areas with levels of TBT high enough to cause environmental concern if there is no legislative restriction and enforcement for the sale and use of these chemicals in Tunisia. These results further confirmed that B. brandaris is a good bioindicator of butyltin pollution in the studied areas. In addition, this study provided recent and new data on sediment butyltin concentrations that could serve for long-term monitoring of TBT pollution in Tunisia and the Mediterranean Sea.
Ammonia is released in the environment by many industries and other human activities. The major quantifiable sources of ammonia released to aquatic ecosystems across Canada are municipal wastewater treatment plants, at an estimated total quantity of 62,000 tonnes per year. Given the sources of ammonia releases in the environment and the properties of the substance, terrestrial plants and aquatic organisms are potential risk targets. A tiered assessment approach has been used to determine the ecological risk in the aquatic environment from ammonia released in municipal wastewater effluents. The results obtained for two case studies with the probabilistic risk analysis used in the highest tier support the conclusion that the conditions encountered in these two locations can lead to ammonia concentrations capable of producing an adverse ecological impact.
This paper contrasts the natural and anthropogenic controls on the conversion of unreactive N2 to more reactive forms of nitrogen (Nr). A variety of data sets are used to construct global N budgets for 1860 and the early 1990s and to make projections for the global N budget in 2050. Regional N budgets for Asia, North America, and other major regions for the early 1990s, as well as the marine N budget, are presented to Highlight the dominant fluxes of nitrogen in each region. Important findings are that human activities increasingly dominate the N budget at the global and at most regional scales, the terrestrial and open ocean N budgets are essentially disconnected, and the fixed forms of N are accumulating in most environmental reservoirs. The largest uncertainties in our understanding of the N budget at most scales are the rates of natural biological nitrogen fixation, the amount of Nr storage in most environmental reservoirs, and the production rates of N2 by denitrification.
Although algal blooms, including those considered toxic or harmful, can be natural phenomena, the nature of the global problem
of harmful algal blooms (HABs) has expanded both in extent and its public perception over the last several decades. Of concern,
especially for resource managers, is the potential relationship between HABs and the accelerated eutrophication of coastal
waters from human activities. We address current insights into the relationships between HABs and eutrophication, focusing
on sources of nutrients, known effects of nutrient loading and reduction, new understanding of pathways of nutrient acquisition
among HAB species, and relationships between nutrients and toxic algae. Through specific, regional, and global examples of
these various relationships, we offer both an assessment of the state of understanding, and the uncertainties that require
future research efforts. The sources of nutrients potentially stimulating algal blooms include sewage, atmospheric deposition,
groundwater flow, as well as agricultural and aquaculture runoff and discharge. On a global basis, strong correlations have
been demonstrated between total phosphorus inputs and phytoplankton production in freshwaters, and between total nitrogen
input and phytoplankton production in estuarine and marine waters. There are also numerous examples in geographic regions
ranging from the largest and second largest U.S. mainland estuaries (Chesapeake Bay and the Albemarle-Pamlico Estuarine System),
to the Inland Sea of Japan, the Black Sea, and Chinese coastal waters, where increases in nutrient loading have been linked
with the development of large biomass blooms, leading to anoxia and even toxic or harmful impacts on fisheries resources,
ecosystems, and human health or recreation. Many of these regions have witnessed reductions in phytoplankton biomass (as chlorophylla) or HAB incidence when nutrient controls were put in place. Shifts in species composition have often been attributed to changes
in nutrient supply ratios, primarily N∶P or N∶Si. Recently this concept has been extended to include organic forms of nutrients,
and an elevation in the ratio of dissolved organic carbon to dissolved organic nitrogen (DOC∶DON) has been observed during
several recent blooms. The physiological strategies by which different groups of species acquire their nutrients have become
better understood, and alternate modes of nutrition such as heterotrophy and mixotrophy are now recognized as common among
HAB species. Despite our increased understanding of the pathways by which nutrients are delivered to ecosystems and the pathways
by which they are assimilated differentially by different groups of species, the relationships between nutrient delivery and
the development of blooms and their potential toxicity or harmfulness remain poorly understood. Many factors such as algal
species presence/abundance, degree of flushing or water exchange, weather conditions, and presence and abundance of grazers
contribute to the success of a given species at a given point in time. Similar nutrient loads do not have the same impact
in different environments or in the same environment at different points in time. Eutrophication is one of several mechanisms
by which harmful algae appear to be increasing in extent and duration in many locations. Although important, it is not the
only explanation for blooms or toxic outbreaks. Nutrient enrichment has been strongly linked to stimulation of some harmful
species, but for others it has not been an apparent contributing factor. The overall effect of nutrient over-enrichment on
harmful algal species is clearly species specific.
