The science of the biosphere

This paper considers the needs and potentials for the development of the biosphere. An emphasis is placed on the unusual qualities of the biosphere, such as important time lags, interactions between life and its environment at large scales, and biological evolution, which has led to large scale changes in the environment during the Earth's history. These qualities require a different approach to the development of a theory for this large scale system than has been used in the past, when the biosphere was treated as a steady-state, quasilinear system. Other aspects of the development of the science of the biosphere, including the use of remote sensing, are reviewed, and the application of these techniques to the estimation of certain biological variables is discussed.     

The biosphere theory of V. I. Vernadsky and the Gaia theory of James Lovelock: a comparative analysis of the two theories and traditions

James Hutton (1726-1797) regarded Earth as a super-organism and physiology the science to study it. A strong line of evidence for an intimate relationship of biological and abiotic processes on Earth leads from Hutton to the Gaia theory of J. Lovelock. A less known in the West but important approach to the biosphere as a self-regulating system (the biosphere theory) was proposed V.I. Vernadsky (1863-1945). The main concern of this paper revolves around the question: What is the difference between Gaia and the biosphere? To approach the problem of Earth as a super-organism one can use also the biosphere theory of V. N. Beklemishev (1890-1962), who examined the biosphere from a morphological viewpoint.     

Origin of biosphere

Concepts of origin of life on the planet are briefly considered. The problem of origin of biosphere is discussed, with a suggestion that the origin of living organisms and biosphere are two aspects of the same process. There is put forward a hypothesis of embryosphere—the primary medium, in which preorganisms could appear. The ecosystemic approach to origin of life poses question about sources of the matter and energy used by the primary life as well as about causes of the biochemical unity that exists in all Earth organisms.     

Ecosphere,biosphere, or Gaia? What to call the global ecosystem

The terms biosphere, ecosphere, and Gaia are used as names for the global ecosystem. However, each has more than one meaning. Biosphere can mean the totality of living things residing on the Earth, the space occupied by living things, or life and life-support systems (atmosphere, hydrosphere, lithosphere, and pedosphere). Ecosphere is used as a synonym of biosphere and as a term for zones in the universe where life as we know it should be sustainable. Gaia is similar to biosphere (in the sense of life and life-support systems) and ecosphere (in the sense of biosphere as life and life-support systems), but, in its most extreme form, refers to the entire planet as a living entity. A case is made for avoiding the term Gaia (at least as a name for the planetary ecosystem), restricting biosphere to the totality of living things, and adopting the ecosphere as the most apt name for the global ecosystem.     

Open systems living in a closed biosphere: a new paradox for the Gaia debate

While energetically open, the biosphere is appreciably closed from the standpoint of matter exchange. Matter cycling and recycling is hence a necessary and emergent property of the global-scale system known as Gaia. But how can an aggregate of open-system life forms have evolved and persisted for billions of years within a planetary system that is largely closed to matter influx and outflow? The puzzling nature of a closed yet persistent biosphere draws our attention to the course of evolution of fundamental metabolic strategies and matter-capture techniques. It suggests a facet of the Gaia hypothesis, framed in terms of persistence. The oceans, atmosphere, soils and biota constitute a complex system which maintains and adjusts matter cycling and recycling within the constraints of planetary closure such that open-system forms of life can persist. This weaker version of the Gaia hypothesis may be useful because it readily lends itself to at least one form of test. What is the solution to the closed biosphere puzzle, and does it indicate that Gaia merits status as a discrete entity? We suggest several disciplines within the field of biology that might provide tools and perspectives toward reaching a solution. These disciplines include artificial closed ecosystems, prokaryote evolution, the nexus of thermodynamics and evolutionary biology, and hierarchy theory in ecosystem modeling and evolution theory.     

Review: from chemosphere to biosphere

An understanding of how the Earth's chemosphere was transformed to a biosphere is central to our understanding of the origin of life and the search for extraterrestrial life or life signatures. Once early prokaryotic life originated and colonized the Earth, the biosphere was well on its way to being formed. In this paper, information and knowledge is integrated to examine the possibility how life first self-assembled and transformed a lifeless chemosphere into a complex biosphere that we still do not understand today.     

