Evaluation of Microcystis as food for zooplankton in a eutrophic lake

Four experiments were conducted to evaluate Microcystis as food for zooplankton in Lake Kasumigaura, and the following results were obtained. (1) Moina micrura (Cladocera) showed little growth and no reproduction when the animal was reared with Microcystis cultured in the laboratory. The animal did not grow nor reproduce well when Chlorella was mixed with Microcystis as food. (2) Moina micrura assimilated Microcystis much less than Chlorella when the animal fed on single species of Microcystis or a mixture with Chlorella. (3) Microcystis collected from Lake Kasumigaura could not be utilized by Moina micrura even though the colonies were broken up into edible sizes. However, the alga turned into utilizable food when it was decomposed. (4) No inhibitors of Moina micrura population growth could be found in the non-filtered water of Lake Kasumigaura where Microcystis was blooming heavily. Decomposed Microcystis seemed to be utilized by zooplankton as an important food source in Lake Kasumigaura.     

Aerobic heterotrophic bacteria and petroleum-utilizing bacteria from cow dung and poultry manure

In this study, enumeration and identification of total aerobic heterotrophic bacteria and petroleum-utilizing bacteria as well as the degradative potential of petroleum-utilizing bacterial isolates were carried out. The average counts of total aerobic heterotrophic bacteria in cow dung and poultry manure were 74.25 × 10⁵ c.f.u. g⁻¹ and 138.75 × 10⁵ c.f.u. g⁻¹ respectively. Acinetobacter sp, Bacillus sp, Pseudomonas sp, and Serratia spp. occurred as aerobic heterotrophs in both cow dung and poultry manure. However, Alcaligenes spp. occurred only in cow dung while, Flavobacterium sp, Klebsiella sp, Micrococcus sp, and Nocardia spp. occurred only in poultry manure as aerobic heterotrophs. The average counts of petroleum-utilizing bacteria in cow dung and poultry manure were 9.25 × 10⁵ c.f.u. g⁻¹ and 17.25 × 10⁵ c.f.u. g⁻¹ respectively. Pseudomonas spp. occurred as petroleum utilizer in both cow dung and poultry manure. However, Bacillus spp. occurred only in cow dung while Acinetobacter spp. and Micrococcus spp. occurred only in poultry manure as petroleum utilizers. Relative abundance of petroleum utilizers in total aerobic heterotrophs ranged from 6.38% to 20.00% for cow dung and from 9.38% to 17.29% for poultry manure. Introduction of pure cultures of petroleum-utilizing bacteria from cow dung and poultry manure into sterile oil-polluted soil revealed oil degradation in one week period.     

Fish-zooplankton interactions and their effects on water quality of a tropical Brazilian reservoir

The influence of zooplanktivorous fishes on the plankton community and water quality of Americana Reservoir, Brazil was studied experimentally in 4 floating enclosures during the dry seasons (July–September) of 1982 and 1983. Two enclosures were stocked with adult fish (Astyanax bimaculatus in 1982;A. fasciatus in 1983) at near maximal densities measured in the reservoir upper surface waters (35 m^–2) and two were fish-free during each experiment lasting about one month. Marked differences were evident between the fish and fish-free enclosures after a 2–3 week period in each experiment, particularly with respect to water transparency, phytoplankton biomass, and zooplankton abundance as well as species and size composition. By the end of each experiment water transparencies were lower and phytoplankton biomass higher in the fish enclosures compared to those without fish. Also at that time Rotifera were the prominent zooplankters in the fish enclosures and Cladocera in the fish-free ones. Larger or more conspicuous species of Cladocera asDaphnia gessneri, D. ambigua, andMoina micrura were present in the fish-free enclosures but not in the fish enclosures. The interactions between fish predation, zooplankton grazing, phytoplankton biomass and water quality conditions are discussed in relation to eutrophication of a tropical aquatic ecosystem.     

Potential of Allolobophora parva (Oligochaeta) in vermicomposting

The aim of this study was to assess the potential of Allolobophora parva Eisen as a candidate for vermicomposting practices. Five organic waste mixtures: cow dung (CD), biogas plant slurry (BGS), cow dung + vegetable waste (CD + VW), BGS + VW and VW + Soil were vermicomposted using A. parva. Vermicomposting showed a decrease in pH, organic C and C:N ratio, but increase total N, available P and exchangeable K at the end. C:N ratio of end material (vermicompost) was within the agronomic acceptable limit (<20). The high level of NPK in worm-processed material indicates the candidature of this species for waste management operations. The earthworm also showed an excellent growth in different wastes. Results thus indicate that A. parva appeared a potential tool for conversion of organic wastes into value added products for sustainable land restoration practices.     

