Volume VII: Nature — Chapter 13: Biosphere Interactions
"There is no separate stone. There is no separate leaf. There is no separate breath. Everything is one touch, passed through billions of hands. The biosphere is not the sum of organisms. It is their product." — Institute of Systems Ecology, treatise "Unity," +3,940 Y.E.
Related sections: → see [Volume I, Ch.04, "Biochemistry"], → see [Volume I, Ch.12, "Geological Evolution"], → see [Volume I, Ch.15, "Atmosphere and Climate"], → see [Volume I, Ch.21, "Ecosystems"], → see [Volume VII, Ch.03, "Marine Ecosystems"], → see [Volume VII, Ch.09, "The Plant Kingdom"], → see [Volume VII, Ch.10, "Symbiosis and Coevolution"], → see [Volume VII, Ch.12, "Extinction Events"] Length: 18 pages
Introduction
The biosphere of Théxar is not simply "life on a planet," but a planetary system linking the atmosphere, hydrosphere, lithosphere, and cryosphere into a single metabolic cycle. Organisms do not adapt to the environment — they create it. The atmosphere of Théxar (22.6% O₂, 0.8% CO₂, 0.0008% H₂S) is a product of life, not its precondition. The climate of the planet is regulated not only by the star and albedo, but also by forest transpiration, the ocean's emission of dimethyl sulfide, and the deposition of carbonates by reefs.
Carbon, nitrogen, sulfur and silicon cycles are linked by metabolism and mineralisation. Silicon also has an active biological cycle on Earth; on Théxar, silicon structures are particularly widespread.
This chapter examines the biosphere as a single organism — a hypothesis that on Théxar is called not a hypothesis but an observation.
13.1 The Carbon Cycle
Carbon is the basis of life, the currency of energy, the regulator of climate. Its cycle on Théxar spans time scales from seconds (respiration) to hundreds of millions of cycles (carbonate burial).
13.1.1 Carbon Reservoirs
| Reservoir | Exchange process |
|---|---|
| Atmosphere (CO₂) | Rapid biological exchange |
| Ocean (dissolved) | Dissolution and carbonate exchange |
| Biomass (terrestrial) | Growth and decomposition |
| Biomass (marine) | Rapid plankton turnover |
| Soils and peat | Decomposition |
| Carbonate rocks | Burial and geological recycling |
| Organogenic rocks | Burial and geological recycling |
13.1.2 Carbon Fluxes
Théxar carbon cycle
- Atmosphere
CO₂ = 0.8%
- Terrestrial biosphere
- Soils
Humus, peat, detritus
- Ocean
Marine production: 36 Gt C/cycle
- Lithosphere
Carbonates, organogenic rocks
Transfers, Gt C/cycle
- AtmospherephotosynthesisTerrestrial biosphere
- Terrestrial biosphererespiration, firesAtmosphere
- Terrestrial biospheredeath, erosionSoils
- SoilsleachingOcean
- Oceanburial in sedimentsLithosphere
- Lithospherevolcanism, metamorphismAtmosphere
13.1.3 The Biological Carbon Pump
The oceanic carbon pump of Théxar is based on three mechanisms:
- The carbonate pump — reefs and plankton build skeletons of silicon-calcium composite (→ see [Volume VII, Ch.03, "Marine Ecosystems"]), binding CO₂; the skeletons settle to the floor;
- The organic pump — dead biomass and fecal pellets descend into the depths, carrying carbon;
- Vertical migration — zooplankton feeds at the surface at night, metabolizes in the depths by day, releasing CO₂ into the deep waters.
Heavy mineral skeletons accelerate the sinking of some organic matter. Another fraction decomposes in the water column, returning carbon to dissolved form.
13.1.4 Climate Regulation
CO₂ contributes to the greenhouse effect alongside water vapour and other gases. Climate also depends on clouds, albedo, ocean circulation and the distribution of land. Increased weathering binds some atmospheric carbon in carbonates.
Negative feedback: if CO₂ rises → temperature rises → silicate weathering intensifies → CO₂ is bound into carbonates → the concentration falls. Response time: 100,000–500,000 cycles.
13.2 The Nitrogen Cycle
Nitrogen (N₂) makes up 71.8% of the atmosphere of Théxar, but is biologically accessible only in bound form (ammonia, nitrates).
13.2.1 Nitrogen Reservoirs
| Reservoir | Form |
|---|---|
| Atmosphere | N₂ (gas) |
| Biomass | Proteins, DNA |
| Soils | NH₃, NO₃⁻, organics |
| Ocean (dissolved) | NO₃⁻, NH₄⁺ |
| Sedimentary rocks | Organic compounds |
13.2.2 Biological Fixation
Nitrogen fixation — the conversion of N₂ into a bioavailable form — is carried out by diazotrophs (nitrogen-fixing bacteria and cyano-like forms).
| Mechanism | Main agents |
|---|---|
| Symbiosis with legumes | Mor-Bean and analogues |
| Free-living diazotrophs (soil) | Soil bacteria |
| Cyano-like (ocean) | Marine phytoplankton |
| Lightning | Abiogenic fixation |
| Anthropogenic (fertilizers) | Industrial synthesis |
Industrial nitrogen fixation supplements soil and symbiotic diazotrophs. Fertilisers raise yields, but nitrogen carried into water can cause eutrophication; runoff controls reduce this risk.
