Effect of Body Size on Toxicity of Zinc in Neonates of Four Differently Sized <Emphasis Type="Italic">Daphnia</Emphasis> Species

The sensitivity of neonates of four Daphnia species to zinc was tested in relation to their mean body size. These mean sizes of these four Daphnia spp were: D. magna, 0.813 ± 0.055 mm, D.␣pulicaria, 0.745 ± 0.063 mm, D. pulex, 0.645 ± 0.044 mm and D. galeata, 0.611 ± 0.058 mm. A positive relationship between EC₅₀ (24, 48) values and neonates size was found. The smaller the size of the daphnid the higher was the sensitivity to heavy metal toxicity. For all tested species did the EC₅₀ values decrease with time; the decrease was most marked for D. magna and the least for D. galeata. The EC₅₀ values of D. magna were higher than would be expected on basis of its body size.     

Characteristics of six cladocerans in relation to ecotoxicity testing

Investigation was made to compare some biological characteristics relevant to ecotoxicity testing among six cladoceran species, including Daphnia magna, Daphnia carinata, Daphnia pulex, Ceriodaphnia quadrangular, Bosmina longirostris, and Simocephalus vetulus. The results show that D. carinata had advantages over other cladoceran species for being used as a test organism, particularly for ecotoxicological assessment of aquatic environments in tropical and subtropical areas. D. carinata had similar body size and total number of offspring per female to D. magna. However, D. carinata was more sensitive to the reference toxicant and had much shorter reproduction cycle than D. magna. D. carinata had similarity to D. pulex, C. quadrangular, S. vetulus and B. longirostris in terms of sensitivity to the reference toxicant and length of reproduction cycle. However, D. carinata was much larger in size and produced much more offspring per female than any of D. pulex, C. quadrangular, S. vetulus and B. longirostris. Among the investigated cladocerans, only the neonates (2- and 4-day-old) of D. carinata exhibited phototaxis that was sufficiently remarkable. The low among-generation variation in phototaxis index (I_p) of D. carinata and the close relationship between I_p and the concentration of the ISO standard toxicant (K₂Cr₂O₇) appears to suggest that I_p can be used as an excellent test endpoint for ecotoxicity testing.     

Contaminated sediments in the Elbe estuary: Ecological and economic problems for the Port of Hamburg

The effects of food density on competition between Bosmina longirostris and Bosmina fatalis from Lake Kasumigaura were examined in the laboratory. When the animals were reared with a high concentration of Chlorella, B. fatalis, which is slightly larger than B. longirostris in body length, had larger brood sizes and a higher rate of population growth than B. longirostris. When the species were reared together at high food density, B. fatalis overcame B. longirostris. But B. longirostris won the competition at low food density.The effects of Microcystis on the competition were also examined. When the two species of Bosmina were reared in a mixture of Chlorella and Microcystis, the populations of both species hardly increased, although individual B fatalis showed slightly better individual growth and reproduction than B. longirostris. Decomposed Microcystis, however, was utilized well by both species.In Lake Kasumigaura, the decomposition of abundant Microcystis seemed to raise the food level, favouring B. fatalis over B. longirostris.     

Application of individual growth and population models of Daphnia pulex to Daphnia magna, Daphnia galeata and Bosmina longirostris

Daphnia models for individual growth and population dynamics have been developed in the manner of models developed by Gurney, McCauley, Andersen and others. All or most of the earlier models were parameterized for Daphnia pulex; we have used the D. pulex model as a baseline model for other species of Daphnia such as magna, galeata and also Bosmina longirostris. Because of the lack of ample data for D. magna, D. galeata and B. longirostris, some of the physiological data had to be relied on the other species whose data were available and in some case calibrated. We were able to produce reasonable results for individual growth as well as population dynamics under the controlled laboratory conditions. Most of the results were compared with the available laboratory data for population as well as growth. All the simulations have been done under high and low food concentrations. The animals are assumed to be feeding on green algae (Chlamydomonas reinhardtti) under the laboratory conditions of 18–20°C. The continuous growth until the end of the life was observed in smaller B. longirostris, whereas rapid growth in the beginning and slower after the start of the reproduction was observed in Daphnia species. The smaller species matured earlier than larger species. B. longirostris population sustained better than Daphnia species in medium food concentrations.     

