Toxicity of Cadmium for Silver Catfish <Emphasis Type="Italic">Rhamdia quelen</Emphasis> (Heptapteridae) Embryos and Larvae at Different Alkalinities

The present study evaluated the effect of waterborne Cd in eggs and larvae of silver catfish, Rhamdia quelen, at two alkalinity levels (63 and 92 mg · L⁻¹ CaCO₃): 0.5 (control), 4.5, 8, and 18 μg · L⁻¹ Cd. The fertilization rate was similar in all treatments, but the number of eggs with irregular surface was significantly higher in those exposed to 18 μg · L⁻¹ Cd and 63 mg · L⁻¹ CaCO₃. Three days after hatching survival of larvae exposed to 4.5 and 8 μg · L⁻¹ Cd and 63 mg · L⁻¹ CaCO₃ was significantly lower than that of control larvae, and 21 days after hatching survival decreased with the increase in waterborne Cd levels and total cadmium accumulation in the larvae. These significant differences and relationships were not observed in larvae maintained at 92 mg · L⁻¹ CaCO₃. Furthermore, in the lower alkalinity, a higher incidence of barbels and spinal column deformities was observed in the highest waterborne Cd concentration. At the end of the experimental period, 21 days after hatching, larval survival rate, length, weight, head height, membranous layer thickness, and biomass decreased with the increase in waterborne Cd levels in the lower alkalinity. However, these relationships were not observed in larvae maintained at 92 mg · L⁻¹ CaCO₃. The percentage specific growth rate was lower in larvae exposed to the highest waterborne Cd concentration at 63 mg · L⁻¹ CaCO₃. These results suggest that alkalinity of 92 mg · L⁻¹ CaCO₃ reduces waterborne Cd toxicity in silver catfish larvae.     

Cadmium,Lead and Zinc Concentrations in Water,Sediment and Oyster (<Emphasis Type="Italic">Crassostrea virginica</Emphasis>) of San Andres Lagoon,Mexico

The spatial distribution of cadmium, lead and zinc concentrations in water, sediment and oysters from San Andres Lagoon was evaluated. Significantly higher cadmium (0.33 mg L⁻¹) and lead (0.70 mg L⁻¹) concentrations in water were observed in front of the mouth of Tigre river, whereas, zinc concentration (5.0 mg L⁻¹) was significantly higher in the south part of the lagoon. Similarly, lead and zinc values in sediment (1.01 and 9.29 μg g⁻¹, respectively) and oyster tissue (0.86 and 3.19 μg g⁻¹, respectively) were significantly higher in the south part of the lagoon. Levels of cadmium and lead in oyster tissue were positively related to those found in sediment. However, concerning zinc no evident relationship was found. Such differences in regression analyses may be explained by differential bioaccumulation of xenobiotic (cadmium, lead) and essential (zinc) metals.     

Removal of Cadmium by <Emphasis Type="Italic">Myriophyllum heterophyllum</Emphasis> Michx. and <Emphasis Type="Italic">Potamogeton crispus</Emphasis> L. and Its Effect on Pigments and Total Phenolic Compounds

In this study, cadmium biosorption by Myriophyllum heterophyllum Michx. and Potamogeton crispus L. was investigated. Although both species were found to be capable of removing cadmium from water, the performance of P. crispus was the most significant. These species were treated with 0, 4, 8, 16, 32, and 64 mg L⁻¹ cadmium solutions for 24, 48, 72, and 96 h, respectively. Cadmium uptake of both species was lowest at 4 mg L⁻¹ and highest at 64 mg L⁻¹. Photosynthetic pigments and total phenolic compounds in both species were determined after exposure to various concentrations of cadmium for various times. Depending on the cadmium accumulation in both species, it was shown to decrease the level of chlorophyll a, chlorophyll b, and carotenoids (24 and 96 h). The anthocyanin concentration in P. crispus increased at all cadmium concentrations studied (0, 4, 8, 16, 32, and 64 mg L⁻¹), whereas in Myriophyllum heterophyllum it increased at the lower cadmium concentrations (0, 4, and 8 mg L⁻¹) but decreased at higher cadmium concentrations (16, 32, and 64 mg L⁻¹), for all exposure periods. The total phenolic compound level in both species increased with cadmium concentration during the 24 and 96 h exposure periods.     

