Ecology: biology of interaction. 2.04. Biogeochemical cycles

Ukrainian Language (latest version) / Russian Language (update stopped)

2.03. Gaia hypothesis (metaphor)

D. Shabanov, M. Kravchenko. Ecology: Biology of Interactions Chapter 2. Biospherology

2.05. Energy Sources for BGC Cycles

{ "translated_text": "Ukrainian language (latest version) / Russian language (update discontinued)\n\n2.03. Gaia hypothesis (metaphor)\n\nD. Shabanov, M. Kravchenko. Ecology: the biology of interaction\nChapter 2. Biospherology\n\n2.05. Energy sources for biogeochemical cycles\n\n2.4. Biogeochemical cycles\nI am a collection of water, calcium and organic molecules, called Carl Sagan. You represent a nearly identical system of molecules with a different collective name. And only that? Is there really nothing in us but molecules? Some people think this degrades human dignity. Personally, I find it inspiring that our world allows such fine and complex molecular machines as we are to develop.\nCarl Sagan\nEarth life is built on a very complex chemical basis. Many chemical elements are required for its existence (Fig. 2.4.1). Although the main compound in organisms is water, organic substances composed of diverse atoms are absolutely necessary for life processes. Among the elements that are important resources for the biosphere, the most important are the so‑called biogenic elements or biogens. Approximately half of the 54 elements occurring in the Earth’s crust are biogens. Especially important are the macro‑elements—C, H, N, O, P, S, Ca, K and Mg—and certain micro‑elements—Fe, Cl, Na, Zn, V, Mo, B, Co, Cu, Si, Se, Cr, Ni, I, F, Sn and As.\n[IMG_1]\nFig. 2.4.1. Elements important for living organisms, in D.I. Mendeleev’s table\nThe roles performed by biogens are diverse. Four of them (the so‑called organogenic elements: carbon, hydrogen, nitrogen and oxygen) constitute the structural basis of organic molecules. Phosphorus is necessarily part of nucleic acids, and sulfur is part of some amino acids (and therefore proteins). Calcium, potassium, sodium and chlorine ions are essential for the life activity of cells. Many metals are components of key organic molecules. For example, magnesium is part of the chlorophyll molecule, and an iron ion is one of the components of heme (a constituent of hemoglobin—the oxygen‑transporting blood protein—as well as some other proteins).\nFor organisms to incorporate these elements into their bodies, the elements must be available in a form accessible in the environment inhabited by organisms. Once an atom enters a living organism, the same atom can move from one molecule to another, from one organism to another. However, over time any atom of any biogen will leave the living matter and return to the surrounding environment. To replenish the resulting deficiency of necessary elements, biogeochemical cycles must operate in the environment.\nThe beginning of the study of biogeochemical cycles is probably linked to the name of the Scottish geologist James Getty (more familiar transliteration—Gettton, 1726–1797). Before Getty, geology was dominated by Neptunism, which interpreted geological features of the Earth as consequences of the biblical flood. Getty opposed this with Plutonism—the idea that Earth material is destroyed by erosion, forms new rocks on the sea floor, passes through the interior, transforms and rises again, where it is subjected to erosion once more. Getty opposed the prevailing catastrophism in geology with actualism—the concept of a long geological history during which the same processes that operate now have been acting. For eighteenth‑century thinking, Getty’s views can be considered a true revolution. He can be seen both as a predecessor of Vernadsky’s ideas about the biosphere and even as a forerunner of the Gaia hypothesis. The point is that Getty compared Earth’s activity to the life activity of an organism.\nA biogeochemical cycle (BGC) is defined as a set of relatively closed pathways of matter movement through living organisms and their habitat. They are called biogeochemical cycles because both biological and geochemical processes participate in their functioning. Of course, it is not required that elements move in a perfect circle while traveling through a BGC. However, as atoms pass from one molecule to another within organisms and the environment, the same atom can repeatedly return to a particular state. This is where the cyclicity of biogeochemical processes manifests.\nExamining the diagrams below that illustrate BGCs, one can see that they consist of “funds” and “flows”. Funds are pools of substances containing the element in a specific form. Flows are transformation pathways that transfer the element from one fund to another.