Brachionus Plicatilis Research Articles

Detrimental impacts of the dinoflagellate Karenia mikimotoi in Fujian coastal waters on typical marine organisms

Blooms of the toxic dinoflagellate Karenia mikimotoi (K. mikimotoi) have occurred frequently in the East China Sea in recent decades and were responsible for massive mortalities of abalones in Fujian coastal areas in 2012, however, little is known about the effects of these blooms on other marine organisms. In this study, the toxic effects and the possible mechanisms of toxicity of K. mikimotoi from Fujian coastal waters on typical marine organisms at different trophic levels, including zooplankton (Brachionus plicatilis, Artemia salina, Calanus sinicus, and Neomysis awatschensis) and aquaculture species (Penaeus vannamei and Scophthalmus maximus) were investigated. At a bloom density of 3×104cells/mL, the Fujian strain of K. mikimotoi significantly affected the tested organisms, which had mortality rates at 96h of 100, 23, 20, 97, 33, and 53%, respectively. Moreover, the intact cell suspension was toxic to all tested species, whereas cell-free culture and the ruptured cell suspension had no significant effects on the tested organisms. Possible mechanisms for this toxic effect, including reactive oxygen species (ROS) and hemolytic toxins, were evaluated. For K. mikimotoi, 0.014±0.004 OD/(104 cells) superoxide (O2−) and 3.00±0.00nmol/(104 cells) hydrogen peroxide (H2O2) were measured, but hydrogen peroxide did not affect rotifers at that concentration, and rotifers were not protected from the lethal effects of K. mikimotoi when the enzymes superoxide dismutase and catalase were added to counteract the ROS. The lipophilic extract of K. mikimotoi had a hemolytic effect on rabbit erythrocytes but exhibited no significant toxicity. These results suggest that this strain of K. mikimotoi can have detrimental effects on several typical marine organisms and that its toxicity may be associated with intact cells but is not related to ROS or hemolytic toxins.

Comparison of low temperature adaptation ability in three native and two hybrid strains of the rotifer Brachionus plicatilis species complex

The low temperature adaptation ability of five selected strains of the Brachionus plicatilis species complex, i.e., three native strains [ Japanese (NH1L), Australian, German] and two hybrid strains [♀NH1L and ♂Australian (N × A) and ♀NH1L and ♂German (N × G),was investigated in terms of life history traits, reproductive characteristics, and mobility under different thermal conditions (12 and 25 °C). The life history traits of these five strains included a longer lifespan, reproduction period and generation times at 12 °C than at 25 °C, combined with reduced lifetime egg and offspring production. At 12 °C, the intrinsic rate of natural increase was higher in NH1L and N × A strains. Reproductive characteristics determined at 12 °C by batch culture showed active population growth for NH1L and N × G strains, while no resting egg production was observed in all of the strains tested. The ratio of swimming rotifers at 12 °C was monitored every hour for 6 h (short term) and every day for 10 days (long term). In the short-term study there was a 81% ratio of swimming rotifers of the NH1L strain, while other strains exhibited low swimming ratios ( 75% swimming ratio from the initial day of the study. These results suggest that outcrossing of rotifer strains is useful to obtain live food resources for the larviculture of cold water fish.

Contaminating microzooplankton in outdoor microalgal mass culture systems: An ecological viewpoint

Ecological studies of contaminating microzooplankton in microalgal mass culture are important for large-scale cultivation risk management and remediation strategies, with the ultimate goal to ensure the sustainable high-yield production of microalgal biomass. Using multivariate statistical techniques, the characteristics and relationships with environmental variables of contaminating microzooplankton species were studied in commercial production of Spirulina platensis in outdoor raceway ponds in East and North China. A total of 16 microzooplankton species were identified from 64 large-scale raceway ponds, including three rotifers, two amoebae, and eleven ciliates. The relative abundance of individual microzooplankton species was in an order, from high to low, of ciliates>rotifers>amoebae. The ciliate Cyclidium marinum was the most frequently occurring species, mainly due to its wide tolerance of environmental conditions; and the rotifer Brachionus plicatilis was the key contaminating species, responsible for major loss of biomass productivity owing to its high level of occurrence and feed characteristics as an algivore. The high salinity habitats of the culture systems in North China featured the ciliate Frontonia didieri as an algophagous indicator species, while in East China the amoebae Nuclearia simplex and Euplaesiobystra hypersalinica were indicators for seed ponds and production ponds, respectively, attributed to the specific physicochemical conditions of the local environments. Fine tuning of salinity and pH away even temporarily from the optima of these contaminating microzooplankton species may be an easy and effective protocol for contamination control. Our investigation indicates the importance of comprehensively considering the environmental optima, tolerances and feed characteristics of contaminating species, together with continuous monitoring and ecological data analysis, for efficient management strategies geared towards the mitigation of biological contamination in microalgal mass culture.

