食物质量对盔形溞(Daphnia galeata)和脆弱象鼻溞(Bosmina fatalis)生活史参数的影响

枝角类体内氮磷比与生活史策略的选择密切相关,大型枝角类通常体内含磷量高、个体生长快、生殖率高,而小型枝角类体内含磷量低,个体生长相对较慢、生殖率低.由于大型枝角类对磷的需求比较高,我们假设大型枝角类生活史各参数对食物磷缺乏比小型枝角类更为敏感.本研究比较分析了食物碳磷比对流溪河水库两种枝角类（盔型溞（Daphnia galeata）和脆弱象鼻溞（Bosmina fatalis））生活史各参数的影响.实验设计了3个食物质量处理组：高磷（碳：磷=105）、中磷（400）和低磷（1450）,食物浓度均为2 mg C/L的蛋白核小球藻（Chlorella pyrenoidosa）.脆弱象鼻溞内禀增长率、幼溞生长速率、平均每窝产仔量和首次生殖时体长均随着食物碳磷比的升高而显著下降;首次生殖时间则随着食物碳磷比的升高而显著延长;新生幼溞体长在各食物处理中无显著差异.盔型溞幼溞生长速率、平均每窝产仔量和首次生殖时体长均随着食物碳磷比的升高而显著下降;内禀增长率和新生幼溞体长在高磷处理组显著高于中磷和低磷处理组,但在中磷和低磷处理组无显著差异;首次生殖时间在高磷处理组显著短于中磷和低磷处理组,但在中磷和低磷处理组无显著差异.结果表明,食物的磷缺乏降低了两种枝角类的内禀增长率和幼溞生长速率,并延长了性成熟时间;盔型溞的内禀增长率、首次生殖时间和平均每窝产仔量等生活史参数受食物磷限制的程度小于脆弱象鼻溞,导致盔型溞对脆弱象鼻溞有竞争优势.     

Life History Characteristics of Cladocerans Cladocera) Fed on Wastewaters

Recycling domestic wastewaters is one way to maximize the utilization of freshwater. Although sewage treatment plants help to remove particulate wastes, organic matter still remains, which can be used to harvest sizeable populations of zooplankton. In an effort to identify cladocerans which could grow on this organic matter, we tested the life table demography of the commonly found cladocerans (Alona rectangula, Ceriodaphnia dubia, Moina macrocopa, and Daphnia pulex) feeding on wastewater at three different stages of purification (tank that receives crude wastes (A), the biological reactor (B), and the penultimate stage of the treatment process (C)) from the Iztacalco water treatment plant in Mexico City. Experiments were conducted using the medium from each of the 3 tanks previously mentioned and a control of Chlorella vulgaris at 1.0 × 106 cells mL^?1. We found that the average lifespan ranged from 5…30 days with D. pulex living the longest. The growth rate, which ranged from ?0.57 to +1.5 was highest for M. macrocopa. Our data indicate that Moina macrocopa, which had higher reproductive rates on wastewater than the controls, was most suited for growing in wastewaters.     

Foraging Inhibition in Two Cladocerans Feeding on Microcystis aeruginosa

Bloom‐forming cyanobacteria are known to negatively affect their herbivores, but the possible reasons leading to the foraging inhibition of different cladoceran species are uncertain and controversial so far. Hence, in order to understand how cyanobacteria affect the feeding behavior of cladocerans with different body sizes, feeding rates (FR) of zooplankton cladocerans Daphnia carinata and Moina macrocopa on the mixture of toxic or non‐toxic Microcystis aeruginosa with Scenedesmus quadricauda during a 24‐h period was investigated. FR of M. macrocopa was found generally low in the mixed toxic Microcystis diets, except for the sudden increase after 8 h of exposure, while FR of D. carinata decreased continuously in the mixed toxic diets. The dynamics of FR of both cladocerans on specific algae was similar to that of the total FR. There is no apparent selectivity displayed for either of the two cladoceran species on the mixed diets. There is no significant difference between the strains of Microcystis, suggesting that the feeding pattern of M. macrocopa maybe more of avoiding Microcystis rather than feeding inhibition resulted from the toxicity of algae. Unlike M. macrocopa, there was a significant difference in D. carinata between the strains of Microcystis over time. The reason for feeding inhibition of D. carinata might be toxicity after continuous exposure to the toxic cyanobacteria.     

