Planktonic Populations Research Articles

Effects of sumithion on growth and production of phytoplankton and zooplankton in aquaculture ponds

Sumithion is an organophosphorous pesticide widely used to control tiger bug in the fish larval rearing pond. The present study was aimed to investigate the effects of sumithion on plankton population abundance in aquaculture pond. The experiment was carried out with three treatments, i.e., ponds with no sumithion (T1), with 1.0 ppm sumithion (T2) and 2.0 ppm sumithion (T3). The water quality parameters, such as temperature, pH, dissolved oxygen and total alkalinity were almost unchanged throughout the study period whereas transparency, NO3-N and PO4-P values were declined with increasing sumithion concentrations but differences were not significant (P > 0.05). No distinct changes were observed in phytoplankton population densities (x cells/L). On the other hand, the zooplankton population densities (x Ind./L) were significantly (P > 0.05) decreased with toxicity of sumithion after 30 days to end of experimental period in both T2 and T3 compared to control group (T1). The ranges of pH, organic carbon (%), available phosphorus (ppm) and total nitrogen (%) of pond bottom-sediment did not differ irrespective of the treatments. This study demonstrated that sumithion has adverse effects on zooplankton which may influence the production in aquaculture pond.

Simulating phytoplankton growth during the spring thermal bar in a deep lake

Phytoplankton growth in Lake Baikal was simulated during thermal bar events using meteorological data from June 1–30, 2017. Dynamics of the thermal bar and the plankton population were reproduced by the coupled physical–biological model that describes hydrodynamic processes and interactions of the components of the nutrient–phytoplankton–zooplankton–detritus system. The key point of the model is consideration of atmospheric impact on the lake surface, taking into account the intraday variability of wind forcing and fluxes of shortwave and longwave radiation and latent and sensible heat. Numerical modeling showed that a combination of cabbeling instability, associated with the thermal bar, and wind-driven currents lead to sinking of the phytoplankton biomass from the surface area to the lower layers of the lake. The increase in phytoplankton results in a degradation of the nutrients in the corresponding water environment. Simulations demonstrated that the maximum concentrations of phytoplankton are localized in the inshore side of the thermal bar. At the same time, the thermal bar acted as a barrier preventing the horizontal propagation of the biological substances into open waters. A comparative analysis of the calculated temperature and phytoplankton distributions with available field data was performed. • Plankton dynamics during the spring thermal bar in a deep lake were simulated. • The thermal bar acts as a barrier to horizontal propagation of the plankton biomass. • Wind forcing plays a significant role in the time-space distribution of the phytoplankton. • Wind contributes to sinking of the phytoplankton to the lower layers of the lake.

Respiratory Heterogeneity Shapes Biofilm Formation and Host Colonization in Uropathogenic Escherichia coli.

Biofilms are multicellular bacterial communities encased in a self-secreted extracellular matrix comprised of polysaccharides, proteinaceous fibers, and DNA. Organization of these components lends spatial organization to the biofilm community such that biofilm residents can benefit from the production of common goods while being protected from exogenous insults. Spatial organization is driven by the presence of chemical gradients, such as oxygen. Here we show that two quinol oxidases found in Escherichia coli and other bacteria organize along the biofilm oxygen gradient and that this spatially coordinated expression controls architectural integrity. Cytochrome bd, a high-affinity quinol oxidase required for aerobic respiration under hypoxic conditions, is the most abundantly expressed respiratory complex in the biofilm community. Depletion of the cytochrome bd-expressing subpopulation compromises biofilm complexity by reducing the abundance of secreted extracellular matrix as well as increasing cellular sensitivity to exogenous stresses. Interrogation of the distribution of quinol oxidases in the planktonic state revealed that ∼15% of the population expresses cytochrome bd at atmospheric oxygen concentration, and this population dominates during acute urinary tract infection. These data point toward a bet-hedging mechanism in which heterogeneous expression of respiratory complexes ensures respiratory plasticity of E. coli across diverse host niches.IMPORTANCE Biofilms are multicellular bacterial communities encased in a self-secreted extracellular matrix comprised of polysaccharides, proteinaceous fibers, and DNA. Organization of these components lends spatial organization in the biofilm community. Here we demonstrate that oxygen gradients in uropathogenic Escherichia coli (UPEC) biofilms lead to spatially distinct expression programs for quinol oxidases-components of the terminal electron transport chain. Our studies reveal that the cytochrome bd-expressing subpopulation is critical for biofilm development and matrix production. In addition, we show that quinol oxidases are heterogeneously expressed in planktonic populations and that this respiratory heterogeneity provides a fitness advantage during infection. These studies define the contributions of quinol oxidases to biofilm physiology and suggest the presence of respiratory bet-hedging behavior in UPEC.

