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Aquatic Ecology

Aquatic Ecology. Ecological Principles. What is it?. Aquatic ecology is the study of water based ecosystems Complexity depends upon how ‘close’ we look at any particular system They are under extreme ‘pressure’ Very, very important…WHY???. What pressure are they under?.

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Aquatic Ecology

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  1. Aquatic Ecology Ecological Principles

  2. What is it? • Aquatic ecology is the study of water based ecosystems • Complexity depends upon how ‘close’ we look at any particular system • They are under extreme ‘pressure’ • Very, very important…WHY???

  3. What pressure are they under? • Pressure from development (i.e. loss) • Urbanisation • Land clearing • Pressure from pollution • Toxins • Acid/base • Pressure from stress (water usage) • Stagnation • Water levels

  4. Importance of aquatic ecosystems • Biodiversity • Species richness/trophic structure • Breeding • Breeding grounds for many species • Buffer systems • Physical and chemical • Sinks • Resting places for sediments and chemicals • Only part of the hydrological cycle • What other parts are there?

  5. The important questions of Aquatic Ecosystems • What are they really? • How many types are there? • Classification • What are the physical properties? • What are the chemical properties? • What are the biological properties? • What are the anthropological properties?

  6. Remember Hydrology? • The water cycle??? • Relate to the Hunter Valley • Some basics… • 1 mm of rain = 1 L/m2 • The average annual rainfall in the Hunter is approximately 1300 mm/yr • This is 1300 L/m2/yr • Hunter valley is ~ 22 000 km2 • Where is this ‘water shortage’? • Discuss!

  7. What is an aquatic ecosystem? • They are an area of water, in which ‘significant’ biological activity can occur • This definition excludes most groundwater systems • Aquatic ecosystems can involve flowing or still water, and can be fresh or saline

  8. How many types are there? • Several, depending on how close we look! • Freshwater (Limnology) • Lakes (lentic) • Rivers (lotic) • Groundwater • Brackish water (inter-tidal) • Marine water (Oceanography) • Anthropogenic waters (i.e drinking water)

  9. Still FreshwaterLentic (standing) Systems • Lakes, ponds, dams etc • How are they formed? • Glacial activity • Tectonic activity • Erosion • Man Made • General lye of the land.

  10. Classification of Lentic Waters • Classifications • Oligotrophic • Newer, colder, deeper waters that are low in life and relatively unproductive (low PP). • Eutrophic • Older, warmer, shallower waters that are high in life and highly productive (high PP) • Mesotrophic • Somewhere in-between (i.e. Lake Macquarie)

  11. Freshwater Lentic Systems • What physical properties can they exhibit? • Depth • Surface area • Light • Temperature • Inputs and outputs • Altitude • Longitude and latitude

  12. Lentic WaterDepth, surface area & volume Volume Depth Surface Area

  13. What is the issue with depth? • The depth of water determines the amount of light (which affects what???) • ? • The depth of the water also determines some attributes of temperature • Altitude, latitude and longitude also affect this

  14. Relating depth with light • There is a relationship with depth and light intensity, as well as a depth/wavelength relationship • Light intensity decreases with depth • Some wavelength’s of light travel deeper

  15. Relating depth with light • Within the photic zone, the colours of the light spectrum are able to penetrate through water before being absorbed at varying depths. The following data illustrates how the light spectrum is affected by depth:

  16. Relating depth with light(these values are not valid for all waters) • ColourDepth • Red             5 m • Orange       15m • Yellow            30m • Green            60m • Blue            75m • Indigo            85m • Violet           100m    

  17. Relating depth with light Greens Blues IR Reds Loss of intensity and separation of wavelengths

  18. Lentic water and light Riparian Edge Riparian Edge Littoral Zone Limnetic zone Compensation Depth Profundal zone

  19. Depth & Light • This is obviously an important aspect of aquatic ecology. • Without light, no photosynthesis occurs and PP is very low. • In the profundal zone, different (anerobic) chemistry applies

  20. Depth & Light • Anaerobic zones have ‘no’ oxygen (DO2) • This results in ‘reduction’ chemistry, where chemicals such as methane (CH4) instead of oxidised chemicals such as CO2 being formed. • Example found in swamp gas (CH4, H2S)

  21. Temperature Gradients(thermal stratification) >20OC Epilimnion Metalimnion (Thermocline) >4 but <20OC Do you remember the properties of water? Hypolimnion 4OC Decreasing temperature

  22. Inputs and outputs Input How long does it take to change over the entire volume of a water body? The question ‘residence time’ is very important in ecology and environmental chemistry/engineering. output

  23. Significance? • The residence time for water equates to the residence time for chemicals such as nutrients • If there is a long residence time, then there is a good chance of algal blooms if nutrient overload occurs • This is very important for ecologists who will determine the fate of organisms as a result of eutrophication

  24. Freshwater Lotic Systems (Rivers & Streams)

  25. Freshwater Lotic Systems • How do rivers, streams and creeks differ from lentic systems? • They exhibit significant rates of flow • They exhibit turbulence • They have significant energy • Generally lower in volume • But what are they really?

  26. What is a river? • A silly question?.......No! • Rivers form because of gravity • A river, stream or creek is simply a ‘catchments’ delivery/removal system • Mother nature’s pipelines • Paths of least resistance

  27. A Rivers Flow • There are two aspects of flow that can be measured; • The Flow Rate (Velocity, V) (which is a measure of the speed at which the water is moving i.e. 2 m/s • The volumetric flow rate (which is the volume of the water in 2 m/s) • How could these be relevant pieces of information?

  28. Turbulence • Turbulence is the degree of agitation in the water • This can dramatically affect all aspects of water including biotic structure and DO2 levels • Proportional to flow rate and surface features of the river

  29. Velocity Profiles Velocity profile for a wide river

  30. Velocity Profiles Velocity profile for a narrow creek

  31. Effects of the velocity profile • What effects does velocity have? • Distribution of organisms within the river • Distribution of sediments • More importantly, how does this affect our sampling of these waters?

  32. Flow Rate & Energy

  33. Flow Rate & Energy • Results in distribution of matter • CPOM vs FPOM • Gravel, sand, silt • Determinant in ‘floral’ species distribution • Large plants with roots need fine matter • Algae / bacteria like low energy areas • Determinant in animal species distribution • Animals (zooplankton→fish) follow plants

  34. What about the Ecology? • Discuss the trophic structure of • A river, and, • A small stream (i.e. Toronto)

  35. The zones of freshwater bodies

  36. Lotic or Lentic? • The diagram represents both systems • It is important that you relate the ecology to the water bodies geography • We shall perform several experiments to help you understand this, including; • Physicals, chemicals, bacteria, PP, algae and macro-invertebrate analysis

  37. Class Group Exercises • Volumetric flow rate determination • Lentic habitat profile • Lotic habitat profile

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