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 H 2 0 1: The specifics

Molecular Structure Density Temperature Oxygen Light

The Specifics Molecular Structure Density Temperature Oxygen Light

Structure of H 2 O Polarity Solvent properties

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 Density (g / ml) 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 1  C. 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 O 2 Solubility

Temperature and O 2 Solubility Oxygen Solubility (mg / L)

Salinity and O 2 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 O 2 Solubility Density (g / ml) Anthropogenic Salinization