Impact of a Sacrificial Anode as Assessed by Zinc Accumulation in Different Organs of the Oyster <Emphasis Type="Italic">Crassostrea gigas</Emphasis>: Results from Long- and Short-Term Laboratory Tests

Sacrificial anodes made of zinc are currently used in marine environments to mitigate marine corrosion as part of CP systems of immerged metallic structures. The aim of this work was to study zinc bioconcentration in the oyster Crassostrea gigas by performing two in vivo tests during different time periods and at different zinc concentrations. The first test was conducted during a period of 10 weeks at a concentration of 0.53 ± 0.04 mg Zn L⁻¹ to simulate long-term exposure, and a second test was conducted during a 168-hour period at a concentration of 10.2 ± 1.2 mg Zn L⁻¹ to reproduce short-term exposure. In these experiments, the zinc source was an electrochemical device that included a sacrificial anode to mimic the in situ conditions. During the first 14 days of the long-term experiment, digestive glands of C oysters exhibited bioaccumulation of zinc that varied according to the oysters’ reproductive cycle. Both a bioconcentration factor (BCF) of ≤ 13,397 and a zinc accumulation percentage of +297% of zinc occurred in this organ after 10 weeks. The results obtained from the short-term test showed a lower BCF of 405 but a faster bioaccumulation of zinc (starting from the first day) in the same organ. No mortality was observed in long-term assay, but 81.8% of the oysters died at the end of the short-term assay. These results demonstrate the great capacity of C. gigas to accumulate zinc released from the anode, especially when low concentrations are released, as in the case of anode dissolution used as CP. This study confirmed the necessity to monitor this zinc-contamination source in marine environments in relation to the usual oyster consumption by humans (especially in France). No implication for human health of this zinc-contamination source was demonstrated until now, and this was not the purpose of this study; however, zinc remains one of the most abundant nutritionally essential elements in the human body that may affect the human immune system at high-level uptake.     

Sensitivity of Two <Emphasis Type="Italic">Mesocyclops</Emphasis> (Crustacea,Copepoda, Cyclopidae), from Tropical and Temperate Origins,to the Herbicides,Diuron and Paraquat,and the Insecticides,Temephos and Fenitrothion

Ecotoxicological assessment in the tropics is based mainly on knowledge gained from temperate organisms, although many studies have shown the need for models that are more appropriate to tropical regions. The toxicity of two herbicides and two insecticides to nauplii of two freshwater zooplankton species, Mesocyclops aspericornis (von Daday in Inseln Zool Jb Syst 24:175–206, 1906) from a tropical reservoir and a Mesocyclops sp. from a temperate pond, were compared. Both strains were sensitive to paraquat, temephos and fenitrothion, tropical M. aspericornis being generally more tolerant (EC50s of 207, 1,450 and 1,840 μg L⁻¹ for paraquat, temephos and fenitrothion, respectively) than the temperate Mesocyclops sp. (EC50s of 152, 45 and 1,017 μg L⁻¹ for paraquat, temephos and fenitrothion, respectively) whereas diuron was only slightly toxic (LOEC = 446 μg L⁻¹ for both strains). The nauplii mortality increased with the exposure time for both species during each experiment. Further isolation of model organisms from tropical ecosystems is needed, to meet the requirements for a tropical risk assessment scheme.     

