Dimictic Lakesjoshtabor.com/docs/classes/secondyear/limnology/class... · 2020-02-06 · Dimictic...

Dimictic Lakes are 10m in depth or more.

Epilimnion-

Metalimnion-

Hypolimnion-

Summer Stratification

Winter Inverse Stratification

Limnology: The study of inland surface water including the structure, function, and interrelationship of physical, chemical, and biological components.

-

Rate of Precipitation○

Rain water is distilled, freshened, and available for use.○

Note: Average renewal rate is the time a molecule is tied up in that specific aspect of the biosphere.○

Available water is measured in terms of the rate of water renewal.-

Less than 0.01% of the water in the biosphere is inland fresh water.□Largely unavailable to human use

Sustaining Human, Terrestrial, and Freshwater life. □

Health

Economic

Human Welfare□

Ecosystem Integrity□

Very small amount belies its importance regarding:

About 99.7% of the water of the biosphere is tied up in the ocean and ice caps○

Perspective -

Including the functioning of freshwater aquatic ecosystems.

Freshwater systems have to be understood in order that they be properly managed and protected.○

Freshwater Crisis-

Exponential consumption of water and surface water degradation stress the importance of watershed management.

i.Population Growth - By 2050 9.7 Billion People (French Institute of Demographic Studies)a.

Municipal & Domestic, Industrial and Agricultural demands on freshwater resources.i.Technical Growthb.

Exponential Consumption1.

Particle Detachment by raindrop impact

Transport by runoff

Sedimentation - smothers lakebeds and rivers

Suspended Solids load increase

Eutrophication - "The ecosystem's response to the addition of artificial or natural substances, mainly phosphates, through detergents, fertilizers, or sewage, to an aquatic system."

Ex Fertilizers which lead to Eutrophication of Lakes□

Manure Particles□

Residues on particles - like nutrients

Pesticides

Agriculture - Erosion○

Eutrophication

Forestry○

Sever Degradation2.

Epilimnion

Metalimnion

Hypolimnion

10m +

Dimictic LakesSeptember 13, 2015 10:19 PM

Limnology

Rain drop impact□Road construction□Rutting□Runoff□

Eutrophication

Google: "The initial surface runoff of a rainstorm. During this phase, water pollution entering storm drains in areas with high proportions of impervious surfaces is typically more concentrated compared to the remainder of the storm."

□First Flush - Storm water is directed to surface water.

Urban Development & Highway Construction○

Domestic, Municipal, and Industrial Waste○

Petroleum - ruptured pipelines

Chemical Spills & Leaks○

Riverine to Lake

Change in habitat□

Streams are quite cool

Water from the epilimnion becomes the spill over water that is transferred downstream; which is warmer than the original stream

◊

Water's dissolved oxygen changes because it is temperature dependent◊

Water in the hypolimnion can be oxygen deficient◊

Sedimentation in the hypolimnion causes erosion downstream◊

Trapment of organic matter behind the dam contributes to nutrient deficiency downstream

◊

Trapment of trees and branches behind the dam can cause the release of mercury ◊

Reservoirs are stratified causing water in the epilimnion to be quite warm

Change in Temperature□

Fish Migration

Hydropower & Dams○

Driven by Bacteria

Oxidation of sulfide bearing minerals and generation of □

Causes a drop in pH, higher acidity, higher TDS, higher toxic element concentrations, and higher suspended solid concentrations

□

Acid rock/mine drainage

Mining Activities○

(Sulfuric Acid)□ (Nitric Acid)□

Mercury Deposition: ex. Burning of Coal

Nutrient Input: Nitrate in acid rain is a source of Nitrogen

Results in a drop of pH and an increase in mineral weathering, increase in toxic elements, and increase in nutrient input

□

Acid rain

Atmospheric Inputs○

Lake Mead & Lake Powell on the Colorado Riveri.

Area and degree of exploitation have increased1)Aid in maintaining and increasing per capita consumption of waterii.

Construction of dams, aqueducts, and water diversion projectsa.Uneven distribution of water and people3.

Ex. Alberta going from extreme flooding to extreme droughts in the same year1)Results in weather extremesi.

Changes in patterns of evaporation & precipitation a.Climate Change4.

Limnology

The sum of the reactions that take place in the lake bodyi.All of the chemical reactions in a lake basina.