Crustacean assemblage and environmental characteristics of a man-made solar saltwork in southern France,with emphasis on anostracan (Branchiopoda) population dynamics

Physical and chemical variables, anostracan populations (Artemia parthenogenetica and Branchinella spinosa) and other biota were studied during 1996–1997 in a Camargue saltern (max. depth 1 m). The taxonomic composition and density of macroinvertebrates were investigated twice monthly, based on benthic substrate and water column samples. Fauna was composed of three groups in terms of numerical importance. The benthic macroinvertebrates were represented only by nematodes (< 50 ind. m^–2 to > 500 ind. m^–2 in November–December and May respectively). The zooplankton was dominated by crustaceans, one cladoceran, Moina salina (ranging from 670 to 2350 ind. m^–2 in spring), two anostracans, Artemia parthenogenetica (< 50 ind. m^–2 in autumn), and Branchinella spinosa (max. 190 ind. m^–2 in December to absent in April), and two copepods, Cletocamptus retrogressus (max. density 2000 ind. m^–2 in November), and Eurytemora velox (max. density 650 ind. m^–2 in February–March). Insects (Chironomidae, Culicidae) were rare, with mean densities < 1 ind. m^–2. The phenology of each crustacean population is discussed in relation to physical and chemical water variables. Salinity appeared to be of greatest importance regulating the population abundance.     

Experimental study of trophic cascade effect of silver carp (Hypophthalmichthys molitrixon) in a subtropical lake, Lake Donghu: on plankton community and underlying mechanisms of changes of crustacean community

An enclosure experiment was carried out to test trophic cascade effect of filter-feeding fish on the ecosystem: growth of crustacean zooplankton, and possible mechanism of changes of crustacean community structure. Four fish biomass levels were set as follows: 0, 116, 176 and 316 g m^-2, and lake water (containing ca. 190 g m^-2 of filter-feeding fishes) was comparatively monitored. Nutrient levels were high in all treatments during the experiment. Lowest algal biomass were measured in fishless treatment. Algal biomass decreased during days 21–56 as a function of fish biomass in treatments of low (LF), medium (MF) and high (HF) fish biomass. Crustaceans biomass decreased with increasing fish biomass. Small-bodied cladocerans, Moina micrura, Diaphanosoma brachyurum and Scapholeberis kingii survived when fish biomass was high whilst, large-bodied cladocerans Daphnia spp. and the cyclopoids Theromcyclops taihokuensis, T. brevifuratus, Mescyclops notius and Cyclops vicinus were abundant only in NF enclosures. Evasive calanoid Sinodiaptomus sarsi was significantly enhanced in LF, but decreased significantly with further increase of fish biomass. Demographic data indicated that M. micrura was well developed in all treatments. Our study indicates that algal biomass might be controlled by silver carp biomass in eutrophic environment. Changes of crustacean community are probably affected by the age of the first generation of species. Species with short generation time were dominant and species with long generation time survived less with high fish biomass. Evasive calanoids hardly developed in treatments with high fish biomass because of the (bottle neck) effect of nauplii. Species abundance were positively related to fish predation avoidance. Other than direct predation, zooplankton might also be suppressed by filter-feeding fish via competition.     

The effect of different algal densities of Scenedesmus acuminatus on the population growth of Moina micrura Kurz (Crustacea: Anomopoda,Moinidae)

Six densities (0.5 × 10⁶, 1.0 × 10⁶, 1.5 × 10⁶, 2.0 × 10⁶, 3.0 × 10⁶, and 4.0 × 10⁶ cells ml^–1) of the micro-alga Scenedesmus acuminatus, were fed to the cladoceran, Moina micrura, in 40-litre glass aquaria. Moina population increased with increasing cell densities of Scenedesmus only up to treatment 3 (i.e. 1.5 × 10⁶ cells ml^–1) where a peak population of 11303 individuals per litre was obtained. Moinapopulation growth was inhibited at higher algal densities. The percentage of egg-bearing females and the number of eggs per egg-bearing females, followed a similar pattern. Comparatively, the peak production density of approximately 11000 Moina per litre, is interesting from a mass production point of view and indicates that S. acuminatus is a satisfactory micro-alga food for M. micrura.     