Influence of food density on respiration rate of two crustacean plankters,Daphnia galeata and Bosmina longirostris

Summary The influence of food density on respiration rate was measured for two cladoceran plankton species, Daphnia galeata and Bosmina longirostris, over the range 0 to 2.5 mg C 1^-1, using the modified Winkler technique in order to examine how this affects the respiration rate and whether the functional response is the same in the two species. The respiration rate for animals of equivalent body size did not differ significantly between the two species in the absence of food, but was significantly lower in Bosmina longirostris than Daphnia galeata at high food density. Within a species, the response of respiration rate to changing food density did not differ among individuals of different body size. The respiration rate of D. galeata increased with increasing food density and reached a plateau at a high food density. A similar response curve was also found with the respiration rate of B. longirostris, although the response was less conspicuous. This response curve cannot be explained by the energy cost of known feeding behavior in cladocerans. Since the respiration rate related linearly with the assimilation rate, increase in food density seemed to increase the respiration rate by increasing the energetic cost required to process food biochemically, known as specific dynamic action.     

Copper-induced oxidative damage, antioxidant response and genotoxicity in Lycopersicum esculentum Mill. and Cucumis sativus L.

Adequate copper (Cu²⁺) concentrations are required for plants; however, at higher concentrations it can also cause multiple toxic effects. In the present study, lipid peroxidation, hydrogen peroxide levels as well as ascorbate peroxidase (APX: EC 1/11/1/11) and catalase (CAT: EC 1.11.1.6) activities were determined in Lycopersicum esculentum Mill. and Cucumis sativus L. seedlings after 7-day exposure to copper sulfate. In addition, DNA damage in these two crops was assessed by measuring micronucleus (MN) frequency and tail moments (TM) as determined by Comet assay. Inhibitory copper concentrations (EC₅₀: 30 and 5.5 ppm for L. esculentum and C. sativus, respectively) were determined according to dose-dependent root inhibition curves, and EC₅₀ and 2×EC₅₀ were applied. Malondialdehyde (MDA) and H₂O₂ levels significantly increased in all groups studied. CAT activity increased in treatment groups of C. sativus. APX activity increased in L. esculentum seedlings due to 2×EC₅₀ treatment. Reductions in mitotic indices (MI) represented Cu²⁺dependent root growth inhibition in all treatment groups studied. According to TMs and MN frequencies, copper exposure induced significant DNA damage (p < 0.05) in all study groups, whereas the DNA damage induced was dose dependent in C. sativus roots. In conclusion, Cu²⁺induced oxidative damage, elevations in H₂O₂ levels and alterations in APX and CAT activities, as well as significant DNA damage in nuclei of both study groups. To our knowledge, this is the first comparative and comprehensive study demonstrating the effects of copper on two different plant species at relevant cytotoxic concentrations at both biochemical and genotoxicity levels with multiple end points.     

Toxicity of cadmium and zinc on two microalgae, <Emphasis Type="Italic">Scenedesmus obliquus</Emphasis> and <Emphasis Type="Italic">Desmodesmus pleiomorphus</Emphasis>, from Northern Portugal

Aquatic environments often contain toxic heavy metals that may enter the food web via uptake by microalgae and eventually cause severe poisoning problems at higher trophic levels. The effects of Cd and Zn cations upon growth of two native green microalgal species, Scenedesmus obliquus and Desmodesmus pleiomorphus (previously isolated from a polluted site in Northern Portugal), were accordingly evaluated. Growth inhibition of the microalgal cells was determined following exposure for 96 h to several initial concentrations of aqueous solutions of either of those two metals. At the higher end of Cd and Zn experimental concentration ranges, a significant reduction in cell density was observed in the cultures; EC₅₀ values, calculated after fitting a Weibull model to the experimental data, were 0.058 and 1.92 mg L⁻¹ for Cd and 16.99 and 4.87 mg L⁻¹ for Zn in the case of S. obliquus and D. pleiomorphus, respectively. One observed that S. obliquus can tolerate higher Zn concentrations than D. pleiomorphus, but the reverse holds regarding exposure to Cd.     