Includes physical, chemical, biological, and metabolic functioning and the dynamics of their interrelationship

i.Water is a unique substance and it is the controlling influence on entire lake functionb.

Lake Metabolism1.

Water's Molecular Structurei.

Hydrogen Bondsa)Make for a cohesive mass in both liquid & solid forms of waterb)

Bonding characteristics ii.

Intermolecular lattice crystalline structureOne.

As the temperature increases the density decreasesFirst.Temperature is a measurement of kinetic energyTwo.

Increase in thermal energy increases the kinetic energy, which collapses the crystal structure of the ice.

i)

Potential Exam Questionii)

Reduction in kinetic energy at 0C that results in the formation of strong hydrogen bonds

a)0.9168 g/cc - icea)

Arrangement of water in liquid, solid, and gaseous states are important properties of water as the relate to lake function

iii.

The unique features of water center on:a.

Maximum density of 1.0 g/cc at 3.98 degrees Celsius i)Water density is also a function of its salinityii)

4 Degrees is the minimuma)

Reference limnology handout #1b)

Mixing Barrier: warmer less dense water rises above colder more dense water

First.Gives rise to the mixing barrierOne.

As you move down the metalimnion, there is a gradation in temperature and density

i)

Lakes are more 'mechanically stable' when they are stratifiedii)

This allows a lake to stratify into three zonesc)

Heat doesn’t transmit downwardi)This function of water allows for lake thermal density stratification

ii)

Water has a low thermal conductivityd)

The density difference between a given temp and that at 1 degree lower increases markedly above and below 4 degrees Celsius

a)Special Thermal - Density Propertiesi.

Resultb.

1.0g of ice heated and vapourizedi.Water has a high specific heat c.

Characteristics of Water2.

Water as a SubstanceSeptember 19, 2015 7:06 PM

Limnology

High latent heat of fusion @80 cal./gi.High heat capacity @1.0cal./gii.

As molecules with high 'KE' escape, it has a cooling effecta)High latent heat of vapourization @540cal./giii.

This is what drives storms and hurricanes a)Energy is released by water changing from the vapour phase to the liquid phaseiv.

Centipoise is the English unit for viscositya)mPa is the metric unit for viscosity b)

1.0 Centipoise = 1 mPa.s @ 20 Ci.

Viscosity will doubt between 20C and 4Cii.

Greater resistance impedes organism movementa)Affects the locomotion of organismsiii.

Affects the vertical distribution and sinking of passive organisms & suspended solids

iv.

Viscosity of Waterd.

Viscosity is the ratio of stress/straini.

Makes elastic film at surface of watera)Greater attraction to water molecules than air moleculesi.

Special habitatii.

High surface tension at the air-water interfacee.

Limnology

Make up most of the Pleuston One.Neuston - Micro florai)

Pleuston - Animal & Planta)Provides surface for organisms to livea)

Special habitatii.

Surface tension will decrease with temperature, salinity, and dissolved organicsiii.

Limnology

Lake Distribution-

Occupy 2% of the earth's surface○

Lake Victoria, Tirana □East African Rift

Athabasca (Alberta/Saskatchewan Border)□Canada

Holes 20% of earth's total volume of fresh water

1642m deep; deepest on earth

Oldest lake in the world; 25-30 million years old

Ongoing rifting; 9 km deep◊

Occurs on rift

Only one outlet; Selenga River

Two-thirds only exist in Lake Baikal◊

1700 species in lake

Holds more water than all the great lakes of North America combined

Lake Baikal □Russia

Saline Lake□Closed lake; no outlet except evaporation□

Caspian Sea

Closed lake□Formed 5.5 million years ago□Aral meaning island in Mongolian □

The Amu Darya in the south and the Syr Darya in the east

Shrivelling up to nothing due to diverting the inlet for irrigation□

Was once 4th largest lake by area□Diverted for irrigation; cotton fields□

Aral Sea

~40% of the earth's total volume of fresh water is contained in the world's great lakes○

Lake Distribution, Origin, & FormSeptember 28, 2015 10:15 PM

Limnology

Diverted in 1913; caused lake to desiccate by 1926□Owens River was diverted□Before diversion of the river the lake was 12 miles long by 8 miles wide□Covered an area of 108 square miles□

Would sometimes overflow to the south into the Mojave Dessert

Has an average depth of 23-50 feet□

Even before 1913, farmers were diverting tributaries leading into Owens River which was slowing causing the lake to lower

□

Owen's Lake, California

Glaciers contributed to the depressions in the landscape□Glacial activity drove the creation of many of these lakes

Most lakes are smaller in terms of area, depth, and volume and they are concentrated in sub-arctic and temperate zones of the northern hemisphere

○

Lake Origin-

Lakes can be classified by their origin○

Is the lake deep enough to stratify?

