Why is biogeochemical cycles considered sustainable

This is a view of a large colony of fish-eating guanay cormorants Phalacrocorax bougancillii near Paracas off the coast of Peru. The dried guano is periodically scraped from the rocks and used for agricultural purposes. Enviromental Issues 5. Too Much of a Good Thing — Pollution by Nutrients Nutrients are essential to the healthy metabolism of organisms and to the proper functioning of ecosystems.

Often, an increase in the supply of certain nutrients will enhance the productivity of wild and cultivated plants — this is the principle behind the use of fertilizer in agriculture.

However, there are also cases in which an excessive supply of nutrients has caused important environmental problems. However, the use of agricultural fertilizer can result in concentrations of NO 3 — in drinking water that are high enough to be toxic to humans, especially to infants see Chapter Yet gaseous NO and N 2 O are air pollutants if they occur in high concentrations, especially in sunny environments where they are involved in the photochemical production of toxic ozone see Chapter There are other examples of environmental problems caused by excessive nutrients.

For instance, CO 2 is one of the most important plant nutrients because carbon comprises about half of plant biomass. But this critical nutrient occurs in a relatively small atmospheric concentration — only about 0. This well-documented change is contributing to global warming, an important environmental problem see Chapter Eutrophication, or an excessive productivity of waterbodies, is another environmental problem related to an excessive supply of nutrients.

It is most often caused by an excess of PO 4 3— , usually because of sewage dumping or runoff from fertilized agricultural land see Chapter Highly eutrophic lakes are degraded ecologically and may no longer be useful as a source of drinking water or for recreation.

Clearly, these examples show that there is a fine balance between chemicals serving as beneficial nutrients, or as damaging pollutants. Sulphur is a key constituent of certain amino acids, proteins, and other biochemicals. Sulphur is abundant in some minerals and rocks and has a significant presence in soil, water, and the atmosphere. Atmospheric sulphur occurs in various compounds, some of which are important air pollutants see Chapter Sulphur dioxide SO 2 , a gas, is emitted by volcanic eruptions and is also released by coal-fired power plants and metal smelters.

SO 2 is toxic to many plants at concentrations lower than 1 ppm. In some places, such as the Sudbury area, important ecological damage has been caused by this gas Chapter In the atmosphere, SO 2 becomes oxidized to the anion negatively charged ion sulphate SO 4 2— , which occurs as tiny particulates or is dissolved in suspended droplets of moisture. Hydrogen sulphide H 2 S , which has a smell of rotten eggs, is emitted naturally from volcanoes and deep-sea vents.

It is also released from habitats where organic sulphur compounds are being decomposed under anaerobic conditions, and from oxygen-poor aquatic systems where SO 4 2— is being reduced to H 2 S. Dimethyl sulphide is another reduced-sulphur gas that is produced in the oceans and emitted to the atmosphere.

In oxygen-rich environments, such as the atmosphere, H 2 S is oxidized to sulphate, as is dimethyl sulphide, but more slowly. Most emissions of SO 2 to the atmosphere are associated with human activities, but almost all H 2 S emissions are natural. An important exception is the emission of H 2 S from sour-gas wells and processing facilities, for example, in Alberta. Overall, the global emission of all sulphur-containing gases is equivalent to about million tonnes of sulphur per year.

Sulphur occurs in rocks and soils in a variety of mineral forms, the most important of which are sulphides, which occur as compounds with metals. Iron sulphides such as FeS 2 , called pyrite when it occurs as cubic crystals are the most common sulphide minerals, but all of the heavy metals such as copper, lead, and nickel can exist in this mineral form.

Wherever metal sulphides become exposed to an oxygen-rich environment, the bacterium Thiobacillus thiooxidans oxidizes the mineral, generating sulphate as a product. This autotrophic bacterium uses energy from this chemical transformation to sustain its growth and reproduction. This kind of primary productivity is called chemosynthesis in parallel with the photosynthesis of plants.

In places where large amounts of sulphide are oxidized, high levels of acidity are associated with the sulphate product, a phenomenon referred to as acid-mine drainage see Chapter Sulphur also occurs in a variety of organically bound forms in soil and water. These compounds include proteins and other sulphur-containing substances in dead organic matter.

Soil microorganisms oxidize organic sulphur to sulphate, an ion that plants can use in their nutrition. Plants satisfy their nutritional requirements for sulphur by assimilating its simple mineral compounds from the environment, mostly by absorbing sulphate dissolved in soil water, which is taken up by roots. In environments where the atmosphere is contaminated by SO 2 , plants can also absorb this gas through their foliage.

