Effect of humic acids on speciation and toxicity of copper to Paracentrotus lividus larvae in seawater

The effects of humic acid (HA) on the toxicity of copper to sea urchin Paracentrotus lividus larvae were studied in chemically defined seawater. Square Wave Anodic Stripping Voltammetry (SWASV) was employed to study the complexation of copper in seawater medium. A simple complexation model assuming one ligand type and a 1:1 reaction stoichiometry successfully explained the inverse titration experiments. A conditional stability constant of 6.53+/-0.05 and a complexating capacity of 230+/-7 micromol Cu/g HA were obtained. Sea urchin bioassay tests with two endpoints, embryogenesis success and larval growth were carried out in order to study the toxicity of dissolved copper in both the presence and absence of HA. The toxicity data obtained fitted well into a logistic model, and the high sensitivity of both endpoints (EC(50) were 41.1 microg Cu/l and 32.9 microg Cu/l, respectively) encourages their use for biomonitoring. The HA had a clearly protective effect, reducing the toxicity of Cu to the sea urchin larvae. The labile copper, rather than the total copper concentrations, explained the toxicity of the Cu-HA solutions, and the Cu-HA complexes appeared as non-toxic forms. These results are in agreement with the Free Ion Activity Model, because the labile Cu concentrations in this buffered and chemically defined medium covary with the free ion activity of the Cu, validating the model to naturally occurring HA in the marine environment.     

Long-term acclimation of Pseudokirchneriella subcapitata (Korshikov) Hindak to different copper concentrations: changes in tolerance and physiology

The effect of long-term copper acclimation of the freshwater green algae Pseudokirchneriella subcapitata to copper was investigated using different physiological and toxicological endpoints. The algae were exposed to seven-five of which are ecologically relevant for European surface waters-copper concentration ranging from 0.5 to 100 microgCul(-1) during a 3-month period. A standard medium was used as culture and test medium with an addition of 2 mg DOCl(-1) (replacing EDTA). At certain intervals, experiments were performed to assess algal biomass, growth rate, chlorophyll and carotenoid content, pigment diversity, autotrophic index, intracellular and adsorbed copper, and the sensitivity of the algae to copper. Chronic copper tolerance (mean +/- standard deviation) increased significantly from 88 +/- 15 to 124 +/- 25 microg Cul(-1) for P. subcapitata acclimated to 0.5 and 100 microg Cul(-1), respectively. Based on the algal biomass, the growth rate, the pigment diversity and the autotrophic index, an optimal concentration range was observed between 1 and 35 microg Cul(-1). Significant decreases in algal biomass, pigment diversity and autotrophic index were observed in algal cultures acclimated to 0.5 microg Cul(-1) and 100 microg Cul(-1). Chlorophyll a content (mean +/- standard deviation) increased from 8.4 +/- 3.1 to 28.6 +/- 7.5 x 10(-14) g per cell and carotenoid content (mean +/- standard deviation) increased from 3.7 +/- 0.8 to 7.1 +/- 1.2 x 10(-14) g per cell for algae exposed to 1 and 100 microg Cul(-1), respectively. Intracellular copper increased from 0.099 to 20.6 x 10(-15) g Cu per cell and adsorbed copper increased from 0.026 to 1.8 x 10(-15) g Cu per cell for algae acclimated for 12 weeks to 0.5 and 100 microg Cul(-1), respectively. This research demonstrates that the use of standard culture media, some of which may be deficient in copper, can result in sub-optimal performance of the organisms, which in turn may affect toxicity test results. Additionally, this work also established an optimal concentration range for copper for this algal species. This phenomenon should be taken in consideration when performing environmental risk assessments of essential elements.     