Shallow lakes with shallow sides tend to be more biologically productive□

A lake with a large sediment/water interface to lake volume ratio tends to be much more biologically productive

It is useful to classify a lake by its origin because it can affect its morphology○

Limnology

Shallow lakes with shallow sides tend to be more biologically productive□Deep lakes with steep sides tend to be less biologically productive□

Ex. Lake Baikal, lakes along the African rift basin

Referred to as Grabben Lakes

Less biologically active◊

Deep lakes with steep sides

Formed by uplifting and then plucking by glacial activity

Formation of great lakes of North America◊

Was formed by uplifting followed by wind erosion

Aral Sea◊

Many of the large lakes of Nova Scotia were formed by folding, synclines and anticlines, followed by glaciers plucking away at the material

◊

Uplifting causing fracturing, coupled with subsequent erosion

Rifting□Tectonic Lake Basins

Circular, deep, with steep sides

Example lakes exist in Germany

Water filled volcanic cone

Maar Lakes□

Collapse of an emptied magma chamber

Super structure collapses

More deep than a Maar Lake

Example lake is Crater Lake in Oregon

Not biologically active◊

Blue lakes due to lake of biological activity◊

Deep with steep sides

Caldera Lakes□

Volcanic Lakes

Lake Types and Origin○

Limnology

A stream valley blocked off by a lava flow

Lava Flow Lakes□

Landslide material blocks off a stream valley□Sometimes temporary or permanent □

Saturated soils flow down into the stream valley and block it off

Sometimes occur after an earthquake or large rainfall event□

Landslide Lake

Most lakes form through glacial activity□

Lateral Moraine - Material builds up on sides of glacier

End Moraine - Material at the end of a glacier builds up

Ground Moraine - Uneven ground formed under a glacier

Moraine Lakes□

Glacial Lakes

Limnology

Kettles are fluvioglacial landforms occurring as the result of blocks of ice calving from the front of a receding glacier and becoming partially to wholly buried by glacial outwash

◊

Melting of large blocks of ice to form a lake

Shallow, narrow, circular

Many of these lakes in the arctic

Kettle Lakes□

Mountain valley lake formed by glacial scouring

Many in the western areas

Related to moraine lakes but not dependent on a moraine forming; deep scouring allows ridges to be form where water can be held back

Cirque Lakes□

Limnology

Paternoster Lakes - A series of cirque lakes

Millions in Arctic & Subarctic

Related to low temperatures

Accumulation of melt water◊

Forms as a result of permafrost

Polygons of ridges◊

Repeated freeze thawing, resulting in the formation of ridges

Cryogenic Lakes□

"A pingo, also called a hydrolaccolith, is a mound of earth-covered ice found in the Arctic and subarctic that can reach up to 70 metres (230 ft) in height and up to 600 m (2,000 ft) in diameter."

Cryogenic Lakes form as a result of melting pingos.

Glacier moves through and scours up material from weak fractured zones

◊

Results in orientation similarities of NS lakes◊

Anticlines and Synclines

Scouring of weak fractured zones□

Limnology

Referred to Dolines□

Evaporate deposits like Gypsum or soluble salts from the six major ions

Groundwater flow through fractures & fissures in a soluble bedrock□

Erodes the superstructure until it collapses □Found in Nova Scotia along the Windsor formation□Typically round□

Solution Lakes

Meandering rivers/streams

Oxbow Lakes □River Action

Limnology

Form at the base of waterfalls

Plunge Pool Lakes□

Occur behind levees

Often temporary lakes

Levee Lakes□

Significant erosion with deposition forms these in a delta system

Not large lakes

Delta Lakes□

Form in sandy areas

Dry/arid areas

Ephemeral - temporary

Dune lakes□Wind Action

Limnology

Plateau in arid areas

Ex. Aral Sea◊

Western Australia ◊

Wind abrasion on an area of fracture

Quite often ephemeral

Shallow Lakes

Playa Lakes□

Irregular coastline combined with sedimentation by waves & currents can isolate a fresh or brackish water body