A study of oxidative stress induced by two polybrominated diphenyl ethers in the rotifer Brachionus plicatilis

Polybrominated diphenyl ethers (PBDEs) are widely dispersed persistent organic pollutants in the marine ecosystem. However, their toxic mechanisms in marine organisms, especially invertebrates, remain poorly understood. Two common congeners of PBDEs, tetrabrominated diphenyl ether-47 (BDE-47) and decabrominated diphenyl ether-209 (BDE-209), were investigated. Their toxic mechanisms, with a focus on oxidative stress, were examined in rotifer Brachionus plicatilis. Overproduction of reactive oxygen species (ROS) was induced by two PBDEs. The expression of superoxide dismutase (SOD) mRNA was increased, suggesting SOD play a main role in ROS-scavenging. The intercellular concentrations of calcium ([Ca2+]in) and the expression of calmodulin (CaM) mRNA were increased. This indicates the calcium ion (Ca2+) signaling channel is involved in PBDEs stress. Further analysis showed that the reproductive system might be the target site for toxicity of PBDEs. Moreover, high value of detection indexes in BDE-47 experimental groups suggested BDE-47 might cause higher oxidative damage than BDE-209 in rotifers.

Effect of microalgal diets on filtration and ingestion rates of the rotifer Brachionus plicatilis

Effect of marine microalgal diet on filtration and ingestion rates of Brachionus plicatilis was studied. Marine microalgae viz., Nannochloropsis oculata, Isochrysis galbana, Chaetoceros calcitrans and a combination of N. oculata and I. galbana (Nanno+Iso) at different cell concentrations were selected for the experiment and triplicates were maintained for each feed. Significant difference (p<0.05) was observed in the filtration and ingestion rates of B. plicatilis, between the treatments. Peak filtration rate of 12.2x10-5 cells ml-1 ind-1 min-1 was recorded in B. plicatilis fed with Nanno+Iso, followed by I. galbana. Ingestion rate was found to be significantly high (p<0.05) for those fed with C. calcitrans, followed by Nanno+Iso. Filtration rate was significantly high (p<0.05) in rotifers stocked at an initial density of 50 nos. ml-1 fed with Nanno+Iso. The results indicated that a combination of Nanno and Iso is the best suitable microalgal diet for rotifer with peak filtration (12.2x10-5cells ml-1 ind-1 min-1) and ingestion (5.4x10-3 cells ml-1 ind-1 min-1) rates during the first 60 min.

Optimal Enrichment Temperature, Time and Materials for L-type Rotifer (Brachionus plicatilis) Cultured at a Low Temperature

Optimal Enrichment Temperature, Time and Materials for L-type Rotifer (Brachionus plicatilis) Cultured at a Low Temperature

Technical and economic feasibility of adding pure oxygen for rotifer production (Brachionus plicatilis) spotted snapper (Lutjanus guttatus) larvae feeding

A study to technically and economically evaluate the addition of pure oxygen in a culture of rotifers for feeding marine fish in the Pacific Marine Park, Puntarenas, Costa Rica was performed. The results showed no significant differences (ANOVA P> 0.05) between the cultivation with addition of oxygen treatment and control, regarding the instantaneous growth rate, crop yield, doubling time, rotifers length and maximum densities reached. Concerning the economic analysis, control culture was 53% less expensive compared to the addition of oxygen system.

