Linking biokinetics and consumer-resource dynamics of zinc accumulation in pond abalone Haliotis diversicolor supertexta

A dynamic model that links biokinetics and consumer–resource dynamics for describing zinc (Zn) accumulation in abalone Haliotis diversicolor supertexta has been developed and then applied to Zn data from real abalone farms. The biokinetic parameters used in this study, uptake and depuration rate constants of abalone and their food source, red alga Gracilaria tenuistipitata var. liui, were obtained from a laboratory 14-d exposure experiment. We carried out a sensitivity analysis of the model by using the fractional factorial design technique, taking into account the influence of consumer–resource-related parameters such as growth and death rates and biomass and biokinetic parameters characterized by bioconcentration factor. Results indicate that the response time of biomagnification dynamics of Zn accumulation in abalone was influenced mainly by the growth rate of algae and biomass and the death rate of abalone and by interactions algae biomass and abalone death rate and abalone and algae biomass. New algae production results in substantially higher values of biomagnification factor. The linked model was then applied to field observations from a real-life situation of variable Zn concentrations occurring in abalone farms. Simulation results show that the predicted values are within a factor of 2 of the measured values (% errors range from 5.3±4% to 44.1±8%). Both model analysis and model application to the abalone farms suggest that the linking influences between biokinetics and consumer–resource dynamics support Zn accumulation in H. diversicolor supertexta and in G. tenuistipitata var. liui as functions of Zn concentration in water and abundance of food occurring in abalone farms.     

A systemic biokinetic model for polonium

Although the biokinetics of polonium has been studied extensively, interpretation of the data is complicated by potential differences with species and route of exposure and the questionable reliability of much of the reported excretion data for man. A study was undertaken to identify the data that are most likely to represent the typical behavior of polonium and apply those data to construct an improved, physiologically realistic systemic biokinetic model for polonium in man. Such a model is needed for interpretation of urinary excretion data for workers exposed to 210Po and reconstruction of the radiation doses received by those workers. This paper reviews the database on the biokinetics of polonium and describes a new systemic biokinetic model for polonium in man.     

Biomonitoring of maritime pollution by heavy metals (Pb and Zn) in the coast of Jijel (Algeria)

This paper reports a study of pollution in the coastal waters of Jijel, Algeria, using algae Ulva lactuca and Corallina officinalis as bioindicators. Samples of seawater and algae were collected at four different stations from the coast of Jijel, during the period of April–June 2014. The heavy metal content (Pb and Zn) was determined in seawater and in the algae tissue by the technique of atomic absorption spectrophotometry. In seawater, the contents of heavy metals vary from 0.017 to 0.03 mg/l (Pb) and 0.235 to 0.873 mg/l. In the algae tissues, metals concentrations vary between 1.88 to 6.25 μg g^?1 dry weight (Pb), and from 92 to 178.9 μg g^?1 dry weight (Zn). These levels differ by site and species. The calculation of the bioconcentration factor (BCF) leads us to conclude that algae bioaccumulate significant levels of Pb and Zn metals in their tissues. Our results shows that the species of C. officinalis bioaccumulate the metals Pb and Zn more than U. lactuca, where, high biosorption of Zn was observed with BCF values between 203.21 and 238.40. Zn content in seawater and algae tissues appear higher than standards set by USEPA and guides values of Certified Reference Materials, but Pb levels appear lower than this standard.     

A laboratory model for evaluating the behavior of heavy metals in an aquatic environment

A dynamic biological system capable of simultaneously distinguishing between bioaccumulation and biomagnification through successive trophic levels in an aquatic ecosystem is described. The organisms used in the system were algae, predominantly Scenedesmus sp., Daphnia magna, fresh water mussels (Ligumia sp. and Margaritifera sp.) and the fathead minnow, Pimephales promelas.Thiosulfate complexed mercury and silver were each studied at two concentrations. The water and organisms were analyzed for the metals periodically during the 10-week tests. Both mercury and silver can be bioaccumulated by fish. The concentration factors for mercury are greater than for silver. Further, mercury is biomagnified by fish whereas silver is not. Fresh water mussels were found to be poor indicator species for metal contamination.     