□Coastal Lakes

Limnology

Formed by build-up of detritus; organic material

Bog Lakes□

Beaver Dams□

Biogenic Lakes

Lakes created by humans□

Drainage patterns and water balance

They have a large effect on topography and ecology□

Decay of organic matter (nutrients released, CO2 released, mercury released)

□

Dam project in Quebec

Hydropower project

Changing the climate in the Hudson Bay

Toxic elements like mercury released

Caribou death of 10,000 in one season◊

Effecting fish & animal migration

Falls are warmer and springs are colder due to the specific heat capacity of water

◊

Climate is changing in the whole area

Downstream erosion increases◊

Reservoir deposition increases◊

Nutrient supply is affected◊

Sedimentation patterns

Ocean currents changed

La Grande River□

Reservoirs

Limnology

Ocean currents changed

Social impact on the local people

Lake Morphology-

Max length, max width, area, maximum and mean depths, & volume

Ex. Drainage patterns and the size/shape of the watershed, water balance, nutrient balance of the lake ecosystem, lake stratification and mixing, distribution and cycling of chemicals and nutrients, distribution of gases, distribution and behaviour of organisms and lake productivity

Lake morphology and the geomorphic setting of lakes has a large influence on lake function and is strongly related to lake origin

□

I-O

Water balance□

Includes entire watershed

Sometimes you need to look at the airshed as well

Nutrient Balance of the lake ecosystem□

Lake stratification and mixing□Distribution cycling of chemicals & nutrients□Distribution of gases□

Importance of establishing lake morphology

Major Parameters○

Limnology

Water economy of lakes relates to the water balance of lakes and it is tied to the global hydrologic cycle

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Oceans, atmosphere, ice caps and glaciers, continents (lakes and rivers, groundwater)

Evaporated/transpired, absorbed by soil, stored in the groundwater zone, move by gravity to lakes and streams

□

Much of it is evaporated; can be up to 80%□Function of climate, vegetation, seasonal effects□Taking away forest like in the rain forests can cause more water to penetrate the subsurface, causing the air to become drier causing desertification downstream

□

Some water can move by gravity to lakes & streams by gravity□Water is adsorbed and held by capillary forces□

Continental Water may be

Reservoirs of the hydrologic cycle○

The hydrologic cycle involves the transport, storage and change in physical state of water in different reservoirs

-

Ex. Colorado River - most of the water is being used for irrigation and by the time the river flows into the ocean there is a very small amount remaining

□

Ex. The Aral Sea - local water balance has affected the air mass which is drier, colder winters, warmer summers

□

75-80% of all water people use is for irrigation

Irrigation○

Industrial and Domestic Use○

Devoid due to less transpiration of plants□Air downstream will be devoid of water contributing to desertification

Deforestation○

Changes drainage patterns○

Heat mass of water changes the local climate

Reservoir Development○

Removing groundwater before its normal recharge time (600 years)□'Short Circuiting' groundwater

Ex. Nubian Aquifer□25% of sea level rise is due to aquifer mining

Exploitation of groundwater○

Human activity has influenced retention times of water in the hydrologic cycle thereby affecting regional and local water balances and climates

-

Water EconomyOctober 5, 2015 10:56 PM

Limnology

Spans across Libya & Egypt

The world's largest known fossil water aquifer

Contains 150,000km3 of groundwater

Most of the water is being used for irrigation

Enough water being pumped for 4700 years

Man-made river, 10' Diameter Pipeline

Ex. Nubian Aquifer□

Used for irrigation

Ex. Ogallaca Aquifer in US□

Change in patterns of evaporation/precipitation □

A 1 degree Celsius rise in atmosphere = 7% increase in water vapour

◊

As water condenses is releases 540cal/g of energy which drives weather systems

◊

A warming atmosphere

The hydrologic cycle is being energized □

Two major effects

Climate Change○

Establishing water budgets is critical to good water management○

Drinking, wastewater disposal, industry, recreation, hydropower, irrigation, nature preserves

