freshwater ecology test 1

amount of earths freshwater

• 2.5% of earths water

• 68% of freshwater is in glaciers

• 30% is ground water

what lakes make up most of surface freshwater

• african great lakes

• Laurentian Great Lakes

• lake baikal

lake winnipeg

• 11th largest lake on Earth

• 3.5 year residence time

• Inflows from Winnipeg, Saskatchewan,
  Red Rivers

• Outflow is through the Nelson River to Hudson Bay

• Glacial origin (Glacial Lake Agassiz)

lentic

• open and have distinct flows into, through, and out of their basins

• slow moving

• ex: lakes

lotic

• unidirectional water movement along a slope in
  response to gravity

• flowing water

• ex: rivers and streams

unique characteristics of rivers

• unidirectional

• rapid water renewal rates

• 0.1 % of land surface

• drain basins

• Directional movement of water
  dissipates energy and affects
  morphology, sedimentation, water chemistry, and biology

6 types of drainage networks

• dendritic

• parallel

• rectangular

• angular

• contorted

• trellis

how are rivers assigned to basins

• follow gravity

• move from high to low elevation

• determined by surface features

drainage basin definition

an area drained by a river and its tributaries (aka watershed)

basin length

Straight line distance from outlet to the point on the basin divide used to determine the main channel length

basin width

• Average width of the basin determined by dividing the area, A, by the basin length

• WB = A / LB

  
  

basin perimeter

The length of the line that defines the surface of the basin

basin density

• total length of streams divided by area

• Measures the efficiency of the basin drainage (i.e., how well or poorly a watershed is drained by rivers)
  • Depends on climate and physical characteristics (geology, slope, soil,
  land cover) of the drainage basin

• High density means lots of streams and ground not very permeable (vice versa)

river channel

Trough containing flowing water

meandering river characteristics

• suspended sediment load

• finer grained sediment

• increasing stability

• low variability

• low slope

braided river characteristics

• more bedload

• coarser grains of sediment

• decreasing stability

• high variability

• high slope

flood plain

channel is bordered by a flat area

bankfull discharge

a flow that fills the entire cross-section of the river (capacity of the channel)

sinuosity ratio (P)

• The ratio of the main channel length to the basin length

• P = LC/LB

compare sinuosity of a straight river and a highly convoluted river

• straight river: has a sinuosity ratio of 1 because basin length is equal to channel length

• highly convoluted: high sinuosity ratio (above 1) because basin length is much shorter than channel length 

hydrology

The and through near surface environments flow of water across

precipitation

• Single strongest variable driving hydrologic processes

• Formed by water vapor in the atmosphere

• As air cools its ability to ‘hold’ water decreases and some turns to liquid or ice (snow)

hydrograph

• measures flow and discharge of water at a single point over a period of time

impact of urbanization on watersheds

• increase runoff because ground less permeable (concrete) and less trees to absorb excess water

• decreased evapotranspiration

• more runoff= more water in lakes

losing stream

• in arid environments with dry streambeds

• increased amount of ground water because rain replenishes it

• causes less water to be in the stream

gaining stream

• in humid environments with wet streambed

• increases amount of water in stream

• decrease in ground water because excess water goes to stream

Geomorphology

The sub-discipline of geology that describes the physical changes of
the surface of the earth over time

catastophism

• sudden and violent events have shaped the earth’s crust
  • E.g., floods, earthquakes, eruption, tsunamis, meteors

uniformitarianism

• continuous and uniform actions have shaped the earth’s crust

• E.g., mountain building, erosion, deposition, glaciers

missoula floods

• example of both catastrophism and uniformatarianism

• floods caused  by sudden ruptures of ice dams that drained a giant glacial
  lake

• Periodic (several types over a 2000 year period) reforming of the ice
  dams would then create the giant lake again until the dam failed again

2 things need to form a lake

1. a hole

2. water

tectonic basins/lakes

• Depression formed by the movement of deeper portions of the
  earth’s crust

• 2 tectonic plates move away from each other creating a depression filled with precipitation and ground water

• ex: Lake Baikal and Great rift valley lakes

ways lakes can form by volcanic activity

• Material is ejected upward creating a void

• Release magma cools and is distorted in various ways

• Depressions and cavities form

2 types of volcanic lakes

• Maars

• Calderas

Maars

• volcanic lake

• Violent ejection of material, or collapse of overlying materials
  creates a depression

