Cycles of Matter: The Role of Water

Interconnected Systems: The Coastal Rainforest Case Study

• Nutrient Transfer Dynamics: Unlike most flora, the trees of the Pacific Northwest coastal rainforest do not rely solely on nitrogen from the soil. Instead, biological research from the University of British Columbia indicates these trees depend on the Pacific Ocean as a primary nitrogen source.
• The Role of Salmon: Pacific salmon transport nitrogen-containing tissue from the ocean to inland ecosystems. Approximately $60 \text{ million kg}$ of salmon tissue "feeds" the forest soil annually.
• Trophic Connections: Bears and other scavengers feast on salmon; the subsequent release of nutrients occurs through their urine and feces.
• Symbiotic Ecosystem Stability:
  • Salmon require healthy streams and forests to reproduce successfully.
  • Forests require the nutrients provided by salmon to maintain growth.
  • Streams depend on standing trees to prevent soil erosion and provide shade to regulate water temperature.
• Biological Impact: Tree ring studies demonstrate that during periods of salmon abundance, trees grow up to three times faster than during periods of salmon scarcity.

Ethical Perspectives on Environmental Management

• Integrated Management: Due to the connection between salmon and tree health, biologists suggest that forest, wildlife, and fish management must be fully integrated rather than treated as separate industries.
• Human Rights vs. Environmental Rights: Some ethical perspectives suggest extending human rights—such as the basic right to exist without interference—to all living things.
• Legal Standing for Nature: There are proposals to grant legal standing in courts to natural entities like streams, oceans, and forests to protect them from human decisions.
• Conflict Scenarios:
  • Habitat Ownership: Questioning if humans should be allowed to "own" habitats that other species rely on for survival.
  • Economic Rights vs. Species Protection: The tension between loggers supporting families and laws protecting endangered organisms like owls or old-growth trees.
  • Recreational Access: The ethics of using technology (helicopters, motorboats) to access delicate alpine terrains or sensitive wetlands for tourism.

Section 2.1: The Role of Water in Cycles of Matter

• The Hydrologic Cycle: Water is a finite resource that is naturally recycled, making it available to living organisms repeatedly.
• Biological Water Context:
  • The human body loses and must replace approximately $3\%$ of its total water volume daily.
  • Water accounts for more than $50\%$ of all plant and animal tissue by mass.
  • An adult human is approximately $70\%$ water, while a radish is $95\%$ water.
  • Dormant life forms (fungal spores, bacterial spores, seeds) contain significantly lower percentages of water.
• Water Movement Processes:
  • Transpiration: The loss of water from plants through pores in leaves called stomata, which are primarily used for gas exchange.
  • Evapotranspiration: The combined effect of evaporation from the ground/water and transpiration from terrestrial plants.
• Metabolic Water: Water produced as a byproduct of the chemical breakdown of glucose during cellular respiration. The hydrogen and oxygen atoms in this water originate from glucose and atmospheric oxygen.

Chemical and Physical Properties of Water

• Molecular Structure: A water molecule consist of two hydrogen atoms covalently bonded to one oxygen atom.
• Polarity: Water is a polar molecule. The oxygen end carries a slight negative charge, while the hydrogen end carries a slight positive charge.
• Hydrogen Bonding: These are weak attractions between the positive hydrogen of one molecule and the negative oxygen of another. While individual bonds are weak, many together are strong, requiring significant energy to break.
• Thermodynamic Constants:
  • Boiling Point: $100\,^{\circ}\text{C}$.
  • Melting Point: $0\,^{\circ}\text{C}$.
• Universal Solvent: Water’s polarity allows it to dissolve a wide variety of substances, including molecular compounds (like $CO_2$) and ionic compounds (like $NaCl$).
• Specific Heat Capacity: Water has a high heat capacity, meaning it requires large amounts of energy to change its temperature. This helps organisms maintain internal thermal stability and allows bodies of water to moderate the climate of nearby land.

Water Density and Global Dynamics

• Density Anomalies: Unlike most substances, frozen water (ice) is less dense than liquid water due to hydrogen bonds holding molecules in an open crystal structure.
• Density Values: Water reaches its maximum density of $1\,kg/dm^3$ at $4\,^{\circ}\text{C}$.
• Seasonal Turnover:
  • In spring, melting ice warms to $4\,^{\circ}\text{C}$, sinks, and forces cooler water to the surface to be warmed.
  • In winter, as surface water cools to $4\,^{\circ}\text{C}$, it sinks. This cycling moves oxygen and nutrients throughout the water column.
• Insulation: Because ice floats, it insulates deep water, preventing lakes from freezing solid and providing a refuge for aquatic life.
• Global Heat Distribution:
  • As a greenhouse gas, water vapor traps and transfers heat.
  • Water evaporates in the tropics, moves toward the poles as vapor, and releases heat as it cools and expands.
  • Ocean currents transfer warm water to cooler regions, moderating global temperatures.

Cohesion, Adhesion, and Plant Physiology

• Cohesion: The attraction of water molecules to each other. This creates surface tension, allowing organic debris and insects (like the water strider, Gerris remigis) to stay on the water surface.
• Adhesion: The attraction of water molecules to other substances, such as the cellulose in the cell walls of a tree’s xylem.
• The Transpiration Pull: Adhesion provides upward force against gravity. As transpiration removes water from leaves, cohesion pulls the entire water column up through the xylem from the roots.