Important for appropriation of supple for various water uses○

Direct precipitation onto lakes

If it encourages runoff or infiltration

Soil type - how conductive it is□

Topography - slope gradients□

Surface influents

Seepage into lakes below the surface

Natural water input to lakes○

Called open lakes or drainage lake□Flow from an outlet

Mostly through the littoral zone□Seepage through basin walls

Natural Water Losses from Lakes○

Water Budgets in Lakes-

Limnology

These lakes are called closed lakes

In some areas this is the only loss of water□Direct evaporation

Macrophytes with large leaves in the littoral zone□Evapo-transpiration from floating and emergent plants

Clime, season, lake morphology, topography, geographic location, soil, geology, vegetation

The entire catchment area has to be considered

All lake inputs and losses vary as to○

Limnology

Solar radiation (light) is radiant energy of the electromagnetic spectrum-

Biochemical conversion of radiant energy to potential chemical energy

Accomplished by the absorption of radiant energy by chlorophyll by primary producers

Mediated as driven by chlorophyll□

Within lake basin by aquatic flora (autochthonous - indigenous to the place it was formed)□

Imported into lake basins as dissolved & suspended organic matter

Outside a lake basin by terrestrial and wetland plants (allochthonous - transported into the area it was found)

□

Primary producers thereby provide a reserve of food and energy for lake ecosystems

Photosynthesis ○

Absorbed as heat

Absorbed in the water column○

Light energy is transformed in lakes by:-

Absorption of Radiant Energy in the Lake Water Column-

Absorption of radiant energy results in its conversion to thermal energy (heat)○

Development of thermal-density stratification

Lake hydraulics (fall and spring turnover)

All chemical cycles and lake metabolism

Population dynamics

In lakes this affects: ○

Hence, overall lake function and biological productivity is affected○

Solar radiation occurs as pulses or packets of electromagnetic energy called photons

Photons behave like particles that travel in a wave like configuration

Comprised of oscillating electric and magnetic force fields at right angles to one another and the direction of travel

Light waves have characteristic wavelength, frequency and amplitude that defines the energy involved

Electromagnetic Spectrum○

Frequency = number of wavelengths per distance□Radiant energy is directly proportional to frequency & amplitude

Inversely proportionate to wavelength

Visible light: 380-800nm□

Increases in wavelength ->

Violet, indigo, blue, green, yellow, orange, red, infrared, UV◊

Seven colours of the rainbow

The colour of a material is dependent on the wavelength of light that is reflected, scattered, or transmitted

Mixture of the visible light spectrum = white light□

Flux: amount of something transmitted per area per time

Dusk/Dawn the path through which the light travels through is longer which filters out certain light and leaves reds/oranges reflecting off the atmosphere

Midday the light has less of a distance to travel through which results in blue light reflecting off the atmosphere

Transformation of Radiant Energy to Heat-

The ability of a given material to do so is related to the pattern of vibration of electrons of the material

When the vibration pattern of the electrons of a material corresponds to the energy state (wavelength & amplitude) of the incoming light, photon energy is absorbed by the electrons causing an increase in

Each molecular and atomic species of material can absorb light having a specific energy state in terms of wavelength, (frequency) and amplitude

○

Light in LakesTuesday, October 13, 2015 12:28 PM

Limnology

The increase in KE is expressed as thermal energy (heat) of the substance □

& amplitude) of the incoming light, photon energy is absorbed by the electrons causing an increase in amplitude of their vibrations

The 50% is within the red-orange - infrared light spectrum□Magnifies the amplitude of water molecules which increases the heat□

Has major thermal effects for lakes since more than 50% of solar energy impinging on the earth's surface is within this portion of the electromagnetic spectrum

Water preferentially absorbed light of several spectrums (preferably red-oranges)○

The Greenhouse Effect-

Some is reflected by the atmosphere

Some is absorbed by the atmosphere

Some is reflected at the Earth's surface

Some is absorbed at the Earth's surface and transformed into heat

Solar radiation impinges on the Earth's outer atmosphere @ 343 Watts/ ○

Some passes through the atmosphere and out into space

Some is absorbed by greenhouse gases in the atmosphere resulting in additional heating