Field experiments on mitigation of harmful algal blooms using a Sophorolipid—Yellow clay mixture and effects on marine plankton

This study examined a new method of mitigating harmful algal blooms (HABs) by combining biosurfactant sophorolipid and yellow clay. To investigate the effects and practicability of this HAB mitigation method, field experiments were carried out during a Cochlodinium bloom near Miruk Island, South Korea, in August 2002. Field experiments examined the effects of sophorolipid and yellow clay on Cochlodinium bloom mitigation and on marine plankton such as bacteriaplankton, heterotrophic protists, and zooplankton. A mixture of 5 mg l⁻¹ sophorolipid and 1 g l⁻¹ yellow clay was sprayed directly on the sea surface and its effect was compared with that of 10 g l⁻¹ of yellow clay applied under similar conditions. The sophorolipid–yellow clay mixture more efficiently mitigated the Cochlodinium bloom (95% removal efficiency after 30 min) than yellow clay alone (79% after 30 min). Further, no variation in bacterial abundance occurred 30 min after spraying the sophorolipid–yellow clay mixture. After 30 min, heterotrophic protist abundance at the surface decreased 21 and 41%, respectively, following the sophorolipid–yellow clay mixture and yellow clay treatments. Zooplankton decreased by 38% 15 min after spraying the mixture and 67% 30 min after spraying the yellow clay. These results indicate that the mixture of sophorolipid and yellow clay had a less adverse effect on bacteriaplankton, heterotrophic protists, and zooplankton than the yellow clay, suggesting that the sophorolipid–yellow clay mixture can mitigate HABs efficiently with fewer negative effects on the pelagic ecosystem.     

Studies on functional response and prey selection using zooplankton in the anostracan Chirocephalus diaphanus Prevost, 1803

Freshwater cladocerans and rotifers were used as prey to study functional response and prey selection by adult females of Chirocephalus diaphanus under laboratory conditions. For functional response studies, we offered three rotifer species (Brachionus calyciflorus, B. patulus and Euchlanis dilatata) and three cladoceran species (Alona rectangula, Ceriodaphnia dubia and Moina macrocopa) at various densities ranging from 0.5 to 16 ind. ml^–1. We found increased zooplankton consumption with increasing prey density but beyond 4 ind ml^–1 cladocerans and 8 ind. ml^–1 rotifers, the number of animals eaten plateaued. In general, C. diaphanus consumed fewer large prey (cladocerans) and many more smaller zooplankton (rotifers). For prey selection experiments, we used B. calyciflrous, B. patulus, C. dubia and M. macrocopa, offered at the ratio of two rotifers: one cladoceran and at three prey densities (total zooplankton numbers: 3, 6 and 12 ind. ml^–1). Prey selectivity patterns followed the functional response trends. In general, regardless of prey types, with an increase in the available zooplankton, there was an increase in the number of prey consumed. At any given prey density, C. diaphanus consumed higher numbers of rotifers than cladocerans. Among the prey offered, B. patulus and M. macrocopa were positively selected. Results are discussed in light of possible control of zooplankton by anostracans in temporary ponds.     

Zooplankton as a compound mineralising and synthesizing system: phosphorus excretion

Data on phosphate excretion rates of zooplankton are based on measurements using the pelagic crustacean zooplankton of Lake Vechten and laboratory-cultured Daphnia galeata. In case of Daphnia sp we measured the effects of feeding on P-rich algae and P-poor algae (Scenedesmus) as food on the P-excretion rates at 20°C. The excretion rates of the natural zooplankton community, irrespective of the influence of the factors mentioned, varied by an order of magnitude: 0.025–0.275µg PO₄-Pmg^–1C in zooplankton (C _zp ) h^–1. The temperature accounted for about half the observed variation in excretion rates. The mean excretion rates in the lake, computed for 20°C, varied between 0.141 and 0.260 µg Pmg^–1C _zp h^–1. Based on data of zooplankton biomass in the lake the P-regeneration rates by zooplankton covered between 22 and 239% of the P-demand of phytoplankton during the different months of the study period.In D. galeata, whereas the C/P ratios of the Scenedesmus used as food differed by a factor 5 in the experiments, the excretion rates differed by factor 3 only. Despite the higher P-excretion rates (0.258± 0.022 µg PO₄-P mg^–1 C h^–1) of the daphnids fed with P-rich food than those fed with P-poor food (0.105 ± 0.047 µg PO₄-P mg^–1 C h^p–1), both the categories of the animals were apparently conserving P. A survey of the literature on zooplankton excretion shows that in Daphnia the excretion rates vary by a factor 30, irrespective of the species and size of animals and method of estimation and temperature used.About two-thirds of this variation can be explained by size and temperature. A major problem of comparability of studies on P-regeneration by zooplankton relates to the existing techniques of P determination, which necessitates concentrating the animals several times above the in situ concentration (crowding) and prolonged experimental duration (starving), both of which manifest in marked changes that probably lead to underestimation of the real rates.     

