1. Aquatic Ecology Lecture 1: General Principles of Aquatic Ecology

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. Q. 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 Q. What are they really? Q. How many types are there? Classification Q. What are the physical properties? Q. What are the chemical properties? Q. What are the biological properties?

6. 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

7. How many types are there?  Several, depending on how close we look!  Freshwater (Limnology) Lakes (lentic) Rivers (lotic)  Brackish water (inter-tidal)  Marine water (Oceanography)

8. Still Freshwater Lentic (standing) Systems  Lakes, ponds, dams etc QHow are they formed?  Glacial activity  Tectonic activity  Erosion  Man Made

9. 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)

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

11. Lentic Water Depth, surface area & volume Surface Area Depth Volume

12. Q. 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

13. 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

14. 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:

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

17.  Photic zone  light is sufficient for photosynthesis to 100 (or 200 m)  Dysphotic zone  light is too weak for photosynthesis  < 5% sunlight  100 to 200 m  Aphotic zone  no light Relating depth with light

18. IRReds GreensBlues Loss of intensity and separation of wavelengths

19. Lentic water and light Compensation Depth Limnetic zone Profundal zone Riparian Edge Riparian Edge Littoral Zone compensation depth : the depth at which the daily or seasonal amount of light is sufficient for photosynthesis to supply algal metabolic needs without growth

20. Depth & Light

21.  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

22. Depth & Light  Anaerobic zones have ‘no’ oxygen (DO 2 )  This results in ‘reduction’ chemistry, where chemicals such as methane (CH 4 ) instead of oxidised chemicals such as CO 2 being formed.  Example found in swamp gas (CH 4, H 2 S)

23. Temperature Gradients (thermal stratification) Epilimnion Metalimnion (Thermocline) Hypolimnion >20 O C >4 but <20 O C 4OC4OC Do you remember the properties of water? Decreasing temperature

24. Temperature Effects  Can control distribution, degree of activity, and reproduction of an organism  Temperature controls the rate of chemical reactions within organisms, thus their rate of growth and activity  10 O C rise in temperature, doubles the activity  Polar organisms grow slower, reproduce less frequently, and live longer than tropical organisms  Tolerance to variation in temperature varies greatly between species and within an organism’s lifespan  Temperature can indirectly control organisms by limiting their predators or restricting pathogens

25. Temperature Effects  more activity with higher temperature

26. Salinity  Can control the distribution of organisms and force them to migrate in response to changes  Availability of various dissolved chemicals (calcium and silicon) can limit an organism’s ability to construct shells  Epipelagic organisms are more tolerant to changes, since they are more accustomed to them  Marine organisms’ body fluids have the same proportion of salts than sea water, but lower salinity

27. Inputs and outputs Input output 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.

28. 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

29. Freshwater Lotic Systems (Rivers & Streams)

30. Freshwater Lotic Systems Q. 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?

31. 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  P aths of least resistance

32. 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) Q. How could these be relevant pieces of information?

33. Turbulence  Turbulence is the degree of agitation in the water  This can dramatically affect all aspects of water including biotic structure and DO 2 levels  Proportional to flow rate and surface features of the river

34. Velocity Profiles Velocity profile for a wide river

35. Velocity Profiles Velocity profile for a narrow creek

36. Effects of the velocity profile Q. 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?

37. Flow Rate & Energy

38.  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