Chemical and Physical Features of Seawater and the World Ocean

Detailed Study Guide: Chemical and Physical Features of Seawater and the World Ocean

1. Introduction to Marine Organisms and Environment

  • Quote by Charles Dudley Warner: "Everybody talks about the weather, but nobody does anything about it."

    • This quote relates to marine life, emphasizing how organisms must adapt to their environment rather than change it.

2. Importance of Water in Marine Biology

  • Marine Organisms and Water Composition:

    • Marine organisms are composed of 80% or more water, with jellyfish being over 95% water.

    • Water is essential for life, forming the basis for all biological processes in marine organisms.

3. Unique Properties of Water

3.1 Molecular Structure

  • Water Molecules: Comprised of one oxygen atom and two hydrogen atoms, forming weak hydrogen bonds.

    • These bonds give water unique physical and chemical properties.

3.2 States of Water

  • Three Phases: Water exists in solid, liquid, or gas form:

    • Solid (Ice): Molecules form a fixed structure, making ice less dense than liquid water (important for aquatic life).

    • Liquid Water: Hydrogen bonds hold molecules loosely; denser as temperature decreases down to ~4 °C.

    • Gas: Water vapor, molecules widely spaced apart without hydrogen bonding.

3.3 Heat and Water

  • Latent Heat of Melting: Water requires significant heat to melt (highest among substances).

  • Latent Heat of Evaporation: A lot of heat is absorbed during evaporation, providing evaporative cooling.

  • High Heat Capacity: Water can absorb heat without significant temperature changes, stabilizing climate and marine environments.

4. Salinity and Dissolved Materials in Seawater

4.1 Composition of Seawater

  • Seawater contains many dissolved substances primarily from river runoff and hydrothermal vents.

  • Salinity: The total amount of salt in seawater is typically 35‰.

  • Major ions in seawater (e.g., sodium and chloride make up ~85%).

    • Rule of Constant Proportions: The relative proportions of most ions in seawater remain constant despite variations in total salinity.

4.2 Impact on Marine Life

  • Changes in salinity affect marine organisms, many of which are adapted to specific salinity levels and can suffer from fluctuations.

5. Physical Properties of Seawater

5.1 Density

  • Influencing Factors: Temperature and salinity determine seawater density; denser when saltier and colder.

  • Temperature profiles in open oceans: Varies significantly, necessitating measurements at different depths.

6. Ocean Dynamics

6.1 Ocean Circulation

  • Surface Circulation: Driven by wind and influenced by the Coriolis effect.

  • Thermohaline Circulation: Deep water currents driven by differences in temperature and salinity.

  • Global conveyor belt: A critical system for oxygen distribution and climate regulation.

7. Waves and Tides

7.1 Waves

  • Formation: Caused by wind; characterized by crest, trough, height, wavelength, and period.

  • Types of Waves: Seas (short, chaotic) versus swells (more regular); both move energy, not water.

7.2 Tidal Patterns

  • Causes of Tides: Result from gravitational pull from the moon and sun.

    • Tidal range varies: spring tides (greatest range) and neap tides (smallest range).

  • Types of Tides: Semidiurnal (two highs and lows daily), mixed semidiurnal (varying heights), and diurnal (one high and one low daily).

8. Conclusion

  • Understanding water's chemical and physical features is crucial for appreciating marine organisms' adaptability and ecosystems. Knowledge of currents, tides, and salinity is essential for studying marine life patterns and health.

Study Guide on the Ocean

Overview of the Ocean

  • The ocean is a body of salt water covering approximately 70.8% of the Earth's surface.

  • Contains 97% of Earth's water and is essential for life, influencing climate, weather, and the carbon and water cycles.

  • Traditionally divided into five oceans:

    • Pacific Ocean

    • Atlantic Ocean

    • Indian Ocean

    • Antarctic/Southern Ocean

    • Arctic Ocean

Zones of the Ocean

Vertical and Horizontal Zones

  • Pelagic Zone: Open ocean extending from the surface to the ocean floor, divided based on depth and light penetration.

    • Photic Zone:

      • Depth where light intensity is at least 1% of surface value (up to ~200m).

      • Area for photosynthesis by phytoplankton and algae, contributing to biodiversity and oxygen production (about 50% of Earth's oxygen).

    • Mesopelagic Zone:

      • The twilight zone with limited light penetration.

    • Aphotic Zone:

      • Dark deep ocean where no sunlight penetrates, relying on marine snow (organic debris) or chemosynthesis for energy.

Continental Shelf

  • Shallow area where the ocean meets land, generally under a few hundred meters deep. Human activities here significantly impact marine ecosystems.

Ocean Temperature and Salinity

  • Tropical water can reach temperatures over 30°C (86°F); polar water is around −2°C (28°F).

  • Deep Ocean Temperatures: Ranges from −2°C (28°F) to 5°C (41°F).

  • Salinity: Average is about 35 grams of salt per kilogram of seawater (3.5%). Influenced by evaporation and fresh water input from rivers.

Ocean Currents

  • Surface Currents: Driven by wind, affecting climate and weather patterns globally.

  • Deep Ocean Currents: Determine circulation patterns influenced by temperature and salinity (thermohaline circulation).

  • Tidal Currents: Caused by gravitational pull of the moon and the sun, influencing coastal ecosystems.

Biological Diversity

  • Known to host over 230,000 species, possibly over two million yet to be discovered.

  • Major organisms include:

    • Phytoplankton (primary producers)

    • Zooplankton (primary consumers)

    • Various marine mammals, birds, fishes, and benthic organisms.

Benefits to Humans

  • Ocean provides:

    • Ecosystem services (carbon cycling, oxygen production)

    • Seafood and resources (fishing industry valued globally)

    • Transportation (major trade routes).

Environmental Threats

  • Threats include:

    • Marine Pollution: Plastic debris, chemicals affecting ecosystems and human health.

    • Overfishing: Leads to unsustainable fish populations.

    • Climate Change: Ocean warming, acidification, altered currents, and rising sea levels pose risks to marine life and coastal populations.

Human Interaction

  • Ocean governance involves regulation and protection of marine environments through measures like marine protected areas (MPAs).

  • Notable agreements include UNCLOS and the recent High Seas Treaty to protect more areas of the ocean.

Conclusion

  • Understanding the ocean's complex systems and the threats it faces is essential for not only marine conservation but also for the well-being of human life on Earth.