• Comes into contact with ground water

• small in diameter and deep

Calderas

• volcanic lake

• Roof of a partially emptied magmatic chamber subsides
  (through collapse, not explosion)

• larger in diameter than Maars

Lakes formed by Landslides

• Sudden movements of large quantities of unconsolidated material fall to valley floor blocking a stream or river

• Lake forms behind blockage

• Sometimes, only last for a few weeks to several months

Lakes formed by Glacial activity

• most common at higher latitudes

• ¾ of all lakes are glacial in origin

• many types

cirque lakes

• Formed by repeated frost-riving due to repeated freezing and thawing

• 2 variations: fjord lakes and paternoster lakes

• glacial lake

paternoster lakes

a chain of cirque lakes

fjord lakes

cirque lakes near mountains that develop narrow and deep basins

moraine lakes

• movement of vast amounts of rock debris were deposited inland in terminal
  moraines (damming valleys and creating even more lakes)

• also a kettle lake if meltwater of a glacier ends up in the depression

• glacial lake

kettle lake

• when meltwater of a glacier ends up in a depression

• not always a morraine lake

• glacial lake

cryogenic lake

• Formed as a result of permafrost

• Found in the Arctic

• Types: thermokarst lakes, pingo lakes

Thermokarst lakes

• a cryogenic lake

• Melting of massive ice in the ground resulting in collapse of parts of
  the ground

• Leads to landscape having an irregular surface with local internal
  drainage

pingo

• cryogenic lake

• forms permafrost freezes water in a layer of unfrozen ground underneath a lake, pushing the ice up and making a depression

solution lakes

• Lake depression created in area where there are deposits of soluble rock

• Rock is slowly dissolved by percolating water

• Mostly are formed from the solution of limestone (calcium
  carbonate) and slightly acidic water containing CO2

2 types of lakes formed by river activity

• plunge-pool lakes

• oxbow lakes

plunge-pool lakes

depression made at the foot of a waterfall

oxbow lakes

formed when the narrow neck of a meandering river is eroded and eventually the curve is completely cut off from the river

wind formed lakes

• dune lakes

• Wind deflates sediment down to the water table

lakes formed by shoreline activity

• Result from the growth of spits across the mouth of bays or estuaries

• substrate moves and isolates part of water body
  

meteorite lakes

meteor leaves a crater that gets filled with water

reservoirs

• no depression created

• a back stop created by building a dam

maximum lake length

distance on the lake surface between the two most distant points on the lake shore

maximum width/breadth of lake

distance on the lake surface at right angle of to the line of the maximum length on a lake

mean width of lake

area of lake divided by the maximum length

lake area

planar area of the surface of any given contour within the lake

lake volume

• water volume of the lake

• Integral of the areas of each stratum at successive depths from the surface to the point of maximum depth

• Can be estimated by summation of the frustra of a series of truncated cones
  of the strata

maximum lake depth

greatest depth of the lake

mean lake depth

the volume divided by the surface area

relative lake depth

The ratio of the maximum depth as a percentage
of the mean diameter of the lake at the surface

importance of water polarity

• Water can easily dissolve other polar substances

• Positive ends are attracted to water’s negative end, and vice versa

cohesion

• Water is attracted to itself and results in surface tension

• due to multiple hydrogen bonding between oxygen and hydrogen

surface tension

Produces a surface film on water that allows insects to walk on the
surface of water

adhesion

• Hydrogen bonds form with surfaces like glass, soil, plant tissues, and cotton

• Results in capillary action necessary for transpiration process in plants and trees

• Water can climb structures

specific heat of water

• Amount of heat needed to raise or lower 1 g of a substance 1 °C

• Means that water resists temperature change (heating and cooling)

• Water can absorb or release large amounts of heat energy with little change
  in temperature

• water has high specific heat

water heat vaporization

• high 

• Amount of energy to convert 1 g or a substance from a liquid to a gas

• to evaporate, must brake hydrogen bonds

• As evaporation occurs, a lot of heat is removed

waters HoV

540 cal/g

at what temperature does water not change

100 degree celsius

planetary importance of HoV

• Water vapor forms a kind of global “blanket” which helps to keep the
  Earth warm