Trace metals in marine,brackish and freshwater prawns (Crustacea,Decapoda) from northeast Algeria

The concentrations of the trace metals Zn, Cu, Fe, Cd and Pb were measured in four caridean decapods; Atyaephyra desmaresti, Palaemonetes varians, Parapenaeus longirostris and Aristeus antennatus, from freshwater , estuarine and marine habitats in northeast Algeria variably affected by anthropogenic metal contamination. The two coastal species (P. longirostris and A. antennatus) are a food source for the local population. Accumulated metal concentrations varied interspecifically, and intraspecifically between sites and between seasons, except in the case of Aristeus antennatus. The fresh and brackish water species (Atyaephyra desmaresti and Palaemonetes varians) accumulated more Cd and Pb than their marine counterparts. Results are discussed with respect to anthropogenic inputs and the environmental conditions of the regions studied.     

Tolerance of a ruminant ciliate <Emphasis Type="Italic">Entodinium caudatum</Emphasis> against mercury,copper and chromium

The effects of three heavy metal cations, mercury (II), copper (II), and chromium (VI), on the growth of the rumen ciliate Entodinium caudatum in vitro culture was studied. The E. caudatum culture was challenged by HgCl₂, CuCl₂, and K₂Cr₂O₇ for a period of 4 days. The tested concentrations of mercury (II) and copper (II) were 1, 5, 10, 20, 50 mg/L and 2, 10, 20, 40 mg/L for chromium (VI) at single dose with either untreated or inhibited bacterial co-culture population. Effective metal concentrations required to reduce ciliate growth by 50% (EC₅₀) for mercury (II), copper (II), and chromium (VI) either with untreated or inhibited bacterial co-culture population after 24 h of metal application were 24, 20, and 21 or 15, 20, and 19 mg/L, respectively. After 4 days of metal application, corresponding EC₅₀ values for mercury (II), copper (II), and chromium (VI) were 16, 20, and 17 (with untreated bacterial population) or not determinable, 20, and 15 mg/L, respectively (with inhibited bacterial population). Increased sensitivity of E. caudatum to tested heavy metals with inhibited bacterial co-culture population indicate that the ciliate resistance to the heavy metal tested depends on detoxification abilities of rumen bacterial population.     

Comparative sensitivity of the several zooplankton species (Cladocera,Copepoda) to sumicidine-alpha insecticide

The sensitivity of seven zooplankton species (Daphnia magna, D. longispina, D. pulex, Simocephalus vetulus, Scapholeberis mucronata, Eudiaptomus graciloides, and Cyclops strenuus) to an insecticide, sumicidine alpha was studied. LD₅₀ values upon a 24-hour exposure were determined. Daphnia pulex and D. longispina turned out to be highly susceptible to the insecticide, while the individuals representing the natural population of D. magna happened to be the most resistant. The data on sensitivity distribution among different zooplankton species are provided, as well as the concentrations potentially hazardous for 5% and 50% of the population are calculated.     

Effects of the non-indigenous cladoceran Cercopagis pengoi on the lower food web of Lake Ontario

1. In North America, the invasive predatory cladoceran Cercopagis pengoi was first detected in Lake Ontario. We explored the impact of Cercopagis on the lower food web of Lake Ontario through assessments of historical and seasonal abundance of the crustacean zooplankton, by conducting feeding experiments on the dominant prey of the invader, and by estimating its food requirements. 2. Between 1999 and 2001, a decrease in the abundance of dominant members of the Lake Ontario zooplankton community (Daphnia retrocurva, Bosmina longirostris and Diacyclops thomasi) coincided with an increase in the abundance of Cercopagis. Daphnia retrocurva populations declined despite high fecundity in all 3 years, indicating that food limitation was not responsible. Chlorophyll a concentration generally increased, concomitant with a decline in the herbivorous cladoceran zooplankton in the lake. 3. Laboratory experiments demonstrated that Cercopagis fed on small‐bodied species including D. retrocurva and B. longirostris. 4. Consumption demand of mid‐summer populations of Cercopagis, estimated from a bioenergetic model of the confamilial Bythotrephes, was sufficient to reduce crustacean abundance, although the degree of expected suppression varied seasonally and interannually. 5. Predatory effects exerted by Cercopagis on the Lake Ontario zooplankton, while initially very pronounced, have decreased steadily as the species became established in the lake.     

