Aquatic Ecology

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Aquatic Ecology

• Ecological Principles

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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 importantWHY???

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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

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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?

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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?

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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!

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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

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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)

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Still FreshwaterLentic (standing) Systems

• Lakes, ponds, dams etc
• How are they formed?
• Glacial activity
• Tectonic activity
• Erosion
• Man Made
• General lye of the land.

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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)

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Freshwater Lentic Systems

• What physical properties can they exhibit?
• Depth
• Surface area
• Light
• Temperature
• Inputs and outputs
• Altitude
• Longitude and latitude

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Lentic WaterDepth, surface area volume
Volume
Depth
Surface Area
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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

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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 wavelengths of light travel deeper

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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

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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    

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Relating depth with light
Greens
Blues
IR
Reds
Loss of intensity and separation of wavelengths
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Lentic water and light
Riparian Edge
Riparian Edge
Littoral Zone
Limnetic zone
Compensation Depth
Profundal zone
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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

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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)

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Temperature Gradients(thermal stratification)
gt20OC
Epilimnion
Metalimnion (Thermocline)
gt4 but lt20OC
Do you remember the properties of water?
Hypolimnion
4OC
Decreasing temperature
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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
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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

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Freshwater Lotic Systems

• (Rivers Streams)

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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?

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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 natures pipelines
• Paths of least resistance

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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?

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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

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Velocity Profiles
Velocity profile for a wide river
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Velocity Profiles
Velocity profile for a narrow creek
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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?

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Flow Rate Energy
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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

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What about the Ecology?

• Discuss the trophic structure of
• A river, and,
• A small stream (i.e. Toronto)

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The zones of freshwater bodies
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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

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Class Group Exercises

• Volumetric flow rate determination
• Lentic habitat profile
• Lotic habitat profile