Formation of evolutionary approach as an explanatory principle for ecology

Although the connection of ecology with evolutionary idea and specifically with Darwinism was proclaimed for a long time it seems that Herbert Spencer's approach with its emphasize on natural equilibrium was much more often used as its real theoretical base. Elements of Darwinian approach appeared only in 1920-30s in works of those few researchers who studying the distribution and population dynamics of different species tried to understand general mechanisms providing their continuing existence. Later, in the middle of 1950s the first attempts were undertaken to consider the population life history (primarily the age specific schedule of death and reproduction) as a result of natural selection aimed to maintain the necessary level of fitness. A special attention in these studies that burgeoned in 1980-90s was paid to looking for various trade-offs between particular parameters of life history, e.g., between the survival of juveniles and fecundity of adults. The problem of life history optimization became central for the whole branch of science named "evolutionary ecology". Though traditionally this branch is connected with Darwinism, it is rooted rather in Spencer's ideas on moving equilibrium and deals more with static than dynamic. Disproportionately less attention was paid to the evolution of communities since these formations could be hardly interpreted as units of Darwinian selection. Moreover, the ecologists dealing with biosphere as a unified biogeochemical system began insist on "nondarwinian" nature of its evolution. The author considers this opinion as not sufficiently grounded. Darwin's ideas about unavoidable exponential growth, intrinsic for any population, consequent deficiency of resources, and differential survival and reproduction of individuals are still useful while studying the evolution of living organisms (phylogenetics) or the development of biosphere as a global ecosystem.     

Microbial diversity of deep-sea extremophiles--Piezophiles, Hyperthermophiles, and subsurface microorganisms]

Knowledge of our Planet's biosphere has increased tremendously during the last 10 to 20 years. In the field of Microbiology in particular, scientists have discovered novel "extremophiles", microorganisms capable of living in extreme environments such as highly acidic or alkaline conditions, at high salt concentration, with no oxygen, extreme temperatures (as low as -20 degrees C and as high as 300 degrees C), at high concentrations of heavy metals and in high pressure environments such as the deep-sea. It is apparent that microorganisms can exist in any extreme environment of the Earth, yet already scientists have started to look for life on other planets; the so-called "Exobiology" project. But as yet we have little knowledge of the deep-sea and subsurface biosphere of our own planet. We believe that we should elucidate the Biodiversity of Earth more thoroughly before exploring life on other planets, and these attempts would provide deeper insight into clarifying the existence of extraterrestrial life. We focused on two deep-sea extremophiles in this article; one is "Piezophiles", and another is "Hyperthermophiles". Piezophiles are typical microorganisms adapted to high-pressure and cold temperature environments, and located in deep-sea bottom. Otherwise, hyperthermophiles are living in high temperature environment, and located at around the hydrothermal vent systems in deep-sea. They are not typical deep-sea microorganisms, but they can grow well at high-pressure condition, just like piezophiles. Deming and Baross mentioned that most of the hyperthermophilic archaea isolated from deep-sea hydrothermal vents are able to grow under conditions of high temperature and pressure, and in most cases their optimal pressure for growth was greater than the environmental pressure they were isolated from. It is possible that originally their native environment may have been deeper than the sea floor and that there had to be a deeper biosphere. This implication suggests that the deep-sea hydrothermal vents are the windows to a deep subsurface biosphere. A vast array of chemoautotrophic deep-sea animal communities have been found to exist in cold seep environments, and most of these animals are common with those found in hydrothermal vent environments. Thus, it is possible to consider that the cold seeps are also one of slit windows to a deep subsurface biosphere. We conclude that the deep-sea extremophiles are very closely related into the unseen majority in subsurface biosphere, and the subsurface biosphere probably concerns to consider the "exobiology".     