Zooplankton community structure and ecology of the tropical-highland Lake Hayq, Ethiopia

Lake Hayq, a highland lake in Ethiopia, was stocked with Tilapia fish (Oreochromis niloticus) in late 1970s, offering an opportunity to study the effect of fish predation in a natural lake. Since 1930s, some limnological surveys have been done sporadically documenting a change in zooplankton composition including the disappearance of cladocerans, hypothesizing the stocked planktivorous fish could be a cause. Nevertheless, no detailed research was conducted to identify potential effects of fish stocking predominantly due to its remote location. The article presents data about zooplankton composition, abundance and biomass done between October 2007 and January 2009 on short-time intervals including the underlying limnological variables. The zooplankton community was depauperate comprising two copepods, three cladocerans, and six rotifers taxa, as typical for tropical lakes. Total mean standing biomass of all crustacean zooplankton was 237 mg dry mass m⁻³, which gave Lake Hayq an intermediate position when compared with other tropical lakes. Of copepods, Thermocyclops ethiopiensis was almost an exclusive species, and its temporal variation was influenced by food supply and water temperature. We refute the hypothesis that Tilapia was the cause for the seasonal disappearance of cladocerans, and attribute it to the adverse effect of episodic mixing. Nevertheless, the planktivorous fish probably plays a key role in structuring the cladocerans in particular the large-sized Daphnia magna. In January 2008, we observed a massive planktivorous fish mortality that triggered high algal biomass, which was later grazed by large-sized D. magna demonstrating the trophic cascade hypothesis in a natural ecosystem.     

Food Type Effects on the Population Growth Patterns of Littoral Rotifers and Cladocerans

Littoral rotifers and cladocerans feed on bacteria, phytoplankton, and detritus. In comparison to planktonic organisms their species diversity is high, yet little is known about their biology. In this study we present data on the functional response of the cladocerans Macrothrix triserialis and Alona rectangula, and the rotifer Brachionus macracanthus to different levels of the alga Chlorella vulgaris. Based on the incipient limiting level, we chose the food concentration and tested the population growth on four types of diets for three cladoceran species — Macrothrix triserialis, Alona rectangula, and Chydorus sphaericus — and three rotifer species — Brachionus macracanthus, Lecane quadridentata, and Platyias quadricornis. We studied growth rates of each of these species on diets of live Chlorella vulgaris, heat‐killed Chlorella vulgaris, baker's yeast (Saccharomyces cerevisiae), and field collected detritus. The incipient limiting level was around 0.9 · 10⁶ cells mL^?1 of Chlorella for the tested zooplankton species. The population growth patterns showed that, in general, the cladocerans took 25…50 d to reach their peak population densities, which ranged from 10…75 ind. mL^?11. Among the rotifers L. quadridentata and B. macracanthus had equally high growth rates on live and heat‐killed forms of C. vulgaris while P. quadricornis grew best on detritus. The growth rates ranged from 0.03…0.21 d^?1. The similarities and differences between littoral and planktonic organisms in relation to food type and availability have been discussed.     

Competition Between Littoral Cladocerans Macrothrix triserialis and Alona rectangula (Cladocera) in Relation to Algal Food Level and Inoculation Density

We studied the relative competitive abilities of littoral cladocerans M.triserialis and A. rectangula using green algal food at two levels (0.5 · 10⁶ and 2 · 10⁶ cells mL⁻¹ of Chlorella) under five different inoculation ratios. Both the cladoceran species were influenced by food availability and mutual competitive pressure. Macrothrix could withstand competition better under conditions of lower food availability while Alona grew better, despite competition, when more Chlorella was available. Population growth rates (r) ranged from 0.022…0.070 for Alona and from 0.024…0.075 for Macrothrix. There was a significant impact of the inoculation ratio on the maximal population density reached by either test species. Food concentration had a significant influence on the peak population density reached only for Alona rectangula. Data on the body sizes of M. triserialis and A. rectangula showed that there was a higher somatic growth with increasing food availability and decreased competitive pressure in both the test species. In Macrothrix, food concentration and the competition from Alona through different initial inoculation densities had a significant impact on the body size. At the lower food concentration, the body size was significantly smaller when the inoculation density was lowest (highest competitive pressure). The body size of Alona, on the other hand, was not affected by the competition but was significantly higher under conditions of greater food availability. These results have been discussed in light of different theories of competition.     

