BIOL 4120: Principles of Ecology Lecture 4: Aquatic Environment

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BIOL 4120 Principles of Ecology Lecture 4
Aquatic Environment

• Dafeng Hui
• Room Harned Hall 320
• Phone [phone]
• Email dhui_at_tnstate.edu

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• Topics for this class
• 4.1 Global water cycling between Earth and
  atmosphere
• 4.2 Physical properties of water (H2O)
• 4.3 Light in aquatic environments
• 4.4 Temperature in aquatic environments
• 4.5 Oxygen (O2) in aquatic environments
• 4.6 Acidity in aquatic environments
• 4.7 Water movement in fresh water and marine
  environments
• 4.8 Tides in marines coastal environment
• 4.9 Transition zone (estuaries)

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4.1 Global Hydrologic (water) cycle between Earth
and atmosphere Cycle

• Water is essential for life (75-95 weight of
  living cell)
• Over 75 of the Earths surface is covered by
  water
• Oceans contain 97.
• Polar ice caps and glaciers contain 2.
• Freshwater in lakes, streams, and ground water
  make up less than 1.
• (Saltwater and fresh water)

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Water Cycles between Earth and the Atmosphere

• The water (or hydrologic) cycle is the process by
  which water travels in a sequence from the air to
  Earth and returns to the atmosphere
• Solar radiation is the driving force behind the
  water cycle because it provides energy for the
  evaporation of water

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The Hydrologic Cycle

• Precipitation (PPT)
• Interception
• Infiltration
• Groundwater recharge
• Runoff
• Evaporation (E)
• Transpiration (T)

Distribution of water is not static (processes)
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Global water budget
Land Pools (103 km3) Glaciers
29,000 Groundwater4,000 Lake 229 Soil
67 Fluxes (km3/yr) PPT 111,000 ET 71,000 River
flow40,000 Ocean Pools Ocean1.37106 Fluxes
PPT385,000 ET 425,000
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Water Reservoirs and fluxes
Renewal Time 300-11,000 yrs 12,000 yrs 60-300
yrs 330 days 7-11 days 7 days
(Horne Goldman, 1994)
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4.2 Water Has Important Physical Properties

• In water (H2O), the atoms are asymmetrically
  bound to one another
• The hydrogen atoms share an electron with the
  oxygen atom through a covalent bond
• Because electrons are unequally shared and spend
  more time around oxygen, water is considered a
  polar molecule
• Because of their polarity, water molecules bond
  with one another due to hydrogen bonding

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4.2 Physical properties of water (H2O)
Basic Structure 1. Covalent bonding of 2H O
atoms 2. Polar-covalent bond 3.
Inter-molecule attraction 4. H-bonds among
water moleculars
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Physical and chemical properties

• High specific heat capacity
• Specific Heat 1.0 (also called Heat
  Capacity)
• calories required to raise 1 g H2O 1oC high
• (e.g. from 10 to 11oC)
• Latent heat energy released or absorbed in
  the transformation of water from one state to
  another.
• 1 calorie to raise 1oC 536 calories to
  change 100oC water to vapor 86 calories ice to
  1oC water
• Peculiar density-temperature relationship
• density increases as T decreases (when Tgt
  4oC), then decrease to 0oC, freezing (ice)
• Cohesion
• Due to the hydrogen bonding, water molecules tend
  to stick firmly to each other, resisting external
  forces that would break the bonds (drop of
  water, transpiration).

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Properties (cont.)

• Surface tension-strong attraction within the
  water body and weaker attraction in the surface
  caused that molecules at the surface are drawn
  downward.

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• High viscosity
• Viscosity property of a material that
  measures the force necessary to separate the
  molecules and allow passage of an object through
  liquid.
• Frictional resistance is 100 times greater than
  air.
• Water is 860 times denser than air.
• Organisms in water have similar density to water,
  the neutral buoyancy helps against the force of
  gravity, thus require less investment in
  structure material such as skeletons
• Organisms in deep water need to adapt to the high
  pressure (20 to 1000 atm).