A draft update of the U.S. Environmental Protection Agency ambient water quality criteria (AWQC) for ammonia substantially lowers the ammonia AWQC, primarily due to the inclusion of toxicity data for freshwater mussels. However, most of the mussel data used in the updated AWQC were generated from water-only exposures and limited information is available on the potential influence of the presence of a substrate on the response of mussels in laboratory toxicity tests. Our recent study demonstrated that the acute sensitivity of mussels to ammonia was not influenced by the presence of substrate in 4-d laboratory toxicity tests. The objective of the current study was to determine the sensitivity of mussels to ammonia in chronic 28-d water exposures with the sediment present (sediment treatment) or absent (water-only treatment). The chronic toxicity test was conducted starting with two-month-old juvenile mussels (fatmucket, Lampsilis siliquoidea) in a flow-through diluter system, which maintained consistent pH (≈8.3) and six concentrations of total ammonia nitrogen (N) in overlying water and in sediment pore water. The chronic value (ChV, geometric mean of the no-observed-effect concentration and the lowest-observed-effect concentration) was 0.36 mg N/L for survival or biomass in the water-only treatment, and was 0.66 mg N/L for survival and 0.20 mg N/L for biomass in the sediment treatment. The 20% effect concentration (EC20) for survival was 0.63 mg N/L in the water-only treatment and was 0.86 mg N/L in the sediment treatment (with overlapping 95% confidence intervals; no EC20 for biomass was estimated because the data did not meet the conditions for any logistic regression analysis). The similar ChVs or EC20s between the water-only treatment and the sediment treatment indicate that the presence of sediment did not substantially influence the sensitivity of juvenile mussels to ammonia in the 28-d chronic laboratory water exposures.
The Clinch River watershed of the upper Tennessee River Basin of Virginia and Tennessee, USA supports one of North America’s greatest concentrations of freshwater biodiversity, including 46 extant species of native freshwater mussels (Order Unionida), 20 of which are protected as federally endangered. Despite the global biological significance of the Clinch River, mussel populations are declining in some reaches, both in species richness and abundance. The aim of this study was to evaluate the exposure of adult resident mussels to a suite of inorganic and organic contaminant stressors in distinct sections of the Clinch River that encompassed a range of mussel abundance and health. To provide insight into the potential role of pollutants in the decline of mussels, including within a previously documented “zone of mussel decline”, the mainstem Clinch River (8 sites) and its tributaries (4 sites) were examined over two consecutive years. We quantified and related metals and organic contaminant concentrations in mussels to their associated habitat compartments (bed sediment, suspended particulate sediment, pore water, and surface water). We found that concentrations of organic contaminants in resident mussels, particularly the suite of 42 polycyclic aromatic hydrocarbons (PAHs) analyzed, were related to PAH concentrations in all four habitat (media) compartments. Further, PAH concentrations in mussel tissue (range 37.8-978.1 ng/g dry weight in 2012 and 194.3-1,073.7 ng/g dry weight in 2013) were negatively related to the spatial pattern in mussel densities (rs = -0.64, p ≤ 0.05 in 2012 and rs = -0.83, p ≤ 0.05 in 2013) within the river, and were highest in the “zone of mussel decline”. In contrast, the suite of 22 metals analyzed in resident mussels were largely unrelated to the spatial pattern of variation of metals in the four habitat compartments except for Manganese (Mn; range 3,630.5-23,749.2 μg/g dry weight in 2012 and 1,540.4-12,605.8 μg/g dry weight in 2013) in surface water (rs = 0.58, p <0.1) and pore water (rs = 0.76, p ≤ 0.05. This study revealed that PAHs and Mn are important pollutant stressors to mussels in the Clinch River and that they are largely being delivered through the Guest River tributary watershed. Accordingly, future conservation and management efforts would benefit by identifying, and ideally mitigating, the sources of PAHs, Mn, and other current or legacy mining-associated pollutants to the mainstem river and its tributaries.
Phosphorus (P) release from sediment is a key process affecting the effectiveness of eutrophication mitigation. We hypothesized that high nitrate (NO3⁻) input may have dual effect on sediment P release: reduce the sediment P release by improving the oxidation of sediment or promote P release by stimulating the growth of phytoplankton and increase the decomposition rates and oxygen consumption at the sediment water interface. To test the effect of different NO3⁻ concentrations, we conducted a three-month experiment in 15 cement tanks (1 m³), with five targeted concentrations of NO3⁻: control, 2 mg L⁻¹, 5 mg L⁻¹, 10 mg L⁻¹, and 15 mg L⁻¹. The results showed that: i) when NO3⁻ was maintained at high levels: NO3⁻≥5–7 mg L⁻¹ (range of median values), there was no effect of NO3⁻ on net P release from the sediment, likely because the positive effects of NO3⁻ (increasing oxidation) was counteracted by a promotion of phytoplankton growth. ii) after NO3⁻ addition was terminated NO3⁻ dropped sharply to a low level (NO3⁻≤0.4 mg L⁻¹), followed by a minor P release in the low N treatments but a significant P release in the high N treatments, which likely reflect that the inhibition effect of NO3⁻ on P release decreased, while the promotion effects at high NO3⁻ concentrations continued. The results thus supported our hypotheses of a dual effect on sediment P release and suggest dose-dependent effect of NO3⁻ loading on stimulating P release from the sediment, being clear at high NO3⁻ exceeding 5–7 mg L⁻¹.