The conversion of radiant energy to thermal energy at the earth's surface results in the emission of long wave infrared radiation back into the atmosphere

○

Thermal energy cannot be transmitted through a vacuum. We are receiving radiant energy which is converted to heat in the atmosphere

○

With more of the ice caps melting, more radiant energy is being absorbed instead of reflected○

, , are all greenhouse gases that are effective in absorbing light in the infrared spectrum○

Light Impinging on Lakes-

Assumes light is striking the earth vertically□

Greater distance travelled = greater selective absorption◊

Affects selective absorption of light by , , &

Midday: Blue wavelengths

Dawn/Dusk: Red-Orange Wavelengths

Angle changes at higher latitudes and at dawn/dusk in which case the light must pass through a greater distance of Earth's atmosphere

□

Summer - Full Amount◊

Results in fall turnover

Fall - Half Amount◊

Nova Scotia @ 45 Parallel

Light amounts vary by time of year□

Angle of Incidence

Atmospheric Effects

The amount of light and composition of light impinging on water bodies in influenced by:○

Fate of Light Impinging on Lakes-

Limnology

Fate of Light Impinging on Lakes-

5% of light is reflected in Summer at midday○

10% of light is reflected in Winter at midday○

Increases with the angle of incidence

Increases the effective angle of incidence□10-20% increase in light reflected at midday□

Increases with wave action

Increases light reflected

Cloudy Ice - Ice with bubbles□

75-95% of radiant energy is reflected back into the atmosphere with snow/cloudy ice cover on lakes

□

Increases dramatically with cloudy ice/snow cover

Reflected at the water surface○

Scatter the blue spectrum□Water molecules

Humic Compounds - Tannin (from the decay of leaves & bark)◊

Tends to scatter back reds/yellows◊

Organic

Organic or inorganic□Solutes

Inorganic: Silts & Clays

Organic: Live or Dead

Organic-Inorganic□Suspended Matter

Scattered in the water column○

Transformed into heat

Absorption by water molecules is highest in the red-infrared part of the electromagnetic spectrum

Effectively absorb UV, blue and green wavelengths□DOM (Dissolved Organic Matter) - Humic Compounds

Absorbed in the Water Column○

Light Attenuation in Lakes-

Scattering

Absorption

This is an exponential lessening of radiant energy with depth in a lake as a result of:○

Rapid depletion of radiant energy at depth○

Suspended solids causes turbidity (scattering of light)

Function of turbidity (suspended solids) and colour□

Less secchi depth, greater phytoplankton, greater productivity◊

A measure of lake productivity

Affected by phytoplankton content□

Rule of thumb: Light can penetrate ~3 times the secchi depth□

Measures water clarity and transparency

Secchi Disk○

Limnology

Limnology

Water is very efficient in absorbing radiant energy of several bands within the portion of the spectrum○

About 50% of the radiant energy impinging on lakes is in the red-infrared region of the electromagnetic spectrum > 750 nm

-

The effect increases significantly when humic substances are present (tannin) ○

The upper ~1m of a lake body can absorb >50% of the radiant energy striking the lake surface-

Light doesn't have to travel as far through the Earth's atmosphere□High daily totals of solar radiation reaching lake surfaces having a lower angle of incidence

Strong absorption tendencies within the lake water column

Heat in the water cannot be conducted to lower portions of the lake□High heat capacity = low thermal conductivity of water

Lake surfaces in temperate regions accumulate heat in springtime as a result of:○

Heating can happen rapidly during several days of sunny, calm weather○

High heat capacity = low thermal conductivity of water

Allows for the formation of the epilimnion□Travelling surface waves help create the epilimnion□Langmuir circulations - all for downward mixing in upward part of the lake□

Physical work of the wind

The distribution of accumulated heat is controlled by:○

Consequently-

Rivers & streams setting up currents□Convection currents□

Currents

Length & width = windfetch - distance over which wind has to act

Area of lake: length, width, depth□Basin Morphology

Fate of HeatOctober 17, 2015 4:41 PM

Limnology

Shallow lake - uniform heat□Deep lake - stratified heat□

Water losses from the lake

Lake Heat Budgets-

Heat gains/losses are high in temperate zones as a result of seasonal effects

Refers to the balance between heat input and heat losses○

Direction absorption of radiant energy

Due to the low thermal conductivity of water

Minor effect that doesn't affect the lake significantly□Conduction of heat from the atmosphere