13.2.3 Denitrification
Closes the cycle: bound nitrogen returns to the atmosphere as N₂ or N₂O. The main process is anaerobic respiration of denitrifying bacteria in soils and sediments.
| Environment |
|---|
| Soils (anaerobic zones) |
| Oceanic sediments |
| Freshwater sediments |
| Oxygen-minimum zones (ocean) |
Bound nitrogen changes through fixation, denitrification, transport and burial. Local accumulation does not imply the same excess in every ecosystem.
13.3 The Sulfur Cycle
Sulfur cycling connects chemosynthesis, decomposition, mineralisation and volcanic sources. H₂S supplies energy to adapted organisms; the same principle operates in Earth’s chemosynthetic communities.
13.3.1 Sulfur Reservoirs
| Reservoir | Form |
|---|---|
| Atmosphere | H₂S (0.0008%) |
| Biomass | Sulfur-containing amino acids |
| Ocean (dissolved) | SO₄²⁻, H₂S |
| Soils | Sulfides, sulfates, organic S |
| Evaporites, pyrites | FeS₂, CaSO₄ |
13.3.2 Sulfur Fluxes
Théxar sulfur cycle
- Atmosphere
H₂S = 0.0008%
The planet’s biomarker
- Terrestrial biosphere + soils
- Ocean
Dissolved SO₄²⁻ and H₂S
- Lithosphere
FeS₂, CaSO₄
Transfers, million ru S/cycle
- Terrestrial biosphere + soilsbiogenic emissionAtmosphere
- Atmospherewet/dry depositionTerrestrial biosphere + soils
- Terrestrial biosphere + soilsriver runoff of sulfatesOcean
- Oceanpyrite burial in sedimentsLithosphere
- Lithospherevolcanism, degassingAtmosphere
- volcanic H₂S from the floor
- Ocean–lithosphere exchange.
13.3.3 Sources of Sulfur Gases
The 0.0008% H₂S in the atmosphere is the biomarker of Théxar, visible from space. Sources:
| Source |
|---|
| Oceanic phytoplankton (DMS and other sulfur compounds) |
| Decomposition of organics in swamps |
| Thexophyta epiphytes (H₂S oxidation + re-emission) |
| Hydrothermal fields (direct release) |
| Volcanism |
Marine dimethyl sulfide oxidises in the atmosphere. Oxidation products contribute to aerosols and cloud droplets; the outcome depends on weather and other particle sources.
13.3.4 Chemosynthesis as a Dominant
Chemosynthetic carbon fixation through H₂S oxidation:
- Ocean: 340 million ru S/cycle → 8.4 Gt C/cycle (23% of marine production);
- Land (soils, caves): 52 million ru S/cycle → 1.2 Gt C/cycle (1.4% of terrestrial).
In total, chemosynthesis provides 8% of the planet's primary production — 40 times the terrestrial figure.
13.4 The Silicon Cycle
Silicon supports structures in many local organisms. Biomineralisation links tissue growth, mineral dissolution and sedimentation; an active biological silicon cycle also exists on Earth.
13.4.1 Silicon Reservoirs
| Reservoir | Form |
|---|---|
| Ocean (dissolved) | H₄SiO₄ |
| Biomass (diatoms, plants) | Amorphous SiO₂ |
| Soils | Silicates, silica |
| Earth's crust | Silicates, quartz |
13.4.2 Biological Mobilization
Silicon biomineralization covers:
- Silodiatoma (silica-flagellates) — 24% of marine phytoplankton;
- Silophyta — 45,000 species of terrestrial silicon plants;
- Mycorrhizal fungi — dissolve and transport SiO₂ to the roots;
- Reef polyps — silicon-calcium skeletons;
- Sponge-analogues — silicon spicules.
Turnover: the biota extracts 12 Gt Si/cycle from the ocean, deposits it in skeletons that, after death, settle to the floor and dissolve again. The biological silicon pump accelerates the silicon cycle 14-fold relative to the abiotic one.
13.4.3 Climate Feedback
Silicate weathering (reaction with CO₂) is a long-term climate regulator:
CaSiO₃ + CO₂ → CaCO₃ + SiO₂
The biological acceleration of weathering (plant roots, mycorrhiza) intensifies CO₂ binding. With warming, plants grow faster → more roots → more weathering → CO₂ falls → cooling. Feedback with a response time of 100,000 cycles.