Phenol and free ammonia inhibition to Nitrosomonas activity

Laboratory evaluations were conducted of the rate of ammonia bio-oxidation to nitrite by an autotrophic culture of strict nitrifiers. Ammonia oxidation biokinetics was found to follow Michaelis-Menten type relationships. Experiments were conducted to quantify the influence of phenol, and the influence of un-ionized (free) ammonia on biokinetic parameters. Results show that the Michaelis-Menten constant varies with the square root of ambient phenol concentration, and that the influence of un-ionized ammonia on ammonia oxidation may be best described by a “substrate-inhibition” model which follows from classical Monod kinetics. This model explains, to a large degree, observed differences in ammonia bio-oxidation rates as functions of pH. Conclusions based on engineering calculations are presented to illustrate design and operational considerations for the biological removal of wastewater ammonia.     

Algal growth in primary settled sewage: The effects of five key variables

Photoperiod, at 3240 lx (300 ft candle) light intensity, was found to be the primary limiting factor for algal biomass growth in a bench scale series of experiments using primary settled sewage. At a retention time of seven days, a total effective photoperiod of greater than 6 h a day was required to produce algae at concentration above 500 mg 1⁻¹.Increasing dissolved CO₂ concentration promoted green algae production and resulted in a higher yield than that obtained from the blue green algae which dominated at low levels of dissolved CO₂. Unfortunately, most of the green algae were unicellular, discrete, small particles, and would be expensive to harvest compared with blue-green algae which often grow in colonies possessing a gelatinous sheath or are of filamentous construction.Low temperature favoured algal biomass production because of its effect upon the solubility of CO₂. The addition of bicarbonate also increased algal biomass yield but an excess of ammonium nitrate inhibited algal production.The removal of nitrogen and phosphorus by algae varied with the quantity of algal biomass produced. Under the experimental conditions, nitrogen removal corresponded to about 3 mg per 100 mg of biomass produced and phosphorus removal to about 0.5 mg per 100 mg biomass produced.     

Distribution and biokinetic analysis of Pb and Po in poultry due to ingestion of dicalcium phosphate

Dicalcium phosphate (DCP) is used as a calcium supplement for food producing animals (i.e., cattle, poultry and pig). When DCP is produced via wet acid digestion of the phosphate rock and depending on the acid used in the industrial process, the final product can result in enhanced ²¹⁰Pb and ²¹⁰Po specific activities (∼ 2000 Bq·kg⁻¹). Both ²¹⁰Pb and ²¹⁰Po are of great interest because their contribution to the dose received by ingestion is potentially large. The aims of this work are to examine the accumulation of ²¹⁰Pb and ²¹⁰Po in chicken tissues during the first 42 days of life and to build a suitable single-compartment biokinetic model to understand the behavior of both radionuclides within the entire animal using the experimental results. Three commercial corn-soybean-based diets containing different amounts and sources of DCP were fed to broilers during a period of 42 days. The results show that diets containing enhanced concentrations of ²¹⁰Pb and ²¹⁰Po lead to larger specific accumulation in broiler tissues compared to the blank diet. Radionuclides do not accumulate homogeneously within the animal body: ²¹⁰Pb follows the calcium pathways to some extent and accumulates largely in bones, while ²¹⁰Po accumulates to a large extent in liver and kidneys. However, the total amount of radionuclide accumulation in tissues is small compared to the amounts excreted in feces. The single-compartment non-linear biokinetic model proposed here for ²¹⁰Pb and ²¹⁰Po in the whole animal takes into account the size evolution and is self-consistent in that no fitting parameterization of intake and excretions rates is required.     

The effect of bacterial contamination on the heterotrophic cultivation of Chlorella pyrenoidosa in wastewater from the production of soybean products

This study examined the impacts of bacteria on the algal biomass, lipid content and efficiency of wastewater treatment during the heterotrophic cultivation of Chlorella pyrenoidosa. Our results showed that soybean-processing wastewater can enhance the accumulation of lipids in algal cells and thus raise the lipid yield in the pure culture. The bacteria coexisting with algae improved the degradation of total nitrogen (TN), total phosphorus (TP), glucose and chemical oxygen demand (COD). Although the biomass productivity of algae was not significantly affected, the total algal lipid content and lipid production rate were slightly reduced when bacteria coexisted with algae. The difference in the compositions of the medium is presumed to be the main contributing factor for the variation in total lipid content in presence and absence of bacteria. The TN, TP, and COD decreased during the assimilatory process undertaken by C. pyrenoidosa, and the removal efficiency of TN by bacteria depended on the type of nitrogen species in the medium. Additionally, the apparent interaction between the bacterial and algal cultures varied with the changes in experimental conditions. Algae could compete with bacteria for the carbon and energy sources, and inhibit the growth of the bacteria in the presence of high organic matter concentration in the medium.     