Pharmacodynamics of ciprofloxacin against Pseudomonas aeruginosa planktonic and biofilm-derived cells.

The influence of growth phase and state on the survival and recovery of Pseudomonas aeruginosa exposed to ciprofloxacin was investigated using batch culture grown planktonic cells and disaggregated biofilm populations. Biofilms were either nonantibiotic exposed or previously exposed to ciprofloxacin before disaggregation and subsequent challenge with ciprofloxacin. Viable counts showed that late stationary phase cells were tolerant to ciprofloxacin over 24h exposure, while all other populations presented a biphasic killing pattern. In contrast, the metabolic activity of planktonic and biofilm-derived cells remained similar to controls during the initial 6h of ciprofloxacin exposure, despite a significant reduction in viable cell numbers. A similar effect was observed when assessing the postantibiotic effect of 1h ciprofloxacin exposure. Thus, although cell reduction occurred, the metabolic status of the cells remained unchanged. The recovery of disaggregated biofilm cells previously exposed to ciprofloxacin was significantly quicker than naïve biofilm cells, and this latter population's recovery was significantly slower than all planktonic populations. Results from this work have implications for our understanding of biofilm-related infections and their resilience to antimicrobial treatment. SIGNIFICANCE AND IMPACT OF THE STUDY: Removal of biofilms from surfaces and infection sites via disaggregation and induction of dispersion may reverse their antibiotic tolerant state. However, little is known of the recovery of the cells upon disaggregation from biofilms. Driven by this gap in knowledge we quantified the effect of ciprofloxacin on disaggregated biofilms of Pseudomonas aeruginosa, including those previously exposed to ciprofloxacin. Our results provide further insight into bacterial resilience, regrowth, and antimicrobial efficacy, as reduction in cell viability does not directly correlate with the metabolic activity of bacteria at the time of the exposure to antimicrobials. Thus, despite a perceived reduction in viability, the potential for cell persistence and regrowth remains and recovery is quicker upon subsequent exposure to antimicrobial, supporting the increase in resilience and recurrence of infections.

Investigating the effect of alkaline stress on biofilm formation by Salmonella enteritidis

Bacterial biofilm formation is an important survival strategy in multiple environments. It is affected by the attachment surface, the bacterial strain and the surrounding environment. In Salmonella enteritidis, a biofilm-forming foodborne pathogen, the molecular biofilm regulators act as on-off controls between the sessile and the planktonic population, while the exact underlying formation mechanism still remains unclear. The aim of this project is to study the effect of alkaline environment on the formation of Salmonella biofilms and to examine the architecture of biofilm produced under alkaline conditions, by use confocal microscopy. Neutral pH was found to be the optimal pH for Salmonella biofilm formation, while pH 10 significantly reduces it (P-value=0.015). However, cell viability remains high at pH 10, which suggests that the pathogen can easily survive the alkaline stress. Biofilm morphology at pH 7 is characterized by thick cell clusters, whereas at pH 10 it is characterised by thin layers of individual cells. These findings can help us understand how Salmonella enteritidis survives under highly alkaline conditions, potentially leading to the design of new and more effective disinfection strategies involving highly alkaline detergents.

Discovering millions of plankton genomic markers from the Atlantic Ocean and the Mediterranean Sea.