Toxicity of nitromusks in early lifestages of South African clawed frog (Xenopus laevis) and zebrafish (Danio rerio)

Musk xylene (MX), musk ketone (MK) and musk moskene (MM) are synthetic nitro-containing fragrances. Due to their inherent lipophilicity and environmental persistence, they are frequently detected in environmental samples and especially in aquatic ecosystems. Despite this, the current environmental toxicity database of nitromusks is limited. Although nitromusks have been shown to accumulate in aquatic organisms, little is known about their potential developmental effects in the respective aquatic species. To investigate the developmental toxicity of these compounds to amphibians and fish, early lifestages of xenopus (Xenopus laevis) and zebrafish (Danio rerio) were exposed to three nitromusks for 96 h to examine the developmental effects of these compounds in the two species. Nitromusk body concentration measurements were carried out in parallel for correlation with potential developmental effects. No increased mortality, malformation or growth inhibition was observed in either species following 96-h exposure to 400 microg/l MX, MK and MM. However, an approximately 20% reduced viability was observed in xenopus larvae when exposed to 400 microg/l MX, MK and MM for 11 days. Xenopus and zebrafish exposed to 10, 153, 871 and 1637 microg/l 14C-MX for 96 h resulted in whole-body concentrations of 0.7 +/- 0.1, 11.1 +/- 1.1, 38.7 +/- 1.9 and 76.3 +/- 18.3 microg/g, and 4.3 +/- 0.6, 73.3 +/- 11.8, 440.0 +/- 72.7 and 664.0 +/- 47.7 microg/g wet body weight, respectively. Exposure of xenopus larvae to 400 microg/l MX, MK and MM for 11 days, resulted in whole body concentrations (extrapolated from gas chromatographic determinations) of 4700 +/- 5000, 1300 + 300 and 4600 + 4800 microg/g wet weight for MX, MK and MM, respectively. The latter toxicity results, in conjunction with the fact that the concentrations used for the above experiments were between 400- and 10000-fold higher than those detected in the environment, suggest that environmental concentrations of nitromusks are not hazardous for early lifestages of fish and amphibians.     

Uptake and internalisation of copper by three marine microalgae: comparison of copper-sensitive and copper-tolerant species

Although it has been well established that different species of marine algae have different sensitivities to metals, our understanding of the physiological and biochemical basis for these differences is limited. This study investigated copper adsorption and internalisation in three algal species with differing sensitivities to copper. The diatom Phaeodactylum tricornutum was particularly sensitive to copper, with a 72-h IC50 (concentration of copper to inhibit growth rate by 50%) of 8.0 microg Cu L(-1), compared to the green algae Tetraselmis sp. (72-h IC50 47 microg Cu L(-1)) and Dunaliella tertiolecta (72-h IC50 530 microg Cu L(-1)). At these IC50 concentrations, Tetraselmis sp. had much higher intracellular copper (1.97+/-0.01 x 10(-13)g Cu cell(-1)) than P. tricornutum (0.23+/-0.19 x 10(-13)g Cu cell(-1)) and D. tertiolecta (0.59+/-0.05 x 10(-13)g Cu cell(-1)), suggesting that Tetraselmis sp. effectively detoxifies copper within the cell. By contrast, at the same external copper concentration (50 microg L(-1)), D. tertiolecta appears to better exclude copper than Tetraselmis sp. by having a slower copper internalisation rate and lower internal copper concentrations at equivalent extracellular concentrations. The results suggest that the use of internal copper concentrations and net uptake rates alone cannot explain differences in species-sensitivity for different algal species. Model prediction of copper toxicity to marine biota and understanding fundamental differences in species-sensitivity will require, not just an understanding of water quality parameters and copper-cell binding, but also further knowledge of cellular detoxification mechanisms.     