• Heat radiated from the sun warmed surface of the Earth is absorbed
  and held by the vapor

lake effect

living close to water results in less temperature change because the water moderates the temperature

ice vs water density

• ice is less dense as a solid than as a liquid (ice floats)

• Liquid water has hydrogen bonds that are constantly being broken
  and reformed

• Frozen water forms a crystal-like lattice whereby molecules are set at
  fixed distances

steady state of water

a) Water makes a good insulator
b) Resists temperature change
c) Universal solvent
d) Coolant
e) Ice protects against temperature extremes 

water as a universal solvent

• It dissolves more substances than any other liquid (even the strongest acids)

• it carries dissolved chemicals, minerals, and nutrients that support
  living things

viscosity-density relationship of water

• High density of water makes organisms relatively buoyant against gravitational pull

• Therefore, less energy is needed to maintain position in water or to
  support body

reynolds number

• Density x speed x length divided by viscosity

• Large vertebrate, Re is is high (move with ease)

• For alga or bacteria, Re is very low (move sluggishly, life is “sticky”)

abiotic frame

the sum of all physical and chemical characteristics of a specific lake or pond or
stream or river

abiotic factors that make up the abiotic frame

• Turbulence

• Temperature

• pH

• Habitat permanence

• Availability of:
  • Light
  • Carbon
  • Nutrients
  • Oxygen

Influence of wind and turbulence

• Exposure to wind creates waves and turbulence
• Leads to mixing but degree of impact depends on wind direction, speed
and duration.
• Turbulence has more of an impact on wind-exposed lakes

Fetch

• The length of the lake that the wind acts on

• Varies by wind direction

• Bigger the fetch, bigger the waves

• high fetch lakes have a rocky shoreline

• low fetch lakes have soft sediment shorelines

Langmuir rotations

• phenomenon where you get spiral-formed subsurface turbulence that creates surface foam lines

• Foam consists of small organisms

• Foam lines are parallel with wind

• Buoyancy predicts where organisms are located in the rotation

impact of langmuir rotations on organisms

• buoyant particles/ small organisms swept downward

• non buoyant organisms swept upward

• large animals (fish) impacted because they follow the movement of food

positive effects of turbulance

• If an organism is small or attached to something,
  food can be depleted and waste (e.g., CO2) can build up

• Very important for algal cells that are not in motion

• Turbulence is therefore the utmost importance for nutrient supply and
  removal of excretion products in some freshwater organisms

importance of lake turnover

1) Oxygenates water
2) Mixes nutrients
3) Changes many habitat variables
4) Changes biota distributions

Lake turnover

start with a weakening thermocline, and then windier
conditions, lake turns over

light that water absorbs

ultraviolet, visible, and infrared

importance of UV

is a mutagen

importance of visible light

represents what can be fixed by plants and algae

importance of infrared

crucial for its warming effects on water

different wavelength penetration

• red absorbed in first meter

• UV, violet, green, and blue can penetrate deeper water

rate of attenuation

• sum of absorption and scattering

• more particles in water = more scattering of light= less light absorbed

DOC impact on light penetration

higher DOC= less light penetration

Danger of UV

• harmful to DNA and cell metabolism

• most organisms stay away from direct surface to avoid UV radiation

autochthonous

energy stored in photosynthetically formed organic matter is synthesized inside the water

allochthonous

energy stored in photosynthetically formed
organic matter is synthesized within the drainage basin and
brought to lake or stream

photosynthesis

• Light is used by plants (and algae) to build up large energy-rich
  molecules from carbon dioxide and water.

• in most organisms PS is done in the chloroplasts, in cyanobacteria,
  pigments are throughout the cytoplasm

adaptations to optimize light acquisition

• perennial macrophytes will store energy in their roots so that they can be the first to grow in the spring

• Diatoms will move towards light

• The rate of photosynthesis plays a big role in cell turgor and collapse of gas
  vesicles...which means cyanobacteria can rise and fall depending on light
  conditions

P

light and heating water

• Vital for thermal structure, stratification, mixing, circulation, dissolved gases

• High specific heat of water permits the dissipation of light energy and its
  accumulation of heat

• most heat is absorbed in first few meters

• most light is absorbed as heat