Response of Phytoplankton to Copper Treatment with Reference to Species Sensitivity

Responses of different planktonic algae species to copper treatment were tested using semi-continuous culture and compared with studies on copper-induced changes in species composition of phytoplankton samples. Blue-green algae exhibit lower EC₁₀₀-values than diatoms and Scenedesmus. The four tested strains of Microcystis aeruginosa showed different copper sensitivity. Four response types can be distinguished. 1. rapid biomass loss after copper application but subsequent growth recovery. 2. fluctuations of growth but no loss of biomass at sublethal concentrations 3. continuous recovery of growth rates after initially affected growth. 4. growth inhibition (dormancy) and recovery after inoculation into a copper-free medium. Species response to copper application within a phytoplankton sample agrees with pure culture behaviour.     

Some factors influencing the density of subarctic populations of Bosmina longirostris,Holopedium gibberum,Codonella cratera and Ceratium hirundinella

Changes in the density of 2 populations of Bosmina longirostris, Holopedium gibberum and Codonella cratera were correlated through multiple regression analyses with shifts in temperature, light, nannoplankton densities and seston weight. Sampling took place every 2 weeks between June 1975 and November 1976 in the Yellowknife River and Yellowknife Bay, both in the Canadian subarctic. Temperature was usually the main factor influencing all 3 species, accounting for up to 60% of the seasonal variability in B. longirostris, 37% in H. gibberum and 62% in Codonella cratera. Seston (the major food source) ranked second overall and in one instance accounted for 60% of density changes in B. longirostris. Nannoplankton were consumed in only small numbers and had little influence on densities. Light was of minor importance to all species. Temperature was also the main factor effecting reproduction and feeding in B. longirostris and H. gibberum (the only species studied). The simultaneous collections of Ceratium hirundinella made in the river and bay indicated that temperature accounted for 30–55% of the seasonal variability of this species, followed by light (4% and nutrients (3–4%).     

Predation impact of Leptodora kindtii on population dynamics and morphology of Bosmina fatalis and B. longirostris in mesocosms

1. We assessed the impact of predation by the invertebrate predator Leptodora kindtii on Bosmina longirostris and B. fatalis, which show seasonal and reciprocal succession patterns in Lake Suwa, in a mesocosm experiment using 20‐L tanks with or without the predator under different food conditions. We also analysed morphological responses of the two Bosmina species to the predator in the tanks. 2. Bosmina fatalis dominated B. longirostris regardless of predator presence under high food density. However, the presence of Leptodora induced the dominance of B. fatalis more rapidly than its absence. On the contrary, no dominance of B. fatalis was observed in tanks with low food density, irrespective of the presence of the predator. Only B. fatalis showed morphological changes in response to the presence of Leptodora. 3. Mucrone length and antennule shape (angle between body and antennule and angle between antennules) showed marked responses at both high and low food densities, but antennule length responded only at high food density. Mucrone length seems to be a more effective defence against Leptodora. 4. The results suggest that B. fatalis is a superior competitor against B. longirostris and is more resistant to Leptodora predation, especially in good food conditions. The repeatedly observed seasonal succession of the two Bosmina species in the eutrophic Lake Suwa – the replacement of B. longirostris by B. fatalis following the occurrence of abundant Leptodora– seems to be caused by the selective predation of Leptodora on B. longirostris as well as the competitive ability of B. fatalis.     