Biological Water Budgets: Thought Lab 2.1

• Human Water Budget (Daily):
  • Gains ($1900\,cm^3$ total): Metabolic water ($190\,cm^3$), Drinking ($1045\,cm^3$), Eating ($665\,cm^3$).
  • Losses ($1900\,cm^3$ total): Urine ($900\,cm^3$), Feces ($200\,cm^3$), Evaporation ($800\,cm^3$, including $350\,cm^3$ from breathing).
• Ord's Kangaroo Rat (Dipodomys ordii) Budget (Daily):
  • Gains ($60.0\,cm^3$ total): Metabolic water ($54.0\,cm^3$), Absorbed water ($6.0\,cm^3$). The rat rarely drinks and survives mainly on metabolic water.
  • Losses ($60.0\,cm^3$ total): Urine ($13.5\,cm^3$), Feces ($2.6\,cm^3$), Evaporation ($43.9\,cm^3$).
• Metabolic Yield per Gram of Food:
  • Glucose: $0.6\,g$ water per $1.0\,g$ glucose.
  • Fat: $1.07\,g$ water per $1.0\,g$ fat.
  • Protein: $0.4\,g$ water per $1.0\,g$ protein.

Water as an Ecosystem Service and Global Concerns

• Natural Disasters in Canada: The two largest natural disasters were droughts in the prairie provinces (1930s and 1980s).
• Historical Data: Research from Moon Lake, North Dakota, suggests extreme droughts lasting decades or centuries occurred before $1200\,\text{C.E.}$
• Alberta's Water Status: Currently possesses rich supplies (rivers, lakes, wetlands, underground), but population growth, agriculture, and industrial use are increasing demand.
• Water Quality: Water is only a renewable resource if quality is maintained; toxic chemicals and pathogens can render it unusable.
• Amazon Drought Simulation (Woods Hole Research Center):
  • Experiment: $4000\,m^2$ of forest shielded by plastic panels for five years.
  • Results: Tree trunk growth slowed, roots grew deeper, and many of the largest, centuries-old trees died.
  • Photosynthetic Impact: Under water stress, plants close stomata to save water, which stops $CO_2$ intake and reduces photosynthetic activity. A $4000\,m^2$ cornfield can transpire $16\,000\,dm^3$ in one day.

Questions & Discussion

• 1. Biogeochemical Cycle Definition: Based on the hydrologic cycle, it is the pathway by which chemical nutrients move through the biotic (living) and abiotic (non-living) components of the biosphere.
• 2. Global Temperature Regulation: Water vapor acts as a greenhouse gas that traps and redistributes heat via atmospheric currents.
• 3. Universal Solvent Rationale: The polarity of water molecules (partial charges) allows them to surround and isolate ions or other polar molecules, pulling them into solution.
• 4. Surface Tension and Insects: Cohesion creates a "skin-like" surface tension on water, supporting the weight of insects like water striders.
• 5. Animal Water Management: Animals cope with water loss by drinking, eating, metabolic production, and physiological strategies (like nocturnal behavior or efficient kidneys).
• 6. Water Quality Importance: For society, it ensures safe drinking/industrial use; for ecosystems, it maintains the health of aquatic life and nutrient cycles.

• The Hydrologic Cycle: Water is a finite resource that is naturally recycled, making it available to living organisms repeatedly.
• Biological Water Context: - The human body loses and must replace approximately 3 ext{%} of its total water volume daily.
  • Water accounts for more than 50 ext{%} of all plant and animal tissue by mass.
  • An adult human is approximately 70 ext{%} water, while a radish is 95 ext{%} water.
  • Dormant life forms (fungal spores, bacterial spores, seeds) contain significantly lower percentages of water.
• Water Movement Processes: - Transpiration: The loss of water from plants through pores in leaves called stomata, which are primarily used for gas exchange.
  • Evapotranspiration: The combined effect of evaporation from the ground/water and transpiration from terrestrial plants.
  • Metabolic Water: Water produced as a byproduct of the chemical breakdown of glucose during cellular respiration. The hydrogen and oxygen atoms in this water originate from glucose and atmospheric oxygen.

Chemical and Physical Properties of Water

• Molecular Structure: A water molecule consists of two hydrogen atoms covalently bonded to one oxygen atom.
• Polarity: Water is a polar molecule. The oxygen end carries a slight negative charge, while the hydrogen end carries a slight positive charge.
• Hydrogen Bonding: These are weak attractions between the positive hydrogen of one molecule and the negative oxygen of another. While individual bonds are weak, many together are strong, requiring significant energy to break.
• Thermodynamic Constants: - Boiling Point: $100 ext{°C}$.
  • Melting Point: $0 ext{°C}$.
• Universal Solvent: Water’s polarity allows it to dissolve a wide variety of substances, including molecular compounds (like $CO_2$) and ionic compounds (like $NaCl$).
• Specific Heat Capacity: Water has a high heat capacity, meaning it requires large amounts of energy to change its temperature. This helps organisms maintain internal thermal stability and allows bodies of water to moderate the climate of nearby land.

Water Density and Global Dynamics

• Density Anomalies: Unlike most substances, frozen water (ice) is less dense than liquid water due to hydrogen bonds holding molecules in an open crystal structure.
• Density Values: Water reaches its maximum density of $1 ext{kg/dm}^3$ at $4 ext{°C}$.
• Seasonal Turnover: - In spring, melting ice warms to $4 ext{°C}$, sinks, and forces cooler water to the surface to be warmed.
  • In winter, as surface water cools to $4 ext{°C}$, it sinks. This cycling moves oxygen and nutrients throughout the water column.
• Insulation: Because ice floats, it insulates deep water, preventing lakes from freezing solid and providing a refuge for aquatic life.
• Global Heat Distribution: - As a greenhouse gas, water vapor traps and transfers heat.
  • Water evaporates in the tropics, moves toward the poles as vapor, and releases heat as it cools and expands.
  • Ocean currents transfer warm water to cooler regions, moderating global temperatures.