The toxicity of brass dust to the microalgae Ankistrodesmus falcatus and Selenastrum capricornutum

The toxicity of brass dust was examined by conducting 96 h growth inhibition tests. Two species of algae were used, Ankistrodesmus falcatus (EC50 = 0.316 mg brass/l) and Selenastrum capricornutum (EC50 = 0.056 mg brass/l). Brass dissociates into two components, Cu (68.5%) and Zn (27.5%). Enhanced algal growth was exhibited at concentrations of 0.01 and 0.001 mg brass/l. Available literature on the toxicity of copper to S. capricornutum (EC50 = 0.047 mg Cu/l), indicate that the toxicity of brass dust is due to the ionized copper. Reported toxicities of zinc are orders of magnitude lower than copper. The ionization of the brass is dependent on pH and hardness. The literature cites cases in which copper toxicity varies with pH, clay content and dissolved organics. At present little is known of the fate and distribution of brass dust upon the release into the environment. However, the presence of heavy metals has consistently been shown to impact aquatic systems.     

Morphological abnormalities and sensorimotor deficits in larval fish exposed to dissolved saxitoxin

The dietary uptake of one suite of dinoflagellate-produced neurotoxins, that are commonly called paralytic shellfish poisoning (PSP) toxins, is known to cause acute fish kills. However, little is known about the effects of dissolved phase exposure and the potential sublethal effects of this route of exposure on early developmental stages of fish. Toxin exposure during early development is of particular concern because the embryos and larvae of some marine fish species may be unable to actively avoid the dissolved toxins that algal cells release into the water column during harmful algal blooms. Here we use the zebrafish (Danio rerio) as a model experimental system to explore the sublethal effects of a dissolved PSP toxin, saxitoxin (STX), on early development in fish, including sensorimotor function, morphology, and long-term growth and survival. Aqueous phase exposures of 229 +/- 7 microg STX eq. l(-1) caused reductions in sensorimotor function as early as 48 h postfertilization (hpf) and paralysis in all larvae by 4 days postfertilization (dpf). Rohon-Beard mechanosensory neurons appeared to be more sensitive to STX than dorsal root ganglion neurons at this dose. Additionally, exposure to 481 +/- 40 microg STX eq. l(-1) resulted in severe edema of the eye, pericardium, and yolk sac in all exposed larvae by 6 dpf. The onset of paralysis in STX-exposed larvae was stage-specific, with older larvae becoming paralyzed more quickly than younger larvae (5 h at 6 dpf as compared to 8 and 46 h for 4 and 2 dpf larvae, respectively). When transferred to clean water, many larvae recovered from the morphological and sensorimotor effects of STX. Thus, the sublethal effects of the toxin on larval morphology and behavior were reversible. However, zebrafish exposed to STX transiently during larval development (from 2 to 4 dpf) had significantly reduced growth and survival at 18 and 30 days of age. Collectively, these data show that (1) dissolved phase STX is bioavailable to fish embryos and larvae, (2) the toxin is a paralytic with potencies that are stage-specific for fish larvae, (3) the observed toxicological effects of STX exposure are reversible, and (4) a short-term toxin exposure can negatively impact the survival of fish several weeks later. Dissolved algal toxins may therefore have important sublethal effects on vulnerable species of fish.     

The use of a brine shrimp (Artemia salina) bioassay to assess the toxicity of diatom extracts and short chain aldehydes.

Water soluble algal extracts, the aldehydes 2E,4E-decadienal, decanal, undecanal and the fatty acid eicosapentaenoic acid (EPA) were assayed for toxicity to hatching success and larval mortality of the brine shrimp Artemia salina. Both crude cellular extracts of the diatoms Skeletonema costatum and Nitzschia commutata and the diatom-derived short chain aldehyde decadienal were found to inhibit hatching success of A. salina cysts in a dose-dependent manner. Decadienal also significantly affected larval mortality rates in 24 and 72 h exposure incubations. The Artemia hatching success assay was the least sensitive of the three (EC50=3.94 microg ml(-1)). A greater sensitivity was observed for the 72 h compared with the 24 h exposure trials (EC50 for 24h=2.14, 72 h=0.023 microg ml(-1)). Decanal did not significantly affect survival or hatching success at the concentrations tested. Undecanal and EPA showed a limited toxic effect in naupliar mortality trials. We suggest that 72 h Artemia exposure trials represent an acceptable bioassay for diatom toxicity where alternative bioassays are unavailable.     