Comparison of the molecular diversity in all plankton populations present in geographically distant water columns may allow for a holistic view of the connectivity, isolation and adaptation of organisms in the marine environment. In this context, a large-scale detection and analysis of genomic variants directly in metagenomic data appeared as a powerful strategy for the identification of genetic structures and genes under natural selection in plankton. Here, we used discosnp++, a reference-free variant caller, to produce genetic variants from large-scale metagenomic data and assessed its accuracy on the copepod Oithona nana in terms of variant calling, allele frequency estimation and population genomic statistics by comparing it to the state-of-the-art method. discosnp ++ produces variants leading to similar conclusions regarding the genetic structure and identification of loci under natural selection. discosnp++ was then applied to 120 metagenomic samples from four size fractions, including prokaryotes, protists and zooplankton sampled from 39 tara Oceans sampling stations located in the Atlantic Ocean and the Mediterranean Sea to produce a new set of marine genomic markers containing more than 19 million of variants. This new genomic resource can be used by the community to relocate these markers on their plankton genomes or transcriptomes of interest. This resource will be updated with new marine expeditions and the increase of metagenomic data (availability: http://bioinformatique.rennes.inria.fr/taravariants/).

Evaluation of biocidal efficacy of Chloramine T trihydrate on planktonic and sessile bacteria in a model cooling tower water system.

A model cooling tower system was experimentally seeded with Legionella pneumophila and real industrial cooling tower (CT) water has been run at the closest to full-scale system operating conditions. The water/biofilm samples were taken from the model system monthly, and the effectiveness of the different concentrations of Chloramine T trihydrate biocide was evaluated in terms of its ability to control both planktonic/sessile microbial populations. Although Chloramine T is a recommended commercial formulation for disinfecting CTs, there is a lack of published data on the efficacy of this compound against both planktonic and sessile populations in the cooling tower. Biocide response in both sessile/planktonic bacteria counts varied according to months. Tested biocide concentrations provided the clean tower conditions by reducing the concentration of heterotrophic plate count (HPC) below <104 cfu mL-1, L. pneumophila <10 cfu mL-1 and of adenosine triphosphate (ATP) values <300 relative light units (RLU), after 1, 3 and 24 h of exposure, during a 6-month period. There were no statistically significant differences in efficacy between concentrations in terms of reduction in the number of bacteria, decrease in ATP value and viability. The results revealed that Chloramine T can effectively control biofouling in cooling systems according to the limit values of the successful control program.

Monitoring microbial communities’ dynamics during the start-up of microbial fuel cells by high-throughput screening techniques

Microbial Electrochemical Technologies are based on the use of electrochemically active microorganisms that can carry out extracellular electron transfer to an electrode while they are oxidizing the organic compounds. The dynamics and changes of the bacterial community in the anode biofilm and planktonic broth of an acetate fed batch single chamber air cathode MFC have been studied by combing flow-cytometry and Illumina sequencing techniques. At the beginning of the test, from 0 h to 70 h, microbial planktonic communities changed from four groups to two groups, as revealed by DNA content, and from three groups to one group based on the cell membrane polarization revealed by a DiOC6(3) probe. Between 4th day and 13th day, microbial communities changed from one group to a maximum of three groups, monitoring DNA content, and from one group to two based on the cell membrane polarization. The 16S rDNA gene profiling confirmed the shift in microbial communities, with Acinetobacter (39.34%), Azospirillum (27.66%), Arcobacter (4.17%) and Comamonas (2.62%) being the most abundant genera at the beginning of MFC activation. After 70 h the main genera detected were Azospirillum (46.42%), Acinetobacter (34.66%), Enterococcus (2.32%), Dysgonomonas (2.14%). Data obtained have shown that flow cytometry and illumina sequencing are useful tools to monitor “online” the changes in microbial communities during the MFCs start-up and the increase of Azospirillum and Acinetobacter genera is in good agreement with the MFC voltage generation. Moreover, monitoring planktonic populations, instead of the less accessible anode biofilm, was in good agreement with the evolution of MFC voltage.

Zooplankton selectivity and nutritional value of phytoplankton influences a rich variety of dynamics in a plankton population model.

Mathematical modeling may be an excellent tool to analyze and explain complex biological phenomena. In this paper, we use a mathematical model to reveal various interesting dynamical features of phytoplankton-zooplankton interaction and attempt to explain the reason for contrasting dynamics shown by different laboratory and field experiments. Our study shows that the phytoplankton-zooplankton interaction in a pelagic system is very complex and the plankton dynamics, including the bloom phenomenon, strongly depends on the selective predation of zooplankton and the nutritional value of phytoplankton. The study supports the existing hypothesis that decoupling at the plant-animal interface may occur due to strong fish predation on zooplankton. In addition, we argue that decoupling of the food chain may also occur under low to intermediate nutrient inflow if zooplankton feeds on phytoplankton having lower nutritional value. It is also shown that nutrient enrichment can destabilize an otherwise stable system if zooplankton feeds on highly nutritious prey, but unable to destabilize the system if zooplankton feeds on low-nutritious prey. This may be one possible explanation to the longstanding question: Why do some experiments show the paradox of enrichment and others do not?

