Applying the Balaton Sector Model for Analysis of Phosphorus Dynamics in Lake Balaton, 1976-1978

The Balaton Sector Model was developed at IIASA. It includes the interaction between five phosphorus fractions (dissolved organic P, dissolved inorganic P, nonliving particulate P, phytoplankton P, and bacterial P) and takes into account the wind- and temperature-regulated phosphorus exchange between sediment and water as well as the horizontal transport of phosphorus fractions from basin to basin by wind induced and advective water flow. This model was applied to a real set of field observations on the state of the environment, such as temperature, radiation, wind, water balance, and phosphorus loading, in order to examine the feasibility of the model to represent the phosphorus dynamics in different parts of Lake Balaton for the environmental conditions from 1976-1978. The model adequacy in describing phosphorus measurements is analyzed by statistical methods which show that the simulated phosphorus dynamics agree sufficiently with the available phosphorus measurements for Lake Balaton. The results of sensitivity analysis to determine the relative importance of measurements (temperature, radiation, and phosphorus loading) or the quality of input data determining the conditions of simulated phosphorus transformation are discussed in terms of changes in phosphorus concentrations, averaged on a monthly and annual basis. Some preliminary information on the phosphorus exchange in the sediment-water layer, extracted from the simulation results, is presented for discussion in this report. Furthermore, the analysis of phosphorus fluxes, external as well as internal, and the conditions of phosphorus cycling in 1976-1978 were conducted in order to clarify the specificity of phosphorus transformation within the Lake Balaton ecosystem

Mathematical Modeling of Phosphorus Transformation in the Lake Balaton Ecosystem

An ecological model of the phosphorus system is described. This model includes five phosphorus forms found in water, namely: phytoplankton-P, bacterial-P, dissolved inorganic-P, dissolved organic-P and nonliving particulate-P, and also three phosphorus forms in interstitial water: inorganic, organic and particulate phosphorus fractions. It is assumed that this model will be used as a tool for synthesizing and analyzing the phenomena of eutrophication in Lake Balaton's ecosystem. The purpose of this study was to obtain the best calibration between existing observation data on Lake Balaton from 1977 and model output. This is considered one of the important steps that must be carried out before application of the model for prediction and management purposes. A hypothesis of three seasonal phytoplankton groups yielded model output that agreed reasonably well with the observation data for total-P, dissolved-P, dissolved organic and inorganic phosphorus, particulate organic-P and phytoplankton chlorophyll "a" in the water of the different basins in Lake Balaton. This provides indirect evidence that the model considered, is a reasonable representation of complex ecological processes in phosphorus transformations and phytoplankton dynamics in the lake. On the basis of simulation results for 1977, the phosphorus material flows and the turnover times of phosphorus fractions in the lake are evaluated. These data provide additional insights for understanding the conditions of phosphorus cycling and the eutrophic state of the basins within Lake Balaton

A Study of the Transformation of Chemical Compounds and Biochemical Oxygen Consumption Dynamics in the Chemical and Ecological Water Quality Simulation

This report includes information about mathematical models of biogenic compound transformations and biochemical oxygen consumption (BOC). These models were constructed in the State Oceanographic Institute (Moscow, USSR). Mathematical models of the nitrogen and phosphorus compound transformation and BOC are presented in this report. These models attempt to give a detailed description of the complex processes, including physical and chemical reactions and biochemical interactions, that determine the transformation rates of chemical compounds and oxygen consumption in different water solutions. The main attention was given to the representation of the experimental observations in a batch microsystem because this stage is necessary for intelligent mathematical modelling of the biochemical transformation processes in natural conditions to characterize the water quality. The published experimental data for batch systems were used to identify the rate constants at separate stages and to reconstruct the dynamics of organic, mineral biogenic compounds, biomasses and to estimate the BOC both at individual stages and as a whole. The models can satisfactorily reflect the transformation dynamics of chemical compounds, microorganisms and oxygen consumption in different water solutions (lake and sea water and sewage). The simulations have showed that despite all the difficulties in descriptions of chemical matter transformation there are a definite number of main elements and they are quite enough for the detailed mathematical simulations of water system behavior and for the prediction of some essential peculiarities of ecosystems important for water quality characterization. The given models may be used as ready blocks connected with the corresponding hydrophysical blocks during model construction for research of the natural water chemical-ecological system

