Quantitative criteria for estimation of natural and artificial ecosystems functioning.

Using biotic turnover of substances in trophic chains, natural and artificial ecosystems are similar in functioning, but different in structure. It is necessary to have quantitative criteria to evaluate the efficiency of artificial ecosystems (AES). These criteria are dependent on the specific objectives for which the AES are designed. For example, if AES is considered for use in space, important criteria are efficiency in use of mass, power, volume (size) and human labor and reliability. Another task involves the determination of quantitative criteria for the functioning of natural ecosystems. To solve the problem, it is fruitful to use a hierarchical approach suitable for both individual links and the ecosystem as a whole. Energy flux criteria (principles) were developed to estimate the functional activities of biosystems at the population, community and ecosystem levels. A major feature of ecosystems as a whole is their biotic turnover of matter the rate of which is restricted by the lack of limiting substances. Obviously, the most generalized criterion is to take into account the energy flux used by the biosystem and the quantity of limiting substance included in its turnover. The use of energy flux by ecosystem, E(USED)--is determined from the photoassimilation of CO2 by plants (per time unit). It can be approximately estimated as the net primary production of photosynthesis (NPP). So, the ratio of CO2 photoassimilation rate (sometimes, measured as NPP) to the total mass of limiting substrate can serve as a main universal criterion (MUC). This MUC characterizes the specific cycling rate of limiting chemical elements in the system and effectiveness of every ecosystem including the global Biosphere. Comparative analysis and elaboration of quantitative criteria for estimation of natural and artificial ecosystems activities is of high importance both for theoretical considerations and for real applications.     

“Biospherics” approach for studies of natural and artificial ecosystems

The main unifying feature of natural and artificial ecosystems is their biotic turnover (cycling) of substances which is induced with energy fluxes. A new integrating scientific discipline – Biospherics – studies biotic cycles (both in experiments and in mathematical models) of different degree of closure and complexity. By its origin, Biospherics is to be connected with extensive studies of Biosphere by Russian academician Vladimir Vernadsky. He developed and used “empirical generalizations” based on innumerous observations, comparisons and reflections. His “bio-geo-chemical principles” of Biosphere and ecosystems development have more qualitative than quantitative nature. Quantitative criteria to evaluate the efficiency of natural and artificial ecosystems are to take into account energy fluxes and their use in ecosystems of different types. At least, three of them are of value for estimation of natural and artificial ecosystems’ functional activities. Energy principle of extensive development (EPED), energy principle of intensive development (EPID) and main universal (generalized) criterion (MUC). The last criterion (Principle) characterizes the specific cycling rate of limiting chemical elements in multi-organism systems, developing under external energy fluxes. Its value can be a quantitative measure of effectiveness for every ecosystem functioning, including our global Biosphere. Different examples of these (above-mentioned) integrated criteria actions are presented and analyzed in the paper.     

Understanding plant-soil relationships using controlled environment facilities.

Although soil is a component of terrestrial ecosystems, it is comprised of a complex web of interacting organisms, and therefore can be considered itself as an ecosystem. Soil microflora and fauna derive energy from plants and plant residues and serve important functions in maintaining soil physical and chemical properties, thereby affecting net primary productivity (NPP), and in the case of contained environments, the quality of the life support system. We have been using 3 controlled-environment facilities (CEF's) that incorporate different levels of soil biological complexity and environmental control, and differ in their resemblance to natural ecosystems, to study relationships among plant physiology, soil ecology, fluxes of minerals and nutrients, and overall ecosystem function. The simplest system utilizes growth chambers and specialized root chambers with organic-less media to study the physiology of plant-mycorrhizal associations. A second system incorporates natural soil in open-top chambers to study soil bacterial and fungal population response to stress. The most complex CEF incorporates reconstructed soil profiles in a "constructed" ecosystem, enabling close examination of the soil foodweb. Our results show that closed ecosystem research is important for understanding mechanisms of response to ecosystem stresses. In addition, responses observed at one level of biological complexity may not allow prediction of response at a different level of biological complexity. In closed life support systems, incorporating soil foodwebs will require less artificial manipulation to maintain system stability and sustainability.     