Mathematical analysis on deterministic and stochastic lake ecosystem models.

In this paper, we propose and study the deterministic and stochastic lake ecosystem models to investigate the impact of terrestrial organic matter upon persistence of the plankton populations. By constructing Lyapunov function and using the LaSalle's Invariance Principle, we establish global properties of the deterministic model. The dynamical behavior of solutions fits well with some experimental results. It is concluded that the terrestrial organic matter plays an important role in influencing interactions between phytoplankton and zooplankton. Based on the fluctuations of lake ecosystem, we further develop a stochastically perturbed model. Theoretic analysis implies that the stochastic model exists a stationary distribution which is ergodic. The key point of our analysis is to enhance our knowledge of the factors governing the dynamics of plankton population models.

Impact of Nypa Palm (&lt;i&gt;Nypa fruticans&lt;/i&gt;) and Mangroves Forests on Plankton Community along Andoni River, Nigeria

The invasion of mangroves forest by nypa palm is said to affect the ability of the mangroves to act as a spawning ground for fishes. It is thus hypothesized that nypa palm presence in mangrove forest will impact their fish spawning ability due to the reduction in plankton population. A total of four stations were chosen: station 1 (open water), Station 2 (nypa palm dominant), station 3 (Rhizophora and Avicennia dominant), Station 4 (Mixed forest). Results of water quality parameters include; pH (6.99 ± 0.16), temperature (28.20°C ± 0.05°C), DO (4.71 ± 0.18 mg/L), conductivity (19.52 ± 0.20 µm/s), salinity (10.76 ± 0.07 ppt) and TDS (13.45 ± 0.27 ppt). Mean values of the physico-chemical parameters were not significantly different from each other (P > 0.05). In all 737 zooplankton in eleven genera were collected. Copepoda dominated with 75.1%. Similarly, 4774 phytoplankton in six taxa were collected. Bacilliarophyceae dominated with 87.45%. Shannon Weiner index across the stations was highest in station 4 (0.36) and lowest in station 1 (0.33). Margalef’s index was highest in stations 2, 3, and 4 (3.48) and lowest in station 1 (2.67). Pielou’s index of evenness was highest in station 4 (0.099) and lowest in station 1 (0.089). The composition and abundance of plankton showed no significant difference across the four stations (P > 0.05). This implies that the presence of Nypa fruticans (Wurmb) did not have negative impact on the abundance and diversity of plankton.

Mathematical modeling of nonlinear effects in dynamic of interacting plankton and fish populations of Azov Sea

Mathematical modeling of nonlinear effects in dynamic of interacting plankton and fish populations of Azov Sea

Feeding of plankton in turbulent oceans and lakes

AbstractAnalytical models for the statistical distribution of the gut content of fish larvae in a turbulent ocean environment are compared to data obtained in a field experiment. The proposed model allows the nutrition state and thereby the survival probability of plankton populations to be estimated for given conditions and parameters characterizing their environment, i.e., prey concentrations and turbulence levels. These parameters are all available in the field data. Other parameters such as the capture range and fields of view together with a characteristic time for digesting prey are assumed to be known. The analysis allows an estimate for the probability density of the gut content of plankton in terms of the number of nauplii in the gut. In particular, the analytical results give a basis for evaluating the average gut content of a given plankton population on the basis of basic information concerning the prey concentration and the turbulence intensity. Also analytical models for the prey capture rates are compared with results based on the field data. The analysis emphasizes the effects of turbulence.

