Lake Ecosystem Lecture Notes

Introduction to the Ecosystem

• Ecosystems are categorized into:
  • Terrestrial ecosystem
  • Aquatic ecosystem
    • Freshwater ecosystem
    • Marine water ecosystem
    • Brackish water ecosystem
• Lake ecosystem is a type of freshwater ecosystem.

Characteristics of Lake Ecosystem

• Lentic Water Bodies: Characterized by still water, unlike lotic systems (rivers) which have flowing water.
• Photosynthesis: Occurs due to the presence of autotrophs.
• Nutrient Cycling: Decomposition, mineralization, and circulation of nutrients occur.

Zonation in Lakes

• Lakes are divided into three zones:
  1. Littoral Zone
  2. Limnetic Zone
  3. Profundal Zone

Littoral Zone

• Location: Near the shore, edge of the lake.
• Sunlight penetrates to the bottom, enabling high photosynthesis.
• High vegetation and oxygen levels.
• Known as the euphotic zone due to light penetration.

Limnetic Zone

• Location: Central open water, away from the shore.
• Does not reach the bottom of the lake.
• Moderate photosynthesis, plants, and oxygen levels.
• Separated from the profundal zone by the compensation zone.

Profundal Zone

• Location: Deepwater, below the limnetic zone.
• No light penetration; opposite conditions to the littoral zone.
• Low oxygen levels, high decomposition, and nutrient recycling.
• Known as the recycling zone.

Biotic Components

• Littoral Zone:

  • Flora: Free-floating hydrophytes (e.g., Pistia), rooted hydrophytes (e.g., Nymphaea), submerged hydrophytes, phytoplanktons (e.g., diatoms, green algae).
  • Fauna: Zooplanktons (e.g., Daphnia, rotifers), nekton (e.g., fishes and snakes).

• Limnetic Zone:

  • Similar phytoplanktons and nektons as the littoral zone.

• Profundal Zone:

  • No flora due to absence of light.
  • Presence of decomposers, detritus feeders, and organisms like chironomid larvae that survive in low oxygen.

Key Points for Examinations

• Zonal characteristics, light penetration, and associated biota are crucial for understanding Lake ecosystems.
• Important MCQs:
  • Which zone is called the euphotic zone?
  • Which zone has no light?
  • Recycling zone identification.

Conclusion

• Understanding the structure and function of lake ecosystems is vital for ecology studies.
• The sequence and characteristics of each zone are important for exams like NEET and other tests.

Note: Always remember the sequence and features of each zone for multiple-choice questions and long answer questions in exams.