Uptake and partitioning of copper and cadmium in the coral Pocillopora damicornis

Coral-reef ecosystems are increasingly being impacted by a wide variety of anthropogenic inputs, including heavy metals, which could be contributing to coral reef stress and bleaching episodes. Fragments of Pocillopora damicornis were exposed in the laboratory to cadmium (Cd) or copper (Cu) chlorides (0, 5, 50 microg l(-1)) for 14 days and analyzed for metal content in the whole association, algal or animal fractions. Various physiological and biochemical parameters were also measured, such as, algal cell counts, mitotic index, chlorophyll content and levels of the antioxidant glutathione (GSH). Cd and Cu accumulation were observed at all time points and doses; there was no evidence of differential metal partitioning between the algal or animal fractions. No changes in algal cell density, mitotic index or chlorophyll content from the controls were observed in any of the metal treatments. GSH levels were significantly higher in the 5 microg l(-1) Cd (Day 4) and Cu (Days 4 and 14) treatments compared with controls at the same time point. Although no evidence of a bleaching response occurred, corals in both 50 microg l(-1) metal exposures sloughed off tissues and did not survive the duration of the exposure period. Our results demonstrate the accumulation of Cd and Cu in P. damicornis and mortality in the absence of a bleaching response.     

Toxicity of the antimicrobial compound triclosan and formation of the metabolite methyl-triclosan in estuarine systems

Triclosan, a commonly used antimicrobial compound, has been measured in aquatic systems worldwide. This study exposed marine species to triclosan to examine effects primarily on survival and to investigate the formation of the degradation product, methyl-triclosan, in the estuarine environment. Acute toxicity was assessed using the bacterium Vibrio fischeri, the phytoplankton species Dunaliella tertiolecta, and three life stages of the grass shrimp Palaemonetes pugio. P. pugio larvae were more sensitive to triclosan than adult shrimp or embryos. Acute aqueous toxicity values (96 h LC50) were 305 microg/L for adult shrimp, 154 microg/L for larvae, and 651 microg/L for embryos. The presence of sediment decreased triclosan toxicity in adult shrimp (24 h LC50s were 620 microg/L with sediment, and 482 microg/L without sediment). The bacterium was more sensitive to triclosan than the grass shrimp, with a 15 min aqueous IC50 value of 53 microg/L and a 15 min spiked sediment IC50 value of 616 microg/kg. The phytoplankton species was the most sensitive species tested, with a 96 h EC50 value of 3.55 microg/L. Adult grass shrimp were found to accumulate methyl-triclosan after a 14-day exposure to 100 microg/L triclosan, indicating formation of this metabolite in a seawater environment and its potential to bioaccumulate in higher organisms. Triclosan was detected in limited surface water sampling of Charleston Harbor, SC at a maximum concentration of 0.001 microg/L, substantially lower than the determined toxicity values. These findings suggest triclosan poses low acute toxicity risk to estuarine organisms; however, the potential for chronic, sublethal, and metabolite effects should be investigated.     

Cholinesterase activity in gilthead seabream (Sparus aurata) larvae: Characterization and sensitivity to the organophosphate azinphosmethyl

Assessment of cholinesterase (ChE) inhibition is widely used as a specific biomarker for evaluating the exposure and effects of non-target organisms to anticholinesterase agents. Cholinesterase and carboxylesterase activities have been measured in larvae of gilthead seabream, Sparus aurata, during the endogenous feeding stage, and ChE was characterized with the aid of diagnostic substrates and inhibitors. The results of the present study showed that whole-body ChE of yolk-sac seabream larvae possesses typical properties of acetylcholinesterase (AChE) with a apparent affinity constant (K(m)) of 0.163+/-0.008 mM and a maximum velocity (V(max)) of 332.7+/-2.8 nmol/min/mg protein. Moreover, sensibility of this enzyme was investigated using the organophosphorus insecticide azinphosmethyl. Static-renewal toxicity tests were conducted over 72 h and larval survival and AChE inhibition were recorded. Mean mortality of seabream larvae increased with increasing concentrations of azinphosmethyl and exposure duration. The estimated 72-h LC50 value to azinphosmethyl was 4.59 microg/l (95% CI=0.46-8.71 microg/l) and inhibition of ChE activity gave an IC50 of 3.04 microg/l (95% CI=2.73-3.31 microg/l). Larvae exposed to azinphosmethyl for 72h showed a 70% inhibition of the whole-body acetylcholinesterase activity at approximately the LC50. In conclusion, the results of the present study suggested that monitoring ChE activity is a valuable tool indicating OP exposure in S. aurata larvae and that acetylthiocholine is the most appropriate substrate for assessing ChE inhibition in this early-life stage of the fish.     