On the early stages of the evolution of the geosphere and biosphere

The conditions necessary for the existence of nucleic-protein life are as follows: the presence of liquid water, an atmosphere, and a magnetic field (all of which protect from meteorites, abrupt changes in temperature, and a flow of charged particles from space) and the availability of nutrients (macro-and microelements in the form of dissolved compounds). In the evolution of the geosphere, complex interference of irreversible processes (general cooling, gravitational differentiation of the Earth’s interior, dissipation of hydrogen, etc.) with cyclic processes of varying natures and periodicities (from the endogenic cycles “from Pangea to Pangea” to Milankovitch cycles), these conditions have repeatedly changed; hence, in the coevolution of the geosphere and biosphere, the vector of irreversible evolution was determined by the geosphere. Only with the appearance of the ocean as a global system of homeostasis, which provided the maintenance and leveling of nutrient concentrations in the hydrosphere, and the conveyor of nutrients from the mantle, “the film of life” could begin its expansion from the source of the nutrients. Life itself is a system of homeostasis, but not due to the global size and a vast buffer capacity, but because of the high rate of reactions and presence of a program (genome) that allowed its development (ontogeny) independent from the outside environment. The early stages of the origin and evolution of the biosphere (from the RNA-world to the development of the prokaryotic ecosystems) were characterized by the domination of chemotrophic ecosystems. The geographical ranges of these ecosystems were directly or indirectly (through the atmosphere and hydrosphere) tied to the sources of nutrients in the geosphere, which were in turn connected to various sources of volcanic and geotectonic activity (geothermal waters, “black smokers” along the rift zones, etc.). This gave the biosphere consisting of chemotrophic ecosystems a mosaic appearance composed of separate local oases of life. The decrease of methane and accumulation of O₂ in the atmosphere in the geological evolution of the Earth caused the extinction of chemotrophic ecosystems and directed evolution of the biosphere toward autotrophy. Autotrophic photosynthesis gave the biosphere an energy source that was not connected to the geosphere, and for the first time allowed its liberation from the geosphere by developing its own vector of evolution. This vector resulted in the biosphere forming a continuous film of life on the planet by capturing the continents and occupying pelagic and abyssal zones, and the appearance of eukaryotes. The geosphere formed biogeochemical cycles in parallel to the geochemical ones, and comparable in the annual balances of participating matter.     

谈地球生物学的重要意义

地球生物学是地球科学与生命科学交叉形成的一级学科,它研究作为地球系统三大基本过程之一的生命过程,即生物圈与地球其他圈层的相互作用.不仅是地球影响生物圈.而且生物圈也影响地球系统.这种相互作用或影响,从地球历史早期到现在,是一直在协同、耦合地进行着.生命与地球环境的协同演化是地球生物学的核心.当前地球生物学发展的重点是地球微生物学.宏体生物能反映地球环境对它们的影响及它们对环境的适应,但除植物外,它们对环境的影响有限.了解生物圈与地圈双向的相互作用必须研究地球微生物学.生命科学和整个自然科学都在向微观方向发展,不断形成新的理论和技术方法.古生物学不能停留在以古动、植物学为主的阶段,而要与生命科学和整个自然科学保持同步发展.现在我们已经找到了解决微生物与地质研究相结合问题的途径.微生物功能群具有重要的地质学意义,是研究地球微生物学的突破口.地球生物学是古生物学的继承和超越.分类系统学将仍然是研究的基础,但是包含了传统古生物学的地球生物学在学科内容和技术方法上将更多地与物理、化学、生物等学科交叉融合.其结果将使古生物学在时间上更前溯,在空间上更开拓,为古生物学在地球系统科学研究和为国民经济主战场服务中开辟更广阔的前景.     

"Bioplutonism" and the evolutionary implications of beneficial genes from another biosphere

Could exogenous genes from another biosphere have aided the evolution of life on Earth's surface over the last half-billion years? That possibility was considered by Thomas Gold in 1992, when he hypothesized that a “deep hot biosphere” (DHB) resides independently well below its cooler surface counterpart. And he suggested that “… in the long term … there may occasionally be beneficial exchanges of genetic material between microbial life at depth and the surface life.” Thus, the question: what evidence is there to support Gold's notion that exogenous genes from the DHB – let us call them “bioplutons” – ever bestowed benefits on the evolution of surface life? In pursuit of this question I drafted a null hypothesis: “Nothing beyond our own biosphere, as we know it today, renders any kind of genetic benefits to biological evolution.” After objectively analyzing the evidence and arguments pro and con I failed to reject the null hypothesis, given what we know today, especially the fact that no genetic imprint from the DHB has been identified in eukaryotic genomes. But my conclusion is regarded as tentative, because the fundamentals of Gold's argument, collectively referred to herein as “bioplutonism,” might be confirmed eventually with successful probes into the DHB, and with the sampling of its alleged genetic material.     