Growth of Plankton (Scenedesmus acutus (Chlorophyceae) and Moina macracopa (Cladocera)) on Domestic Wastewater

The population growth of the freshwater chlorophyte, Scenedesmus acutus and the cladoceran Moina macrocopa cultured in the laboratory and in microcosms of a wastewater treatment plant was studied. S. acutus was cultured in a defined algal medium and mixed with wastewater. On diets of S. acutus cultured using Bold medium or a mixture with wastewater, the peak densities of M. macrocopa were 6–7 ind. mL^?1, while on a diet of algae cultured on wastewater alone the cladoceran density fluctuated around 2 ind. mL^?1. Population growth rates of M. macrocopa, which ranged from 0.3 to 0.4 d^?1, were significantly lower on alga cultured in wastewater alone. The body size structure of M. macrocopa was larger on algae cultured in Bold medium than in wastewater. Peak densities of M. macrocopa were around 700 ind. L^?1 when the organic matter in the containers was supplemented with algae but it reached lower densities (400 ind. L^?1) when cultured on the organic matter in wastewater alone. Our study indicates that the nutrients in the final stages of wastewater treatment can support the growth of both phytoplankton and zooplankton.     

Effect of Single Species or Mixed Algal (Chlorella vulgaris and Scenedesmus acutus) Diets on the Life Table Demography of Brachionus calyciflorus and Brachionus patulus (Rotifera: Brachionidae)

We tested the effect of two algal diets (Chlorella vulgaris at 1 · 10⁶ cells mL^?1and Scenedesmus acutus at 0.57 · 10⁶ cells mL^?1) offered alone or in combination (50 % each, 75 % or 25 % of either alga), at a total dry weight of 14.2 μg mL^?1on the life table demography of two rotifer species, Brachionus calyciflorus and Brachionus patulus. Data on fecundity indicated that, for any given algal food type or combination of food types, B. calyciflorus had a higher rate of offspring production than B. patulus. Regardless of the rotifer species, the average lifespan varied from 4 to 6 days. The gross and net reproductive rates were higher for B. calyciflorus than for B. patulus. These values ranged from 45 to 71 offspring female^?1 lifespan^?1 and 15 to 24 offspring female^?1 lifespan^?1, respectively, for B. calyciflorus. Generation times (around 4…5 days) were similar for both rotifer species in most of the treatments. Whatever the algal food combination, the rate of population increase (d^?1) of B. patulus was less than half (i.e. 45 %) of that for B. calyciflorus. The observed differences in the life history variables of Brachionus probably explain species‐specific adaptations to the changing phytoplankton composition occurring seasonally in natural waterbodies.     

食物质量和种间竞争对盔型溞(Daphnia galeata)和脆弱象鼻溞(Bosmina fatalis)种群增长的影响

竞争是调控水体浮游动物群落结构的生物因素之一.根据"大小效率假说",大型滤食性枝角类对小型枝角类有竞争优势.然而,大型滤食性枝角类体内磷含量通常高于小型枝角类,生长比小型枝角类更容易受食物磷缺乏的影响,食物的磷缺乏可能会改变大型枝角类和小型枝角类之间的竞争结果.本研究比较分析了食物碳磷比对两种常见枝角类（盔型溞（Daphnia galeata）和脆弱象鼻溞（Bosmina fatalis））的种群增长率、种群密度及种间竞争关系的影响.实验设计了3个食物质量处理组：高磷（碳：磷=105）、中磷（碳：磷=740）和低磷（碳：磷=2400）,食物浓度均为2 mg C/L蛋白核小球藻（Chlorella pyrenoidosa）;针对每一个食物质量处理组,盔型溞和脆弱象鼻溞分别单独培养或混合培养.盔型溞和脆弱象鼻溞平均最大种群密度分别为378~893和364~2399 ind./L;平均种群增长率分别为0.11~0.14和0.09~0.16 d^-1;平均体长分别为1.53~2.50和0.25~0.35 mm.种群增长率和体长均随着食物碳磷比的升高而显著下降,而最大种群密度在中磷处理组显著高于其它两个处理组.盔型溞种群增长率在单独培养和混合培养间无显著差异;脆弱象鼻溞种群增长率在混合培养时显著低于单独培养时.在高磷和中磷处理组,盔型溞最大种群密度在单独培养和混合培养间无显著差异,在低磷处理组,混合培养时最大种群密度显著低于单独培养时;在高磷处理组,脆弱象鼻溞最大种群密度在单独培养和混合培养间无显著差异,在中磷和低磷处理组,混合培养时显著低于单独培养时.结果表明,在食物碳不缺条件下,不管食物磷是否缺乏,盔型溞均比脆弱象鼻溞有竞争优势.     