Effects of chronic copper exposure on the nutritional composition of Hyalella azteca

The toxicity of dietborne metals currently is a topic of high interest in aquatic toxicology. We hypothesized that, in addition to causing direct physiological effects when ingested by organisms, dietborne metals might also cause indirect foodweb effects. One such indirect effect might be alteration of the nutritional content of prey, leading to decreased growth and (or) survival of consumers. Because dietborne and waterborne metal exposures usually occur concurrently in aquatic ecosystems, we exposed two generations of a representative grazer species-the freshwater amphipod Hyalella azteca-to dietborne copper (Cu) concurrent with waterborne Cu in the laboratory for a total of 27 days (first generation) and 45-57 days (second generation). The aqueous Cu concentrations were 0.0099 (control), 0.054 and 0.11 microM (0.6, 3.4 and 7.0 microg Cu per l, respectively) at 24 degrees C, pH 7.5-8.3, alkalinity of approximately 3 mEq/l and hardness of approximately 4 mEq/l; whereas the dietborne Cu exposures were via biofilm growing on cotton gauze in the same exposure aquaria. In a preliminary test, we demonstrated that the highest Cu concentrations were at the threshold for adversely affecting survival and reproduction. In the two-generation test, first- and second-generation amphipods exposed to the intermediate and high aqueous Cu concentrations accumulated significantly higher amounts of Cu than control amphipods. However, none of the traditional nutritional composition categories (protein, total lipid, ash and 'other') differed among the treatments. The only significant difference in nutritional composition was an elevated concentration of linolenic acid (18:3 n-3) in the second-generation amphipods exposed to 0.054 microM Cu.     

Bioaccumulation of cadmium in an experimental aquatic food chain involving phytoplankton (Chlorella vulgaris), zooplankton (Moina macrocopa), and the predatory catfish Clarias macrocephalus x C. gariepinus

The accumulation of cadmium (Cd) was studied in an experimental aquatic food chain involving the phytoplankton Chlorella vulgaris as the primary producer, the zooplankton Moina macrocopa as the primary consumer, and the catfish Clarias macrocephalus x Clarias gariepinus as the secondary consumer. C. vulgaris was first exposed to Cd solutions at 0.00, 0.35, and 3.50 mg l(-1), referred to as control group and experimental groups 1 and 2, respectively. Subsequently, each group was fed to three corresponding groups of M. macrocopa. Finally, three groups of catfish were fed these corresponding groups of M. macrocopa. After C. vulgaris was exposed to 3.50 mg l(-1) Cd (experimental group 2), the residual Cd in solution was only 4.01 microg l(-1), lower than the maximum allowable limit of Cd in natural water sources (5 microg l(-1)). Cd concentrations in C. vulgaris were 0.01+/-0.00 microg g(-1) (dry wt) in the control group, 194+/-1.80 microg g(-1) (dry wt) in experimental group 1, and 1140+/-20.06 microg g(-1) (dry wt) in experimental group 2. The Cd concentrations in M. macrocopa were 0.01+/-0.00 microg g(-1) (dry wt) in the control group, 16.48+/-2.23 microg g(-1) (dry wt) in experimental group 1, and 56.6+/-3.23 microg g(-1) (dry wt) in experimental group 2. The Cd concentrations in catfish muscle increased with increasing Cd concentrations in the food. After 60 days of fish culture, the mean concentrations of Cd in fish muscle were 0.01+/-0.00 microg g(-1) (dry wt) in the control group, 0.61+/-0.02 microg g(-1) (dry wt) in experimental group 1 and 1.04+/-0.06 microg g(-1) (dry wt) in experimental group 2. Cd concentration in fish muscle of experimental group 2 was equal to the permissible limit. Cd accumulation affected fish growth: at the end of the study, the mean fresh weight (12.81 g) of catfish in the control group, was significantly higher than those experimental group 1 (10.43 g) and experimental group 2 (10.00 g). The results showed that the measurement of Cd concentration in water does not necessarily give a measure of the safety of aquatic organisms as human food. Hence, heavy metal contamination is a matter for concern when organisms are harvested, for fish and human consumption, from natural water sources.     