Genotoxicity of Fenpropathrin and Fenitrothion on Root Tip Cells of <Emphasis Type="Italic">Vicia faba</Emphasis>

The genotoxicity of fenpropathrin and fenitrothion on root tip cells of Vicia faba was studied. The symptoms were investigated about the mitotic index, the micronucleus frequency and chromosomal aberration frequency of root tip cells of Vicia faba which were induced by different concentrations of fenpropathrin and fenitrothion (1 × 10⁻¹⁰–1 × 10⁻² g L⁻¹). Results showed that fenpropathrin and fenitrothion could induce the micronucleus of root tip cells of Vicia faba. It occurred in a dose-dependent manner. Peaks were observed at 1 × 10 ⁻⁶ g L⁻¹ fenpropathrin and 1 × 10⁻⁴ g L⁻¹ fenitrothion, and micronucleus frequency reached 14.587 ± 1.511‰ and 14.164 ± 1.623‰, respectively. From 1 × 10⁻¹⁰ g L⁻¹ to 1 × 10 ⁻⁶ g L⁻¹ fenpropathrin and 1 × 10⁻⁴ g L⁻¹ fenitrothion, the micronucleus frequency increased with the increase of the concentrations, but beyond this range, the micronucleus frequency decreased with the further increase of the concentrations. A similar trend was observed for mitotic index. Moreover, fenpropathrin and fenitrothion could induce various types of chromosome aberration, such as lagging chromosomes, chromosome fragment, chromosome bridge, multipolar, nuclear buds, karyorrhexis, etc.     

Effects of Nitrite and Toxic <Emphasis Type="Italic">Microcystis Aeruginosa</Emphasis> PCC7806 on the Growth of Freshwater Rotifer <Emphasis Type="Italic">Brachionus Calyciflorus</Emphasis>

Over the last two centuries, anthropogenic activities have increased the nitrogen amount in aquatic ecosystems, which has resulted in increased occurrences of blooms of cyanobacteria. This study investigated the effects of nitrite and the cyanobacterium Microcystis aeruginosa on population growth in the rotifer Brachionus calyciflorus. The rotifer was treated for 12 days with nitrite alone (medium containing 0, 3, 6, 10 mg NO₂ ⁻ –N L⁻¹), M. aeruginosa alone (medium containing 0 mg NO₂ ⁻–N L⁻¹ + 5.0 × 10⁵ cell ml⁻¹ M. aeruginosa precultured at 0, 3, 6, 10 mg NO₂ ⁻–N L⁻¹), and nitrite in combination with M. aeruginosa (medium containing 3, 10 mg NO₂ ⁻–N L⁻¹ + 5.0 × 10⁵ cell ml⁻¹ M. aeruginosa precultured at corresponding nitrite concentrations). We observed that a nitrite concentration of 10 mg NO₂ ⁻–N L⁻¹ markedly inhibited the growth of B. calyciflorus; however, rotifer growth declined slightly in the presence of M. aeruginosa precultured at 6 mg NO₂ ⁻–N L⁻¹. Furthermore, reduced population growth of B. calyciflorus was observed when it was treated with both nitrite and M. aeruginosa compared to nitrite alone or M. aeruginosa alone. These results suggested that a high tolerance of B. calyciflorus to nitrite levels may be attributed to the absence of specific respiratory structures and pigments; and that the increased toxicity of nitrite in combination with M. aeruginosa may have been due to increased production of microcystin. It is also possible that nitrite and microcystin could act in a synergistic way in causing toxicity.     

Acute and Chronic Effects of the Insecticide-Endosulfan on Freshwater Cladoceran, <Emphasis Type="Italic">Moina macrocopa</Emphasis> Straus

Acute and chronic effects of insecticide-endosulfan on the survival and reproduction performance of Moina macrocopa were determined in a laboratory study. Endosulfan concentrations that cause 50% mortality (LC50) after exposure for 24 and 48 h were 3.34 and 0.16 mg L⁻¹, respectively. Average longevity, initial age of reproduction and intrinsic rate of natural increase were reduced at 0.002 mg L⁻¹. Fecundity was greatly reduced by about 70% at 0.0004 mg L⁻¹ and approximately 97% at 0.002 mg L⁻¹ as compared to control organisms throughout the whole life span of 15 days. If environmental concentration of endosulfan do not exceed 0.0004 mg L⁻¹, application of this insecticide is unlikely to induce detrimental effects on these cladoceran populations in agro-ecosystem.     