System analysis of links interactions and development of ecosystems of different types.

The anthropogenic impact on the Earth's ecosystems are leading to dramatic changes in ecosystem functioning and even to destruction of them. System analysis and the use of heuristic modeling can be an effective means to determine the main biological interactions and key factors that are of high importance for understanding the development of ecosystems. Cycling of limiting substances, induced by the external free energy flux, and trophic links interaction is the basis of the mathematical modeling studies presented in this paper. Mathematical models describe the dynamics of simplified ecosystems having different characteristics: 1) different degrees of biotic turnover closure (from open to completely closed); 2) different numbers of trophic links (including both "top-down", "bottom-up" regulation types); 3) different intensities of input-output flows of the limiting nutrient and its total amount in the system. Adaptive values of the changes of lower hierarchical levels (populational, trophic chain level) are to be estimated by integrity indices for total system functioning (e.g. NPP, total photosynthesis). The approach developed can be used for evaluating the contributions of lower hierarchical levels to the functioning of the higher hierarchical levels of the system. This approach may have value for determining biomanipulation management and their assessment.     

On monitoring the bacterial component as an indicator of the state of small man-made ecosystems.

High reproduction rates make the bacterial component of ecosystems a good indicator of the state of the system on the whole. This determines the necessity to develop rapid monitoring of the functional state of the bacterial component of small ecosystems. Information about substrate concentration in the population is indicative of the state of the bacterial culture. Conventional methods of monitoring the concentration of integral substrate in the system take time much longer than the changes in the ecosystem. The paper presents theoretical foundations for the logical sequence "catalase activity--intracellular substrate concentration--estimate of substrate consumed by bacteria" for experimental verification and as a consequence of development of the integral method of monitoring the bacterial population on the basis of determining bacterial catalase activity. Grant numbers: 04-96017, N25.     

Kinetic characteristics of the theoretical ecosystems with different extent of openness.

In this paper, the influence of the extent of openness of ecosystem that is defined by the dilution rate, which characterizes the extent of flowage of the pond, on the intensity of the biotic circulation in ecosystems with different regulation types, number of trophic links and extent of closing has been investigated. We considered open systems, we took into account the return of the limiting substances, such as nitrogen and phosphorous, into the cycle by degradation of detritus and products of vital functions of consumers. It was shown by the numerical calculations that the increase of the dilution rate in without recycle ecosystems leads to increase of the net primary production up to the maximum value corresponding to the two-link trophic chain (biogenic substance and producer) and then, to gradually decrease. The residual concentration of biogenic limiting substances monotone increases. Net primary production and residual concentration of biogenic limiting substances in systems with recycle with even number of links behaves similarly to that in without recycle ecosystems. In the systems with recycle with the odd number of links that values lies on the stable level. We showed that in wide range of the dilution rate the recycling of the ecosystem can highly increase the net primary production and reduce residual concentration of biogenic limiting substances. The influence of the dilution rate on numbers of links that may exist in the system was analyzed.     

Examination of a smallest CELSS (microcosm) through an individual-based model simulation.

Research of the effect of space environment on an ecosystem consisting of plants and animals is essential when they are to be positively used in space. Although there have been experiments on various organisms under space environment in the past, they mainly studied the effect of space environment on an individual organism or a single species. Microcosm is drawing attention as an experimental material of an ecosystem consisting of multiple species. The object in this research is to understand the nature of this network system called ecosystem. Thus, a mixed microorganism culturing system consisting of three types of microorganisms which form a minimum food chain system as a closed ecosystem (chlorella as the producer, bacteria as the decomposer, and rotifer as the consumer) was taken for the subject, on which to research the universal characteristics of ecosystems. From the results of experiments under the terrestrial environment, formation of colonies, which is an ecological structure, has been observed at its mature stage. The organisms form an optimal substance circulation system. Therefore, formation of colonies in simulation models is important. Many attempts have been made to create ecosystem models. For example, the Lotka-Volterra model forms a simultaneous equation with the differential equation expressing predator and prey relationship and many numerical calculations have been conducted on various ecosystems based on expanded L-V models. Conventionally, these top-down methods have been used. However, since this method only describes the average concentration of organisms that are distributed uniformly throughout the system and cannot express the spatial structure of the system, it was difficult to express ecosystem structures like colonies and density distributions. In actual ecosystems, there is heterogeneity in the number of individuals and in substance density, and this is thought to have great significance in ecosystems. Consequently, an individual-based model was used that applies rules to predator-prey relationship, suppression, production, self suppression, etc., of each species. It enabled the emergence of the overall system only by its local rules, and it was possible to reproduce colony generation. In addition, the transition and the ratio of populations for each species match well with experimental results.     