During the bloom seasons, the dissolved inorganic nitrogen declines, which results in the occurrence of nitrogen limitation. It is unclear where the nitrogen goes. Our enclosure experiments and batch tests suggested that Microcystis blooms could significantly reduce the nitrogen in water bodies and the key mechanisms for the nitrogen reduction in different layers were different. The assimilation was the main pathway for nitrogen reduction in the surface layer, while denitrification played an important role both at the sediment-water interface and in the overlying water. Stable nitrogen isotope experiments showed that the nitrate reduction efficiency at sediment-water interface was enhanced by Microcystis, reaching to 76.5∼84.7 %. Dissimilation accounted for 63.8∼67.3 % of the nitrate reduction, and the denitrification rate was 7.4∼8.5 times of DNRA rate. In the water column, the Microcystis bloom facilitated the formation of dark/anoxic condition, which favored the denitrification. The Microcystis aggregates collected from the field showed a great potential in removing nitrogen, and the TN in the overly water was reduced by 3.76∼6.03 mg L-1 within two days. This study provided field evidences and deeper insights into the relationship between Microcystis blooms and nitrogen reduction in the whole water column and gave more details about the enhancing effects of Microcystis on nitrogen reduction.
Three submerged macrophytes, Ceratophyllum demersum (CD), Myriophyllum spicatum (MS) and Myriophyllum aquaticum (MA), were treated with various concentrations of ammonia for different lengths of time. Ammonium ions (NH 4⁺ ) in the medium severely inhibited plant growth and led to a reduction in total chlorophyll (chl a and b) in CD and MS. The addition of ammonia significantly decreased the soluble protein content and increased the free amino acid content of CD and MS in treatments with high concentrations of NH 4⁺ , but MA showed no significant physiological response. The antioxidant enzyme system of MA was activated, which in turn reduced the peroxidation level in the plant and maintained the plant's normal physiological activities when the ammonia nitrogen in the culture fluid increased. The study continued to use higher concentrations (25, 50, 100, 200 and 400 mg/L) of ammonium nitrogen to treat and observe the peroxidation level and corresponding enzyme production for this species of MA in vivo to explore its resistance mechanism. The experiments show that MA can normally live for a period of time in a high-ammonia environment of up to 100 mg/L. The results of the present study will assist in studies of the detoxification of high ammonium ion contents in submersed macrophytes and the selection of plants suitable for macrophyte recovery.
Freshwater mussels are generally under-represented in toxicity databases used to derive water quality criteria, especially for long-term exposures. Multiple tests were conducted to determine the chronic toxicity of sodium chloride (NaCl) or potassium chloride (KCl) to a unionid mussel (fatmucket, Lampsilis siliquoidea). Initially, a 4-week NaCl test and a 4-week KCl test were conducted starting with 2-month-old mussels in water exposures with and without a thin layer of sand substrate. A feeding study was conducted later to refine test conditions for longer-term 12-week exposures, and 3 chronic NaCl tests were then conducted following the refined method to assess the influence of test duration (4 to 12 weeks) and age of organisms (starting age ∼1 week to 2 months old) on mussel sensitivity. Biomass (total dry weight of surviving mussels in a replicate) was generally a more sensitive endpoint compared to survival and growth (length and dry weight). In the 4-week NaCl or KCl test started with 2-month-old juveniles, a 20% effect concentration (EC20) based on biomass (264 mg Cl/L from the NaCl test or 8.7 mg K/L from the KCl test) in the exposure with sand was 2-fold lower than the EC20 in the exposure without sand. The longer-term 12-week NaCl tests started with the 1-week-old and 2-month-old juveniles were successfully completed under refined test conditions based on the feeding study, and younger juveniles were more sensitive to NaCl than older juveniles. The NaCl toxicity did not substantially change with extended exposure periods from 4 to 12 weeks although the 4-week EC20s for biomass were slightly greater (up to 37%) than the 12-week EC20s in the 2 longer-term exposures. Including the toxicity data from the present study into existing databases would rank fatmucket the most sensitive species to KCl and the second most sensitive species to NaCl for all freshwater organisms. This article is protected by copyright. All rights reserved.
In aquatic ecosystems, ammonium is one of the dominant substances in the effluent discharge from wastewater treatment plants and its impact has been widely explored as it is thought, in its toxic form (NH3), to cause stress on organisms. Little is, however, known about its potential effect on the release of phosphorus (P) from the
sediment. In a two-month mesocosm (150 L) experiment, we tested if high loading of ammonium promotes sediment P release and investigated the dominant underlying mechanisms. A gradient of five target ammonium loading levels was used by adding NH4Cl fertilizer: no addition/control (N0), 3 (N1), 5 (N2), 10 (N3), and 21 (N4) mg NH4Cl L-1 (NH4Cl expressed as nitrogen). We found that: 1) significant sediment P release for N3 and N4 but minor release or retention for N0, N1, and N2 were detected both by the total phosphorus concentration (TP) in the overlying water and in situ measurements of diffusive gradients in thin-films (DGT) at the sediment-water interface; 2) overall, TP correlated significantly and positively with total nitrogen (TN) concentrations in the water. Further correlation and path analyses suggested that stimulated alkaline phosphatase activity (APA) was likely the dominant mechanisms behind the ammonium-induced sediment P release and
decreased dissolved oxygen (DO) levels (an approximate reduction from 9.2 to 6.6 mg O2 L-1 ) was likely a contributing factor, particularly in the beginning of the experiment.