Passage of selected heavy metals from Sphaerotilus (bacteria: chlamydobacteriales) to Paramecium caudatum (protozoa: ciliata)

Sphaerotilus, a bacterium occurring in polluted waters, was found to take up Zn, Pb, Ni and Mn. Metal-containing cultures of this bacterium were employed to feed the protozoan Paramecium caudatum, and analytical results revealed the accumulation of Zn, Pb and Ni. Since Sphaerotilus was the only food source for paramecia during this study, the results indicate that trace amounts of metals were passed from bacteria to protozoa in a predator-prey relationship.     

The use of Stigeoclonium subsecundum (cholorophyceae) as a bioassay organism—III. Response to intermittent chlorination

The toxicity of intermittent chlorination to an attached, filamentous, green alga (Stigeoclonium subsecundum) was found to be related to the biomass of the alga at the beginning of the bioassay. Minimal resistant biomass (MRB) was a term used to describe the lowest biomass of algae able to survive and continue to grow when subjected to a specific level of chlorine at intervals of 6 h for a period of one week. This ability to survive was due to changes in the morphology of the algal filaments and the algal mat.     

Investigation of chromium phytoremediation and tolerance capacity of a weed,Portulaca oleracea L. in a hydroponic system

The present investigation was undertaken to study the growth, biomass, physiological‐biochemical responses and chromium (Cr) accumulation capacity of hydroponically grown Portulaca oleracea cuttings exposed to Hoagland solution supplemented with Cr(VI) (0.0, 0.1, 0.5, 1.0, 2.5, 5.0, 10 mg/L) for 30 days. The cuttings exhibited effective regeneration in Hoagland solution in comparison to deionized water. Plants demonstrated significant reduction in growth (root and shoot length, leaf area), biomass (root and shoot dry weight), pigments (total chlorophylls and carotenoids) and total soluble sugar content at higher concentration of Cr(VI) (10 mg/L). However, plants could tolerate Cr stress through significantly higher accumulation of proline and increased activity of peroxidase resulting in significant Cr accumulation (150–190 mg/kg dry weight) in harvestable parts of Portulaca. Thus, the results suggest application of P. oleracea for phytoremediation of Cr‐contaminated sites for the protection of environment.     

Leisure,amenity, and capital accumulation in a multi-region model

This paper proposes a multi-region growth model with endogenous labor supply, endogenous amenity, and capital accumulation. Although the production side is the same as in the neoclassical growth theory, in order to solve issues related to regional migration with capital accumulation we propose an alternative approach to consumer decisions about time distribution between work and leisure, housing consumption and saving. We show that the dynamics of the J-region national economy can be described by J-dimensional differential equations. We simulate the long-term economic structure of the national economy with three regions. It is demonstrated that with the Cobb–Douglas production functions and specified values of the parameters, the national dynamics has a unique equilibrium. We also carry out comparative statics analysis with regard to productivity levels, amenity parameters, propensity to save, and the population.     

Selenium bioaccumulation in eutrophic lake – Dąbie Małe Lake,Poland

While the world literature presents many studies on the occurrence of selenium in aquatic ecosystems, the risks associated with overexposure of hydrobionts to this element and the consequences of its magnification in the food chain (areas rich in Se), there are few studies on Se concentration in Poland's water bodies and watercourses (Se deficient area). The objective of the study was to assess the Se bioaccumulation in D?bie Ma?e Lake, based on Se concentration in the water, bottom sediments, and organs of Rutilus rutilus and Perca fluviatilis. The accumulation and biomagnification factor averaged 231 ± 69 and 1.2, respectively. Bioconcentration factor, calculated as Se in muscle divided by Se in water, ranged 35–104. Although Se concentrations in bottom sediments and fish were generally lower than the values reported in the literature, Se concentration in the water exceeded 2 µg/L, recommended value as a probable safe water concentration for wildlife.     

