Cycling of Matter in Ecosystems

Introduction to Biogeochemical Cycles

• Earth operates as a recycling system, utilizing biogeochemical cycles to circulate matter.
• Three primary cycles: Water, Carbon, and Nitrogen.

Human Impacts on the Water Cycle

• Damming rivers alters natural flow patterns.
• Pollution of waterways affects water quality and ecosystems.
• Draining swamps disrupts habitats and increases flooding risk.
• Irrigation practices can deplete local water resources.

Carbon Cycle Overview

• Carbon is essential for all living organisms, moving between biotic and abiotic components.
• Major reservoirs of carbon include fossil fuels, plants, oceans, and limestone formations.

Human Impacts on the Carbon Cycle

• Combustion of fossil fuels introduces significant carbon dioxide into the atmosphere, primarily from vehicles and factories.
• Deforestation contributes to increased atmospheric CO2, as fewer trees absorb carbon.

Problems Associated with Excess CO2

• Carbon dioxide acts as a greenhouse gas, leading to climate change.
• Warming ocean temperatures affect marine life.
• Melting ice caps contribute to sea-level rise.
• Disruption of ecosystems affects biodiversity and stability.

Nitrogen Cycle Details

• Nitrogen is abundant in the atmosphere (N2) but is not readily available to most organisms.
• Nitrogen fixation is essential; bacteria convert atmospheric nitrogen into usable forms (nitrates, nitrites, ammonia).
• Additional nitrogen fixation occurs via lightning and UV light.

Sources of Nitrogen

• Atmospheric nitrogen, human-made fertilizers, animal waste (urine), decomposer activity, and denitrifying bacteria (which release nitrogen gas back to the atmosphere).

Human Impacts on the Nitrogen Cycle

• Vehicle exhaust releases nitrous oxide, contributing to acid rain.
• Artificial fertilizers add excessive nitrogen to soils, altering pH levels.
• Concentrated animal feeding operations lead to nitrogen runoff, causing detrimental algal blooms in water bodies.