Fresh and Saltwater Ecosystems Notes

Ecosystems Overview

  • An ecosystem is a biological community of organisms interacting with one another and their environment.
  • Over 75% of Earth's surface is covered by water (freshwater and marine ecosystems).
  • Ecosystem services include:
    • Nutrient exchange
    • Participation in biogeochemical cycles
    • Degradation and dispersal of pollutants
    • Habitat provision for various species.

Freshwater Ecosystems

  • Definition: Ecosystems with low salinity; not highly adaptable to salinity changes.
  • Examples: Streams, rivers, ponds, lakes, springs, wetlands.

Wetlands

  • Often inundated with water; exist in low-lying areas, associated with rivers and lakes.
  • Types:
    • Marshes: Dominated by grasses and open waters.
    • Swamps: Dominated by trees, providing habitat for diverse wildlife.
Benefits of Wetlands
  1. Water Purification: Marshes absorb nutrients and pollutants, improving water quality.
    • Example sites: Green Cay and Wakodahatchee Wetlands (FL).
  2. Flood Control: Wetlands cover 10% of land can reduce flooding by 60%. If they cover 20%, flooding can be reduced by 90%.
  3. Temperature Moderation: Wetlands stabilize temperatures by retaining heat.
  4. Water Storage: Support fish and insects in deeper water pockets during low water periods.
  5. Climate Control: Soils (muck and peat) sequester carbon.
  6. Wildlife Habitat: Provide food, shelter, and nesting areas for various species.

Swamps

  • Trees like Bald Cypress and palm are common in Florida swamps, providing diverse habitats.
  • Cypress trees, with unique root structures known as 'knees', thrive in these environments.

Case Study: The Everglades

  • Once a vast wetland (11,000 square miles) now reduced due to human intervention.
  • Conservation Efforts: Comprehensive Everglades Restoration Plan (CERP) aims to restore water flow and improve habitat conditions.

Lakes and Ponds

  • Characteristics: Bodies of still or non-moving water; vary in size and depth.

Zonation of Lakes

  1. Littoral Zone: Shallow, rich in biodiversity; photosynthesis occurs here.
  2. Limnetic Zone: Open water zone where light penetrates and photosynthesis can occur.
  3. Profundal Zone: Deep water; lacks light penetration.

Aging of Lakes (Eutrophication)

  • Stages:
    1. Oligotrophic: Clear water, few organisms.
    2. Mesotrophic: Moderate nutrient levels; healthy ecosystems.
    3. Eutrophic: High nutrients, low oxygen levels, decay of plant life; ecosystem degradation.

Springs

  • Definition: Natural sources of groundwater flow; significant in Florida.
  • Magnitude: Classified based on water discharge; first magnitude springs release over 65 million gallons/day.
  • Environmental Impact: Water flow and temperature maintain ecosystem; human activities can deplete flow and pollute water.

Rivers and Streams

  • Defined as moving waters; fed by springs and rainfall.
  • Watershed: Area contributing to river water; impacts water quality and biodiversity.
  • Key Characteristics:
    1. Velocity of flow affects oxygen and sediment.
    2. Dissolved oxygen levels are crucial for organism health.
    3. Pollutants from urban runoff can degrade ecosystems.

Human Impacts

  • Pollution from agriculture and urban sources significantly affects river health.

Coastal Ecosystems

Coastal Uplands and Dunes

  • Comprising beaches, coastal scrubs, and maritime forest; critical for ecosystem stability.
  • Sea Turtles: Nesting occurs in open beaches, vulnerable to human activity (light pollution, predators).

Coastal Strand

  • An ecotone between dune and maritime forest; provides habitat for various species.
  • Invasive Species: Australian pines disrupt local ecosystems.

Maritime Forest

  • Characterized by stable ancient dunes; home to diverse flora and fauna, converting due to human activity.

Intertidal Zones

  • Covered by ocean waters at high tides; variable salinity and temperature.
  • Home to uniquely adapted organisms (chitons, limpets) that survive harsh conditions.

Mangroves

  • Thrive in salty, muddy coastal conditions; crucial for shoreline protection and biodiversity.
  • Human Threats: Rapid disappearance due to coastal development and rising sea levels.

Salt Marshes and Estuaries

  • Salt marshes host diverse fauna and flora; essential for juvenile fish survival.
  • Estuaries characterized by unique geologic formations and salinity gradients; critical for ecological health.

Human Impacts on Estuaries

  • Agricultural runoff can disrupt salinity and oxygen levels; promotes algal blooms.

Marine Ecosystems

Coral Reefs

  • High biodiversity; composed of coral polyps, essential for coastal protection.
  • Human Threats: Pollution, acidification, and overfishing severely impact coral ecosystems.

Pelagic and Abyssal Zones

  • Pelagic zones crucial for marine food chains; deep sea ecosystems are less understood but critical for global biodiversity.

Conclusion

  • Protecting and restoring freshwater and marine ecosystems is vital for maintaining Earth’s biodiversity and human quality of life.