13.5 Interactions of the Cycles
13.5.1 The C-N-S-Si System
The four cycles are not independent — they are interwoven through biological processes:
| Link | Process |
|---|---|
| C ↔ N | Amino acids, DNA |
| C ↔ S | Sulfur-containing amino acids |
| N ↔ S | Sulfate reduction + ammonification |
| Si ↔ C | Photosynthesis of diatoms |
13.5.2 The Redfield Ratio of Théxar
The average composition of plankton biomass: C₁₀₆N₁₆P₁S₀.₅Si₁₅
This is an average for the community described: individual groups vary, and not all plankton has silicon structures.
13.5.3 Limiting Elements
| Environment | Limiting element | Consequence |
|---|---|---|
| Open ocean (gyre centers) | Phosphorus (P) | Low production |
| Coastal ocean | Nitrogen (N) | Eutrophication when in excess |
| Silicate upwellings | Iron (Fe) | "Rusty" zones |
| Temperate forests | Nitrogen (N) | Slow growth |
| Deserts | Water + phosphorus | Minimal production |
13.6 The Biosphere and the Atmosphere
13.6.1 Composition of the Atmosphere
| Gas | Source | Sink |
|---|---|---|
| N₂ | Volcanism (primary) | Fixation ↔ denitrification (balance) |
| O₂ | Photosynthesis | Respiration, rock oxidation |
| Ar | Decay of ⁴⁰K | — |
| CO₂ | Respiration, volcanism | Photosynthesis |
| H₂O | Evaporation | Precipitation |
| H₂S | Biogenic emission | Oxidation, deposition |
KEY FACT
Photosynthesis supplies atmospheric oxygen; respiration and rock oxidation consume it. Nitrogen, carbon dioxide and sulfur compounds also participate in geological processes. Atmospheric composition reflects their combined action.
13.6.2 Regulation of Oxygen
The O₂ concentration (22.6%) is higher than on Earth (21%). Reason: higher photosynthetic efficiency (4.2% against 3%), but the same rate of respiration. However, the rise of O₂ is limited by the risk of fires — at 25% spontaneous combustion becomes frequent.
Feedback: if O₂ rises → fires become more frequent → biomass burns → production falls → O₂ falls. Stabilization at 22.6%.
13.6.3 Greenhouse Gases
| Gas |
|---|
| H₂O |
| CO₂ |
| CH₄ |
| H₂S |
CH₄ (0.0003%) is biogenic, from anaerobic decomposition in swamps and the guts of herbivores. Lifetime in the atmosphere: 8.4 cycles (oxidized to CO₂).
13.7 The Biosphere and the Hydrosphere
13.7.1 Biological Influence on the Ocean
| Parameter | Reason |
|---|---|
| pH | Carbonate buffer of the reefs |
| Surface salinity | Salt exchange by coastal organisms; the overall balance depends on water and salt transport |
| Transparency | Phytoplankton |
| O₂ in the depths | Mixing, vertical migration |
13.7.2 Biological Regulation of Salinity
The mangrove forests of Théxar excrete excess salt through the silicon membranes of their roots (→ see [Volume VII, Ch.09, "The Plant Kingdom"]), desalinating coastal waters by 0.2–0.4%. The area of the mangroves (49,600 mo²) is sufficient to affect global salinity.
13.8 Feedbacks and Homeostasis
13.8.1 The Living Planet Hypothesis
The aggregate of biospheric feedbacks creates planetary homeostasis — the ability of a system to return to equilibrium after disturbances.
| Disturbance | Feedback | Response time |
|---|---|---|
| Rise of CO₂ | Intensification of photosynthesis → absorption of CO₂ | 10–100 cycles |
| Fall of O₂ | Fewer fires → growth of biomass → more O₂ | 100–1,000 cycles |
| Warming | DMS release can alter aerosols and clouds; the effect depends on weather | Depends on atmospheric conditions |
| Cooling | Less weathering → growth of CO₂ → warming | 10,000–100,000 cycles |
13.8.2 The Limits of Homeostasis
Homeostasis is not absolute. The five major biological crises (→ see [Volume VII, Ch.12]) show: under a sufficiently strong disturbance the system switches into a new state. Examples:
- The Oxygen Catastrophe: transition from an anaerobic to an aerobic biosphere;
- Total glaciation: transition into a "snowball" (reversible only thanks to volcanism).
Chapter Summary
- The biosphere of Théxar is a planetary system linking the four biogeochemical cycles (C, N, S, Si) with the atmosphere, hydrosphere, and lithosphere in a single metabolic circuit.
- The carbon cycle links photosynthesis, respiration, ocean transport and geological burial.
- Sulfur cycling links living communities with ocean and rock; chemosynthesis supports food webs far from sunlight.
- The silicon cycle connects dissolved minerals with plant tissues, plankton skeletons and bottom sediments.
- Atmospheric composition depends on biological and geological sources and sinks.
- Planetary homeostasis is maintained by feedbacks (response times 1–100,000 cycles), but has limits — the five major biological crises show switches into new states.