Intracellular haemolytic agents of Heterocapsa circularisquama exhibit toxic effects on H. circularisquama cells themselves and suppress both cell-mediated haemolytic activity and toxicity to rotifers (Brachionus plicatilis)

A harmful dinoflagellate, Heterocapsa circularisquama, is highly toxic to shellfish and the zooplankton rotifer Brachionus plicatilis. A previous study found that H. circularisquama has both light-dependent and -independent haemolytic agents, which might be responsible for its toxicity. Detailed analysis of the haemolytic activity of H. circularisquama suggested that light-independent haemolytic activity was mediated mainly through intact cells, whereas light-dependent haemolytic activity was mediated by intracellular agents which can be discharged from ruptured cells. Because H. circularisquama showed similar toxicity to rotifers regardless of the light conditions, and because ultrasonic ruptured H. circularisquama cells showed no significant toxicity to rotifers, it was suggested that live cell-mediated light-independent haemolytic activity is a major factor responsible for the observed toxicity to rotifers. Interestingly, the ultrasonic-ruptured cells of H. circularisquama suppressed their own lethal effect on the rotifers. Analysis of samples of the cell contents (supernatant) and cell fragments (precipitate) prepared from the ruptured H. circularisquama cells indicated that the cell contents contain inhibitors for the light-independent cell-mediated haemolytic activity, toxins affecting H. circularisquama cells themselves, as well as light-dependent haemolytic agents. Ethanol extract prepared from H. circularisquama, which is supposed to contain a porphyrin derivative that displays photosensitising haemolytic activity, showed potent toxicity to Chattonella marina, Chattonella antiqua, and Karenia mikimotoi, as well as to H. circularisquama at the concentration range at which no significant toxicity to rotifers was observed. Analysis on a column of Sephadex LH-20 revealed that light-dependent haemolytic activity and inhibitory activity on cell-mediated light-independent haemolytic activity existed in two separate fractions (f-2 and f-3), suggesting that both activities might be derived from common compounds. Our results suggest that the photosensitising haemolytic toxin discharged from ruptured H. circularisquama cells has a relatively broad spectrum of phytoplankton toxicity, and that physical collapse of H. circularisquama cells can lead not only to the disappearance of its own toxicity, but also to mitigation of the effects of other HABs.

Morphological and taxonomic demarcation of Brachionus asplanchnoidis Charin within the Brachionus plicatilis cryptic species complex (Rotifera, Monogononta)

Three well-defined groups, consisting of 15 species, have recently been ascribed to organisms historically identified as the Brachionus plicatilis species complex. One of these groups, the large clade, is composed of two named species (Brachionus plicatilis s.s. and Brachionus manjavacas) and two species identifiers (B. ‘Nevada’ and B. ‘Austria’). B. ‘Austria’ has been confirmed to be B. asplanchnoidis. As no type specimen exists for this species, and the original taxonomic description is lacking in detail, we give a detailed account of this species using material from Obere Halbjochlacke in Austria where B. ‘Austria’ was first identified genetically. Our analysis of B. asplanchnoidis populations was of global scope, an approach that revealed a great degree of morphological variability. However, combining aspects of both the dorsal and ventral surfaces clearly discriminated B. asplanchnoidis from the rest of the large-type members. This approach may prove useful in taxonomic studies of other cryptic species with relatively few morphological features. We also observed a geographic pattern of genetic divergence within B. asplanchnoidis. Average uncorrected COI divergences for a 554-bp fragment of the COI gene ranged from 3.9% within species to 17.5% between species of the large clade and indicate deep divisions within the cryptic species complex.

Diapausing egg banks, lake size, and genetic diversity in the rotifer Brachionus plicatilis M\xfcller (Rotifera, Monogononta)

Diapausing egg banks are reservoirs of ecological and genetic diversity in continental zooplankton. However, although habitat size has often been used as a proxy for population size, the relationship between diapausing egg bank size and genetic diversity has not been explicitly tested in zooplankton. We estimated the density and size of diapausing egg banks, habitat size and genetic diversity (for mitochondrial and nuclear markers) of 14 populations of the rotifer Brachionus plicatilis in an endorheic basin in the SE Iberian Peninsula. The size of B. plicatilis diapausing egg banks ranged across eight orders of magnitude (from 257 to 4.9 × 1010 eggs). Despite the small geographical scale, populations were strongly structured genetically, but with no evidence of isolation by distance. Habitat size (lake area) was a better predictor of genetic diversity than total diapausing egg bank size, but only for mtDNA haplotype diversity. However, as these results were driven by the strong effect of the largest lake in the database, they should be taken with caution. Our results suggest that large lakes could have a disproportionate effect on genetic diversity and that more work is needed to support the use of habitat size as a proxy of population size in rotifers.