A number of studies have revealed ammonia to be toxic to aquatic organisms; however, little is known about its effects under natural conditions. To elucidate the role of ammonia, we conducted 96-h acute toxicity tests as well as a whole-ecosystem chronic toxicity test for one year in ten 600-m² ponds. Three common cyprinids, silver carp Hypophthalmichthys molitrix Val. (H.m.), bighead carp Aristichthys nobilis Richardson (A.n.), and gibel carp Carassius auratus gibelio Bloch (C.g.), were used as test organisms. The 96-h LC50 values of un-ionized ammonia (NH3) for H.m., A.n., and C.g. were 0.35, 0.33, and 0.73 mg L− 1, respectively. In the ponds, annual mean NH3 ranged between 0.01 and 0.54 mg L− 1, with 4 ponds having a NH3 higher than the LC50 of A.n. (lowest LC50 in this study). No fish were found dead in the high-nitrogen ponds, but marked histological changes were found in livers and gills. Despite these changes, the specific growth rate of H.m. and A.n. increased significantly with NH3. Our pond results suggest that fish might be more tolerant to high ammonia concentrations in natural aquatic ecosystems than under laboratory conditions. Our finding from field experiments thus suggests that the existing regulatory limits for reactive nitrogen (NH3) established from lab toxicity tests might be somewhat too high at the ecosystem conditions. Field-scale chronic toxicity tests covering full life histories of fish and other aquatic organisms are therefore encouraged in order to optimize determination of the effects of ammonia in natural environments.
High nitrite concentrations may occur mainly in recirculating aquaculture systems, but can also be found under certain conditions in natural waters. Among studied freshwater organisms, molluscs and worms followed by fish are the most resistant to nitrite. On the other hand, crustaceans and aquatic insects followed by amphibians are the most sensitive. Wide interspecific differences in nitrite susceptibility can be found within freshwater insects, crustaceans and amphibians. Chloride concentration in water is supposed to be the most important factor influencing nitrite toxicity. Generally, a positive chloride effect on nitrite toxicity reduction can be expected in all aquatic animals (or their early stages) employing gills for breathing and ion exchange. This phenomenon has already been observed in an amphipod (Eulimnogammarus toletanus, Pinkster & Stock), a planarian (Polycelis felina, Dalyell), two species of crayfish, several fish species and in amphibians in early development stages. A relatively huge amount of data on nitrite effects is available for fish, but other freshwater organisms were less frequently studied. Information on chronic effect of nitrite is nearly completely missing.
Aqueous ammonia exists in the form of both unionized ammonia (NH3) and ionized ammonium (NH4+). NH3 is more toxic than NH4+ to aquatic organisms, because NH3 can readily diffuse through cell membranes and is highly soluble in lipids. The toxicity of ammonia can be affected by environmental parameters such as temperature, pH, alkalinity, salinity and oxygen concentration. The effects of water pH and temperature on toxicities of ammonia for two freshwater benthic invertebrate species (Corbicula fluminea and Limnodrilus hoffmeisteri) were investigated by the semi-static methods. The data gathered provide more information on the effects of ammonia toxicity to indigenous aquatic organisms. Temperature and pH had significant effects on the acute toxicity to C. fluminea and L. hoffmeisteri. The LC50s of total ammonia decreased with increasing pH, ranging from 11.78 mg/L to 83.82 mg/L. Ammonia toxicities to the two aquatic species were similar. At temperatures 20, 25 and 30 ℃, the LC50s of C. fluminea and L. hoffmeisteri were 70.86, 37.85, 19.14 mg/L and 65.88, 42.73, 21.21 mg/L. The values at 20 ℃ were 3.70 and 3.11 times those at 30 ℃, respectively. The toxicity generally increased with increasing pH and temperature. Comparison of LC50s and the final acute values used to derive the acute water quality criterion (WQC) indicates that acute WQC may adequately protect C. fluminea and L. hoffmeisteri. In addition to our acute toxicity results, it is recommended that chronic ammonia toxicity should also be studied in order to better understand the long-term effects of toxic nitrogenous compounds.
Pollutants are an important factor that causes among others drift (i.e. downstream transport of aquatic organisms in the current) in aquatic invertebrates. However, drift response is taxon-specific, which necessitates the investigation of a wide variety of taxa. Additionally, no information on the effects of the common toxicant ammonia on this endpoint is available. Our study focuses on the effects of exposure and post-exposure to ammonia on the drift of the common aquatic mollusc: Potamopyrgus antipodarum (Hydrobiidae, Mollusca). The effects of ammonia were tested using percentage of drift and stay time (i.e. time that animals stay without dislodging), which were monitored during 2 days of exposure and 2 days of post-exposure in a laboratory stream microcosm. Drift was observed at concentration 4.3 times lower than the LC50 48 h to this species. Our results show that ammonia increases the percentage of drift and caused a reduction in stay time of the exposed animals, both endpoints recover to their normal values after 24 h of post-exposure to ammonia.