However, too much absorption can be toxic to plants — there is a fine line between SO 2 as a plant nutrient and as a poison. Human activities have greatly influenced certain fluxes of the sulphur cycle.

Important environmental damage has been caused by SO 2 toxicity, acid rain, acid-mine drainage, and other sulphur-related problems. However, sulphur is also an important mineral commodity, with many industrial uses in manufacturing and as an agricultural fertilizer.

Nutrients are chemicals that are essential for the metabolism of organisms and ecosystems. If they are insufficient in quantity, then ecological productivity is less than it potentially could be.

Nutrients can also be present in excess, in which case environmental damage may be caused by toxicity and other problems. Nutrients routinely cycle among inorganic and organic forms within ecosystems. Key aspects of nutrient cycles are illustrated by the carbon, nitrogen, phosphorus, and sulphur cycles. Atlas, R.

Microbial Ecology: Fundamentals and Applications. Blasing, T. Recent Greenhouse Gas Concentrations. Botkin, D. Environmental Science: Earth as a Living Planet. Brady, N. The Nature and Properties of Soils. Freedman, B.

Hutchings, D. Gwynne, J. Smol, R. Suffling, R. Turkington, R. Walker, and D. Ecology: A Canadian Context. Nelson Canada, Toronto, ON.

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Biogeochemistry: An Analysis of Global Change. Skip to content Biogeochemical cycles Nutrients Nutrients are any chemicals that are needed for the proper functioning of organisms. The system can be divided into four major compartments: The atmosphere consists of gases and small concentrations of suspended particulates and water vapour. Rocks and soil consist of insoluble minerals that are not directly available for uptake by organisms.

Available nutrients are present in chemical forms that are water soluble to some degree, so they can be absorbed by organisms from their environment and contribute to their mineral nutrition. The organic compartment consists of nutrients present within living and dead organic matter.

This compartment can be divided into three functional groups: a living biomass of autotrophs such as plants, algae, and autotrophic bacteria, b living heterotrophs including herbivores, carnivores, omnivores, and detritivores, and c and all forms of dead organic matter. The Soil Ecosystem Soil is a complex and variable mixture of fragmented rock, organic matter, moisture, gases, and living organisms that covers almost all terrestrial landscapes.

Previous: Ecology. Next: Energy and Ecosystems. Share This Book Share on Twitter. Biogeochemical cycles are a form of natural recycling that allows the continuous survival of ecosystems. What do you mean by biogeochemical cycle? A biogeochemical cycle is one of several natural cycles, in which conserved matter moves through the biotic and abiotic parts of an ecosystem.

The abiotic components can be subdivided into three categories: thehydrosphere water , the atmosphere air and the lithosphere rock. How do biogeochemical cycles impact the ecosystem?

Ecological systems ecosystems have many biogeochemical cycles operating as a part of the system, for example the water cycle, the carbon cycle, the nitrogen cycle, etc. These compounds are oxidized to release carbon dioxide, which can be captured by plants to make organic compounds. What is a biogeochemical cycle example? Many biogeochemical cycles affect our daily lives in many ways.

A prime example of one of these cycles is the water cycle. Some key words with the water cycle include condensation, precipitation, and evaporation. Water Cycle. Another great example in our everyday lives is the flow of oxygen and carbon dioxide. How many biogeochemical cycles are there? In what ways are humans affecting biogeochemical cycles? Human activities have greatly increased carbon dioxide levels in the atmosphere and nitrogen levels in the biosphere.

Altered biogeochemical cycles combined with climate change increase the vulnerability of biodiversity, food security, human health, and water quality to a changing climate. What is the cycle? You play as a prospector sent on Fortuna III, a living and unstable planet swarming with hostile alien wildlife.

Compete or deal a fragile pact with other Prospectors to claim as many resources as possible. Why is this cycle important to the environment? The retention of heat in the atmosphere increases and stabilizes the average temperature, making Earth habitable for life. More than a quarter of the atmospheric CO 2 pool is absorbed each year through the process of photosynthesis by a combination of plants on land GtC and at sea 90 GtC.

Photosynthesis is the process in which plants use energy from sunlight to combine CO 2 from the atmosphere with water to make sugars, and in turn build biomass.

Almost as much carbon is stored in terrestrial plant biomass GtC as in the atmospheric CO 2 pool. On land, biomass that has been incorporated into soil forms a relatively large pool GtC. At sea, the phytoplankton that perform photosynthesis sink after they die, transporting organic carbon to deeper layers that then either are preserved in ocean sediments or decomposed into a very large dissolved inorganic carbon pool 37, GtC.