The role of anaerobic fungi in fundamental biogeochemical cycles in the deep biosphere

A major part of the biologic activity on Earth is hidden underneath our feet in an environment coined the deep biosphere which stretches several kilometers down into the bedrock. The knowledge about life in this vast energy-poor deep system is, however, extremely scarce, particularly for micro-eukaryotes such as fungi, as most studies have focused on prokaryotes. Recent findings suggest that anaerobic fungi indeed thrive at great depth in fractures and cavities of igneous rocks in both the oceanic and the continental crust. Here we discuss the potential importance of fungi in the deep biosphere, in particular their involvement in fundamental biogeochemical processes such as symbiotic relationships with prokaryotes that may have significant importance for the overall energy cycling within this vast subsurface realm. Due to severe oligotrophy, the prokaryotic metabolism at great depth in the crust is very slow and dominantly autotrophic and thus dependent on e.g. hydrogen gas, but the abiotic production of this gas is thought to be insufficient to fuel the deep autotrophic biosphere. Anaerobic fungi are heterotrophs that produce hydrogen gas in their metabolism and have therefore been put forward as a hypothetical provider of this substrate to the prokaryotes. Recent in situ findings of fungi and isotopic signatures within co-genetic sulfide minerals formed from bacterial sulfate reduction in the deep continental biosphere indeed seem to confirm the fungi-prokaryote hypothesis. This suggests that fungi play a fundamental biogeochemical role in the deep biosphere.     

Geochemical ecology and problems of health.

The state of health or disease is determined by the nature of the organism, the properties of the biosphere, the heterogeneity of its natural geochemical composition and changes brought about by technology (technogenic changes). For a systematic study of the conditions of health and endemic diseases we have suggested a system of biogeochemical regionalizing of the biosphere with the aid of biospheric taxa: regions of the biosphere, subregions of the biosphere, biogeochemical provinces. The main criteria of the regionalizing are biogenous cycles of chemical elements (links of the biogeochemical food chain from soil-forming rocks to man). An important criterion of the biogeochemical regionalizing is threshold concentrations of chemical elements. The organism regulates its metabolism within the ranges of chemical element concentration between the upper and lower thresholds (necessity range). When chemical elements are present in concentrations above the upper threshold and below the lower threshold, dysfunctions and endemic diseases are observed. Hence, the biogeochemical food chain allows us to establish critical links responsible for the state of health or endemic disease. Principles of optimizing the conditions of the environment and life have been worked out. The creation by us in the U.S.S.R. of biogeochemical maps relating conditions of the environment to biological reactions of organisms has proved a useful method of studying the ecological structure of the biosphere.     

Astrobiology of life on Earth

Astrobiology is mistakenly regarded by some as a field confined to studies of life beyond Earth. Here, we consider life on Earth through an astrobiological lens. Whereas classical studies of microbiology historically focused on various anthropocentric sub-fields (such as fermented foods or commensals and pathogens of crop plants, livestock and humans), addressing key biological questions via astrobiological approaches can further our understanding of all life on Earth. We highlight potential implications of this approach through the articles in this Environmental Microbiology special issue ‘Ecophysiology of Extremophiles’. They report on the microbiology of places/processes including low-temperature environments and chemically diverse saline- and hypersaline habitats; aspects of sulphur metabolism in hypersaline lakes, dysoxic marine waters, and thermal acidic springs; biology of extremophile viruses; the survival of terrestrial extremophiles on the surface of Mars; biological soils crusts and rock-associated microbes of deserts; subsurface and deep biosphere, including a salticle formed within Triassic halite; and interactions of microbes with igneous and sedimentary rocks. These studies, some of which we highlight here, contribute to our understanding of the spatiotemporal reach of Earth'sfunctional biosphere, and the tenacity of terrestrial life. Their findings will help set the stage for future work focused on the constraints for life, and how organisms adapt and evolve to circumvent these constraints.     

The fundamental processes in ecology: a thought experiment on extraterrestrial biospheres

Ecological science is often organised as a hierarchical series of entities: genes, individuals, populations, species, communities, ecosystems and biosphere. Here, I consider an alternative process‐based approach to ecology, and analyse the nature of the fundamental processes in ecology. These fundamental processes are discussed in the context of the following question:‘for any planet with carbon‐based life, which persists over geological time scales, what are the minimum set of ecological processes that must be present?‘I suggest that the following processes would be present on any such planet: energy flow, multiple guilds, ecological tradeo ffs leading to within‐guild biodiversity, ecological hypercycles, merging of organismal and ecological physiology, carbon sequestration and possibly photosynthesis. Nutrient cycling is described as an emergent property of these fundamental processes. I discuss reasons why a biosphere based on a single species with no nutrient cycling is very unlikely to exist. I also describe the concept of ‘Gaian effect’. This suggests that some processes will always tend to extend the lifespan of a biosphere in which they develop (positive Gaian effect) while others could either increase or decrease (negative Gaian effect) such a lifespan. These ideas are discussed in the context of astrobiology, ecosystem services, conservation biology and Gaia theory.     