Biomass Determination in Some Species Using a Geometric Equivalent Technique of Plankton Organisms

The plankton collected from three fish ponds shows a considerable variability within a pond, between the ponds and in the course of the year. The individual volumes or weights are (minimum—mean—maximum): Gleotrichia echinulata 41–252–879 μg³, Chlorella vulgaris 18–42–94 μm³, Oscillatoria amphigranulata 99–306–827 μm³, Brachionus plicatilis 1–4.918 μg, nauplia 0.5–1.25–2.35 μg, Mesocyclops hyalinus 4–45–369—μg, Heliodiaptomus viduus 41–202–288 μg, Daphnia carinata 186–1468–4578 μg.     

Relationships between body size and trophic position of consumers in temperate freshwater lakes

Animal body size is a driving force behind trophic interactions within biological communities, yet few studies have explored relationships between body size and trophic position (based on δ¹⁵N) at a broad-scale in freshwater lakes. Therefore, our goals were to (1) determine whether body size is a good predictor of trophic position for multiple pelagic zooplankton taxa and fish communities, and (2) examine how body size-trophic position relationships at the community level compare to species level for fish. Zooplankton and fish were collected from 12 and 7 lakes, respectively, located in the Kawarthas, southern Ontario, Canada. The results indicated that for zooplankton, significant positive but different relationships were found between body size and trophic position for cladocerans, in general, and Daphnia, but not Holopedium. For fish, at the lake community level six out of seven relationships were positive and significant, but again, different among lakes. In contrast, at the species level only three of eight species-specific relationships were significant. Furthermore, for two widespread species, Perca flavescens and Micropterus dolomieu, significant differences were found between community- and lake-specific species relationships. Our community-level models and most species-level models provide evidence that trophic interactions in freshwater lakes are size-based. These results demonstrate that general species models should be applied with caution when using body size to predict trophic position. Additionally, the predictive power of some relationships found here is questionable since, albeit significant, their strengths are generally low. Together, our results suggest that body size may have limited use in predicting trophic position of some biota in temperate freshwater lakes.     

Selective zooplanktivory of an invasive Ponto-Caspian mysid and possible consequences for the zooplankton community structure of invaded habitats

The impact of invasive alien species on native species is of increasing global concern. Invasive species can cause food-web shifts that have severe consequences for native species and ecosystems. However, the mechanisms by which the invaders influence the native communities are poorly understood. Here we investigated the interactions of the invasive Ponto-Caspian mysid Limnomysis benedeni with native freshwater zooplankton in laboratory and mesocosm experiments. This mysid migrates between benthic and pelagic zones and thereby forms a potential trophic link between these habitats. In laboratory predation experiments, L. benedeni fed both on Daphnia galeata and D. magna, and predation rates depended on the sizes of predator and prey but not on the availability of light. However, no predation was observed at prey sizes greater than 2 mm, which appears to be the upper size limit for a successful prey capture by L. benedeni. In outdoor mesocosm experiments, L. benedeni strongly decreased the densities of cladocerans, rotifers and copepod nauplii within a few days, while the densities of copepods were unaffected. Prey selection indices provide further evidence for strongly selective predation of L. benedeni on different zooplankton taxa. The presence of phytoplankton as an additional resource for the omnivorous mysid led to a lower predation pressure of L. benedeni on Cladocera and rotifers, indicating that the presence of alternative prey modulates the strength of the top-down effect of invasive mysids on the zooplankton community. These results suggest that the invasion of L. benedeni can have profound and complex impacts on the community structure of the native zooplankton fauna and that mysid invasions potentially have whole-ecosystem consequences.     