Acute Toxicity of Antimony Chloride and its Effects on Oxygen Consumption of Common Carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>)

The purposes of this study were to investigate the acute toxicity and effects of sublethal antimony (sb) concertrations on respiratory activity changes in the common carp (Cyprinus carpio). Median lethal concentrations were determined in acute tests. The 96-h LC50 value was 14.05 (11.09~17.80) mg L⁻¹. Common carp were exposed to 4 different sublethal levels of antimony (1.0, 2.0, 4.0, and 8.0 mg L⁻¹) over a 28-day test period and a 14-day recovery period. On days 14 and 28, decreases in oxygen consumption were significant (p < 0.05) for the higher-exposure level groups (4.0 and 8.0 mg L⁻¹). An increase in oxygen consumption was observed in the recovery period (on day 42) compared to the respective groups at the same level on day 28 at the higher exposure levles.     

Trace Metals in Oysters, <Emphasis Type="Italic">Crassotrea</Emphasis> sps., from UNESCO Protected Natural Reserve of Urdaibai: Space-Time Observations and Source Identification

The seasonal and spatial variability of trace metal concentrations of oyster tissues (Crassostea sps.) was studied. The samples were collected between 2002 and 2004 along the Urdaibai estuary (Murueta, Kanala and Arteaga). The seasonal influence on some metal concentrations (higher values in spring–summer season than in autumn–winter season) is more pronounced than the local site-specific influence. Furthermore, within each location a significant time-specific dependence on the trace metal concentration variations can be detected. Substantially higher concentrations of Zn (445.5–2,403.3 mg kg⁻¹) and Mn (29.4–169.6 mg kg⁻¹) were recorded in oysters inhabiting estuarine locations, possibly indicating a markedly higher natural bioavailability at these locations. Principal component analysis demonstrated that oysters could be separated depending on the inhabiting areas: Sn for Murueta, essential metals for Kanala, and Co and Cd for Arteaga sampling points, respectively.     

Water-Quality Parameters and Total Aerobic Bacterial and <Emphasis Type="Italic">Vibrionaceae</Emphasis> Loads in Eastern Oysters (<Emphasis Type="Italic">Crassostrea virginica</Emphasis>) From Oyster-Gardening Sites

Oyster gardening is a practice designed to restore habitat for marine life and to improve water quality. This study determined physical and chemical water-quality parameters at two oyster gardening sites in the Delaware Inland Bays and compared them with total aerobic bacteria and Vibrionaceae concentrations in Eastern oysters (Crassostrea virginica). One site was located at the end of a man-made canal, whereas the other was located in an open bay. Measured water parameters included temperature, dissolved oxygen (DO), salinity, pH, total nitrogen, nitrate, nitrite, total phosphorus, and total suspended solids. The highest Vibrionaceae levels, as determined by the colony overlay procedure for peptidases, were at the canal site in September (3.5 × 10⁵ g⁻¹) and at the bay site in August (1.9 × 10⁵ g⁻¹). Vibrionaceae levels were significantly greater during the duration of the study at the canal site (P = 0.01). This study provides the first baseline levels for total Vibrionaceae in the Delaware Inland Bays. Minimum DO readings at the bay and canal sites were 3.0 and 2.3 mg l⁻¹, respectively, far less than the state-targeted minimum threshold of 5.0 mg l⁻¹. Total phosphorus levels exceeded recommendations of ≤0.1 mg l⁻¹ at the bay and canal sites for all monthly samplings, with mean monthly highs at both sites ≥0.68 mg l⁻¹ in August. Nitrogen occasionally exceeded the recommended level of 1.0 mg l⁻¹ at both sites. Overall, waters were highly degraded from high phosphates, nitrogen, and total suspended solids as well as low DO.     