Natural diet of herbivorous zooplankton in Lake Xolotlán (Managua)

The natural diet of herbivorous zooplankton was analyzed for a better understanding of the trophic relationships in Lake Xolotlán (Managua). Gut content of the most common zooplankton species (Arctodiaptomus dorsalis, Moina micrura andDiaphanosoma fluviatile) were analyzed. The quality and the relative abundance of ingested algae was studied. The most consumed algae during the dry season (February) wereCyclotella, Oocystis andLyngbya, and during the rainy season (November)Cyclotella, Oocystis andChroococcus. The kind of food ingested byA. dorsalis andM. micrura was similar in both periods. There was no similarity with the diet ofD. fluviatile. During the dry season, when algal biomass in the lake was high,A. dorsalis andM. micrura ingested a higher proportion of diatoms. During the rainy season, when food was scarce, the diet was more diverse and bluegreen algae (Chroococcus) were ingested in a larger proportion.Diaphanosoma fluviatile ingested predominantly tiny particles (bacteria and detritus) and algal food consisted mainly of green algae (Oocystis) and probably (not studied) nanoplanktonic algae. The results were consistent with those obtained in other lakes, indicating the importance of diatoms and green algae for zooplankton nutrition.     

Biology of Moina mongolica (Moinidae,Cladocera) and perspective as live food for marine fish larvae: review

Moina mongolica, 1.0-1.4 mm long and 0.8 mm wide, is an Old World euryhaline species. This paper reviewed the recent advances on its autecology, reproductive biology, feeding ecology and perspective as live food for marine fish larviculture. Salinity tolerance of this species ranges from 0.4–1.4 to 65.2–75.4. Within 2–50 salinity, Moina mongolica can complete its life cycle through parthenogenesis. The optimum temperature is between 25 °C and 28 °C, while it tolerates high temperature between 34.4 °C and 36.0 °C and lower temperature between 3.2 °C and 5.4 °C. The non-toxic level of unionised ammonia (24 h LC₅₀) for M. mongolica is <2.6 mg NH₃–N l^–1. Juvenile individuals filter 2.37 ml d^–1 and feed 9.45×10⁶ algal cells d^–1, while mature individuals filter 9.45 ml d^–1 and consume 4.94×10⁶ algal cells d^–1. At 28 °C, M. mongolica reaches sex maturity in 4 d and gives birth once a day afterward; females carry 7.3 eggs brood^–1 and spawn 2.8 times during their lifetime. A variety of food can be used for M. mongolica culture including unicellular algae, yeast and manure, but the best feeding regime is the combination of Nannochloropsis oculata and horse manure. Moina mongolica reproduces parthenogenetically during most lifetime, but resting eggs can be induced at temperature (16 °C) combined with food density at 2000–5000 N. oculata ml^–1. The tolerance to low dissolved oxygen (0.14–0.93 mg l^–1) and high ammonia makes it suitable for mass production. Biochemical analyses showed that the content of eicospantanoic acid (20:53) in M. mongolica accounts for 12.7% of total fatty acids, which is higher than other live food such as Artemia nauplii and rotifers. This cladoceran has the characteristics of wide salinity adaptation, rapid reproduction and ease of mass culture. The review highlights its potential as live food for marine fish larvae.     