Etude du transfert de Cd, Pb, Cu et Zn dans les chaines trophiques neritiques et estuariennes—II. Accumulation biologique chez les poissons planctonophages

Plankton-feeder fish and their preys (mainly Copepods and Mysids) were obtained from the Loire estuary (France). Trace elements (Cd, Pb, Cu, Zn) concentrations in organisms from different steps in the food chain were compared using the transfer factor:It is generally lower than 1 for Cd, Pb and Cu but often higher than 1 for Zn. Before interpreting this last data as a consequence of biomagnification of Zn in food chain, we have to emphasize that the level of Zn in the predator, used for the calculation of f.t., results of accumulation from both food and water.During the digestion, we often observed a light decrease of metal concentrations between prey and stomach content followed by an increase of the metal levels in intestine content compared to stomach.     

Diastereomer-specific bioaccumulation of hexabromocyclododecane (HBCD) in a coastal food web, Western Norway

The present study reports diastereomer-specific accumulation of HBCD from a point source in five marine species representing a typical food web in a Norwegian coastal area. Samples of mussels, polychaetes, crabs and seabird eggs were analyzed for the diastereomers α-, β- and γ-HBCD, as well as lipid content and stable isotopes of nitrogen (¹⁵N/¹⁴N) to estimate trophic level. Accumulated HBCD did not correlate well with lipid content for most of the species, thus wet-weight based concentrations were included in an assessment of biomagnification. In contrast to β- and γ-HBCD, the α-diastereomer increased significantly with trophic level, resulting in magnification factors > 1 in this coastal marine ecosystem. Data for poikilotherms did not show the same positive correlation between the α-diastereomer and trophic position as homeotherms. The apparent biomagnification of the α-HBCD could be due to bioisomerization or diastereomer-specific elimination that differed between poikilotherms and homeotherms.     

Etude descriptive fondamentale et modelisation de la croissance d'un film biologique—II. Nouveau concept de modelisation de la croissance d'un film biologique

In a recent publication [Belkhadir et al. (1988) Wat. Res.22, 59–69], the different characteristic phases of anaerobic biological film growth were described.To explain the evolution of the different parameters studied (substrate, biomass, fermentation products) with time (Figs 1 and 2), a new model was proposed based upon the definitions:

• — of an active bacterial growth intrinsic kinetic: r_Ma = μ₀ · M_a

• — an inactivity kinetic dependant upon cellular density (confinement effect) and the accumulation of inhibitors: r_Md = k_i · I · M_a.

One can thus define the accumulation rate of an active biomass on a given surface by the following expression: With (M_a)_max representing the maximal density in active microorganisms when the surface is entirely colonized (end of the dynamic phase). Moreover, this equation is compatible with the hypothesis of a limitation in growth imposed by the fraction of available surface (biological space concept): The study of the model was based on the knowledge of three parameters: μ₀, (M_a)₀ and (M_a)_max, that were evaluated experimentally (Figs 4 and 5) and by parametric estimation (Fig. 6).Model simulation permitted the characterization of the evolutions, with time, of the active (M_a), and inactive biomass (M_d) which then enabled us to determine the corresponding accumulation rates (Figs 7 and 8).The proposed model corresponded well with the experimental results obtained in the dynamic and linear growth phases.Biological processes thus seem to be controlled by physiological factors (inhibition, diffusional limitations in the vicinity of the bacteria …), which is contrary, to the view of most authors who attribute this phenomenon to a limitation of substrate diffusion in the biofilm. This concept, inspired by the notion of the heterogeneous catalysis in a porous medium, arbitrarily introduces the stratification structure of a biological film. A critical study of this approach will be presented in a future publication.     

The impact of cattle farming best management practices on surface water nutrient concentrations,faecal bacteria and algal dominance in the Lake Oconee watershed

The objective of this study was to assess water quality in the Lake Oconee watershed and evaluate the best management practices used by cattle farms to reduce water contamination. Inorganic nutrient concentrations, algal abundance and faecal bacteria were highest in the cattle farming areas. The diatom community where cattle had no access was dominated by Achnanthidium minutissimum (Kützing) Czarnecki and Fragilaria crotonensis Kitton, and in sites where cattle were allowed direct access to the lake, Asterionella formosa Hassal, Nitzschia palea (Kützing) Smith and Navicula rostellata Kützing dominated. The latter three taxa are well‐known high‐nutrient diatoms. High populations of green algae (coccoid Desmidiaceae) were found where cattle had access. Sources of faecal pollution were identified using polymerase chain reaction detection, with Bifidobacterium adolescentis as a marker of human faecal pollution and Bacteroides (BoBac) indicating cattle faecal pollution. Overall, riparian buffers were most effective at reducing pollution from cattle operations.     

