nitrogen

Nitrogen Cycle

  • Element symbol: N

  • Nitrogen exists as a gas normally, primarily in the form of nitrogen gas, N₂(g).

  • The atmosphere is composed of approximately 78% nitrogen.

  • Nitrogen must be converted into usable forms for biological organisms.

Terrestrial Ecosystems

  • Definition: Terrestrial ecosystems are land-based ecosystems.

  • Some soil bacteria function to convert nitrogen into various usable forms.

  • Plants absorb nitrogen primarily in two forms: ammonium (NH₄⁺) and nitrate (NO₃⁻), with a majority being nitrate absorbed through roots.

Aquatic Ecosystems

  • Definition: Aquatic ecosystems are water-based ecosystems, where nitrogen plays a crucial role.

  • Cyanobacteria convert nitrogen into ammonia (NH₃), which is then absorbed by aquatic plants.

  • Eutrophication: A process that occurs when excess nutrients, especially nitrates from fertilizers used on land, leach into aquatic ecosystems. It's when too much plant food, like nitrates from farm fertilizers, washes into water.

    • These nutrients can lead to an overgrowth of algae and aquatic plants.

  • Consequences of Eutrophication:

    • If photosynthesis is impeded due to excessive plant and algae growth, oxygen production ceases, jeopardizing the survival of aquatic organisms.

    • The water column can become "choked off", preventing sunlight from reaching deeper waters, thus limiting photosynthesis.

Sources of Nitrogen

  • Nitrogen is also released from natural sources such as volcanic eruptions.

  • Fossil fuels contribute to nitrogen emissions when burned, enhancing nitrogen availability in ecosystems.

  • Lightning can fix atmospheric nitrogen into usable forms, contributing to nitrogen availability.

Phosphorus Cycle

  • Unlike carbon and nitrogen, both of which are gaseous elements found in the atmosphere, phosphorus is primarily stored in the lithosphere.

  • Phosphorus is found in rocks and sediments located on the ocean floor.

Processes of Phosphorus Release

  • Natural processes, such as weathering and erosion, break down rocks to release phosphorus in the form of phosphate (PO₄³⁻) into the soil.

  • Phosphate rock can be mined to produce fertilizers and detergents.

Biological Interaction with Phosphorus

  • Animals consume plants, and then larger animals consume those smaller herbivores.

  • When organisms die, their organic waste is broken down by decomposers, which release phosphates back into the soil.

  • Phosphate can also enter aquatic ecosystems through leaching and runoff, mirroring the land-based phosphorus cycle.