Lecture goal: To identify and describe the properties of water that are most important to understanding broader patterns of habitat structure and ecology.

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