Toxic Cyanobacteria in Greek Freshwaters, 1987—2000: Occurrence,Toxicity, and Impacts in the Mediterranean Region

In a survey in Greece from 1987 to 2000 hepatotoxic cyanobacterial blooms were observed in 9 out of 33 freshwaters. Microcystins (MCYSTs) were detected by HPLC in 7 of these lakes, and the total MCYST concentration per scum dry weight ranged from 50.3 to 1638 ± 464 μg g^—1. Cyanobacterial genera (Microcystis, Anabaena, Anabaenopsis, Aphanizomenon, Cylindrospermopsis) with known toxin producing taxa were present in 31 freshwaters. From our data and a review of the literature, it would appear that Mediterranean countries are more likely 1) to have toxic cyanobacterial blooms consisting of Microcystis spp. and 2) to have higher intracellular MCYST concentrations. A case study in Lake Kastoria is used to highlight seasonal patterns of cyanobacterial and MCYST‐LR occurrence and to assess cyanotoxin risk. Cyanobacterial biovolume was high (> 11 μL L^—1) throughout the year and was in excess of Guidance Level 2 (10 μL L^—1) proposed by WHO for recreational waters and Alert Level 2 for drinking water. Further, surface water samples from April to November exceeded Guidance Level 3, with the potential for acute cyanobacterial poisoning. Intracellular MCYST‐LR concentrations (max 3186 μg L^—1) exceeded the WHO guideline for drinking water (1 μg L^—1) from September to November with a high risk of adverse health effects. Preliminary evidence indicates that in 3 lakes microcystins are accumulated in some aquatic organisms. Generally, a high risk level can be deduced from the data for the Mediterranean region.     

Occurrence of an Algal Mass Development in an Acidic (pH 2.5):, Iron and Aluminium‐rich Coal Mining Pond

A bloom of Chlamydomonas botryopara was observed in an extremely acid coal mining pond (pH 2.5) with high concentrations of iron and aluminium (1160...3760 mg L^–1 Fe, 133...387 mg L^–1 Al). Cell density of algae was counted as 6.45 · 10⁶ mL^–1 corresponding to 700 mg L^–1 fresh weight and 2660 μg L^–1 chlorophyll‐a. The nutrient concentrations were 3.5 mg L^–1 soluble reactive phosphorus and 0.15 mg L^–1 dissolved inorganic nitrogen. This observation supports the hypothesis that a low nutrient availability rather than extreme conditions (e.g. high acidity and low pH) limit the development of phytoplankton in many acidified lakes.     

Differential Pulse Polarographic Determination of the Oxime Carbamante Insecticide Alanycarb

As basis for the development of a sensitive analytical method for the determination of the insecticide alanycarb, a study of the differential pulse polarographic (DPP) reduction of alanycarb on a dropping mercury electrode (DME) was performed. The pesticide was found to give a single DP peak over the pH range 1.0 to 6.0 and the pH dependency of the peak potential showed a linear segment with a slope of 65.2 mV (at 20°C). For the analytical DPP method running at pH 6.0 (peak at –503.4 mV), the relationship between the peak current and alanycarb concentration was linear in the range of 1.10 to 9.76 μg mL^–1 with a detection limit of 0.33 μg mL^–1. The proposed method was applied for the determination of alanycarb in spiked dam water and orange juice samples. The recoveries calculated for both types of dam water and orange juice samples spiked with 12.0 μg mL^–1 alanycarb were 96.3 and 99.0% with relative standard deviations of 5.2 and 1.3%, respectively. The sufficiently good recoveries and low relative standard deviations for the data reflect the high accuracy and precision of the proposed differential pulse polarographic method. The effects of diverse metal ions and other commonly used pesticides on the determination of alanycarb were also investigated.     