Sensitivity of the glochidia (larvae) of freshwater mussels to copper: assessing the effect of water hardness and dissolved organic carbon on the sensitivity of endangered species

The assessment of the potential impact of waterborne contaminants on imperilled freshwater mussels is needed. Acute copper toxicity was assessed in a standardized soft water (hardness 40-48 mg CaCO(3)equivalents L(-1)) using the larvae (glochidia) from three common and six (Canadian) endangered mussel species. The resulting 24h EC50s ranged from 7 to 36 microg Cu L(-1), with the EC50s of two endangered species <10 microg Cu L(-1). Acute copper sensitivity was also determined in Ptychobranchus fasciolaris, a species that employs conglutinates (packets of glochidia) in its reproductive strategy. Conglutinates were found to provide significant protection from acute copper exposure as the EC50 of the encased glochidia was more than four-fold higher than freed glochidia (72.6 microg Cu L(-1) vs. 16.3 microg Cu L(-1)). The glochidia from two endangered species, Epioblasma triquetra and Lampsilis fasciola, were used to examine the influence of water hardness and dissolved organic carbon (DOC) on copper sensitivity. Exposures in moderately-hard water (165 mg CaCO(3) L(-1)) demonstrated that an increase in water hardness resulted in a significant reduction in copper sensitivity. For example, in L. fasciola the 24 h EC50s were 17.6 (14.2-22.6) microg Cu L(-1) and 50.4 (43.5-60.0) microg Cu L(-1) in soft water and moderately-hard water, respectively. The addition of DOC (as Aldrich Humic Acid) also resulted in a significant decrease in Cu sensitivity, such that a 10-fold increase in the EC50 of E. triquetra was observed when the reconstituted soft water was augmented with 1.6 mg DOC L(-1). To determine if current water quality regulations for copper would protect all glochidia, the USEPA's Biotic Ligand Model (BLM) was used to derive water quality criteria for these exposures. While BLM-derived criteria for the soft water exposures indicate that protection would be marginal for the sensitive endangered species, the criteria derived for the DOC exposures suggest that the natural complexity of most natural waters in Southern Ontario (Canada) will provide glochidia with protection from acute copper exposure.     

The effects of metals on embryo-larval and adult life stages of the sea urchin, Diadema antillarum

Since the massive population decline of the long-spined sea urchin, Diadema antillarum, in the early 1980s, the dynamics of coral reef ecosystems in the Caribbean have changed tremendously. The absence of D. antillarum, once a keystone herbivore, has led to macroalgal dominance in many of these reef communities. D. antillarum is not only important ecologically, but may also be a sensitive bioindicator species for toxicant exposure. Echinoderm larval development tests were conducted with D. antillarum exposed to elevated levels of aqueous copper (Cu), silver (Ag), nickel (Ni), or selenium (Se). All metals significantly affected larval development, based on normal development to the pluteus stage. The EC50s based on dissolved metal concentrations were 11 microg/L Cu, 6 microg/L Ag, 15 microg/L Ni, and 26 microg/L Se. Adult sea urchins were exposed to aqueous copper under flow through conditions for 96 h. The 96-h LC50 for this exposure was 25 microg/L dissolved Cu. Additionally, behavioral and physiological disturbance was observed. The physiological responses included both acid-base balance disturbance, as evidenced by reduced coelomic fluid pH and apparent ionoregulatory effects. In addition, behavioral effects included spatial orientation within the exposure tank, spine closure, and loss of spines. The high sensitivity of both adult and larval D. antillarum to these metals supports the use of this organism as an important biological indicator for metal exposure in marine environments.     

