Aquatic Ecology and Resources: Limnology.pptx

Limnology

1. LIMNOLOGY (Freshwater) PCF 106 Aquatic Ecology and Resources

2. the study of inland waters - lakes (both freshwater and saline), reservoirs, rivers, streams, wetlands, and groundwater - as ecological systems interacting with their drainage basins and the atmosphere. study of the structural and functional interrelationships of organisms of inland waters as their dynamic physical, chemical, and biotic environments affect them. Limnology

3. constitutes only a very small portion of the total water present on Earth, yet it is crucial for sustaining life on the planet. these freshwater resources are found in diverse forms such as lakes, rivers, ponds, and streams, each with unique ecosystems. Freshwater habitats support distinct compositions of plant (floral) and animal (faunal) life, making them vital for biodiversity and ecological balance. FRESHWATER

4. The survival and stability of freshwater habitats are highly sensitive to a range of influencing factors: Natural Changes: Seasonal shifts, weather patterns, and natural events such as floods or droughts significantly impact freshwater ecosystems. Ecological Interactions: The balance of life within plant and animal communities directly affects the health of these habitats. Human Activities: Pollution, deforestation, industrial runoff, overfishing, and habitat modification greatly endanger the sustainability of freshwater ecosystems. Freshwater

5. Freshwater systems are not isolated or static; they are intricately linked with other water bodies and landmasses through the hydrological cycle. The hydrological cycle is a continuous process that involves the movement of water through various stages, such as evaporation, condensation, precipitation, and runoff. Evapotranspiration: A key element of this cycle, it refers to the combined process of water evaporation from non-living sources (e.g., soil, water bodies) and the transpiration of water through plants. It contributes to water loss and affects the availability of water resources (Brewer, 1979). Freshwater

6. Hydrologic Cycle

7. Physical Features of Water States of Water: Freshwater, one of Earth's most vital resources, primarily exists in its liquid state. it has the unique ability to solidify (turn into ice) and convert into a gaseous phase (through evaporation). These state changes are essential components of natural processes like the water cycle. Abiotic Features of Water

8. Buoyancy in water: the buoyancy of water is a critical property that aids aquatic organisms in their survival and movement. Floating and Swimming: Many organisms take advantage of this feature, floating or actively swimming on the surface or within the water. Abiotic Features of Water Water Strider Freshwater Phytoplankton Duckweeds

9. Role of Solar Radiation: Sunlight plays a crucial role in freshwater ecosystems, driving multiple processes that sustain life. Thermal Effects of Radiation: Sunlight heats the water, creating density variations. These density changes result in water mixing, which maintains temperature balance and supports diverse aquatic life. Photosynthetic Activity: Solar radiation provides the energy necessary for photosynthesis in plants such as micro-algae and macrophytes, enabling them to grow and serve as the base of the food chain. Radiation Characteristics

10. Light Penetration and Depth Zones: As sunlight enters the water, its intensity decreases with depth, creating distinct zones: Compensation Point: The depth where the amount of light available is just sufficient for photosynthesis to match the energy demands of plant respiration. Euphotic Zone: The well-lit zone above the compensation point, where light is abundant and supports active plant growth and photosynthesis. Profundal Zone: A deeper, darker layer below the compensation point, where little to no light penetrates, making it inhospitable for photosynthetic organisms. Radiation Characteristics

11. Measuring Light Penetration: Secchi Disc Method: The Secchi Disc, a checkered black-and-white device, is used to measure water transparency and light penetration. It is lowered into the water until it is no longer visible. The depth at which it disappears helps determine the extent of the euphotic zone and assess water clarity. Radiation Characteristics

12. Temperature Influence on Life: Temperature has a profound effect on aquatic organisms. Every species has a specific range of temperature tolerance, with minimum and maximum thresholds necessary for their survival. Fluctuations in temperature can significantly impact their growth, reproduction, and overall behavior. Radiation Characteristics