The Fauna of Different Drinking Water Sources of Bhagalpur,India

In three drinking water sources i. e. river, well and filter water, there were detected 50 taxa of animals: 10 amoebae and 2 ciliates (protozoa), 24 rotifera, 5 cladocerans, and 9 copepods. Chief components of the rotifers population were Brachionus and Keratella, although K. cochlearis is the most common form at all the sites. The presence of Entamoeba histolytica in well water was indicative of faecal contamination which may become a causative agent of amoebiasis in human beings.     

Comparing grain size distribution of sediment and original soil under raindrop detachment and raindrop-induced and flow transport mechanism

The grain size distribution (GSD) of sediment in comparison with the original soil GSD is discussed under different slopes (5, 15 and 25%) and rainfall intensities (30, 60 and 90 mm h^–1 with respective duration of 30, 15 and 10 min) but identical runoff (15 mm). The sediment quantification was carried out by raindrop-induced flow transport (RIFT) or/and transport by flow (FT) using a rainfall simulator and a 6 × 1 m² erosion plot and a silt loam. The results show a high degree of enrichment for size classes of 2–4 and 4–8 μm and a high degree of depletion for size classes of >63 μm under different slopes and rainfall intensities. In addition, the results show that the experimental enrichment ratio (ER) for particle size <16 μm under different slopes and rainfall intensities was greater than 1, while the ER for particle size >32 μm was less than 1.     

不同碳磷比的斜生栅藻(Scenedesmus obliquus)对同型溞(Daphnia similis)生长和繁殖的影响

食物质量会影响浮游动物的生长和繁殖,表征食物质量的指标包括食物大小、元素比、生物化学组成和毒性有无等.用斜生栅藻(Scenedesmus obliquus)的碳磷比(C/P)表征食物质量,分析不同C/P斜生栅藻对同型溞(Daphnia similis)生长和繁殖的影响.研究中4个处理组斜生栅藻C/P分别为881.8、512.3、124.3和42.4.培养9 d后不同处理组同型溞的生长速率分别为0.15、0.27、0.47和0.44 d-1.C/P比为881.8的处理组同型溞在整个培养过程中没有产仔,其余3个处理组的同型溞第1成龄期的产仔量分别为1.2±1.3、9.8±2.3和9.5±2.5 ind./female.结果表明,与斜生栅藻C/P为124.3处理条件相比,斜生栅藻C/P过高(512.3和881.8)及C/P过低(42.4)处理条件下同型溞生长速率和产仔量均降低.本研究表明食物C/P的高低会影响溞的生长和繁殖,从而影响其在湖泊中的生存.     

Crustacean zooplankton distribution patterns and their biomass as related to trophic indicators of 29 shallow subtropical lakes

A comparative limnological study was carried out to present a snapshot of crustacean zooplankton communities and their relations to environmental factors to test whether there is a consistent relationship between crustacean biomass and trophic indicators among lake groups with similar trophic conditions. The study lakes showed a wide range of trophic status, with total phosphorus (TP) ranging from 0.008 to 1.448 mg L⁻¹, and chlorophyll a from 0.7 to 146.1 μg L⁻¹, respectively. About 38 species of Crustacea were found, of which Cladocera were represented by 25 taxa (20 genera), and Copepoda by 13 taxa (11 genera). The most common and dominant species were Bosmina coregoni, Moina micrura, Diaphanosoma brachyurum, Cyclops vicinus, Thermocyclops taihokuensis, Mesocyclops notius and Sinocalanus dorrii. Daphnia was rare in abundance. Canonical correspondence analysis showed that except for four species (D. hyalina, S. dorrii, C. vicinus and M. micrura), almost all the dominant species had the same preference for environmental factors. Temperature, predatory cyclopoids and planktivorous fishes seem to be the key factors determining species distribution. TP was a relatively better trophic indicator than chlorophyll a to predict crustacean biomass. Within the three groups of lakes, however, there was no consistent relationship between crustacean biomass and trophic indicators. The possible reason might be that top-down and bottom-up control on crustaceans vary with lake trophic state. The lack of significant negative correlation between crustacean biomass and chlorophyll a suggests that there was little control of phytoplankton biomass by macrozooplankton in these shallow subtropical lakes.