Macroinvertebrate contaminated with metals in the Clark Fork River of Montana have been demonstrated to be a potentially toxic component in the diet of trout. Because sediment was the suspected source of metals to these invertebrates, bioaccumulation of As, Cd, Cu, Pb, and Zn from sediment was evaluated by exposing the amphipod Hyalella azteca for 28 d in the laboratory to samples of sediment collected from depositional areas of the Clark Fork River. Benthic invertebrates collected from riffles adjacent to the depositional areas were also analyzed for metals. The pattern of metal accumulation between laboratory-exposed and field-collected animals was similar; however, the concentrations of metals in laboratory-exposed amphipods were often 50 to 75% less than were the concentrations of metals in the field-collected invertebrates. These findings indicate that sediment is a significant source of metals to invertebrates in the Clark Fork River. Additional studies should be conducted to determine threshold concentrations for effects of dietary metals on fish. Long-term monitoring of the river should include sampling benthic invertebrates for metal accumulation.
An underlying assumption of laboratory-based toxicity tests is that the sensitivity of organisms in the laboratory (in vitro) is comparable to that in the field (in situ). The authors tested this assumption by exposing estuarine amphipods (Chaetocorophium cf. lucasi) to a concentration series of cadmium-spiked sediments in vitro and in situ for 10 d. In situ exposures were conducted within plastic-mesh cages on an intertidal mudflat. To characterize exposure, they measured interstitial water cadmium concentrations (IW{sub Cd}), acid volatile sulfide (AVS), and simultaneously extracted Cd (SEM{sub Cd}) at the beginning and end of the exposures. Between day 0 and day 10, AVS decreased in both in vitro and in situ exposures, while IW{sub Cd} levels declined less in vitro than in situ (median 76%). Despite more extreme conditions of temperature and salinity in situ, in vitro and in situ exposures showed comparable survival responses based on SEM{sub Cd}/AVS with the onset of marked mortality above a SEM{sub Cd}/AVS value of about one and minimal survival (< 5%) above a value of two. Based on IW{sub Cd} concentrations, however, sensitivity was significantly greater in vitro. They concluded that, in their tests, amphipod sensitivity in vitro was equal to or greater than its sensitivity in situ.
Crepipatella dilatata is an estuarine gastropod that broods its encapsulated embryos in the pallial cavity for several weeks before releasing juveniles. When environmental quality declines (e.g., in response to decreased salinity), females seal themselves against the substrate and isolate the pallial cavity from surrounding seawater, altering the chemistry of the pallial fluid surrounding the embryos. We documented rates at which total ammonia concentrations (NH4+–N+NH3) increased in the pallial cavity during these extended periods of isolation, as well as excretion rates for both adult females and developing embryos (veligers). Also, we quantified the effects of elevated ammonia concentrations on both adults (mortality, egg capsule abandonment, and neck-radular activity) and veligers (mortality, and activity of the velum and velar cilia). In the pallial fluid, ammonia concentration increased about 150% during the first 16h of female isolation from about 7–17μg ammonial−1, while excretion rates decreased nearly 85%, from an average of 5.5 to about 0.85μg ammoniah−1g−1 after 12h of isolation. Brooded veligers also decreased their individual excretion rates over time, from 0.0035 to 0.0007μg ammoniah−1veliger−1 over 12h. Ammonia accumulation eventually caused females to abandon their egg capsules and to detach from the substrate; in the field, this would probably lead to the death of both the encapsulated embryos and the detached females, but this happened only at concentrations of ≥0.1mg ammonial−1. In contrast, veligers withstood concentrations up to 34mg ammonial−1 for 72h without dying, although ciliary activity and velar lobe activity decreased at concentrations of ≥0.1mg ammonial−1. Ammonia tolerance did not seem to change with continued development. Although previous studies have shown that prolonged isolation causes dangerous declines in oxygen and pH in pallial fluid for this species, the accumulation of ammonia in itself seems too low to cause direct harm to adults or developing embryos.
The energy budget ofBellamya earuginosa in a shallow algal lake, Houhu Lake (Wuhan, China) was investigated by the measurement of flesh production (32.8 kJ/(m2·a)), egestion (337.7 kJ/(m2·a)), metabolism (246.7 kJ/(m2·a)), and estimation of excretion (21.4kJ/(m2·a)). The net growth efficiency of the species is about 10.9%, which accords with the generally reported value for gastropods.
In addition, the relationships between starvation respiration (R, mgO2/(Ind·d)), body weight (Wd, mg in dry wt) and temperature (T, °C) were also determined. The regression equationR=0.044Wd
0.537
e
0.061T
was obtained by the least square method, The measured SDA of the species is 26.51% of its gross metabolism.
Using both mature and immature snails and cadmium as the toxicant, 50 percent tolerance limits (TLââ) for various exposure durations were determined graphically. The immature snails 96-hour TLââ of 0.43 ppM indicates they are three times as sensitive to Cd as mature snails whose 96-hour TLââ was 1.37 ppM. Survivors of bioassays and their offspring were observed. The rate of Cd uptake by snails exposed to 1.30 ppM Cd solution over a 24-hour period was 0.550 ppM/hour. Following the 24-hour exposure, the rate of elimination during the next 24 hours was 0.229 ppM/hour. The rate of uptake was nearly twice the rate of elimination, allowing accumulation of Cd in the snail. The higher the Cd concentration to which snails were exposed, the fewer the survivors, the lower their reproductive potential, and the shorter the period the young survived.