Herbicide Formulation with Glyphosate Affects Growth, Acetylcholinesterase Activity, and Metabolic and Hematological Parameters in Piava (Leporinus obtusidens)

The teleost fish Leporinus obtusidens (piava) was exposed to different concentrations of Roundup, a commercial herbicide formulation containing glyphosate (0, 1, or 5 mg L⁻¹), for 90 days. Acetylcholinesterase (AChE) activity was verified in brain and muscle. Hepatic and muscular metabolic parameters as well as some hematological parameters were determined. The results showed that brain AChE activity was significantly decreased in fish exposed to 5 mg L⁻¹ Roundup, whereas muscular AChE activity was not altered. Both Roundup concentrations significantly decreased liver glycogen without altering the muscle glycogen content. Hepatic glucose levels were reduced only in fish exposed to 5 mg L⁻¹ Roundup. Lactate levels in the liver and muscle significantly increased in fish exposed to both Roundup concentrations. Hepatic protein content remained constant at 1 mg L⁻¹ but increased at 5 mg L⁻¹ Roundup. In the muscle however, protein content decreased with increasing exposure concentration. The herbicide exposure produced a decrease in hematological parameters at both concentrations tested. The majority of observed effects occur at environmental relevant concentrations, and in summary, the results show that Roundup affects brain AChE activity as well as metabolic and hematologic parameters of piavas. Thus, we can suggest that long-term exposure to Roundup causes metabolic disruption in Leporinus obtusidens.     

Temporal Variation of Metals in Water,Sediment and Tissues of the European Chup (<Emphasis Type="Italic">Squalius cephalus</Emphasis> L.)

The aim of this study was to analyze seasonal variation of levels of Chromium (Cr), Manganese (Mn), Nickel (Ni), Copper (Cu), Zinc (Zn), Cadmium (Cd) and Lead (Pb) in water, sediment and tissues of Squalius cephalus (L., 1758) taken from five different stations chosen at Yamula Dam Lake (Kayseri, Turkey). Concentrations of metals were generally sorted as water<tissue<sediment. The highest concentration of metals in water was observed in the samples taken in the summer (Mn, 1.04 ± 0.15 mg L⁻¹; Ni, 0.42 ± 0.12 mg L⁻¹; Cu, 1.25 ± 0.88 mg L⁻¹; Zn, 3.61 ± 1.53 mg L⁻¹; Pb, 0.58 ± 0.09 mg L⁻¹). While the highest Zn (24.85 ± 21.82 μg g⁻¹) and Pb (10.89 ± 4.2 μg g⁻¹) concentrations in sediment were observed in the winter samples, the highest Mn concentration (167.2 ± 99.37 μg g⁻¹) was observed in the summer. Cd pollution was determined in sediment according to international criteria. The highest metal concentration in tissues was generally observed in the liver and the other tissues; following liver were gills and muscles. In liver tissues, while the highest accumulation of Zn (110.34 ± 13.1) and Mn (22.5 ± 14.85 μg g⁻¹), which are essential for the body, were observed in the winter, Pb (22.58 ± 7.83 μg g⁻¹) and Cd (11.77 ± 7.83 μg g⁻¹), which are toxic, were found to be higher in the summer. Also, concentrations of Mn, Cd and Pb in muscle tissues were found to be above the limits permitted.     

Toxicity of Metal Elements on Germination and Seedling Growth of Widely Used Medicinal Plants Belonging to Hyacinthaceae

In South Africa, pollution of agricultural soils is on the increase primarily due to excessive application of fertilizers, sewage disposal and mining activities. This study was done to determine the effect of trace elements (Cu, Zn) and heavy metals (Cd, Pb, Hg) on germination and seedling development of Bowiea volubilis, Eucomis autumnalis and Merwilla natalensis. These medicinal plant species are highly recommended for cultivation in South Africa to reduce the pressure on wild populations. Copper and Zn at 1 mg L⁻¹ significantly (p < 0.05) reduced the percentage germination of E. autumnalis. Low concentrations (≥1 mg L⁻¹) of Cu and Zn negatively affected the roots of all three species. Mercury concentrations of 0.5 and 1 mg L⁻¹ significantly (p < 0.05) decreased the percentage germination of B. volubilis and E. autumnalis respectively. Cadmium and Hg at 2 mg L⁻¹ showed a detrimental effect on the root growth of B. volubilis. Concentrations of 0.5 mg L⁻¹ of all heavy metals tested significantly (p < 0.05) decreased shoot length of M. natalensis.     