\nElements in different funds change at different rates. Consider the hydrological cycle (Fig. 2.5.1). The amount of water vapor present in the atmosphere at any moment passes through the atmosphere several times a year. At the same time, only a small amount of water bound in the lithosphere changes over millions of years. That is why BGCs distinguish between reserve and exchange funds.\nSeveral types of cycles are identified, the main ones being cycles of gaseous substances with reserve funds in the atmosphere and hydrosphere, and sedimentary cycles with a reserve fund in the lithosphere. Biogeochemical cycles that have atmospheric funds (carbon, nitrogen, water cycles, as well as separate oxygen and hydrogen cycles) can be regulated by organisms much better than cycles whose all funds are located in the lithosphere. BGCs differ in the degree of regulation by living organisms. It should be noted that regulation of sedimentary cycles is poorer. If the downward movement of an element into the crust is faster than its upward movement, a shortage arises that limits the cycle but slows the descent. The element lacking for the cycle will be retained more strongly by living matter and will be removed from the cycle more slowly.\nThe role of living organisms in retaining biogens was vividly demonstrated in an experiment conducted at an American biostation in the Hubbard‑Brook area (Fig. 2.4.2). A small plot of land (a gorge) bounded by a watershed was selected. Measuring equipment was installed on the stream flowing out of this plot. After all vegetation on the experimental plot was destroyed, the researchers recorded not only a two‑fold increase in the amount of outflowing water (before the experiment the water was retained by soil and plants and returned to the atmosphere through transpiration) but also an increase in the biogen content of this water.\n[IMG_2]\nFig. 2.4.2. One of the consequences of forest removal at the American experimental station in Hubbard‑Brook was a multiple (more than an order of magnitude) increase in nitrate export from the area where all vegetation had been destroyed (note the break on the ordinate scale!)\nFor example, although metals such as Ca, K, Na, Mg are usually not components of organic molecules, they are absolutely essential for cell life. They are highly mobile in ecosystems. The input of cations into an ecosystem is linked to geological and biological weathering of parent rocks, as well as deposition with dust and sediments. Cation loss occurs through removal by surface and ground waters. The biological community actively retains this loss, increasing cation concentrations in exchange funds. After the forest plot in Hubbard‑Brook was cleared, biogen export increased dramatically (calcium threefold, nitrogen fifteenfold).\nIn tropical forests the overwhelming majority of biogens are stored in plant biomass, in temperate forests—in litter.\nHumans are a powerful geological factor. Humanity uses almost all elements in its activities, including those employed solely for technosphere needs (uranium, plutonium, mercury and others). We intensively intervene in the biogen cycle through fertilizer production, which has caused biogenic pollution of a large part of the biosphere.\nConservation efforts should aim to transform acyclic processes into cyclic ones. In the Philippines there are areas where rice has been cultivated for over 1000 years on fields separated by sacred forests. Unfortunately, such examples are very rare among artificial ecosystems.\nOne method of studying BGCs is linked to radiation ecology. For instance, by adding a labeled phosphorus (i.e., a substance containing a radioactive phosphorus isotope) to a water body, one can study the pathways and dynamics of its fixation by living matter and sediments. Deuterium (a hydrogen isotope) released into the atmosphere during hydrogen bomb tests proved very useful for studying groundwater. The amount of deuterium in modern sediments is known; by measuring how much appears in groundwater, one can determine the rate at which groundwater is replenished by surface water.\nUkrainian / Russian\n\n2.03. Gaia hypothesis (metaphor)\n\nD. Shabanov, M. Kravchenko. Ecology: the biology of interaction\nChapter 2. Biospherology\n\n2.05. Energy sources for biogeochemical cycles" }

2.03. The Gaia Hypothesis (Metaphor)

Д. Шабанов, М. Кравченко. Экология: биология взаимодействия
Глава 2. Биосферология

2.05. Energy Sources for Biogeochemical Cycles