Human biokinetic data and a new compartmental model of zirconium--a tracer study with enriched stable isotopes

Biokinetic models describing the uptake, distribution and excretion of trace elements are an essential tool in nutrition, toxicology, or internal dosimetry of radionuclides. Zirconium, especially its radioisotope ⁹⁵Zr, is relevant to radiation protection due to its production in uranium fission and neutron activation of nuclear fuel cladding material. We present a comprehensive set of human data from a tracer study with stable isotopes of zirconium. The data are used to refine a biokinetic model of zirconium.Six female and seven male healthy adult volunteers participated in the study. It includes 16 complete double tracer investigations with oral ingestion and intravenous injection, and seven supplemental investigations. Tracer concentrations were measured in blood plasma and urine collected up to 100 d after tracer administration. The four data sets (two chemical tracer forms in plasma and urine) each encompass 105-240 measured concentration values above detection limits.Total fractional absorption of ingested zirconium was found to be 0.001 for zirconium in citrate-buffered drinking solution and 0.007 for zirconium oxalate solution.Biokinetic models were developed based on the linear first-order kinetic compartmental model approach used by the International Commission on Radiological Protection (ICRP). The main differences of the optimized systemic model of zirconium to the current ICRP model are (1) recycling into the transfer compartment made necessary by the observed tracer clearance from plasma, (2) different parameters related to fractional absorption for each form of the ingested tracer, and (3) a physiologically based excretion pathway to urine.The study considerably expands the knowledge on the biokinetics of zirconium, which was until now dominated by data from animal studies. The proposed systemic model improves the existing ICRP model, yet is based on the same principles and fits well into the ICRP radiation protection approach.     

Short-term bacterial community composition dynamics in response to accumulation and breakdown of Microcystis blooms

Short-term bacterial community composition (BCC) dynamics in response to accumulation and breakdown of Microcystis blooms were examined by conducting in situ mesocosm experiments with varying levels of Microcystis sp. biomass, ranging from 15 to 3217 μg/L as measured by chlorophyll-a concentration in the freshwater water column. The BCC was assessed by means of terminal restriction fragment length polymorphism (T-RFLP) of 16S ribosomal RNA genes followed by cloning and sequencing of selected samples. The results showed that the composition of both free-living and particle-attached bacterial communities changed during the accumulation and breakdown phases of a Microcystis bloom, and differences were also evident with different levels of Microcystis biomass. The relative abundance of bacteria affiliated with Micrococcineae and Legionellales increased in general after amendment with Microcystis. Significant correlation between the relative abundance of Micrococcineae and breakdown of Microcystis biomass was also observed. Canonical correspondence analysis (CCA) showed that the changes in the free-living and particle-attached bacterial community were mostly related to the changes in the concentrations of chlorophyll-a, dissolved organic carbon (DOC), dissolved oxygen (DO) and pH, which were mainly induced by the breakdown of Microcystis biomass. Overall, our study revealed the following: i) accumulation of Microcystis blooms and their breakdown have strong impacts on bacterial community composition; ii) there might be saprophytic association between Micrococcineae and decomposition of Microcystis biomass; iii) it is necessary to reveal potential associations between Legionellales organisms and Microcystis blooms in eutrophic freshwater lakes.     

Features of the elemental composition of plants of northern Western Siberian palsas

This paper reports the current state of lake and wetland ecosystems in the north of Western Siberia and describes the mechanisms of their formation and succession. Elemental composition of lake water and macrophytes of the four most typical subarctic lake ecosystems in Western Siberia were analysed using ICP MS. We selected the species of Menyanthes trifoliata L. as an example of the biogeochemical system. The general dynamics of concentration of the chemical elements in M. trifoliata L. in all four ecosystems demonstrate the minimal concentrations of rare-earth elements, of which the mobility in fresh waters and the bioavailability are low. Similar properties are exhibited by all tri and tetravalent hydrolysates. We also calculated, at each of the four stages of development of the lake ecosystems, the coefficients of biological accumulation of chemical elements by M. trifoliata L. (Kb) relative to the water. This revealed that the M. trifoliata L. strongly accumulates heavy metals, such as Pb, Zn, Sr and Co. The sources may be both global factors (atmospheric transport, water treatment, etc.) and various types of local pollution occurring as a result of anthropogenic impact on ecosystems of the north.