Early Limnology Temperature Profiles Lake Zones are dynamic

Early Limnology: Temperature Profiles

Lake Zones are dynamic! Input of heat Mixing forces

The stratification and mixing cycle of an average-sized, temperate lake

Stratification and Mixing

Stratification and Mixing

Stratification and Mixing

Stratification and Mixing

Stratification and Mixing

The Whole Cycle in One Confusing Figure!

Factors that influence stratification pattern • Heating / Density Wind / Waves • Depth • Surface Area • Topography / Location / Exposure

Temperature The Family of Lake Cycles Incident Solar Radiation

The Family of Lake Cycles

Amictic • Perennially ice-covered • Inversely stratified

The Family of Lake Cycles

Cold Monomictic • Water temperature never exceeds 4 C • Ice-covered for most of the year = inversely stratified • One period of free circulation in summer at or below 4 C

The Family of Lake Cycles

Dimictic

The Family of Lake Cycles

Warm Monomictic • • • Circulates once in winter at or above 4 C Directly stratified for the rest of the year Not ice covered

The Family of Lake Cycles

Oligomictic • Stable, direct stratification most of the year • Circulation at irregular intervals (scale of years) during cool periods

The Family of Lake Cycles

Polymictic • Frequent periods of mixing per year • Not ice-covered

Cold Polymictic • • Equatorial, high elevation Hovering around 4 C Intense heat during day (stratification) Intense cooling at night (mixing)

Warm Polymictic • Warm throughout (i. e. , well above 4 C) • Sometimes get intense heating of epilimnion = development of weak stratification.

4 C is IMPORTANT

Holomixis: Circulation occurs throughout the entire water column. Meromixis: Primary water mass never mixes with the lower portion.

Stratification in meromictic lakes • Monimolimnion: deep stratum, high salinity • Chemolimnion: strong salinity gradient • Mixolimnion: upper stratum (i. e. , epi-, meta -, and hypolimnion)

How does the salt get there? • Ectogenic meromixis • Crenogenic meromixis • Biogenic meromixis

Consequences of meromixis • Monimolimnion = Dead Zone • Chemolimnion = Heat Trap

Wavelength Frequency More Blue More Red

Consequences of meromixis • • Hot Lake, north-central WA On top of epsom salt excavation High Mg. SO 4 in monimolimnion Temperature in monimolimnion can get to 50 C!

Why Lake Circulation Matters: Lake Nyos Gas Disaster

Lake Nyos Degassing Project • Pipe is 203 m long and 14. 5 cm in diameter. • Upper end attached to raft and supported by lines to shore.

• Oxygen • Light • Temperature

Patterns along the “river continuum” • Oxygen • Light • Temperature

Temperature along streams

Temperature fluctuations along the streams

Effect of Groundwater on Stream Temperature: Nyack Floodplain, MT

Oxygen along streams • DO in unpolluted, flowing water usually at or near saturation, and concentrations are of little biological significance.