Effects of solar UV-B radiation on aquatic ecosystems.

Solar UV degrades dissolved organic carbon photolytically so that they can readily be taken up by bacterioplankton. On the other hand solar UV radiation inhibits bacterioplankton activity. Bacterioplankton productivity is far greater than previously thought and is comparable to phytoplankton primary productivity. According to the "microbial loop hypothesis," bacterioplankton is seen in the center of a food web, having a similar function to phytoplankton and protists. The penetration of UV and PAR into the water column can be measured. Marine waters show large temporal and regional differences in their concentrations of dissolved and particulate absorbing substances. A network of dosimeters (ELDONET) has been installed in Europe ranging from Abisko in Northern Sweden to Gran Canaria. Cyanobacteria are capable of fixing atmospheric nitrogen which is then made available to higher plants. The agricultural potential of cyanobacteria has been recognized as a biological fertilizer for wet soils such as in rice paddies. UV-B is known to impair processes such as growth, survival, pigmentation, motility, as well as the enzymes of nitrogen metabolism and CO2 fixation. The marine phytoplankton represents the single most important ecosystem on our planet and produces about the same biomass as all terrestrial ecosystems taken together. It is the base of the aquatic food chain and any changes in the size and composition of phytoplankton communities will directly affect food production for humans from marine sources. Another important role of marine phytoplankton is to serve as a sink for atmospheric carbon dioxide. Recent investigations have shown a large sensitivity of most phytoplankton organisms toward solar short-wavelength ultraviolet radiation (UV-B); even at ambient levels of UV-B radiation many organisms seem to be under UV stress. Because of their requirement for solar energy, the phytoplankton dwell in the top layers of the water column. In this near-surface position phytoplankton will be exposed to solar ultraviolet radiation. This radiation has been shown to affect growth, photosynthesis, nitrogen incorporation and enzyme activity. Other targets of solar UV irradiation are proteins and pigments involved in photosynthesis. Whether or not screening pigments can be induced in phytoplankton to effectively shield the organisms from excessive UV irradiation needs to be determined. Macroalgae show a distinct pattern of vertical distribution in their habitat. They have developed mechanisms to regulate their photosynthetic activity to adapt to the changing light regime and protect themselves from excessive radiation. A broad survey was carried out to understand photosynthesis in aquatic ecosystems and the different adaptation strategies to solar radiation of ecologically important species of green, red and brown algae from the North Sea, Baltic Sea, Mediterranean, Atlantic, polar and tropical oceans. Photoinhibition was quantified by oxygen exchange and by PAM (pulse amplitude modulated) fluorescence measurements based on transient changes of chlorophyll fluorescence.     

ECOSIMP2 model: prediction of CO2 concentration changes and carbon status in closed ecosystems.

The ECOSIMP2 model, simulating the Plant-Soil-Atmosphere interactions, was developed as a tool for the management of an experimental artificial ecosystem. It consists in three main carbon compartments for production, consumption and decomposition of the biomass. The main biological parameters concern photosynthesis (apparent Km, CO2 compensation point), the harvest index, the rate of consumption, and the kinetics of litter decomposition. From realistic assumptions of kinetics of soil compartments, a steady-state case was obtained, simulating a terrestrial ecosystem. The stability of the atmospheric CO2 concentration was studied after a virtual enclosure of the system in a 20-m high greenhouse. In natural lighting the conditions of stability are severe because of the small size of the atmospheric compartment which amplifies any imbalance between carbon fluxes. The positive consequence of that amplification for research on artificial ecosystems was emphasized.     