13. Water as a Universal Solvent: Water is known as a universal solvent due to its ability to dissolve a wide variety of substances. This property affects the chemical composition of aquatic habitats. Rainwater's Impact: As rain falls, it dissolves chemicals from the atmosphere and the soil it contacts, carrying them into freshwater habitats. The presence of dissolved chemicals characterizes water as acidic, alkaline, or nutrient-rich, shaping the types of organisms that can thrive in these environments. Chemical Features of Water

14. Dissolved Oxygen Levels: The amount of oxygen that water can hold is influenced by factors such as temperature, atmospheric pressure, and biological activity. Cooler waters generally hold more dissolved oxygen, whereas warmer waters hold less. Oxygen in Water

15. Biological Oxygen Demand (BOD): BOD measures the oxygen consumed by living organisms in water over a standard five-day period at 20°C. It serves as an indicator of organic pollution levels in a water body. High BOD signifies increased microbial activity caused by the decomposition of organic matter, a sign of pollution. Natural waters usually exhibit BOD levels ranging from 0.5 to 7.0 mg/l O₂. Oxygen in Water

16. Daily Oxygen Fluctuations: During daylight, aquatic plants release oxygen through photosynthesis, leading to supersaturation in the euphotic zone. At night, oxygen levels decrease as respiration occurs without photosynthesis, sometimes causing oxygen depletion. Oxygen in Water

17. Chemical Behavior of CO₂: Carbon dioxide dissolves readily in water, much more so than oxygen, especially in cooler temperatures and under high pressure. It plays a vital role in maintaining water's acidity and alkalinity, directly impacting aquatic ecosystems. Carbon Dioxide in Water

18. pH Scale in Aquatic Systems: Neutral water: pH 7. Acidic water: pH below 6. Alkaline water: pH above 8. Elevated pH levels (9–10) trigger active photosynthesis, often leading to algal blooms that can disrupt aquatic ecosystems. Carbon Dioxide in Water

19. Habitat-Specific Distributions: Acidity and alkalinity levels influence the types of organisms that inhabit certain areas. Regions affected by acid rain or other acidifying pollutants may develop unique, habitat-specific ecosystems. Carbon Dioxide in Water

20. Abundance and Key Importance: Nitrogen is one of the most abundant elements on Earth, comprising around 80% of the atmosphere. It plays a significant role in supporting plant growth and productivity in aquatic habitats. Nitrogen is introduced into aquatic systems from decomposing organic matter, such as detritus found in habitats like mangroves and seagrass beds. Nitrogen's Role in Aquatic Systems

21. Scarcity and Limited Use: In contrast to nitrogen, phosphorus is a much rarer element in aquatic ecosystems. It is not found in gaseous form and does not dissolve easily in water. This makes it a limiting nutrient, meaning its availability often restricts plant and algal growth. Plants use phosphorus in limited quantities for their growth and metabolic activities. Its availability is often a bottleneck for ecosystem productivity Phosphorus' Role in Aquatic Systems

22. The levels of nitrogen and phosphorus in an aquatic ecosystem determine its trophic state, which reflects the nutrient richness and biological activity of the area: Oligotrophic: Nutrient levels are low, leading to low biological productivity. Mesotrophic: Nutrient levels are moderate, supporting a balanced ecosystem. Eutrophic: Nutrient levels are high, often causing excessive plant and algal growth, which can lead to problems like hypoxia or algal blooms. Trophic Stratification and Nutrient Levels

23. Carbon-Based Composition and Sources : Organic compounds in aquatic ecosystems are predominantly carbon-based. These compounds play an essential role in the energy flow and nutrient cycling of these environments. Sources of Organic Matter: Organic compounds originate from the secretions of living plant organisms. A significant amount of organic matter is contributed by decomposed detrital materials, particularly from mangrove and seagrass ecosystems, which act as critical carbon sinks. Organic Compounds in Aquatic Habitats

24. Forms and Sizes of Inorganic Matter: Inorganic compounds in water are categorized based on their size and state, ranging from Dissolved Organic Compounds (DOC) to larger Particulate Organic Compounds (POC). Inorganic Compounds in Aquatic Habitats