Aquatic Ecology

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Aquatic Ecology

• Limnology- study of freshwater ecosystems
• Lentic- standing water
• Lotic- moving water

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Lentic Ecosystems

• Depressions in land 1-2,000 meters deep
• In northern hemispheres, glaciers left behind
  carved out basins that filled with rain and snow
• Other causes include
• Silt, driftwood and other materials that block
  the flow of streams
• Streams that were flat get cut off to create
  oxbows

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Lentic Ecosystems

• Craters from extinct volcanoes fill with water

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Lake Formation

• Many lakes are formed by one of two mammals
• Humans- dam rivers for power, irrigation, digging
• Beavers- dam streams to form shallow ponds or
  lakes

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Lake Layers

• 3 layers
• Epilimnion- upper lake consists of a free
  circulating upper layer
• Metalimnion- also called thermocline or middle
  lake has a rapid decline in temperature (1
  degree Celsius for every meter you go down)
• Hypolimnion- lower lake is the deep, colder
  layer

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Lake Structure

• Littoral zone- shallow water zone, light reaches
  the bottom and it usually has plants
• Emergents- plants whose roots and stems are in
  water but upper stems and leaves are out of the
  water
• Limnetic or Pelagic zone- open water, and has
• Plankton- suspended organisms
• Nekton- free swimming fish

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Lake Zones

• Benthic zone- sediment on bottom of lakes and
  ponds
• Photic zone- where light penetrates to the bottom
• Aphotic zone- under water area where light does
  not reach
• Eutrophic- nutrient rich
• Oligotrophic- nutrient poor
• Hypertrophic- excessive nutrients

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Lake Temperatures

• Summer/Spring
• Water is warm on top and cold on bottom

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Lake Temperatures

• Fall/winter
• Temperature on surface drops and metalimnion
  sinks
• Epilimnion increases until all water is the same
  temperature\
• Water circulates oxygen and nutrients
• Overturn- seasonal mixing of water

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Water Chemistry

• Dissolved Oxygen (DO)
• Enters the water through the atmosphere and
  photosynthesis
• Amount of oxygen the water can hold depends on
  pressure, temperature, and salinity
• Cold water holds more oxygen that warm water
• As atmospheric pressure increases, so does the
  amount of oxygen in the water
• Oxygen absorbed by the surface is mixed by
  turbulence of internal currents
• Overturn replenishes oxygen in the water

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Water Chemistry

• Carbon Dioxide
• Carbon dioxide is usually the same concentration
  as that in the atmosphere

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Water Chemistry

• pH
• A measure of the acidic or basic the water is
• On a scale of 1-14
• 1 is very acidic and 14 is very basic
• 7 is neutral
• Freshwater 3-10
• Rainwater 5-6
• Streams and lakes 6.5-8.5
• Limestone under the water causes the pH to
  increase
• (or become more basic)

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Lotic Ecosystems

• Flowing water (rivers and streams)
• Velocity and current decide most things because
  it cuts channels and affects living organisms
• Velocity is determined by size, shape, gradient
  of the channel, roughness of bottom, depth, and
  precipitation

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Streams

• May begin as outlets of ponds or lakes
• Flow is determined by the lay of the land if the
  stream has not been disturbed
• As water flows, it picks up debris that scrapes
  the bottom and makes the stream bigger

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Terms

• Meander- bends in streams (aka. Sinuosity)
• Watershed- body of land where all runoff
  collects in a common body of water
• Turbidity- the amount of particles suspended in
  water prohibiting light to shine through
• Channel- the stream bed and banks formed by
  flowing water
• Flood Plain- a strip of land that is normally dry
  and flat that is on the sides of a river or
  stream and is wet during floods.

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Terms

• Riparian Zone- the land and vegetation bordering
  flowing or standing water
• Riffle- a section of a stream where the water is
  shallow, fast moving, and is broken into waves by
  an obstruction
• Siltation- deposition of fine particles (silt) on
  the beds of streams or lakes
• Pools- water that is relatively deep
• Bankfull Width- where water will stop if it comes
  out of the stream

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How can you tell if a stream is healthy?