Mathematical modeling of response of ecosystems with different structure to external impact.

A mathematical model was used to study the response of ecosystems of different structures to external impact. The response was measured as a sensitivity coefficient: the magnitude of the system's response vs. the change of the factor in the inflow. The formula has been obtained to calculate the sensitivity coefficient for ecosystems containing different numbers of trophic links. The derived sensitivity coefficients demonstrate that the degree of compensation for the external impact can differ depending on the type of system regulation and the length of the trophic chain. E. g. the sensitivity coefficient decreases with complexity of trophic links in an ecosystem for top-down controlled systems and impact of degree of openness on sensitivity e.g. closed ecosystems show higher sensitivity then fully open ecosystem to impacts also bottom-up control system show less sensitivity then top-down. Grant numbers: N99-04-96017, N25.     

Influence of different natural physical fields on biological processes.

In space flight conditions gravity, magnetic, and electrical fields as well as ionizing radiation change both in size, and in direction. This causes disruptions in the conduct of some physical processes, chemical reactions, and metabolism in living organisms. In these conditions organisms of different phylogenetic level change their metabolic reactions undergo changes such as disturbances in ionic exchange both in lower and in higher plants, changes in cell morphology for example, gyrosity in Proteus (Proteus vulgaris), spatial disorientation in coleoptiles of Wheat (Triticum aestivum) and Pea (Pisum sativum) seedlings, mutational changes in Crepis (Crepis capillaris) and Arabidopsis (Arabidopsis thaliana) seedling. It has been found that even in the absence of gravity, gravireceptors determining spatial orientation in higher plants under terrestrial conditions are formed in the course of ontogenesis. Under weightlessness this system does not function and spatial orientation is determined by the light flux gradient or by the action of some other factors. Peculiarities of the formation of the gravireceptor apparatus in higher plants, amphibians, fish, and birds under space flight conditions have been observed. It has been found that the system in which responses were accompanied by phase transition have proven to be gravity-sensitive under microgravity conditions. Such reactions include also the process of photosynthesis which is the main energy production process in plants. In view of the established effects of microgravity and different natural physical fields on biological processes, it has been shown that these processes change due to the absence of initially rigid determination. The established biological effect of physical fields influence on biological processes in organisms is the starting point for elucidating the role of gravity and evolutionary development of various organisms on Earth.     

Increase of atmospheric CO2: response patterns of a simple terrestrial man-made ecosystem.

Simple models of terrestrial ecosystems with a limited number of components are an efficient tool to study the main laws of functioning of populations, including microbial ones, and their communities, as components of natural ecosystems, under variable environmental conditions. Among other factors are the increase of carbon dioxide in the atmosphere and limitation of plants' growth by biogenic elements. The main types of ecosystems' responses to changes in environmental conditions (a change in CO2 concentration) have been demonstrated in a "plants-rhizospheric microorganisms-artificial soil" simple experimental system. The mathematical model of interactions between plants and microorganisms under normal and elevated atmospheric CO2 and limitation by nutrients (nitrogen and phosphorus) yielded a qualitative agreement between calculated and experimental values of limiting substances concentrations and release rates of exudates.     

Key factors in development of man-made and natural ecosystems.

Key factors of ecosystem functioning are of the same nature for artificial and natural types. An hierarchical approach gives the opportunity for estimation of the quantitative behavior of both individual links and the system as a whole. At the organismic level we can use interactions of studied macroorganisms (man, animal, higher plant) with selected microorganisms as key indicating factors of the organisms immune status. The most informative factor for the population/community level is an age structure of populations and relationships of domination/elimination. The integrated key factors of the ecosystems level are productivity and rates of cycling of the limiting substances. The key factors approach is of great value for growth regulations and monitoring the state of any ecosystem, including the life support system (LSS)-type.     

Progress in ultrasonic bioreactors for CELSS applications.