A method linking the toxic effects at community-level with contaminant concentrations

In this study, we developed a method to quantify and link the toxic effects in community-level ecosystems with concentrations of petroleum hydrocarbons. The densities of Platymonas helgolandica var. tsingtaoensis, Isochrysis galbana, and Brachionus plicatilis in single-species tests and customized ecosystems were examined in response to a concentration gradient of petroleum hydrocarbons ranging from 0 to 8.0mgL−1. A three-population ecological model with interspecies competition-grazing relationships was used to characterize population sizes with concentrations of petroleum hydrocarbons. A threshold concentration of the simplified plankton ecosystem of 0.376mgL−1 for petroleum hydrocarbons was calculated from the proposed model, which was higher than the no-effect concentration of 0.056mgL−1 derived from the single-species toxicity tests and the predicted no-effect concentration of 0.076mgL−1 calculated from the species sensitivity distribution. This finding indicates that interspecies competition and grazing reduced the toxic effect of petroleum hydrocarbons at the community level. The sensitivity analysis for model parameters demonstrates that plankton population biomasses are highly sensitive to filtration rates. Antagonism between interspecies interactions and petroleum hydrocarbon toxicity was attributed to the reduced filtration rate and zooplankton grazing pressure. The proposed method is a simple means to address the concern regarding the impacts of ecological interactions on ecological risk assessments of pollutants.

Combined effects of Corexit EC 9500A with secondary abiotic and biotic factors in the rotifer Brachionus plicatilis

We examined lethality and behavioral effects of Corexit EC 9500A (C-9500A) exposure on the model marine zooplankton Brachionus plicatilis singularly and in combination with abiotic and biotic factors. C-9500A exposure at standard husbandry conditions (17.5ppt, 24°C, 200 rotifer*mL−1 density) identified the 24h median lethal concentration, by Probit analysis, to be 107ppm for cultured B. plicatilis. Rotifers surviving exposure to higher concentrations (100 and 150ppm) exhibited a decreased swimming velocity and a reduced net to gross movement ratio. Significant interaction between C-9500A exposure and temperature or salinity was observed. Upper thermal range was reduced and maximal salinity stress was seen as ca. 25ppt. Increased or decreased nutritional availability over the exposure period did not significantly alter mortality of B. plicatilis populations at the concentrations tested. Results from this study may be useful for predicting possible outcomes on marine zooplankton following dispersant application under diverse natural conditions.

Predicting in vivo oxygen consumption rate from ETS activity and bisubstrate enzyme kinetics in cultured marine zooplankton

Oxygen consumption rates (\(R_{{{\text{O}}_{2} }}\)) in the rotifer Brachionus plicatilis and the mysid Leptomysis lingvura during both well-fed conditions and starvation have been modeled using the electron transport system (ETS) activity, bisubstrate kinetics and intracellular concentration of substrates. Furthermore, the influence of the food quality on the respiratory metabolism and metabolite levels has been explored. The highest values of most of the variables both in rotifers and mysids were mainly found on organisms grown on the lipid-rich diet, although no differences were determined between treatments in the response to starvation. Time courses of the \(R_{{{\text{O}}_{2} }}\) and the concentration of pyridine and adenine nucleotides evidenced a sharp decrease during food shortage and a fast recovery with food restoration, whereas the potential respiration (Φ) remained fairly constant. In general, the modeled \(R_{{{\text{O}}_{2} }}\) (\(V_{{{\text{O}}_{2} }}\)) predicted with a high degree of success in the in vivo \(R_{{{\text{O}}_{2} }}\), even though it yielded relatively lower values. Nonetheless, the correlation of the measured \(R_{{{\text{O}}_{2} }}\) with \(V_{{{\text{O}}_{2} }}\) during starvation was much better than with the \(R_{{{\text{O}}_{2} }}\) estimated from ETS measurements and a fixed \(R_{{{\text{O}}_{2} }}\)/Φ ratio. Finally, the observed relationship between the measured \(R_{{{\text{O}}_{2} }}\) and the adenine nucleotide ADP suggests that the contribution of this nucleotide should be included in future applications of this model.

Reproductive Effects of Two Polybrominated Diphenyl Ethers on the Rotifer Brachionus plicatilis.