Vermistabilization of textile mill sludge spiked with poultry droppings by an epigeic earthworm Eisenia foetida

Investigations were made to explore the potential of an epigeic earthworm Eisenia foetida to transform textile mill sludge spiked with poultry droppings in to value added product, i.e., vermicompost. The growth and reproduction of E. foetida was monitored in a range of different feed mixtures for 77 days in the laboratory under controlled experimental conditions. The maximum growth was recorded in 100% cow dung (CD). Replacement of poultry droppings by cow dung in feed mixtures and vice versa had little or no effect on worm growth rate and reproduction potential. Worms grew and reproduced favourably in 70% poultry droppings (PD)+30% solid textile mill sludge (STMS) and 60% PD+40% STMS feed mixtures. Greater percentage of STMS in the feed mixture significantly affected the biomass gain and cocoon production. Net weight gain by earthworms in 100% CD was 2.9-18.2 fold higher than different STMS containing feed mixtures. The mean number of cocoon production was between 23.4+/-4.65 (in 100% CD) and 3.6+/-1.04 (in 50% PD+50% STMS) cocoons earthworm(-1) for different feed mixtures tested. Vermicomposting resulted in significant reduction in C:N ratio and increase in nitrogen and phosphorus contents. Total potassium, total calcium and heavy metals (Fe, Zn, Pb and Cd) contents were lower in the final product than initial feed mixtures. Our trials demonstrated vermicomposting as an alternate technology for the recycling and environmentally safe disposal/management of textile mill sludge using an epigeic earthworm E. foetida if mixed with poultry droppings.     

Effect of Aeolosoma sp. (Aphanoneura: Aeolosomatidae) on the Population Dynamics of Selected Cladoceran Species

Although oligochaete worms naturally coexist with cladocerans in many shallow freshwater ponds and lakes, their influence on the latter is not well established. In this work we studied the effect of Aeolosoma sp. on the population growth of Alona rectangula, Ceriodaphnia dubia, Daphnia pulex, Macrothrix triserialis and Moina macrocopa. Population growth studies were conducted at one algal food density (1 × 10⁶cells ml^–1 of Chlorella vulgaris). The experimental design was similar for all five cladoceran species, where we used 100 ml capacity transparent jars containing 50 ml of EPA medium with the desired algal density and three replicates for each treatment. The test medium was changed daily and fresh algal food was added. The initial density of each of the cladoceran species in the population growth studies was 0.4 ind ml^–1 while that of the worms 1.0 ind ml^–1. Following inoculation, we estimated daily the number of cladocerans and the worms for duration of 21 days. Regardless of the presence of worms, Moina macrocopa and Macrothrix triserialis showed rapid population growth while A. rectangula took more than 2 weeks to reach peak abundances. With the exception of M. triserialis, all the other our cladoceran species declined in the presence of Aeolosoma sp. The lowest peak population density (about 1 ind ml^–1) was observed for M. triserialisin controls. The remaining species had peak densities of about 3–5 ind ml^–1. The rates of population increase per day varied from 0.03 to 0.19 depending on the cladoceran taxa and the treatment. In general we found that pelagic taxa were more adversely affected by the presence of the worms than were the littoral cladocerans.     

Abundance,Species Composition and Spatial Distribution of Planktonic Rotifers and Crustaceans in Lake Ziway (Rift Valley,Ethiopia)

Species composition, abundance, and spatial distribution of rotifer and crustacean zooplankton were studied in Lake Ziway from late April to early July 2004. A total of 49 rotifer species was recorded, with Anuraeopsis fissa, Brachionus angularis, Filinia novaezealandiae, and Trichocerca ruttneri being numerically dominant. Variation in abundance was extremely high, ranging from 2 to 1000+ individuals per litre. There was no significant difference in the distribution of rotifer species between inshore and offshore regions. Crustacean species richness was low, with only five cladoceran and three copepod species occurring in the open water. Moina micrura and Diaphanosoma excisum dominated the cladoceran community, whereas Thermocyclops decipiens was the dominant copepod. Although numerically dominant (75%), rotifers accounted for less than 30% of mean total zooplankton biomass. Peak abundance of crustaceans was observed in May and June, following the onset of the rainy season and increased phytoplankton production. Variation in the spatial distribution of crustacean species was neither observed horizontally between inshore and offshore areas nor vertically in the highly turbid and wind exposed deeper part of the lake. On the other hand, Moina micrura varied significantly in size between inshore and offshore areas. Adult M. micrura dominated offshore, whereas juveniles were more abundant inshore, suggesting a predominantly littoral selective predation on large and adult crustaceans by fish. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Long- and short-term effects of crop residues on aluminum toxicity,phosphorus availability and growth of pearl millet in an acid sandy soil