The toxicity of ammonia to fishes has been attributed to the un-ionized ammonia chemical species present in aqueous solution. Because the percent of total ammonia present as un-ionized ammonia (NH3) is so dependent upon pH and temperature, an exact understanding of the aqueous ammonia equilibrium is important for toxicity studies. A critical evaluation of the literature data on the ammonia–water equilibrium system has been carried out. Results of calculations of values of pKa at different temperatures and of percent of NH3 in aqueous ammonia solutions of zero salinity as a function of pH and temperature are presented.
Denitrification occurs in essentially all river, lake, and coastal marine ecosystems that have been studied. In general, the range of denitrification rates measured in coastal marine sediments is greater than that measured in lake or river sediments. In various estuarine and coastal marine sediments, rates commonly range between 50 and 250 μmol N m-2h-1, with extremes from 0 to 1067. Rates of denitrification in lake sediments measured at near-ambient conditions range from 2 to 171 μmol N m-2h-1. Denitrification rates in river and stream sediments range from 0 to 345 μmol N m-2h-1. The higher rates are from systems that receive substantial amounts of anthropogenic nutrient input. In lakes, denitrification also occurs in low oxygen hypolimnetic waters, where rates generally range from 0.2 to 1.9 μmol N liter-1d-1. In lakes where denitrification rates in both the water and sediments have been measured, denitrification is greater in the sediments. -from Author
An underlying assumption of laboratory-based toxicity tests is that the sensitivity of organisms in the laboratory (in vitro) is comparable to that in the field (in situ). We tested this assumption by exposing estuarine amphipods (Chaetocorophium cf. lucasi) to a concentration series of cadmium-spiked sediments in vitro and in situ for 10 d. In situ exposures were conducted within plastic-mesh cages on an intertidal mudflat. To characterize exposure, we measured interstitial water cadmium concentrations (IWCd), acid volatile sulfide (AVS), and simultaneously extracted Cd (SEMCd) at the beginning and end of the exposures. Between day 0 and day 10, AVS decreased in both in vitro and in situ exposures, while IWCd levels declined less in vitro (median 27%) than in situ (median 76%). Despite more extreme conditions of temperature (10–36°C) and salinity (18–22%o) in situ, in vitro and in situ exposures showed comparable survival responses based on SEMCd/AVS (LC50 [95% CI]: 1.6 [1.46–1.78] and 1.8 [1.76–1.83], respectively), with the onset of marked mortality above a SEMCd/AVS value of about one and minimal survival (<5%) above a value of two. Based on IWCd concentrations, however, sensitivity was significantly greater in vitro (LC50 = 0.41 μg Cd/L [0.171–0.959], in situ LC50 = 1.6 μg Cd/L [1.15–2.16]). We concluded that, in our tests, amphipod sensitivity in vitro was equal to or greater than its sensitivity in situ.
Toxicity of Illinois River bulk sediment, sediment interstitial (pore) water and elutriates to the oligochaete Lumbriculus variegatus, fathead minnow (Pimephales promelas) and the amphipod Hyalella azteca was compared to determine the most representative aqueous fraction for toxicity identification evaluation (TIE) studies. Toxicity of pore water corresponded better than elutriates to bulk sediment toxicity. Subsequent TIE procedures conducted with the cladoceran Ceriodaphnia dubia indicated that ammonia, metals and nonpolar organic compounds (nonylphenols, polycyclic aromatic hydrocarbons, benzenes, long-chain hydrocarbons) were responsible for toxicity of the sediment pore water. Results of TIE manipulations also suggested that methods for recovering pore water that include filtration may eliminate, a priori, a major component of the sediment contaminants responsible for toxicity.
The effects of sediment on growth, survival, food conversion efficiency and acute ammonia toxicity were determined for the school prawn, Metapenaeus macleayi, a species which normally buries in sediment during the day. Survival of prawns in 70-litre acrylic aquaria was high (90–100%) regardless of the absence of sediment (bare plastic) or the type of sediment (mud, fine sand or coarse sand) or whether the prawns were confined in mesh cages. Growth (weight gain) and food conversion efficiency for confined prawns were significantly lower than for non-confined prawns in aquaria with or without sediment. Prawns grew 11–22% faster in aquaria with sediment than in aquaria without sediment although the type of sediment had no effect on growth. In a 96-h acute toxicity experiment, mortality of prawns increased with increasing ammonia concentration and, at a concentration of 31 5–32 mg total ammonia-N (TAN)/I, was higher in aquaria without sediment (30.0 ± 5.8%; mean ± s.e., n = 3) than in those with sediment (6.7 ± 6.7%). Emergence of prawns from the sediment was affected by time of day and ammonia concentration. During the day, emergence increased from 7.3 to 79.2% with increasing ammonia concentration (< 0.05 to 52.8 mg TAN/1), but most prawns were emergent during the night regardless of ammonia concentrations. In aquaria without prawns, ammonia concentrations and pH were always lower in water extracted from the sediment than in the water column. The effects of different arrangements of sediment, filtration and aeration on ammonia concentrations in aquaria are described in relation to conducting and interpreting ammonia toxicity experiments with prawns.