The effects of two polybrominated diphenyl ethers (PBDEs) on the reproduction of the rotifer Brachionus plicatilis were investigated. Results showed that sexual maturation was promoted by tetra-brominated diphenyl ether-47 (BDE-47) and deca-brominated diphenyl ether-209 (BDE-209), whereas fecundity was inhibited by BDE-47, but promoted by BDE-209. Additionally, both PBDEs affected the expression of two genes, vasa and nanos mRNA, related to rotifer reproduction. This suggests a possible regulatory molecular mechanism at the transcriptional level. Our research extends the current knowledge of the ecotoxicological mechanism induced by PBDEs and provides further essential information for assessing the risks of PBDE contamination in marine ecosystems.

Building a model of ammonium excretion in two species of marine zooplankton based on glutamate dehydrogenase kinetics

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 550:83-99 (2016) - DOI: https://doi.org/10.3354/meps11700 Building a model of ammonium excretion in two species of marine zooplankton based on glutamate dehydrogenase kinetics I. Fernández-Urruzola1,*, N. Osma1, M. Gómez1, S. Montesdeoca-Esponda2, T. T. Packard1 1Marine Ecophysiology Group (EOMAR), Universidad de Las Palmas de Gran Canaria, 35017, Spain 2Environmental Chemical Analysis Group, Universidad de Las Palmas de Gran Canaria, 35017, Spain *Corresponding author: ifernandez@becarios.ulpgc.es ABSTRACT: NH4+ production in 2 species of marine zooplankton was predicted from glutamate dehydrogenase (GDH) activity using general bisubstrate enzyme kinetics during a period of starvation. In addition to starvation, we studied the effect of food quality on both NH4+ excretion rates (RNH4+) and the biochemical composition of zooplankton. The mathematical function used here relies on Michaelis-Menten principles and assumes that the synthesis of NH4+ is controlled mainly by the maximum velocity of GDH, the intracellular pool of substrates and the kinetic constants. This simple model described reasonably well the shifts in RNH4+ that occurred within the time course of starvation in both groups of zooplankton. The calculated RNH4+, however, underestimated the actual RNH4+. Furthermore, we used single substrate kinetics to address the magnitude of either the allosteric inhibition or the activation by purine nucleotides. We found that allosterism is more important in healthy physiological conditions. Overall, the use of first-principles kinetics seems to provide better estimates of RNH4+ than applying a general GDH/RNH4+ ratio on the measurements of GDH; therefore, its application may be of potential interest when studying zooplankton RNH4+ in heterogeneous marine ecosystems. KEY WORDS: Glutamate dehydrogenase · NH4+ excretion · Biochemical kinetics · Brachionus plicatilis · Leptomysis lingvura Full text in pdf format PreviousNextCite this article as: Fernández-Urruzola I, Osma N, Gómez M, Montesdeoca-Esponda S, Packard TT (2016) Building a model of ammonium excretion in two species of marine zooplankton based on glutamate dehydrogenase kinetics. Mar Ecol Prog Ser 550:83-99. https://doi.org/10.3354/meps11700 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 550. Online publication date: May 25, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Adverse effects of the SSRI antidepressant sertraline on early life stages of marine invertebrates

Widespread contamination of coastal environments by emerging compounds includes low concentrations of pharmaceuticals. These pollutants are not currently incorporated in monitoring programs despite their effects on non-target organisms are very little documented. Among the selective serotonin reuptake inhibitor (SSRI) antidepressants, sertraline (SRT) is one of the most prescribed globally. In this work, earlier life stages of Amphibalanus amphitrite, Brachionus plicatilis and Mytilus galloprovincialis were exposed to environmental concentrations of SRT in order to study both sub-lethal and lethal responses in 24/48 h-tests. Low concentrations of SRT altered significantly swimming behavior in A. amphitrite and B. plicatilis giving 48 h-EC50 (μg/L) of 113.88 and 282.23, respectively whereas higher values were observed for mortality and immobilization. EC50 embryotoxicity with M. galloprovincialis was 206.80 μg/L. This work add new data about SRT ecotoxicity on marine invertebrates and confirms the applicability of behavioral endpoints to evaluate the environmental impact of antidepressants in marine organisms.