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4.3 Light in aquatic environments
Reflection Interception by particles absorb or
scatter by Absorption by water shortwave Red,
yellow, green and violet Only blue wavelength to
penetrate deeper water
Change in light quantity and quality have
important implications to life in aquatic
environments.
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4.4 Temperature in aquatic environments
Temperature change is the result of the
exponential decline in solar radiation with water
depth. T profile in the ocean The vertical
profile of T varies seasonally. Fall turnover
cool dense surface water sinks, displace the
warmer water below, create uniform T.
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• Flowing body of water (stream or river) has a
  quite different T profile. Must take into account
  all the factors
• Water and its depth
• Temperature Altitude
• Geography Biotic environment

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4.5 Oxygen concentration in aquatic environment
O2 is dissolved in water O2 concentration in
water is determined by solubility and diffusion.
High O2 in the surface due to diffusion
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Vertical profile of oxygen in the Atlantic Ocean
O2 declines to minimum O2 zone (500-1000 m). The
increase caused by influx of O2 rich cold water
sank in the polar water.
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4.6 Water functions as a solvent
Solution a homogeneous liquid with 2 or more
substances mixed. Solvent dissolving
agent Solute substance that is dissolved Aqueous
solution water as solvent Ions Compounds of
electrically charged atoms Cations
positive Anions negative Practical salinity
units (PSU, o/oo) grams of chlorine per kilogram
of water. Ocean 35 unit, Fresh water 0.065-0.30
unit)
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4.7 Acidity has a widespread influence on aquatic
environments
Acidity the abundance of hydrogen ions (H) in
solution. Alkalinity abundance of hydroxyl ions
(OH-) in solution Acidity in water is related
to carbon dioxide (CO2).
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Forms of Carbon

• Carbon-bicarbonate equilibrium
• Carbon dioxide CO2
• Carbonic acid H2CO3
• Bicarbonate HCO3-
• Carbonate CO32-

CO2 H2O? H2CO3 ?HCO3- H ?CO32- 2H
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• Measurement pH -log(H)
• (value between 1-14)
• Pure water 7 Acidic lt7 Alkaline gt7
• Ocean water tends to be slightly alkaline
  with a pH range of 7.5-8.4

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Proportions of the formsof CO2 in Relation to pH
Free
Bicarbonate
Carbonate
pH CO2 HCO3 CO3 4 0.996 0.004 1.26 x
10-9 5 0.962 0.038 1.20 x 10-7
6 0.725 0.275 0.91 x 10-5 7 0.208 0.792 2.60
x 10-4 8 0.025 0.972 3.20 x 10-3
9 0.003 0.966 0.031 10 0.000 0.757 0.243
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4.8 Water movements shape fresh water and marine
environments

• Water movement in the fresh water
• Stream flow rate (velocity of a stream)
• Determined by
• Shape and steepness of stream
• Intensity of rainfall
• If Flow Rategt50 cm/s, remove all gt5 mm in diameter

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• Water movement in the ocean (lake)
• Wave
• Generated by wind

Upwelling
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4.9 Tides dominate the marine coastal environment

• Tides due to the gravitational pulls of the Sun
  and the Moon.

3.49
3.27
Centrifugal force 3.38
Tides are not entirely regular, nor are they the
same all over the Earth. Atlantic semi-daily
Gulf of Mexico one daily tide Pacific mixed
tides.
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Intertidal Zonation
Dramatic shifts in env. Conditions Inundation
and exposure
Intertidal zone area lying between the water
line of high and low tide.
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4.10 Transition zone (Estuary)

• Estuary place where fresh water joins and mixes
  with the saltwater.
• Features
• Considerable fluctuation in temperature, both
  daily and seasonally.
• Large variation in salinity (vertical and
  horizontal)
• Tidal overmixing unstable salinity, saltwater on
  surface tends to sink as lighter fresh water in
  bottom rises, and mixing takes place from the
  surface to the bottom.
• Limited number of species and high production.

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Vertical and horizontal stratification of
salinity from river mouth to the estuary
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The END