Investigation of acute toxicity of fenitrothion on guppies Poecilia reticulata

Fenitrothion, an organophosphothionate insecticide (CAS number: 122-14-5) and potential toxic pollutant contaminating aquatic ecosystems, was investigated in the present study for acute toxicity. Guppy fish (Poecilia reticulata) were selected for the bioassay experiments. The experiments were repeated three times and the 96 h LC(50) was determined for the guppies. The static test method of acute toxicity test was used. The water temperature was regulated at 23 +/- 1 degrees C. In addition, behavioral changes at each fenitrothion concentration were observed for the individual fish. Data obtained from the fenitrothion acute toxicity tests were evaluated using the probit analysis statistical method. The 96 h LC(50) value for guppy was estimated as 3.28 mg l(-1). Values in the range of microg l(-1) and mg l(-1) have been reported for various other fish species.     

Exposure to copper and a cytotoxic polyunsaturated aldehyde induces reproductive failure in the marine polychaete Nereis virens (Sars)

A number of metabolites from microalgae, including polyunsaturated aldehydes (PUAs), have been implicated as inducers of reproductive failure in aquatic invertebrates. Current work describes the impacts of the model PUA 2E, 4E-decadienal and copper sulphate applied in isolation and combination on the reproductive performance of the infaunal polychaete, Nereis virens (Sars). The reproductive and life cycle parameters investigated were; fertilisation success, larval survival, sperm motility (percent motility and curvilinear velocity) and sperm DNA damage. Exposure to decadienal and copper sulphate in isolation resulted in dose- and time-dependent reductions for each evaluated endpoint. Fertilisation success was heavily impacted at concentrations of up to 10μM for both compounds. Copper sulphate was more toxic in larval survival assays. Sperm motility impacts, although variable, exhibited rapid onset with pronounced reductions in sperm swimming performance observed within 3min of exposure. The extent of DNA damage was dose-dependent, and in the case of decadienal, rapid in onset. Dual compound exposures resulted in enhanced overall toxicity in all assays. Logistic regression analysis of fertilisation and larval survival assays showed significant synergistic interactions between decadienal and copper sulphate; an increase in concentration of either compound resulted in enhanced toxicity of the other. Longer exposure durations during larval survival assays demonstrated a further increase in both toxicity and synergism. The results indicate that the effects of additional environmental stressors must be considered when attempting to extrapolate laboratory-derived single compound exposures to field situations.     

High sensitivity of northern pike larvae to UV-B but no UV-photoinduced toxicity of retene

In order to investigate whether increased UV-B radiation is a risk factor, a series of acute laboratory experiments was conducted with larval stages of the northern pike (Esox lucius L.), hatching in Nordic waters in May. Further, a comparative investigation on the acute phototoxicity of retene (7-isopropyl-1-methylphenanthrene), a PAH compound recently revealed to posses UV-B-induced phototoxicity in larval coregonids, was conducted with pike larvae. In semi-static experiment, larvae were pre-exposed to retene (3, 9, 30 and 82 microg/g), with relevant controls, for 24 h and then irradiated for 3 h once a day (two consecutive days) with three UV-B doses (CIE-weighted 1.0, 1.8 or 2.7 kJ/m2 per day) or with visible light only. In 3 days, the UV-B exposure alone increased mortality by 10-20% in all applied dose rates. Retene (up to 82 microg/l) had no direct UV-B-induced toxicity in pike. However, pike larvae were very sensitive to UV-B even in low doses, indicated as severe neurobehavioral disorders. Monitoring of pike with the neurobehavioral syndrome revealed substantial late mortality. As UV-B had no influence on CYP1A content in larval pike, retene (9-82 microg/l) induced this protein substantially with and without UV-B. In pike, the applied UV-B radiation and water retene alone both decreased HSP70 concentrations. Neither UV nor retene changed SOD activity significantly. Overall, data on pike suggest that only a minor increase in ambient UV-B coming to the earth's surface may cause lethal effects to larval fish.     