An important issue in Controlled Ecological Life Support Systems (CELSS) is the recycling of inedible crop residues to recover inorganic plant nutrients such as nitrates, phosphates, potassium and other macro- and micro-nutrients. In a closed system in space, such regeneration is vital to the long term viability of plant growth necessary for the food production and waste handling process. Chemical approaches to recycling such as incineration and wet oxidation are not compatible with low energy and environmentally friendly regeneration of such nutrients. Biological regeneration is more acceptable environmentally, but it is a very slow process and does not typically result in complete recovery of inorganic and organic nutrients. A new approach to biological regeneration is described here involving the combined use of special enzymatic catalysts and ultrasonic energy in a bioreactor system. This new system has the potential for rapid, efficient, environmentally friendly and complete conversion of crop wastes to inorganic plant nutrients and food recovery from cellulose materials. A series of experimental tests were carried out with a soybean crop residue meal substrate. Biochemical conversion rates were significantly expedited with the addition of enzymes and further enhanced through ultrasonic stimulation of these enzymes. The difference in conversion rates was particularly increased after the initial period of soluble organics conversion. The remaining cellulose substrate is much more difficult to biodegrade, and the ultrasonically-enhanced reaction was able to demonstrate a much higher rate of substrate conversion.     

A quarantine protocol for analysis of returned extraterrestrial samples

A quarantine protocol is presented for analysis of samples of extraterrestrial material that might be returned from space to an Earth-orbiting quarantine facility. The protocol is designed to detect biologically active agents in extraterrestrial soil. Its goal is either to certify the sample safe to return to a terrestrial containment facility where extensive biological, chemical, geological and physical investigations can be conducted, or to detect “biological effects” thus dictating second order testing. The protocol requires 46 grams of a one kilogram returned sample plus 54 grams to be reserved for second order testing should that become necessary. The protocol operates at two levels. First, it seeks to detect the presence of any replicating organisms or toxic substances using chemical analyses, microscopy, metabolic tests, and microbiological culturing techniques. The second level involves hazard evaluation by adding any agents found at the first level (or the extraterrestrial soil) to challenge cultures of terrestrial species. The specific types of experiments and the means of executing them were chosen by participants in an American Society for Engineering Education Summer Systems Design Group to provide maximum life detection sensitivity, yet are compatible with a small crew operating behind biological barriers in a condition of weightlessness.     

Mass exchange in an experimental new-generation life support system model based on biological regeneration of environment.

An experimental model of a biological life support system was used to evaluate qualitative and quantitative parameters of the internal mass exchange. The photosynthesizing unit included the higher plant component (wheat and radish), and the heterotrophic unit consisted of a soil-like substrate, California worms, mushrooms and microbial microflora. The gas mass exchange involved evolution of oxygen by the photosynthesizing component and its uptake by the heterotroph component along with the formation and maintaining of the SLS structure, growth of mushrooms and California worms, human respiration, and some other processes. Human presence in the system in the form of "virtual human" that at regular intervals took part in the respirative gas exchange during the experiment. Experimental data demonstrated good oxygen/carbon dioxide balance, and the closure of the cycles of these gases was almost complete. The water cycle was nearly 100% closed. The main components in the water mass exchange were transpiration water and the watering solution with mineral elements. Human consumption of the edible plant biomass (grains and roots) was simulated by processing these products by a unique physicochemical method of oxidizing them to inorganic mineral compounds, which were then returned into the system and fully assimilated by the plants. The oxidation was achieved by "wet combustion" of organic biomass, using hydrogen peroxide following a special procedure, which does not require high temperature and pressure. Hydrogen peroxide is produced from the water inside the system. The closure of the cycle was estimated for individual elements and compounds. Stoichiometric proportions are given for the main components included in the experimental model of the system. Approaches to the mathematical modeling of the cycling processes are discussed, using the data of the experimental model. Nitrogen, as a representative of biogenic elements, shows an almost 100% closure of the cycle inside the system. The proposed experimental model of a biological system is discussed as a candidate for potential application in the investigations aimed at creating ecosystems with largely closed cycles of the internal mass exchange. The formation and maintenance of sustainable cycling of vitally important chemical elements and compounds in biological life support systems (BLSS) is an extremely pressing problem. To attain the stable functioning of biological life support systems (BLSS) and to maintain a high degree of closure of material cycles in than, it is essential to understand the character of mass exchange processes and stoichiometnc proportions of the initial and synthesized components of the system.     