• Stream Quality is determined by
• Area cover
• Do things hang over the stream?
• Embeddedness
• Are there dirt particles on the bottom?
• Depth
• Is the stream shallow or deep?
• Sediment deposits
• Are there sediment build ups?
• Channel flow
• Does water fill up the channel?

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Stream quality continued

• Channel Alteration
• Has concrete, rock, or anything else been added
  to the stream?
• Frequency of riffles or bends
• Does the stream curve or have any white water?
• Bank stability
• Are the banks falling into the stream?
• Vegetative Protection (on the banks)
• Are there plants growing on the banks?
• Riparian zone width
• How big is the area on the bank where plants
  grow?

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Stream Chemistry

• pH
• A range of 6-9 is ideal for running freshwater
  fish and bottom dwelling invertebrates
• Synergistic Effects
• Happens when two things combine to produce
  effects greater than their sum
• Example.) Pollutants can change the pH of a
  stream

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Stream Chemistry

• Dissolved Oxygen (DO)
• If dissolved oxygen drops below 5 mg per liter,
  aquatic life is stressed
• The lower the concentration, the more stress
• Levels below 1-2 mg per liter for a few hours
  result in fish kills

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Stream Chemistry

• BOD (biochemical oxygen demand)
• The amount of oxygen needed for decomposition
• If there is little oxygen, decomposers that use
  it will die
• Too much oxygen causes gas bubble disease
• Rare
• Oxygen blocks blood vessels
• Can see bubbles on the fins and the skin

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Stream Orders

• Streams join together to form rivers. Each time
  one stream joins another order changes.
• A first order stream is one that does not have
  any other stream joining it.
• A stream can only increase in order if a stream
  of a similar order joins it.
• For example, when a first order stream runs into
  another first order stream, it becomes a second
  order stream. Likewise, when two second order
  streams join each other, it becomes a third order
  stream and so on.

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Stream Orders

• Order is not increased when a lower order stream
  joins one of a larger order.
• Generally
• First through third order streams are usually
  called headwater streams
• Fourth through sixth order streams are usually
  called medium-sized streams
• Above sixth order, the streams become rivers
• Lower order streams are usually on steep slopes
  compared to higher order streams
• Higher order streams have flood plains

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• A watershed is a section of land where all the
  water runoff flows into a common basin.

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Stream Restoration

• There are many aspects to stream restoration, but
  some suggestions would be
• Decrease the slope of the banks (if it will not
  compromise or eliminate the riparian zone). This
  is generally accomplished by using a 31
  ratio.Stream3 ft.1 ft.Bank
• Reduces the stress on channel walls from flowing
  water
• Becomes more stable
• Stops erosion and sedimentation
• Creates a surface for vegetation

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Stream Restoration

• Stabilize the Stream Banks
• Riparian Forestation
• Plant native vegetation on the stream banks to
  stop erosion. The roots of the plants will hold
  the soil onto the banks.
• Add big structures to the banks like wood, stone,
  or fabric that will not wash away. Fabric
  provides a surface to hold planted vegetation.
• Drive posts into the bank to keep soil from
  eroding into the stream.
• Make the channel bigger.

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Stream Restoration

• Construct riffles and pools
• Adding large rocks and/or other materials from
  the site to the stream prevents natural areas
  from being disturbed by trucks hauling rock to
  the stream.
• Allows more DO to enter the water
• Slows the velocity of flowing water
• Before adding rock to the stream, organic matter
  must be cleared from the bottom to be sure the
  rock will be stable.
• The rock must be lower than the bank.

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Stream Restoration

• Cut and Fill
• Widening the channel in a particular area to
  allow water a larger surface to pass over
• If the channel has been cut very deep, the water
  will not be able to get into the flood plain. By
  adding rock to the bottom of the channel, the
  water level is raised allowing it to reach the
  flood plain if needed.

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Stream Restoration

• Add a waterfall
• Create a difference in elevation allowing the
  water to fall. This will increase DO, slow the
  flow of the water, and create a habitat for
  aquatic life.
• Remove garbage