Simulation and Analysis of Phosphorus Transformation and Phytoplankton Dynamics in Relation to the Eutrophication of Lake Balaton

A mathematical model of phosphorus transformations has been applied to a real set of physical, biological, chemical observation data in Lake Balaton. The model includes dissolved oxygen and five phosphorus forms in water environments: phytoplankton phosphorus, bacterial phosphorus, dissolved inorganic phosphorus, dissolved organic phosphorus, and unliving particulate phosphorus, and also three phosphorus forms in interstitial water: inorganic, organic, and particulate phosphorus fractions. The purpose of this report was to present the best possible calibration between existing observation data from 1977 and model output. This is one of the important steps that must be performed before application of the model for prediction and management purposes. Hypothesis about three populations of phytoplankton give a model output that agreed reasonably well with the observation data for total P, dissolved P, dissolved organic and inorganic phosphorus, particulate organic phosphorus, and phytoplankton chlorophyll "a" in all basins simultaneously. This provides indirect evidences that the model considered is a reasonable representation of a complex ecological process in phosphorus transformation and phytoplankton dynamics in Lake Balaton

The Study of Nitrogen Transformation in Fresh Water: Experiments and Mathematical Modeling

Two main transformations occur in water environments -- one due to the effect of microorganisms and the other due to chemical reactions. Both transformations are very closely interwoven. Of the transformation processes in the water environment, nitrogen transformation is perhaps the most interesting because nitrogen and its compounds (both organic and mineral), affect the development of practically all aquatic microorganisms and therefore determine the trophic state and the quality of a water environment. Nitrogen compounds are present in sewage and other waste water discharged into water bodies. Therefore, it is quite understandable why during the last few years nitrogen transformation is the subject of study at descriptive and experimental levels, as well as by mathematical modeling techniques. This paper reports on the results of a collaborative study between IIASA and the Institute of Experimental Biology and Ecology of the Slovak Academy of Sciences in Bratislava, on nitrogen transformations. The data of twelve experiments covering a broad set of initial conditions in nitrogen concentrations and at two temperatures (180 degrees Celsius and 120 degrees Celsius) are presented in this report. These experimental data were analyzed with the help of the mathematical model developed at IIASA (WP-80-86) and intended for understanding processes of nitrogen transformation in water environments. The results of model description of nitrogen compound dynamics are evaluated by statistics to find a quantitative criteria in model assessment. In the discussion of simulation results, attention was focused on the analysis of bacterial activities in the conversion of organic as well as mineral nitrogen forms. The results reported here are considered to be the basis for the simulation of nitrogen dynamics in water bodies and for studying various aspects of ecology and aquatic ecosystem behavior

A Review of Mathematical Models of Phosphorus Release from Sediments

This report summarizes the data available on the role of the sediments as an internal source of phosphorus and reviews the literature on the phosphorus exchange processes in the sediment-water interface. Data on the sediment phosphorus release rates is presented. The role of individual processes such as mixing and diffusion as well as important environmental characteristics (oxygen and organic matter concentrations in sediment, temperature, pH and sediment oxidative state and bacterial activity) are discussed. Specific attention is given to analyzing the available information on the mechanisms of phosphorus transformations in the sediment-water interface because it is considered important in choosing the approaches when modeling the phosphorus exchange reactions in the sediment-water layer. The report also includes: models of phosphorus adsorption which are used in calculations of phosphorus removal by sediments. In addition, this report discusses 31 different models that are used for estimations of phosphorus release from the sediment as well as for the simulation of phosphorus transformations in the sediment-water interface. The report summarizes the rate coefficients and model parameters used in the simulation runs

The Chemical-Ecological Modeling of Aquatic Nitrogen Compound Transformation Processes