Water quality requirements for first-feeding in marine fish larvae. II. pH,oxygen, and carbon dioxide

Previously unfed larvae representing eight species of marine teleosts (a soleid, Heteromycteris capensis Kaup; a cynoglossid. Trulla capensis Kaup; a gadid, Gaidropsarus capensis (Kaup); a congiopodid, Congiopodus spinifer (Smith); three sparids, Diplodus sargus (L.), Pachymetopon blochi (Val.), and an unidentified species; and a centracanthid, Pterosmaris axillaris (Boulenger)) were exposed for 24 h to various pH's and concentrations of dissolved oxygen and carbon dioxide and then tested for their ability to first-feed. Mortalities recorded during the 24-h exposure went into the fitting of response curves and the calculation of the LC₅₀ and LC₁₀. The incidence of successful first-feeding during the subsequent 4-h exposure to food yielded values for the EC₅₀ and EC₁₀. The exposure to sub-optimal conditions continued during the 4-h feeding test. The sensitivity of first-feeding larvae to high pH and dissolved oxygen may pose hazards for the marine fish culturist; low pH appears to be harmful (at least in the short term) only at levels below about pH 6.0; carbon dioxide poisoning is of doubtful importance in practical fish culture. There were only minor interspecific differences in calculated 24-h first-feeding EC₅₀'s, which suggests general applicability of the results to a wide variety of first-feeding marine fish larvae.     

Effect of Some Pesticides on Reproduction of Rotifer <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> Müller

Pesticides have been major contributors to environmental pollution and they are now widely distributed in aquatic environments. Zooplankters are frequently used as test animals to detect aquatic contaminants because of their sensitivity and ecological importance. We investigated the effect of a 7-day exposure to four commonly used pesticides (diazinon, fenitrothion, methoprene and isoprothiolane) on reproduction of the rotifer Brachionus plicatilis. Pesticide concentrations of 3–7 times lower than the 24-h 50% lethal concentration (24-h LC₅₀) were tested to determine the ‚no observed effect’ concentration (NOEC), ‚lowest observed effect’ concentration (LOEC), and the ‚50% effective’ concentration (EC₅₀) on specific growth rate (r), sexual reproduction, fertilization, resting egg production, and hatchability of resting eggs. Results showed that the lowest EC₅₀ value of r, mixis, fertilization, and resting egg production of 1.4 μM for diazinon was 63 times lower than its 24-h LC₅₀ of 88.4 μM, while for fenitrothion it was 66 times (3.5 and 229.8 μM, respectively). For isoprothiolane, the lowest EC₅₀ value of r, mixis, fertilization, and resting egg production of 8.9 μM was 25 times lower than its 24-h LC₅₀ of 220.7 μM, while for methoprene was 37 times (2.7 and 100.8 μM, respectively). In all pesticides, hatching rate of resting eggs consistently gave the lowest EC₅₀ values which is about 2–40 times lower than the lowest EC₅₀ of r, mixis, fertilization, and resting egg production. Hatchability of resting eggs therefore is the most sensitive parameter in detecting effects of pesticides exposure in rotifer B. plicatilis.     

Variability of <Emphasis Type="Italic">Botrytis cinerea</Emphasis> sensitivity to pyrrolnitrin,an antibiotic produced by biological control agents

To establish a baseline sensitivity of Botrytis cinerea to pyrrolnitrin, an antibiotic produced by several biological control agents, 204 isolates were tested for sensitivity to pyrrolnitrin using a spore germination assay. The results showed that the isolates exhibited a wide range of sensitivity to pyrrolnitrin, with an 8.4-fold difference in EC₅₀ (effective concentration to reduce spore germination by 50% comparing to the control) values between the least and the most sensitive isolates. The model-based clustering analysis indicates that the distribution of the EC₅₀ values best fit a normal mixture model with three components and unequal variance. The less sensitive isolates were also multidrug resistant isolates. The efficacy of the pyrrolnitrin-producing Pseudomonas chlororaphis ChPhzS24 strain was tested in vitro and on tomato plants with isolates of B. cinerea having different EC₅₀ values. Whatever the EC₅₀ value of the isolates tested, no significant differences in sensitivity were observed towards this bacterium indicating an absence of resistance to this biological control agent within B. cinerea isolates and suggesting also that additional mechanisms of action are probably operated by this biological control agent.     