The effect of copper exposure on a simple aquatic food chain

The effect of copper (44 microg l(-1)) on a simple food chain was studied using indoor experimental channels to identify the changes in periphyton community (metabolism, chlorophyll a content, abundance, composition and lipid and protein content) and in herbivore (Stagnicola vulnerata) growth rate and reproduction. The algal community was sensitive to copper at the beginning but differences between treatments were not significant during the experiment. However, copper affected growth rate, reproduction and embryo hatching on snails. These results indicate that the effects on snails are more sensitive endpoints in assessing sublethal copper toxicity than effects on periphyton.     

Comparison of the Qwiklite algal bioluminescence test with marine algal growth rate inhibition bioassays

Although marine algal bioassays based on growth rate inhibition over 72-96 h have been widely used to assess the toxicity of contaminants in waters and sediments, changes in pH over the test duration can lead to changes in contaminant speciation and consequently an under- or over-estimation of toxicity. In addition, high cell densities are used in order to obtain a detectable response, further reducing the tests' environmental relevance in marine waters. There is a need for rapid acute tests with ecologically relevant test endpoints that may be used as surrogates for longer-term chronic tests. This study compares the sensitivity and reproducibility of a rapid marine dinoflagellate (Pyrocystis lunula) bioluminescence test (QwikLite) with standard algal growth rate bioassays (Nitzschia closterium and Entomoneis c.f. punctulata) using ammonia and several antifouling agents (tributyltin [TBT], copper, and diuron) as reference toxicants. QwikLite was of similar sensitivity to ammonia as standard algal growth rate tests, but was less sensitive to copper, diuron and TBT, with 24-h EC50 values of 10 +/- 1.1 mg N/L, 0.128 +/- 0.021 mg Cu/L, 19 +/- 13 mg diuron/L, and 0.226 +/- 0.028 mg TBT/L. Inter-test precision using different batches of P. lunula was generally acceptable. On the basis of NOEC values, QwikLite was more sensitive to copper and ammonia at 25 degrees C than at 21 degrees C. QwikLite shows promise as a rapid, inexpensive screening test for acute toxicity of contaminants in marine environments.     

Influence of suspended solids on acute toxicity of carbofuran to Daphnia magna: I. Interactive effects

This study explored the effects on Daphnia magna from exposure to the pesticide carbofuran in combination with stress from suspended solids exposure. Our objective was to assess whether suspended solids affects the toxicodynamic response of D. magna to carbofuran. A series of laboratory experiments was performed where animals were exposed to carbofuran concentrations ranging from 0 to 160 microg/l in combination with suspended solids concentrations ranging from 0 to 10000 mg/l. In the absence of suspended solids, effects of carbofuran were dose dependent and resulted in an EC(50) of 92 microg/l. Exposure to suspended solids, up to extreme levels that may be encountered in the environment and in the absence of carbofuran, showed no measurable toxicity. When D. magna were exposed to a constant carbofuran concentration, the numbers of affected organisms increased with increasing suspended solids concentrations. At a suspended solids concentration of 1000 mg/l, the EC(50) for carbofuran was reduced by half to 45 microg/l. The relationship between the toxicity of carbofuran (microg/l) and the concentration of suspended solids (mg/l) can be described with the following equation: carbofuran EC(50)=72 exp(-0.00014 [suspended solids]). An analysis of the data indicates that this relationship is consistent with a potentiated toxicity mechanism rather than an additive model.