Nitrogen compounds are important biogeochemical substances that influence the state of water quality. Since transformation of nitrogen compounds is carried out in various water environments (sewage, river, sea and lake waters), it is important to know the rates of these processes. Mathematical models were used for this purpose. Models for nitrogen compound transformation, including both very simple, purely chemical models and complex ecological models, have already been studied at IIASA (RM-78-34). In this report results from the application of other complex ecological models are presented. The models are constructed using the principles of biogeocoenosis modeling. The primary objective of this paper is to make a comparative study of the simulation capabilities of different nitrogen transformation models using a given set of experimental data. Modeling results of nitrogen transformation are compared with experimental observations of sewage, river, sea and lake waters. Nitrogen transformations are interpreted from the ecological point of view and are defined by interactions between different microorganisms (bacteria, phytoplankton and zooplankton) and nitrogen compounds (organic and mineral). Two ecological models are presented in this report. It is shown that models constructed on the basis of biochemical compound transformations have broader simulation capabilities than simple models. The model presented here shows good agreement between observed and predicted nitrogen compound concentrations. The model also provides an explanation of the effects of nitrogen transformations on the oxygen content in water environments. However, at present the models discussed cannot be considered entirely adequate for the ecological processes which they describe, although they reproduce in detail the nitrogen transformations in various waters. The absence of multi-aspect experimental observations, specifically carried out for determining the boundaries of model adequacy, impedes the development of applied research on water quality modeling. The complex ecological models discussed in this report can be used for understanding processes of nitrogen transformations in different water environments. At the same time, these models can also be applied for constructing models of combined biogeochemical cycles of carbon, phosphorus and oxygen, and for simulating functions of aquatic ecosystems as well as for studying various aspects of water quality

Modeling and Explaining the Phosphorus Dynamics of Lake Balaton, 1976-1979

This report describes a mathematical modeling and systems study of the eutrophication problem in Lake Balaton, Hungary. Since it is generally agreed that phosphorus exerts a major influence on the direction of trophic change within the lake, the work focused on the dynamics of the phosphorus level in the lake ecosystem over the period 1976-1979. The Balaton Sector Model (BALSECT) one of the three ecological models developed at IIASA for examining phosphorus dynamics and phytoplankton growth in the lake ecosystem, was used to simulate the basic biological and chemical interactions between phosphorus compartments in the aquatic environment. BALSECT also considers sediment-water phosphorus exchange and phosphorus transfer between the different basins of the lake by advective and wind-induced water flows

Transformations and turnover of Phosphorous Compounds in the Lake Balaton ecosystem, 1976-1978

Transformation of the phosphorous compounds in Lake Balaton was described in the mathematical model BALSECT (Balaton Sector Model). This model, which deals with five types of phosphorous compounds--dissolved inorganic P, dissolved organic P, nonliving particulate organic P, bacterial P, and phytoplankton P--reflects the basic interactions between these compounds in accordance with the consecutive conversion of phosphorous compounds in the water environment. The rates of change in the phosphorous transformation processes are modeled to be dependent on and regulated by environmental factors such as temperature, radiation, water balance, and nutrient watershed load. The model also takes into account the wind action on the horizontal interbasin transport of phosphorus as well as phosphorous exchange between sediment and water. The measurements of temperature, radiation, wind, water balance, and phosphorous loading were used to examine the feasibility of the model in reproducing the phosphorous dynamics in the fourth basin of Lake Balaton for the environmental conditions of 1976-1978. The improved version of the possible watershed nutrient loading was used in this study. On the basis of the analysis of the turnover time values, the details of the cycling of the individual phosphorous compounds and the total P are presented in this report. The explanation of the trends in the phosphorous cycling in the terms of turnover time is considered useful and important for understanding the regime of the phosphorous transformation within the Lake Balaton Ecosystem for the different environmental conditions and changeable nutrient loading. Thus, the simulation results and calculated values of turnover time may be used for the formulation of suggestions concerning the water quality management of this lake

Inheritance of parental genomes by a hybrid form Rana “esculenta” (Amphibia, Ranidae)

In this study, quantitative analysis of paternal genome inheritance by a hybrid form Rana “esculenta” (= Rana esculenta L., 1758 × Rana ridibunda Pall., 1881) (Amphibia, Ranidae) was examined. The hybrid form examined was characterized by a polymodal mode of inheritance (genome of any of the parental species can be inherited). The absence of correlation between the proportion of normal gametes and either sex or ploidity of the producer was demonstrated. The gametes produced could be both haploid and diploid (hybrid or homozygous). The mechanism of alloploid reproduction is discussed