Plants are called primary producers because they are the primary entry point of carbon into the biosphere. In other words, almost all animals and microbes depend either directly or indirectly on plants as a source of carbon for energy and growth. All organisms, including plants, release CO 2 to the atmosphere as a by-product of generating energy and synthesizing biomass through the process of respiration.

The natural carbon cycle is balanced on both land and at sea, with plant respiration and microbial respiration much of it associated with decomposition, or rotting of dead organisms releasing the same amount of CO 2 as is removed from the atmosphere through photosynthesis. The Carbon Cycle. Source: U. Department of Energy Genomic Science Program. The global carbon cycle contributes substantially to the provisioning ecosystem services upon which humans depend.

In addition, the global carbon cycle plays a key role in regulating ecosystem services because it significantly influences climate via its effects on atmospheric CO 2 concentrations.

Atmospheric CO 2 concentration increased from parts per million ppm to ppm between the start of industrial revolution in the late eighteenth century and This reflected a new flux in the global carbon cycle — anthropogenic CO2 emissions — where humans release CO 2 into the atmosphere by burning fossil fuels and changing land use.

Fossil fuel burning takes carbon from coal, gas, and oil reserves, where it would be otherwise stored on very long time scales, and introduces it into the active carbon cycle. Land use change releases carbon from soil and plant biomass pools into the atmosphere, particularly through the process of deforestation for wood extraction or conversion of land to agriculture.

In , the additional flux of carbon into the atmosphere from anthropogenic sources was estimated to be 9 GtC—a significant disturbance to the natural carbon cycle that had been in balance for several thousand years previously.

Slightly more than half of this anthropogenic CO 2 is currently being absorbed by greater photosynthesis by plants on land and at sea 5 GtC. However, that means 4 GtC is being added to the atmospheric pool each year and, while total emissions are increasing, the proportion absorbed by photosynthesis and stored on land and in the oceans is declining Le Quere et al. Rising atmospheric CO 2 concentrations in the twentieth century caused increases in temperature and started to alter other aspects of the global environment.

Global environmental change has already caused a measurable decrease in the global harvest of certain crops. The scale and range of impacts from global environmental change of natural and agricultural ecosystems is projected to increase over the twenty-first century, and will pose a major challenge to human well-being.

The vast majority of water on Earth is saline salty and stored in the oceans. This means a significant fraction of the water pool is largely isolated from the water cycle. The major long-term stores of fresh water include ice sheets in Antarctica and Greenland, as well as groundwater pools that were filled during wetter periods of past geological history.

In contrast, the water stored in rivers, lakes, and ocean surface is relatively rapidly cycled as it evaporates into the atmosphere and then falls back to the surface as precipitation.

The atmospheric pool of water turns over most rapidly because it is small compared to the other pools e. Evaporation is the process whereby water is converted from a liquid into a vapor as a result of absorbing energy usually from solar radiation. Evaporation from vegetated land is referred to as evapotranspiration because it includes water transpired by plants, i.

Some water from precipitation moves over the land surface by surface runoff and streamflow , while other water from precipitation infiltrates the soil and moves below the surface as groundwater discharge. Water vapor in the atmosphere is commonly moved away from the source of evaporation by wind and the movement of air masses. Consequently, most water falling as precipitation comes from a source of evaporation that is located upwind.

The Water Cycle. Department of the Interior and U. Geological Survey, The Water Cycle. Freshwater supply is one of the most important provisioning ecosystem services on which human well-being depends. By , the rate of our water extraction from rivers and aquifers had risen to almost cubic kilometers per year. The greatest use of this water is for irrigation in agriculture, but significant quantities of water are also extracted for public and municipal use, as well as industrial applications and power generation.

Other major human interventions in the water cycle involve changes in land cover and infrastructure development of river networks. As we have deforested areas for wood supply and agricultural development we have reduced the amount of vegetation, which naturally acts to trap precipitation as it falls and slow the rate of infiltration into the ground.

As a consequence, surface runoff has increased. This, in turn, means flood peaks are greater and erosion is increased. Erosion lowers soil quality and deposits sediment in river channels, where it can block navigation and harm aquatic plants and animals. Where agricultural land is also drained these effects can be magnified.

Urbanization also accelerates streamflow by preventing precipitation from filtering into the soil and shunting it into drainage systems. Additional physical infrastructure has been added to river networks with the aim of altering the volume, timing, and direction of water flows for human benefit. This is achieved with reservoirs, weirs, and diversion channels.

For example, so much water is removed or redirected from the Colorado River in the western United States that, despite its considerable size, in some years it is dry before reaching the sea in Mexico. We also exploit waterways through their use for navigation, recreation, hydroelectricity generation and waste disposal.