Limnology!Limnology!

LimnologyLimnology

““the oceanography of the oceanography of lakes”lakes”

Study of the functional Study of the functional relationships and relationships and productivity of freshwater productivity of freshwater communities, as they are communities, as they are regulated by the regulated by the dynamics of their dynamics of their physical, chemical, and physical, chemical, and biotic environmentsbiotic environments

LimnologyLimnology

Term “limnology” derived Term “limnology” derived from Greek word “limne” from Greek word “limne” meaning pool, marsh, or meaning pool, marsh, or lakelake

The science arose from The science arose from from lake investigationfrom lake investigation

mid-1800s - Henry David mid-1800s - Henry David Thoreau’s observations Thoreau’s observations from Walden Pond (nice from Walden Pond (nice lake)lake)

LimnologyLimnology

Gradually grew to Gradually grew to encompass all inland encompass all inland waterswaters

Today includes Today includes standing water (standing water (lenticlentic habitats) as well as habitats) as well as running water (running water (loticlotic habitats)habitats)

Physical LimnologyPhysical Limnology

Unique properties of Unique properties of water - important role water - important role in penetration, in penetration, distribution of light, distribution of light, heatheat

Water movements Water movements (waves, currents)(waves, currents)

Geology of basin Geology of basin (origin, morphology, (origin, morphology, leaching minerals)leaching minerals)

Chemical LimnologyChemical Limnology

Inorganic , organic Inorganic , organic compoundscompounds

Closely allied to Closely allied to geology (leaching)geology (leaching)

Distribution often Distribution often related to water related to water movementsmovements

Biological LimnologyBiological Limnology

Base is Base is photosynthesis - photosynthesis - primary productivityprimary productivity

Regulated by, and Regulated by, and may regulate, may regulate, physical and chemical physical and chemical factorsfactors

LimnologyLimnology

Everything becomes Everything becomes interconnectedinterconnected

Add in further Add in further complications complications resulting from human resulting from human relations and impactsrelations and impacts

Very complicated Very complicated sciencescience

Properties of WaterProperties of Water

Unique characteristics Unique characteristics of water regulate the of water regulate the chemical, physical, chemical, physical, and metabolic and metabolic activities in freshwater activities in freshwater systemssystems

Properties of WaterProperties of Water

1) non-linear 1) non-linear relationship between relationship between temperature and temperature and densitydensity

2) high specific heat2) high specific heat 3) viscosity-density 3) viscosity-density

relationshiprelationship 4) high surface 4) high surface

tensiontension

Structure of Water MoleculeStructure of Water Molecule

3 atoms arranged into 3 atoms arranged into non-linear moleculenon-linear molecule

104.5° angle104.5° angle

Structure of Water MoleculeStructure of Water Molecule

Polar molecule with Polar molecule with weak chargesweak charges

Allows for weak Allows for weak hydrogen bonding hydrogen bonding between adjacent between adjacent water moleculeswater molecules

Structure of Water MoleculeStructure of Water Molecule

Each water molecule Each water molecule can have hydrogen can have hydrogen bonds with as many bonds with as many as 4 other water as 4 other water moleculesmolecules

Structure of Water MoleculeStructure of Water Molecule

Structure most Structure most obvious in iceobvious in ice

Creates tetrahedral Creates tetrahedral patternpattern

Lots of space Lots of space between moleculesbetween molecules

Low density - it floatsLow density - it floats

Temperature-DensityTemperature-Density

Non-linearNon-linear Maximum density at Maximum density at

4°C4°C Lower density at Lower density at

higher and lower higher and lower temperaturestemperatures

Hydrogen bonding Hydrogen bonding and molecular and molecular movementmovement

Specific HeatSpecific Heat

Or heat capacity - Or heat capacity - high for waterhigh for water

Amount of heat Amount of heat energy required to energy required to raise unit mass 1°Craise unit mass 1°C

Because of hydrogen Because of hydrogen bondingbonding

Specific HeatSpecific Heat

Temperature changes Temperature changes occur more gradually occur more gradually in lakes than in in lakes than in terrestrial environsterrestrial environs

Lakes can buffer Lakes can buffer climate of nearby land climate of nearby land massesmasses Warmer in winter, Warmer in winter,

cooler in summercooler in summer

Viscosity-Density RelationViscosity-Density Relation

Viscosity - resistance Viscosity - resistance to flowto flow

Viscosity of water Viscosity of water increases as density increases as density increasesincreases

It doubles as temp It doubles as temp decreases from 25°C decreases from 25°C to 0°Cto 0°C

Viscosity-Density RelationViscosity-Density Relation

Change not apparent Change not apparent to human eyeto human eye

Profound effect on Profound effect on movements of movements of microscopic plants microscopic plants and animals, and and animals, and sinking of particles in sinking of particles in lakeslakes

High Surface TensionHigh Surface Tension

Hydrogen bonding Hydrogen bonding interrupted at air-interrupted at air-water interfacewater interface

““molecules exert an molecules exert an inward adhesion to inward adhesion to the liquid phase”the liquid phase”

Molecules at surface Molecules at surface resist being pulled resist being pulled apartapart

High Surface TensionHigh Surface Tension

Allows objects that would Allows objects that would normally sink in water to normally sink in water to be supported on the be supported on the surfacesurface

Mercury is the only liquid Mercury is the only liquid with a higher surface with a higher surface tensiontension

Increases slightly with Increases slightly with increased salinity, increased salinity, decreases with increased decreases with increased temperature, addition of temperature, addition of organic compoundsorganic compounds