Effect of Lindane on the Clearance Rate of Daphnia magna

The impact of the insecticide lindane (γ-hexachlorocyclohexane) on the clearance rate (CR) of Daphnia magna was investigated using artificial beads. CR (24-h EC₅₀: 65 μg L⁻¹) was found to be a more sensitive endpoint than acute lethality for D. magna (48-h LC₅₀: 516 μg L⁻¹). The onset of the effect was rapid; after 2 h of exposure to approximately 241 μg L⁻¹ of lindane a significant decrease in CR was observed. Daphnids recovered rapidly after transfer to clean water; after 24 h of exposure to approximately 250 μg L⁻¹ lindane, transfer into clean water resulted in recovery to 80% of control levels within 2 h and complete recovery within 24 h. Received: 6 September 1998/Accepted: 6 December 1998     

Organophosphorous Pesticides in Surface Water of Iran

This research aims to evaluate the presence and distribution of pesticides in Babolrood River of Mazandaran Province in Iran. Mean diazinon levels in surface water ranged from 77.6 to 101.6 μg L⁻¹ with maximum level of 768.9 μg L⁻¹ and mean malathion levels ranged from 55.7 to 75.9 μg L⁻¹ with maximum level of 506.6 μg L⁻¹. The residues of malathion and diazinon pesticides in all of the stations, 2 weeks after spraying, were more than allowed limits.     

Effect of Copper on Growth and Enzyme Activities of Marine Diatom, <Emphasis Type="Italic">Odontella mobiliensis</Emphasis>

The 72-h IC₅₀, 7-d no observable effect concentration (NOEC), low observable effect concentration (LOEC), Chronic values were derived for copper on the growth of marine diatom, Odontella mobiliensis. The effect of copper was also studied on cell morphology, size, nitrate reductase and antioxidant enzymes (Catalase, Superoxide dismutase and peroxidase). The 72-h IC₅₀ of 298.4 ± 28.3, NOEC of 15.6, LOEC of 29.6 and chronic value of 21.5 μg Cu L⁻¹ were found in the present study. The chlorophyll a was significantly decreased with increasing concentrations of copper. The length of the cell (apical axis) was extended from 30.14 ± 5.98 μm at control to 71.4 ± 6.29 μm at 574 μg Cu L⁻¹, the spines were absent at 574 μg L⁻¹ and the cell structure was entirely damaged at 926 μg Cu L⁻¹. The antioxidant enzymes viz. Catalase, Peroxidase activities and Melondialdehyde were increased whereas the Nitrate reductase and activity was reduced at 21.5 μg Cu L⁻¹ during 7 days exposure.     

Reproductive Consequences of Exposure to Waterborne Phytoestrogens in Male Fighting Fish <Emphasis Type="Italic">Betta splendens</Emphasis>

Phytoestrogens are plant compounds that can act as endocrine disruptors in vertebrates. Biologically active levels of phytoestrogens have been found in aquatic habitats near wood pulp and paper mills, biofuel manufacturing plants, sewage-treatment plants, and agricultural fields. Phytoestrogens are known to cause hormonal and gonadal changes in male fish, but few studies have connected these effects to outcomes relevant to reproductive success. In one experiment, we exposed sexually mature male fighting fish Betta splendens to environmentally relevant (1 μg L⁻¹) and pharmacological concentrations (1000 μg L⁻¹) of the phytoestrogen genistein as well as to a positive control of waterborne 17β-estradiol (E2; 1 μg L⁻¹), and a negative control of untreated water. In a second experiment, we exposed male B. splendens to environmentally relevant concentrations (1 μg L⁻¹) of genistein and β-sitosterol singly and in combination as well as to the positive and negative controls. All exposures were 21 days in duration. We measured sex-steroid hormone levels, gonadosomatic index (GSI), sperm concentration and motility, and fertilization success in these fish. We found that exposure to genistein did not affect circulating levels of the androgen 11-ketotestosterone or the estrogen E2 relative to negative-control fish. We also found that neither of the compounds nor their mixture affected GSI, sperm concentration or motility, or fertilization success in exposed fish relative to negative-control fish. However, fish exposed to phytoestrogens showed some evidence of fewer but more motile sperm than fish exposed to the positive control E2. We conclude that sexually mature male B. splendens are relatively immune to reproductive impairments from short-term exposure to waterborne phytoestrogens.     