Expression of cloned genes of transgenic microorganisms introduced into man-made ecosystems.

Modeling of transgenic microorganism introduction into small man-made ecosystems can help forecast changes in expression of cloned genes under different conditions of existence. Introduction of the E. coli Z905/pPHL7 strain containing a plasmid with luminescent system genes of luminous bacteria led to changes in cell and colony morphology, reduction in metabolic activity of cells, and, as a result, a lower level of expression of cloned gene. A low concentration of nutrients has been shown to favor greatly the phenotypic change of cells of the recombinant strain. Expression of cloned genes changed due to: a lower concentration of plasmid DNA, a change in regulation of cloned genes, and a change in cells of biosynthesis of substrates needed for expression of luminescent genes. The conducted investigations can provide a basis for the use of marker transgenic microorganisms in closed ecosystems of different types. Grant numbers: 99-04-96017, 00-07-9011.     

低轨道中等能量电子对地磁扰动的响应

低轨道高度上能量电子通量变化与地磁扰动程度密切相关.利用我国资源2号(ZY-2)03星空间环境监测分系统在轨工作期间所获得的能量电子探测数据,以及美国NOAA-15,NOAA-16,NOAA-17三颗卫星中等能量电子探测器自1998年以来积累的太阳同步轨道中等能量电子探测数据,结合地磁活动观测数据,对低轨道高度上中等能量电子对地磁扰动的响应特性进行了统计分析.结果表明,该区域的中等能量电子通量在磁暴、磁层亚暴期间有显著增强,增幅大小与地磁活动程度呈正相关关系,强磁暴期间增幅可达一个数量级左右,在响应时间上存在电子通量变化滞后于磁扰的时间特性.      

Key ecological challenges for closed systems facilities

Closed ecological systems are desirable for a number of purposes. In space life support systems, material closure allows precious life-supporting resources to be kept inside and recycled. Closure in small biospheric systems facilitates detailed measurement of global ecological processes and biogeochemical cycles. Closed testbeds facilitate research topics which require isolation from the outside (e.g. genetically modified organisms; radioisotopes) so their ecological interactions and fluxes can be studied separate from interactions with the outside environment. But to achieve and maintain closure entails solving complex ecological challenges. These challenges include being able to handle faster cycling rates and accentuated daily and seasonal fluxes of critical life elements such as carbon dioxide, oxygen, water, macro- and mico-nutrients. The problems of achieving sustainability in closed systems for life support include how to handle atmospheric dynamics including trace gases, producing a complete human diet, recycling nutrients and maintaining soil fertility, the maintenance of healthy air and water and preventing the loss of critical elements from active circulation. In biospheric facilities, the challenge is also to produce analogues to natural biomes and ecosystems, studying processes of self-organization and adaptation in systems that allow specification or determination of state variables and cycles which may be followed through all interactions from atmosphere to soils. Other challenges include the dynamics and genetics of small populations, the psychological challenges for small isolated human groups and backup technologies and strategic options which may be necessary to ensure long-term operation of closed ecological systems.     

Microdosimetric measurements of heavy ion tracks.

The biological effectiveness of radiations depends on the spatial pattern of ionizations and excitations produced by the charged particle tracks involved. Ionizations produced by both the primary ion and by energetic delta rays may contribute to the production of biologically relevant damage and to the concentration of damage which may effect the probability of repair. Although average energy concentration (dose) can be calculated using homogeneous track models, the energy is actually concentrated in small volumes containing segments of the ion and delta ray tracks. These local concentrations are studied experimentally using low pressure proportional counters, and theoretically, using Monte Carlo methods. Small volumes near an ion track may be traversed by a delta ray. If they are, the energy deposited will be similar to that produced by a single electron track in a low-energy x-ray irradiation. The probability of a delta ray interaction occurring decreases with the square of the radial distance from the track. The average energy deposited is the product of this probability and the energy deposited in an interaction. Average energy deposited calculated from measured interaction probability is in good agreement with the results of homogeneous track models.