Susceptibilities of different-sized ciliates to direct suppression by small and large cladocerans

• 1 Laboratory experiments compared the susceptibilities of six ciliates and the rotifer Keratella cochlearis to predation and interference from Daphnia pulex and Bosmina longirostris.
• 2 Susceptibilities of the ciliates to D. pulex were similar to or less than that of the rotifer, and decreased with increasing ciliate size. Most ciliates were just as susceptible to B. longirostris as to the much larger D. pulex. The jumping response of the oligotrich Strobilidium gyrans appeared to be an effective defence against B. longirostris.
• 3 Clearance rates of B. longirostris and D. pulex on different ciliate species at a density of 1,3 ciliates ml^?1 ranged from 1–30 to 5–24ml ind.^?1 day^?1, respectively. In natural plankton communities, cladocerans could impose high mortality rates on ciliates and shift the size structure of ciliate assemblages towards larger and less susceptible species.

     

Isolation,Growth, Ultrastructure,and Metal Tolerance of the Green Alga,Chlamydomonas acidophila (Chlorophyta)

An acidophilic volvocine flagellate, Chlamydomonas acidophila (Volvocales) that was isolated from an acid lake, Katanuma, in Miyagi prefecture, Japan was studied for growth, ultrastructural characterization, and metal tolerance.

Chlamydomonas acidophila is obligately photoautotrophic, and did not grow in the cultures containing acetate or citrate even in the light. The optimum pH for growth was 3.5-4.5. To characterize metal tolerance, the toxic effects of Cd, Co, Cu, and Zn on this alga were also studied. Effective metal concentrations, which limited the growth by 50%, EC₅₀ were measured, after 72h of static exposure. EC₅₀s were 14.4 μM Cd²⁺, 81.3 μM Co²⁺, 141μM Cu²⁺, and 1.16 mM Zn²⁺ for 72 h of exposure. Thus, this alga had stronger tolerance to these metals than other species in the genus Chlamydomonas.     

Population dynamics and production of Daphnia hyalina and Bosmina longirostris in a shallow, eutrophic reservoir

SUMMARY. 1. The population densities, dynamics and production of Daphnia hyalina and Bosmina longirostris were studied over a 2-year period in a shallow eutrophic reservoir in eastern England. The diet of the two species was assessed and their ecology was compared in relation to environmental factors. 2. Daphnia hyalina was characterized by small overall body size, probably due to heavy size-selective predation by fish. The first generation produced from the overwintering population appeared in April and Depopulation peaked in late spring and early summer. Adult survival was poor. Peak egg production varied between years, while mean brood size fell in summer probably due to food limitation during the cyanobacterial bloom. At this time selection for individual algal species was high and many guts were empty. Reproductive ratios were inversely related to population density. Bosmina longirostris exhibited a similar annual cycle. 3. Patterns of production were very different in the 2 years in D. hyalina. In 1981 production was high from August to early October, but in 1982 the peak was in spring. Annual production was 32.4 g C m^?2 in 1981 and 13.3 g C m^?2 in 1982. In 1981 B. longirostris production peaked in spring and late summer; in 1982 there was a high production in summer only. Annual production was 3.2 g C m^?2 in 1981 and 2.2 g Cm^?2 in 1982. 4. The number of adult D. hyalina was highly correlated with water temperature and total phytoplankton biomass, but these were negatively correlated with the number of eggs, mean brood size and instantaneous birth rate. In contrast, clutch size of B. longirostris was positively correlated with water temperature while birth rate was positively correlated with both temperature and phytoplankton biomass. The biomass of both species was positively related to total phytoplankton biomass, but neither relationship explained much of the variation in zooplankton biomass. 5. The significance of the observations on plankton in terms of managing the water quality in eutrophic reservoirs is discussed.