Polycyclic aromatic hydrocarbons (PAHs) are prevalent pollutants in the aquatic environment that can cause a wide range of toxic effects. Earlier studies have shown that toxicity of PAHs can be enhanced by ultraviolet (UV) radiation. In situ and laboratory exposures with Ceriodaphnia dubia were used to evaluate photoinduced toxicity of PAHs in wet-weather runoff and in turbid conditions. Exposure to UV increased the toxicity of PAH-contaminated sediment to C. dubia. Toxicity was removed when UV wavelengths did not penetrate the water column to the exposed organisms. A significant correlation was observed between in situ C. dubia survival and turbidity when organisms were exposed to sunlight. Stormwater runoff samples exhibited an increase in chronic toxicity (reproduction) to C. dubia when exposed to UV wavelengths as compared to C. dubia not exposed to UV wavelengths. Toxicity was reduced significantly in the presence of UV radiation when the organic fraction of stormwater runoff was removed. The PAHs are bound to the sediment and resuspended into the water column once the sediment is disturbed (e.g., during a storm). The in situ and laboratory results showed that photoinduced toxicity occurred frequently during low flow conditions and wet weather runoff and was reduced in turbid conditions.
The effects of ammonia on survival, growth, and reproduction of the fingernail clamMusculium transversum were tested in outdoor experimental streams. In the summers of 1983 and 1984 caged clams were exposed in the streams. During the 1983 studies, the weekly mean NH3 ranges in the low, medium and high concentration streams were, respectively, 0.02–0.08, 0.04–0.25 and 0.14–0.56 mg/L; in 1984 the ranges in the same streams were 0.04–0.20, 0.07–0.38 and 0.48–1.17 mg/L. In the first year studies, survival was highest (50–85%) in the control and low NH3 streams, lower (30–55%) in the medium NH3 stream and no clams survived the high NH3 treatment. Growth was also greater in the control and low NH3 streams. In the second year studies, total yields of clams in the control, low, medium, and high NH3 streams, respectively, were 12.8 x, 4.7 x, 1.1 x and 0.03 x the original stock. During 30-day tests, the second year mean growth was 2 mm less and reproduction 90% lower in the low NH3 than in the control stream. Un-ionized ammonia concentrations affecting survival and growth were lower than in previous reports. The site-specific criterion concentration was low enough to protect the clams in the streams.
To study the sublethal effects induced by ethylbenzene and the capability of a freshwater gastropod Bellamya aeruginosa to take up and depurate ethylbenzene, the snail was subjected to two treatments, a 23-day exposure period followed by a 17-day depuration period. Behavioral alteration, namely retraction response, was observed during the exposure period, and the proportion of retracted snails increased under each treatment as the exposure time prolonged but there was no linear relationship between the retracted proportion and the exposure dose. Such behavioral alteration was probably due to the disturbance of membrane permeability stressed by ethylbenzene. Ethylbenzene uptake in unretracted snails was greater than in retracted snails, while the depuration abilities in the two different responses of snails had no significant difference from each other. Because of the limited capability of snails to detoxify ethylbenzene, the depuration was mainly through a slow excretion process and therefore ethylbenzene was still present in the tissue of snail after 17-day depuration. DNA damage was induced significantly in snails exposed to ethylbenzene, and the levels of DNA damage showed positive time-response and dose-response relationships, and moreover the levels of DNA damage had no difference between the two different responses of snails. There was no linear relationship between the level of DNA damage and the amount of residual ethylbenzene in tissue, which may be related to the adaptation mechanism in snail. Overall, the results suggest that the snail has high capability to take up ethylbenzene and low ability to depurate it, and ethylbenzene has potential genotoxicity to snail.
96-h acute toxicity tests were made, using a flow-through system, to determine the toxicity of ammonia and copper to Potamopyrgus jenkinsi. Both lethal and sub-lethal behavioural responses were monitored for three different age groups of snail—juvenile, prime adult and senescent. Juvenile snails were much less tolerant than adults of both toxicants. Senescent adults were also less tolerant of ammonia than prime adults. 96-h LC50 values of 0·315, 0·49 and 0·85 mg N litre−1 unionised NNH3 and 0·054, 0·079 and 0·077 mg Cu litre−1 total copper were recorded for juveniles, senescent adults and prime adults, respectively, in separate experiments. EC50 values were clearly lower in adult snails. Potamopyrgus jenkinsi was relatively intolerant of both ammonia and copper compared with other invertebrate taxa reported in the literature. It is concluded that Potamopyrgus jenkinsi could be a valuable indicator species of these pollutants.
