Spring 2008

Lentic is describe as standing water habitats

Inland depressions that hold waterRange from 1 meter to 2000 metersFormation

Glacial RetreatCutting of the valley Oxbow Lakes Building of damsVolcanic Crater

Lentic systems may be formed by two mammalsBeavers

Dammed streams to make shallow but extensive ponds

HumansCreate artificial lakes by damming rivers and

streamsUsed for power, irrigation, and water storageCan also be used for water, fishing and wildlifeUnion Canal (Stovers, Lions Lake, Strikes Dam)

Quarries to fill in

Because of high specific heat, lentic ecosystems do not experience sharp daily temperature changesResults in seasonal stratification of the systemEach season change brings about changes in

the system

Epilimnion - upper, warm layerGreek for “upper layer”

Metalimnion - middle layer - layer of changeAlso known as ThermoclineRapid decrease in temperature as

descending in depth1°C per meter in depth

Hypolimnion - bottom laterColdest layer (4°C)Cut off from air above

Stratification breaks down during fall and spring called overturn

When fall begins, upper layer become coolerWhen it gets cooler than lower level, it falls

Due to increase density of the waterLower level is lifted up

Brings nutrients from benthic (bottom)Nutrients are evenly distributed in the system,

creating high productivity

As water becomes cooler than 4° C, water becomes lighter

In the spring… water heats above 4°C, and become denseFalls to bottom surface

Slightest winds can cause circulation

Overturn creates uniform dispersal of nutrients

Increase plant growthIncreases productivity of a system

Why would fish spawn in the spring, and fatten up for winter in the fall?

In air, oxygen is rarely limitedIn water, oxygen is limited or excessive

At saturation, dissolved oxygen becomes problematic and meager

Organisms are dependent on oxygen levelsTrout must have high oxygen, which is a

correlation with temperature

Absorption from atmospherePhotosynthesis - produces 7x amount of

oxygen need for respiration of plantsAt night, plants respire!

Amount of oxygen is dependent on:Temperature - lower temperature, increase

oxygenPressure - more force to keep oxygen in solutionSalinity - increase salinity decreases oxygen

levelsHence why marine organisms breed in brackish water

(mixing of fresh and salt water) because of higher oxygen concentration for mating and nursery Also nutrients

Oxygen levels are stratified based on temperature and photosynthetic levelsIn the summer, increase of oxygen near the

surface due to increase photosynthesisOxygen reaches lower level during turn over or if

light penetrates

Carbon dioxide dissolved in water creates Carbonic AcidLow concentration is held as an acid due to gas

lawsOther Forms: carbonate and bicarbonates

Formation of Carbonic AcidCO2 + H2 <--> H2CO3

H2CO3 <--> HCO3- + H+

HCO3 <--> H+ + CO32-

Amount of acid need to free CO2Gauge of buffering capacity of the carbonate

- CO2 equilibrium Seawater and hard water (increase and

high pH) are high bufferspH levels

Freshwater varies = 3 to 10Rainwater = 5-6Usual Range - 6.5-8.5

Low as 3.5 in seasonal (later summer)

Calcium Carbonate helps with buffering high pH Lebanon Valley is a limestone valley with a

pH around 8.0 to 8.5