Oceanography Concepts Chapter 6

Ocean Facts

• The Pacific Ocean is the largest, containing over half of Earth's water and covering one-third of its surface area.
• Oceans collectively account for nearly 98% of Earth's water supply.
• The global ocean is crucial for the water cycle, connecting all forms of life.

Aquatic Life Zones

• Aquatic life zones include marine (saltwater) and freshwater systems.
• Major components of marine life zones: oceans, bays, estuaries, coastal wetlands, shorelines, coral reefs, and mangrove forests.
• Freshwater life zones consist of lakes, rivers, streams, and inland wetlands.
• Estuaries, which mix saltwater and freshwater, are classified as marine systems for discussion purposes.

Organism Types

• Key organism categories in aquatic life zones:
  • Plankton: Divided into phytoplankton (plant-like), zooplankton (animal-like), and ultraplankton (tiny photosynthetic organisms).
• Estuaries are highly productive, providing food sources and nurseries for fish and shellfish.

Wetlands and Ecosystem Services

• Freshwater wetlands include swamps, marshes, bogs, fens, and prairie potholes; coastal wetlands include estuaries and mangrove swamps.
• Wetlands provide crucial ecosystem services:
  • Nurseries for aquatic species.
  • Protection against storms by absorbing wind and wave energy.
• Human activities have significantly affected both freshwater and marine wetlands.

Lake Zones

• Lakes are categorized by nutrient content:
  • Eutrophic lakes have high nutrient levels, leading to high primary productivity.
  • Mesotrophic lakes lie between eutrophic and oligotrophic (lower nutrient levels).
• Deep lakes contain distinct life zones:
  • Littoral Zone: Shallow, sunlit area with high biodiversity.
  • Limnetic Zone: Open water area supporting plankton and fish.
  • Profundal Zone: Deeper, dark area reliant on organic matter for nutrients.

Eutrophication

• Eutrophication is the process where water bodies experience nutrient overload, leading to algal blooms.
• Cultural eutrophication occurs due to human activities adding excessive nutrients (nitrates, phosphates) from fertilizers, sewage, and runoff.
• Algal blooms block sunlight, leading to aquatic plant death and deoxygenation, which affects fish like trout.

River and Stream Dynamics

• Rivers and streams are classified into three distinct zones:
  • Source Zone: Narrow, cold, clear waters with high oxygen content, housing algae and mosses.
  • Transition Zone: Wider, warmer streams that carry sediments and nutrients.
  • Floodplain Zone: Further downstream, features rich ecosystems subjected to seasonal flooding.

Human Impact on Aquatic Ecosystems

• Nutrient pollution from agricultural runoff can lead to significant ecological challenges in freshwater systems, like decreased fish populations due to lowered oxygen levels.
• Alterations to wetlands can impact local fisheries, reducing commercial yield and elevating economic costs from storm damage.

Conclusion

• Aquatic ecosystems play essential roles in biodiversity, climate regulation, and human economies.
• Protecting and restoring these ecosystems is critical for sustaining environmental health and human livelihoods.