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Lecture goal:
• To identify and describe the properties of water that are most important to understanding broader patterns of habitat structure and ecology in freshwater systems.
Properties and behavior of H20 1: The specifics
Properties and behavior of H20 1: The specifics
• Molecular Structure
• Density
• Temperature
• Oxygen
• Light
The Specifics
• Molecular Structure
• Density
• Temperature
• Oxygen
• Light
Structure of H2O
• Polarity
• Solvent properties
Surface Tension
Surface Tension
The Specifics
• Molecular Structure
• Density
• Temperature
• Oxygen
• Light
Temperature and Water Density
Anchor Ice
Depth and Water Density
• Density increases with depth.
• Influenced by atmospheric pressure and other factors.
Salinity and Water Density
Den
sity
(g
/ m
l)
• Freezing point of sea water (35 g/L) = -2ºC
• Max density of sea water = -2ºC
• Salinity of “Freshwater” ranges from 0.01 – 1.0 g/L
• Saline lake 60 g/L
The Specifics
• Molecular Structure
• Density
• Temperature
• Oxygen
• Light
Temperature and Water Density
Specific Heat of Water
• Specific heat: amount of heat in calories required to raise a unit (i.e., a gram) of the substance by 1C.
• Specific heat of water = 1
• Latent heat of fusion = 80
• Latent heat of vaporization = 540
Measuring Water Temperature
• Standard / immediate temperature
• Seasonal max, min, mean
• Degree days
The Specifics
• Molecular Structure
• Density
• Temperature
• Oxygen
• Light
How oxygen gets into water
How oxygen gets into water…or not
Pressure and O2 Solubility
Temperature and O2 SolubilityO
xyg
en S
olu
bil
ity
(mg
/ L
)
Salinity and O2 Solubility
Oxygen Terminology
• Saturation or Equilibrium Concentration
Amount of DO that can be held by water in equilibrium with the atmosphere at a particular temperature, pressure, and salinity.
• Supersaturation
• Anoxia
• Hypoxia
The Specifics
• Molecular Structure
• Density
• Temperature
• Oxygen
• Light
Why is light important in aquatic systems?
• Light is energy, capable of work and being transformed from one form to another.
• Radiant energy of light transformed to potential energy by biochemical reactions (e.g., photosynthesis).
• Light provides the majority of energy input to aquatic systems – but getting light INTO aquatic systems is tough.
More Blue More Red
Frequency
Wavelength
How do plants receive light energy?
• Quanta or photons at specific frequencies
Controls on light input: season and latitude
Controls on light input: direct solar radiation
Other controls on direct solar radiation
• Time of day• Altitude• Meteorological conditions• Topography
Controls on light input: indirect solar radiation
Controls on indirect solar radiation
• Scattering through atmosphere
• Solar height
Controls on light input: reflectivity
Controls on reflectivity
• Angle of incidence
• Surrounding topography
• Surface conditions of water
Albedo
• Ratio of reflected to incident irradiance
• Increases with reflection at surface and scattering within the lake.
Albedo
Light scattering
within lakes
Effect of Salinity on Density and O2 Solubility
Den
sity
(g
/ m
l)
Anthropogenic Salinization
Drinking Water Supply to Baltimore, Maryland
R2 = 0.65
R2 = 0.44
R2 = 0.74
0
10
20
30
40
50
60
M-79
A-81
M-83
F-85
J-87
D-88
N-90
O-92
S-94
A-96
J-98
J-00
M-02
A-04
M-06
Date
Ch
lori
de
Co
nc
en
tra
tio
n (
mg
/L) LMR0015
MDE0026
BEA
A.
White Mountains, New Hampshire
R2 = 0.70
0
20
40
60
80
100
120
140
J-67
A-69
A-71
S-73
O-75
O-77
N-79
N-81
D-83
J-86
J-88
F-90
M-92
M-94
A-96
M-98
M-00
J-02
Date
Ch
lori
de
Co
nc
en
tra
tio
n (
mg
/L) Stream Near Highway
Forested Reference Stream
Construction of Interstate Highway
C.
R2 = 0.81
0
100
200
300
400
500
600
0 10 20 30 40 50
Percent Impervious Surface in Watershed
Me
an
An
nu
al C
hlo
rid
e C
on
ce
ntr
ati
on
(m
g/L
)1998 1999 2000
2001 2002
Damage to Land Plants
Chronic Toxicity to Freshwater Life
Rural Suburban Urban