Fifteen species in one: deciphering the Brachionus plicatilis species complex (Rotifera, Monogononta) through DNA taxonomy

Understanding patterns and processes in biological diversity is a critical task given current and rapid environmental change. Such knowledge is even more essential when the taxa under consideration are important ecological and evolutionary models. One of these cases is the monogonont rotifer cryptic species complex Brachionus plicatilis, which is by far the most extensively studied group of rotifers, is widely used in aquaculture, and is known to host a large amount of unresolved diversity. Here we collate a dataset of previously available and newly generated sequences of COI and ITS1 for 1273 isolates of the B. plicatilis complex and apply three approaches in DNA taxonomy (i.e. ABGD, PTP, and GMYC) to identify and provide support for the existence of 15 species within the complex. We used these results to explore phylogenetic signal in morphometric and ecological traits, and to understand correlation among the traits using phylogenetic comparative models. Our results support niche conservatism for some traits (e.g. body length) and phylogenetic plasticity for others (e.g. genome size).

Remediation of mercury contaminated saltwater with functionalized silica coated magnetite nanoparticles

The study aimed to evaluate the efficiency of dithiocarbamate functionalized silica coated magnetite nanoparticles (NPs) for Hg decontamination of saltwater either contaminated with Hg alone or with As and Cd. For this, the residual levels of Hg in seawater were assessed and Hg-contaminated or Hg+As+Cd-contaminated seawater toxicity to aquatic biota, before and after the sorption process, was compared. The results showed that under highly competitive conditions (water salts, Cd and As), the removal of Hg from seawater, by using these magnetic NPs, for the lowest concentration (50μg/L) was superior to 98% and for the highest concentration (500μg/L) ranged between 61% to 67%. Despite the great affinity of the magnetic NPs for Hg, they were not effective at removing As and Cd from seawater. In relation to the ecotoxicity endpoints after remediation, the mixture with lower Hg concentration exhibited no toxicity to rotifer Brachionus plicatilis and bacteria Vibrio fischeri ; however, the mixture with higher concentration revealed toxicity. In addition, the toxicity of bacteria V. fischeri, rotifer B. plicatilis and algae Phaeodactylum tricornutum, whose responses where inhibited during its exposure to the non-remediate sample was considerably reduced after treatment with NPs. Furthermore, microalgae P. tricornutum appears to be most sensitive species while Artemia franciscana showed no toxic effects to the tested solutions. Both chemical and ecotoxicological approaches revealed a high efficiency for the remediation of Hg-contaminated saltwater.

Ecological differentiation in cryptic rotifer species: what we can learn from the Brachionus plicatilis complex

In recent decades, the use of molecular techniques in rotifers has revealed the existence of many cryptic species. Although strong competition is expected among cryptic species, these species are often sympatric. Here, we present a review of sympatric cryptic rotifer species, focusing on those cases in which niche differentiation has been investigated. There are at least 42 cryptic rotifer species complexes, and species coexistence is commonly reported. Ecological differentiation among cryptic species has been detected in several complexes. However, the only available information regarding mechanisms that allow cryptic species coexistence is for several species of the Brachionus plicatilis complex: B. plicatilis, B. ibericus, B. rotundiformis and B. manjavacas. According to these studies, when species differ in body size, niche differentiation is related to abiotic and biotic factors (e.g. the differential use of resources and vulnerability to predation). In contrast, if species are almost identical in body size, their biotic niches and competitive abilities are very similar, and niche differentiation is facilitated by the differences in the species responses to fluctuating, physical environment in combination with the divergence in life-history traits related to diapause. Further studies of additional cryptic rotifer species are essential to know the generality of these conclusions.

Bacterial Flora of Water and Rotifers in Outdoor Mass Culture Tanks Fed with Different Microalagal Diets

Investigations were carried out on the bacterial flora of water and the quality of rotifers in outdoor mass culture tanks. Brachionus plicatilis and B. rotundiformis were cultured in 10 numbers of 1 tonne tanks and the physico-chemical parameters and microbial loads of water, and total bacterial and Vibrio loads of microalgae and rotifers, during the period 2014-15, were studied. The study revealed a significant variation of the ammonia levels and total bacterial loads with different diets (P < 0.05). A positive correlation was observed between the total bacterial loads of algal concentrations and loads of rotifers, but no correlation was observed between Vibrio loads of water and rotifers. The prevalence of Vibrio loads of rotifers was low in tanks fed with Nannochloropsis oculata and maximum Vibrio loads were recorded in Chaetoceros calcitrans fed rotifers. The Vibrio loads significantly varied with days of culture and also with the algal diets. A positive correlation was observed between the total Vibrio loads of water and rotifers.