Effects of the Glyphosate Active Ingredient and a Formulation on <Emphasis Type="Italic">Lemna gibba</Emphasis> L. at Different Exposure Levels and Assessment End-Points

The use of formulations of the herbicide glyphosate in transgenic crops of the Pampa’s plains of Argentina has extensively increased, though there is scarce information of its impact on non-target vascular plants from agro-ecosystem related surface waters. The sensitivity of a local clone of the macrophyte Lemna gibba L. to glyphosate active principle and Roundup Max formulation was studied in standardized laboratory conditions. Phytotoxic effects, considering the aquatic route, at a concentration range of glyphosate between 0.5 and 80 mg L⁻¹ as active ingredient during 10 days of exposure were assessed on plant population growth, frond growth, shape and number, total chlorophyll content and colony architecture. Exposure to 1 mg L⁻¹ of glyphosate (an expected environmental concentration) affects all the studied assessment endpoints, except for population growth and chlorophyll content. Equivalent concentrations of this herbicide as the active ingredient or RoundupMax indicate higher phytotocity of the formulation. Exposed plants at concentrations of herbicide between 1 and 7.5 mg L⁻¹ exhibit after two days a recovery of the multiplication rate. Frond aggregation and longer stipe was detected between 1 and 15 mg L⁻¹ of glyphosate, determining more open colony architecture. At higher concentrations of the herbicide fronds break-up. Comparisons with literature data indicate a higher sensitivity of the L. gibba local clone with respect to L. minor and algal species, and also a similar response to the herbicide in field experiments with the same species.     

Physiological and Reproductive Effects of Beta Adrenergic Receptor Antagonists in Daphnia magna

Although pharmaceuticals are increasingly found in surface waters, environmental levels of many of these compounds are not acutely toxic to model test organisms. Prior to conducting appropriate ecological risk assessments of pharmaceuticals, the mode of action-based biomarkers needs to be developed for non-target species. To evaluate toxicity of the β-adrenergic blockers propranolol and metoprolol on non-target biota, we assessed standard ecotoxicological endpoints after 9 days of subchronic exposure in a transgenerational study with Daphnia magna. On day 9 of exposure, the lowest observed effects concentration (LOEC) for growth were 0.44 mg L⁻¹ for propranolol and 12 mg L⁻¹ for metoprolol. Total fecundity LOECs for the 9-day exposure were 0.11 mg L⁻¹ and 6 mg L⁻¹ for propranolol and metoprolol, respectively. In addition to typical ecotoxicological endpoints, we evaluated the utility of employing the physiological biomarkers of heart rate and metabolic rate following subchronic and acute exposures to propranolol and metoprolol. Propranolol and metoprolol LOECs for heart rate were 0.055 mg L⁻¹ and 3.1 mg L⁻¹, significantly lower than the LOECs for growth and reproduction. At these concentrations, heart rate was significantly lower than the control values for both compounds. Daphnia magna endpoint sensitivity to chronic propranolol and metoprolol exposure was mortality < growth < fecundity < heart rate. Second generation D. magna were less sensitive to both compounds. Responses of the physiological biomarkers heart rate and metabolic activity suggest that propranolol and metoprolol exerts sublethal toxicity to D. magna at lower concentrations than observed in the classical endpoints.