Biogenic Enhancement of Weathering and the Stability of the Ecosphere

A dynamic model of the global carbon cycle is used to determine the influence of biotic amplification of weathering on the overall stability of the biosphere. It takes into account the most important processes for the long-term evolution of the Earth. The model is solved under the condition of slow changing luminosity, volcanic activity, and continental area. We find that for large enough amplification factors the system has two stable states, the abiotic and biotic solution. Furthermore, this leads to an extension of the life span of the biosphere by 0.7 Gyr compared to previous studies underestimating the effect of biogenic enhancement of weathering. It can be shown that the biosphere is resilient to random perturbation of the global carbon cycle for the next 0.5-1.0 Gyr.     

The carbon cycle on early Earth--and on Mars?

One of the goals of the present Martian exploration is to search for evidence of extinct (or even extant) life. This could be redefined as a search for carbon. The carbon cycle (or, more properly, cycles) on Earth is a complex interaction among three reservoirs: the atmosphere; the hydrosphere; and the lithosphere. Superimposed on this is the biosphere, and its presence influences the fixing and release of carbon in these reservoirs over different time-scales. The overall carbon balance is kept at equilibrium on the surface by a combination of tectonic processes (which bury carbon), volcanism (which releases it) and biology (which mediates it). In contrast to Earth, Mars presently has no active tectonic system; neither does it possess a significant biosphere. However, these observations might not necessarily have held in the past. By looking at how Earth's carbon cycles have changed with time, as both the Earth's tectonic structure and a more sophisticated biology have evolved, and also by constructing a carbon cycle for Mars based on the carbon chemistry of Martian meteorites, we investigate whether or not there is evidence for a Martian biosphere.     

Maximum entropy production and general trends in biospheric evolution

The biosphere has greatly shaped the past evolution of the Earth system. Here I argue that life evolved to maximize planetary entropy production. The evolution of the Earth system through time has thus evolved as far away from thermodynamic equilibrium as possible. I describe the implications of this hypothesis for the evolution of the global cycles of water and carbon and the implied consequences for biospheric evolution. This thermodynamic perspective of Earth’s biospheric evolution extends the views of Vernadski and Lovelock and puts it on a quantitative foundation.     

Millennium bugs

Microbiology has a long way to go. Microbes are ubiquitous, and all other life forms in the biosphere exist solely because of them, but, as less than 1% of microorganisms can be grown in the laboratory, more than a century of research has revealed only the tip of the iceberg concerning this most crucial of life sciences. There are many intellectual challenges remaining. The flow of complete sequences of bacterial genomes is likely to spawn renewed research in answering many questions of concern to academic, medical and industrial interests. Elucidating the roles of microbes, the oldest and most vital inhabitants of the biosphere, in the evolutionary process and in the maintenance of other life forms will be the major thrust in the years to come.     

Deep-sea research ground for the study of living matter properties in extreme conditions

The Black Sea hollow bottom is a promising research ground in the field of deep-sea radiochemoecology and exobiology. It has turned out to be at the intersection of the earth and cosmic scientific interests such as deep-sea marine radiochemoecology from the perspective of the study of extreme biogeocenological properties of the Earth biosphere and exobiology from the standpoint of the study of life phenomena (living matter) outside the Earth biosphere, i.e. on other planets and during hypothetical transfer of spores in the outer space. The potential of this ground is substantiated with the data published by the author and co-workers on accumulation of 90Sr, 137Cs and Pu isotopes with silts of bathyal pelo-contour, on the quality of deep-sea hydrogen sulphide waters (after their contact with air) for vital functions of planktonic and benthic aerobes, as well as the species composition of marine, freshwater and terrestrial plants grown from the spores collected from the bottom sediments of the Black Sea bathyal. Discussion was based on V.I. Vernadsky's ideas about the living matter and biosphere, which allowed conclusions about the biospheric and outer space role of the described phenomena.