Lecture 6

Ecosystems and Matter Cycling

• Chapter Overview

  • Introduction

  • Matter

  • Biogeochemical Cycles

  • Hydrological Cycle

  • Biogeochemical Cycles and Human Activity

  • Implications

1. Introduction

• Matter Cycling in the Ecosphere

• Implications of Disturbing Matter Cycling:

  • Leads to significant environmental challenges such as:

    • Global warming

    • Acid deposition

    • Spread of oceanic dead zones

• Importance of understanding biogeochemical cycles to tackle these issues.

2. Matter

• Core Concepts:

  • Everything consists of matter or energy.

  • Earth's energy supply is virtually infinite; matter is limited to what exists.

  • Matter Characteristics:

    • Has mass and occupies space (atoms: protons, neutrons, electrons).

• Molecules & Compounds:

  • Molecules are formed by two or more atoms; compounds consist of different atoms.

  • Example: Water (H2O).

  • Four major organic compounds in living organisms:

    • Carbohydrates

    • Fats

    • Proteins

    • Nucleic Acids

• States of Matter:

  • Exists in three states: solid, liquid, gas.

  • Transformation occurs through heat/pressure changes.

  • Law of Conservation of Matter:

    • Matter can only be transformed, not created nor destroyed.

3. Biogeochemical Cycles

• Function in Ecosystems:

  • Matter cycles among ecosphere components (biotic and abiotic).

  • Essential for life; nutrients are key elements.

• Nutrient Types:

  • Macronutrients: Needed in large amounts.

  • Micronutrients: Required in smaller amounts.

• Composition of Organic Mass:

  • 97% consists of six nutrients: Carbon, Oxygen, Hydrogen, Nitrogen, Phosphorus, Sulphur.

• Cycle Models:

  • Depicting the flow and storage of nutrients within the Earth's systems.

• Speed of Cycling:

  • Varies among ecosystems; may change based on seasonal factors.

  • Residence Time: Average duration nutrient stays within compartments (e.g., CO2 in the atmosphere: 5–7 years).

• Cycle Classifications:

  • Gaseous Cycles: Faster, matter primarily in atmosphere (e.g., nitrogen cycle).

  • Sedimentary Cycles: Slower, matter held in lithosphere (e.g., phosphorus cycle).

• Natural Balance:

  • Recycling achieves balance; human interference can disrupt inputs/outputs, leading to pollution issues.

4. The Hydrological Cycle

• Water's Role in Life:

  • All organisms are roughly 70% water; liquid water existence is unique to Earth.

• Water Distribution:

  • 97% of Earth's water is in oceans; remaining is freshwater in glaciers, lakes, and groundwater.

• Cycle Dynamics:

  • Driven by solar energy, it involves reservoirs and movement (evaporation, precipitation, transpiration).

  • Residence Times: Varied, with glaciers lasting >100,000 years, while atmospheric water lasts only 9–12 days.

• Human Interference:

  • Activities like wetland drainage, groundwater pumping, and land-use changes significantly impact water cycles.

5. Biogeochemical Cycles and Human Activity

• Societal Dependence:

  • Society relies on biogeochemical cycles which are vulnerable to human-induced disturbances.

• Eutrophication:

  • Natural nutrient enrichment process in water bodies that can be accelerated by human activities, leading to high nutrient levels (cultural eutrophication).

• Effects of Eutrophication:

  • Leads to oxygen depletion from overgrowth of phytoplankton, impacting fish populations.

6. Implications

• Understanding matter and nutrient cycling is critical for addressing environmental issues like acid deposition, eutrophication, and global change, which stem from disturbances in biogeochemical cycles.