Effects of stocking density on the growth, survival and production of endangered bata, Labeo bata (Hamilton, 1822) in primary nursing

Effect of stocking densities on the growth, survival and production of bata, Labeo bata fry and fingerlings were tested in a primary nursery rearing system. The experiment was conducted for a period of 4 weeks in six earthen nursery ponds having an area of 0.032 ha each. Four-day-old fry stocked at 1.0 million/ha was designated as treatment-1 (T1), 1.5 million/ha as treatment-2 (T2) and 2.0 million/ ha as treatment-3 (T3). At stocking, all fry were of same age with a mean length and weight of 1.03±0.03 cm and 0.12±0.01 g, respectively. Fry in all the treatments were fed with Mega commercial fish feed. Physico-chemical parameters such as water temperature, transparency, dissolve oxygen, pH and total alkalinity in all the treatments were suitable ranges for fry and fingerling rearing. Plankton population (both phytoplankton and zooplankton) were found to be at optimum level for fish culture. Highest weight gain was observed in T1 (3.46±0.08) and lowest in T3 (1.98±0.03). Final length, final weight and survival of fingerlings also followed the same trends as weight gain. Fingerlings in T1 produced significantly higher specific growth rate (12.15±0.08) than T2 (11.31±0.03) and T2 (10.22±0.05). Feed conversion ratio was significantly lower in T1 (0.26±0.01) than T2 (0.42±0.02) and T3 (0.65±0.01). Significantly higher number of fingerlings was produced in T3 (1177700±4700) than T2 (963300±9900) and T1 (717850±7350), respectively. Despite of this, consistently higher net benefits were found from T1 than T2 and T3. Overall, highest growth (3.60±0.16 g), survival (71.79 ± 1.04%) and net benefits (TK. 127,087.00) of fingerlings were obtained at a density of 1.0 million hatchlings/ha. Therefore, out of three stocking densities, 1.0 million fry/ha appears to be most suitable stocking density for nursing and rearing of L. bata fry and fingerlings in primary nursing.

Shellfish culture: a complex driver of planktonic communities

AbstractThis review features recent updates on planktonic community alteration attributed to shellfish farming across three major drivers: predation, nutrient availability and the hydrodynamic environment. The grazing pressure generated by filter‐feeder communities (shellfish and epibionts) constitutes a ‘top‐down’ control of planktonic communities in aquaculture areas, inducing a significant depletion of planktonic organism concentration. By selecting larger cells during the filtration process, shellfish also favour smaller organisms in the water column, leading to the dominance of the latter. Direct excretion and the benthic alteration process tend to fertilise the water column and significantly stimulate primary production. The associated epibiont community particularly contributes to this regeneration process. The expected consequence of increasing nutrient availability is generally a planktonic shift in favour of small planktonic species. However, investigation on the relationship between planktonic structure and nutrient conditions has revealed a wide complexity and variability. Finally, all structures used in shellfish farming activities interact with water currents and tend to significantly increase the residence time of planktonic organisms inside shellfish farming areas. In grazing‐dominated systems, an increase in residence time tends to increase the exposure time of planktonic populations to detrimental conditions, reducing biomass and production. The general consequences of shellfish farming are a decrease in primary production in farming ecosystems, and a possible alteration of structure and functioning of planktonic communities. The implications of shellfish farming also appear to be quite different from other aquaculture activities such as fish farming, which tend to promote primary production leading to eutrophication process.

A global analysis of gene expression in Fibrobacter succinogenes S85 grown on cellulose and soluble sugars at different growth rates

BackgroundCellulose is the most abundant biological polymer on earth, making it an attractive substrate for the production of next-generation biofuels and commodity chemicals. However, the economics of cellulose utilization are currently unfavorable due to a lack of efficient methods for its hydrolysis. Fibrobacter succinogenes strain S85, originally isolated from the bovine rumen, is among the most actively cellulolytic mesophilic bacteria known, producing succinate as its major fermentation product. In this study, we examined the transcriptome of F. succinogenes S85 grown in continuous culture at several dilution rates on cellulose, cellobiose, or glucose to gain a system-level understanding of cellulose degradation by this bacterium.ResultsSeveral patterns of gene expression were observed for the major cellulases produced by F. succinogenes S85. A large proportion of cellulase genes were constitutively expressed, including the gene encoding for Cel51A, the major cellulose-binding endoglucanase produced by this bacterium. Moreover, other cellulase genes displayed elevated expression during growth on cellulose relative to growth on soluble sugars. Growth rate had a strong effect on global gene expression, particularly with regard to genes predicted to encode carbohydrate-binding modules and glycoside hydrolases implicated in hemicellulose degradation. Expression of hemicellulase genes was tightly regulated, with these genes displaying elevated expression only during slow growth on soluble sugars. Clear differences in gene expression were also observed between adherent and planktonic populations within continuous cultures growing on cellulose.ConclusionsThis work emphasizes the complexity of the fiber-degrading system utilized by F. succinogenes S85, and reinforces the complementary role of hemicellulases for accessing cellulose by these bacteria. We report for the first time evidence of global differences in gene expression between adherent and planktonic populations of an anaerobic bacterium growing on cellulose at steady state during continuous cultivation. Finally, our results also highlight the importance of controlling for growth rate in investigations of gene expression.