This study aimed to elucidate the physiological effects of high environmental ammonia (HEA) following periods of feeding (2% body weight) and starvation (unfed for 7 days prior to sampling) in gold fish (Carassius auratus). Both groups of fish were exposed to HEA (1 mg/L; Flemish water quality guideline) for 0 h (control), 3 h, 12 h, 1 day, 4 days, 10 days, 21 days and 28 days. Measurements of weight gain (%), oxygen consumption (MO2), ammonia excretion rate, ammonia quotient (AQ), critical swimming speeds (Ucrit), plasma and muscle ammonia accumulation, plasma lactate, liver and muscle glycogen, lipid and protein content were done at various time intervals during the experimental periods. Overall, ammonia excretion rates, plasma ammonia accumulation and AQ were significantly affected by food regime in ammonia free water. HEA, the additional challenge in the present study, significantly altered all the studied parameters among fed and starved groups in days-dependent manner. Results show that weight gain (%), MO2, Ucrit, protein content in liver and muscle, and glycogen content in muscle among starved fish under HEA were considerably reduced compared to control and fed fish. Additionally a remarkable increase in plasma ammonia level, muscle ammonia, lactate accumulation and AQ was seen. However in fed fish, MO2, ammonia excretion rate, AQ and lactate level augmented after exposure to HEA. These results indicate that starved fish appeared more sensitive to HEA than fed fish. Furthermore, as expected, the toxic effect of ammonia exposure in both feeding treatments was exacerbated when imposed to exhaustive swimming (swum at 3/4th Ucrit). Such effects were more pronounced in starved fish. This suggests that starvation can instigate fish more vulnerable to external ammonia during exercise. Therefore, it was evident from our study that feeding ameliorates ammonia handling and reduces its toxicity during both routine and exhaustive swimming. Moreover, recovery was observed for some physiological parameters (e.g. MO2, ammonia excretion, Ucrit, plasma ammonia) during the last exposure periods (21-28 days) while for others (e.g. growth, tissue glycogen and protein content, muscle ammonia) effects only became apparent at this time. In the future, these results need to be considered in ecological context as fish in ammonia polluted may experience different phenomenon (starvation and exercise) simultaneously.
High ammonia (i.e. the total of NH(3) and NH(4)(+)) concentration or nitrogen deficiency in water can exert stress on growth and health of many aquatic plants. To investigate the physiological impacts of high ammonia-N (NH(4)Cl) concentration and nitrogen deficiency on plant physiology, apical shoots of submerged macrophyte Egeriadensa were first treated with five levels of nitrogen: 0, 1, 10, 30, 60 mg L(-1) ammonia-N (NH(4)Cl) for 5d. After having explored the stress range of ammonia-N, its effect on E. densa was further examined at three levels of ammonium (0, 1, 30 mg L(-1) ammonia-N) and at six exposure times (0, 1, 2, 3, 5 and 7d). In testing the concentration-dependent stress, the increase of ammonia-N reduced the amounts of total chlorophyll (chl a and b), soluble proteins and soluble carbohydrates, but increased the activity levels of malondialdehyde (MDA), superoxide dismutase (SOD), catalase and peroxidase in E. densa. In the N-free medium, total chlorophyll, soluble proteins, soluble carbohydrates and the activities of SOD and peroxidase in E. densa decreased significantly compared with the control (1 mg L(-1) ammonia-N). When comparing the ammonia-N impacts over time, the plants showed a declining trend in total chlorophyll, soluble proteins and soluble carbohydrates, but an rising trend in MDA, SOD, peroxidase and catalase in 30 mg L(-1) ammonia-N over 7d. Compared with the control, the N-free medium significantly decreased the amounts of total chlorophyll, soluble proteins, soluble carbohydrates, SOD and peroxidase in E. densa over time. Our study indicates that high ammonium (ammonia-N ≥ 10 mg L(-1)) affects the growth of E. densa through inducing oxidative stress and inhibiting photosynthesis, and nitrogen deficiency can also induce an abiotic stress condition for the E. densa growth by reducing photosynthetic pigments, soluble proteins, soluble carbohydrates, and the activity of antioxidant enzymes.
The effects of high NH(4)(+) concentration on growth, morphology, NH(4) (+) uptake and nutrient allocation of Myriophyllum brasiliense were investigated in hydroponic culture. The plants were grown under greenhouse conditions for 4 weeks using four levels of NH(4)(+) concentration: 1, 5, 10 and 15 mM. M. brasiliense grew well with a relative growth rate of c.0.03 day(-1) at NH(4)(+) concentration up to 5 mM. At the higher NH(4)(+) concentrations the growth of the plants was stunted and the plants had short roots and few new buds, especially when grown in 15 mM NH(4)(+) where the submerged leaves were lost and there were rotten roots and submerged stems. To avoid NH(4)(+) toxicity, the plants may have a mechanism to prevent cytoplasmic NH(4)(+) accumulation in plant cells. The net uptake of NH(4)(+) significantly decreased and the total N significantly increased in the plants treated with 10 and 15 mM NH(4)(+), respectively. The plant may employ NH(4)(+) assimilation and extrusion as a mechanism to compensate for the high NH(4)(+) concentrations. However, the plants may show nutrient deficiency symptoms, especially K deficiency symptoms, after they were exposed to NH(4)(+) concentration higher than 10 mM. The present study provides a basic ecophysiology of M. brasiliense that it can grow in NH(4)(+) enriched water up to concentrations as high as 5 mM.