Pasture swards containing perennial ryegrass (Lolium perenne L.) alone or with one of five different white clover (Trifolium repens L.) cultivars were examined for production and transfer of fixed nitrogen (N) to grass under dairy cow grazing. Grass-only swards produced 21% less than mixed clover-grass swards during the second year after sowing. Production from grass-only plots under a mowing and clipping removal regime was 44% less than from grass-only plots under grazing. Much of this difference could be attributed to N transfer. In swards without clover, the ryegrass component also decreased in favour of other grasses.The average amount of fixed N in herbage from all clover cultivars was 269 kg N ha^–1 yr^–1. Above-ground transfer of fixed N to grasses (via cow excreta) was estimated at 60 kg N ha^–1 yr^–1. Below-ground transfer of fixed N to grasses was estimated at 70 kg N ha^–1 yr^–1 by ¹⁵N dilution and was similar for all clover cultivars. Thus, about 50% of grass N was met by transfer of fixed N from white clover during the measurement year. Short-term measurements using a ¹⁵N foliar-labelling method indicated that below-ground N transfer was largest during dry summer conditions.     

Comparison of the effects of two different handling methods on the subsequent behaviour of Anglo-Arabian foals toward humans and handling

Tactile contact is often used to improve the human–foal relationship, in particular during sensitive periods such as weaning. However, the method used to provide the contact (forced or unforced) may affect subsequent reactions to humans. The aim of our study was to compare the effect of forced and unforced handling at weaning on horses’ behaviour towards humans and handling.A total of 23 Anglo-Arabian foals received individual human contact at weaning. Constrained-handled foals (forced human contact; FC, n = 8) were stroked while being restrained (i.e., held by the halter without being led) so that human contact was forced. Unconstrained-handled foals (unforced human contact; UC, n = 7) were stroked without any restraint and could thus avoid contact if they so wanted. Each individual was handled 5 min twice a day for 14 consecutive days. Control foals were not handled (no contact; NC, n = 8). Foals’ reactions towards a human (e.g. proximity and contact seeking), and their manageability (fitting of a halter) were then assessed. The animals from the different treatments were then mixed and tested again 4 months later. Non-parametric Mann–Whitney U-tests were used to compare experimental groups.Only forced human contact reduced fear reactions toward humans (e.g. shorter latency to approach a passive human, P < 0.01; shorter latency to touch the foal, P < 0.05) in the short-term (immediately after the handling sessions) and increased foals’ manageability in a familiar environment (shorter latency to be placed a halter on and less defences displayed, P < 0.05). It had no effect in an unfamiliar environment. These effects did not last longer than 4 months.Forced human contact thus appears to be more efficient in improving human–horse relationships and subsequent handling than unforced human contact. However, the lack of effect on reactivity towards humans in an unfamiliar environment, and the lack of long-term effects suggest that this method needs to be improved to be more effective. Some of our results suggest that horses could perceive human contact (i.e., stroking) as positive, however further studies are needed to confirm this hypothesis.     

Factors influencing the phytoplankton steady state assemblages in a drinking-water reservoir (Ömerli reservoir, Istanbul)

In situ growth of heterotrophic nanoflagellates (HNF) in Lake Donghu, a eutrophic shallow lake in mainland China, was studied from January 1999 to March 2000 using a modified Weisse protocol. The study results indicated that the growth rates of HNF showed pronounced seasonal variation (–0.37–1.25 d^–1), reaching the maximum during spring to early summer. When the water temperature was higher than 25.5°C, HNF growth was inversely proportional to water temperature. There was an effect by bacterial abundance and autotrophic picoplankton on HNF growth that depended on location. HNF biomass was the highest in late spring, and the HNF production ranged from –2.25 to 35.45 mg l^–1 d^–1 with mean of 3.17 mg l^–1d^–1. When considered in the context of biomass and production data for zooplankton in Lake Donghu, it was evident that HNF contributed significantly to the total zooplankton production in Lake Donghu. These in situ studies indicate that temperature and food supply are the major determinants of HNF abundance and productivity.     

A continuous flow-chamber to study prey preferences of Golden Perch (Macquaria ambigua Richardson) larvae

This paper describes the use of a continuous-flow chamber for maintaining small and fragile fish larvae and their prey in a healthy state and under suitable conditions over a 24 h period for studies on prey preferences. Survival of golden perch (Macquaria ambigua Richardson) larvae and prey was high and ten replicates on food preferences were carried out simultaneously. The larvae preferred small Daphnia carinata King (780–860 m) over larger ones (2000–3120 and 3680–5440 m) and preferred cladocerans (Daphnia carinata King and Moina micrura Kurz) over calanoids (Boeckella de Guerne & Richard). The chamber is also suitable for studies on feeding behaviour and diet requirements of fish larvae.