Global asymptotic stability and equiasymptotic stability for a time-varying phytoplankton–zooplankton–fish system

In this paper, we consider a three-species system which consists of phytoplankton, zooplankton and fish. It is well known that zooplankton are harvested by other creatures besides fish, and it has been reported that zooplankton can absorb energy from other micro-organisms besides phytoplankton in recent decades. For this reason, we add the parts of extra energy source and harvesting effect in the model. Taking account of seasonal variation which can bring affects to many aspects of plankton population, we assume that some factors about the phytoplankton and the zooplankton are time-dependent. In particular, since the environment does not change regularly, we does not require these time-varied factors are periodic, which is quite different with most ecological models. The purpose of this paper is to present sufficient conditions which guarantee that the equilibrium of this three-species system is globally asymptotically stable. Moreover, we will show that the equilibrium is equiasymptotically stable under relatively weaker conditions.

It goes with the flow: Size mediated plankton attenuation through the Niagara River connecting channel

Abstract The Niagara River connecting channel provides a unique system in which to examine the impact of a rapid lentic-lotic-lentic transition on a freshwater ecosystem, particularly on plankton community composition. From June to October 2014, six monitoring sites (three in the upper river and three in the lower river) were sampled monthly for water chemistry, phytoplankton and/or zooplankton composition. Zooplankton biomass decreased exponentially with distance downstream, as expected within a high flow lotic environment. The rapid attenuation of zooplankton occurring within 10 km of the river mouth was likely due to predation by large populations of planktivorous fishes in the river. Densities of phytoplankton, rotifers and bacteria also declined but were less strongly impacted by the lentic-lotic transition. Plankton communities were dominated by species common to Lake Erie, the source waterbody, and also by taxa more resilient to the highly turbulent conditions of the river. These species included siliceous diatoms, filamentous algae, small zooplankters, dreissenid veligers and loricated rotifers. Furthermore, the seasonality of species composition in the Niagara River is the same as its source water body, suggesting no impact from the river on plankton succession. Niagara Falls and the two hydroelectric facilities were not found to be a significant cause of plankton mortality down river. There is some evidence however that entrainment time in the hydroelectric reservoirs may slightly enhance phytoplankton and zooplankton densities, thus contributing to plankton populations downstream of the turbine discharges.

Some Aspects of Limnology and Plankton Population of River Ochekwu, Benue State, Nigeria

Some Aspects of Limnology and Plankton Population of River Ochekwu, Benue State, Nigeria

Inactivation of Listeria monocytogenes on paperboard, a food packaging material, using 410 nm light emitting diodes

Light emitting diodes of wavelength 410 nm were used to inactivate Listeria monocytogenes stains on paperboard, an increasingly popular food packaging material. The integrity of the cell membranes was examined using differential fluorescent staining. Scanning electron microscopy (SEM) was used to obtain a deeper understanding of L. monocytogenes stain formation on paperboard and the damage caused to the cells by the LEDs. While the planktonic L. monocytogenes population could be completely inactivated following a brief lag phase that lasted about 20 min, the illumination of the sessile population left some persisters despite immediate commencement of the inactivation. Planktonic populations of inocula sized 3, 5 and 7 log CFU/mL were reduced below the detection limit in 54, 80 and 84 min respectively, whereas it took 120 and 390 min to reach constancy in the sessile populations of inocula sized 5 and 7 log CFU/cm2. The number of membrane-damaged cells was seen to increase with the illumination time. SEM images provided evidence of the protection conferred by the stain on the underlying cells. This study demonstrates that blue LEDs have the potential to reduce the risk of L. monocytogenes contamination from paperboard cartons under refrigeration.