540 cal/g of heat released when water condenses □Condensation of water vapour at the lake surface

Sediments are heated in the summer and in the fall as the water cools it takes in heat from the sediments

□Transfer of heat from the sediments

Surface water inflow□

Groundwater @ 40ft maintains a temperature of around 10C (about the same as the average air temperature for the air)

Ground water inflow□

Direct Precipitation□

Heat input from:

Heat income to lakes:○

Conduction of heat to the atmosphere

540 cal/g is lost when water goes into the vapour phase□Evaporation at the lake surface

Epilimnion water is the outflow which is the main receiver of heat◊

Especially the surface outflow

Especially surface outflow into the groundwater zone□Outflow from drainage lakes

Heat Losses from Lakes:○

Continued heat loss

Shorter daylight hours□Lessened radiant energy entering lake bodies

In the fall lake surface waters cool:○

Limnology

Shorter daylight hours□Increased angle of incidence□

Thermal Density Stratification & Turnover-

Typical in lakes of at least moderate depth (~10meters) in temperate regions○

Happens quickly over several days of sunny, calm weather□

From top to bottom◊

RTR: Given for water columns 0.5m deep

Expressed as the ratio of the density difference between water at the top and bottom of each 0.5m column: to the density difference of water at 5-4C

One unit of RTR is = to the density difference of water @ 5C & 4C

Mixing barrier◊

If both Top and Bottom temperature values are equal, then RTR will equal 0◊

Defines how mechanically stable a lake will be & how resistant a lake will be to mixing

◊

High RTR will ride on top

As the surface water warms, it becomes less dense and the relative thermal resistance to mixing (RTR) increases:

□

The lake becomes mechanically stable

The degree of stability is proportional to lake depth and the temperature contrast with depth

The lake stratifies into three zones that are resistant to mixing with each other□

The surface water in lakes accumulate heat

Springtime○

Lakes stratify into three zones-

Upper zone of uniformly warm, less dense, turbulent (mixing) water

Established by the wind

Temperature difference from top to bottom of the epilimnion is 0, therefore RTR = 0□RTR = 0

Epilimnion○

Very still water□Lower zone of ~uniformly cool, more dense, quiet (non-mixing) water

Stable due to high thermal conductivity□Initial temperature established at spring turnover

Temperature remains ~stable because of the low thermal conductivity of water

Temperature changes little throughout summer, especially in deep lakes

Hypolimnion○

Transitional zone between the epilimnion and hypolimnion

Metalimnion○

Limnology

Transitional zone between the epilimnion and hypolimnion

Characterized by a rapid reduction in temperature with depth

Represents the mixing barrier between the epilimnion and hypolimnion where the RTR is a maximum

The plane of maximum change in temperature with depth

Occurs within the metalimnion zone

Subsequently moves downward as a result of vertical mixing caused by the wind to create the epilimnion

□Initially occurs at the lake surface in calm, sunny weather

Thermocline○

Fall Turnover-

Higher angle of incidence = more radiant energy is reflected off the lake surface□Heat is lost through outflow□

The epilimnion cools, it becomes eroded by wind-induced mixing as the RTR is lessened

In the fall, loss of heat exceeds heat input○

Turnover continues with ongoing cooling to 4C or less throughout the entire water column

Eventually, the entire column of water circulates to initiate fall turnover○

Winter-

0C water riding on top of warmer 4C water□Less dense 0C water riding on more dense 4C water□

Vs. Summer when it is at a max◊

Due to density difference per degree lowing being a very small difference

Wind is not an effect◊

When ice cover is lost, the lake will turnover immediately◊

Ice cover protects winter inverse stratification

Very fragile balance□

Results in inverse thermal stratification

Very fragile because the water column is nearly isothermal at the temperature of maximum density where the density difference per degree lowering is at a minimum

This low RTR is protected by ice cover

Ice cover forms○

Spring-

Initiated easily in windy, spring weather when ice cover is removed○

Surface water accumulates heat and the annual cycle continues○

Depth-Time Diagram-

Dashed line = thermocline○

For any date you can draw a straight line and you will get a temperature profile○

= wind induced erosion

As temperatures drop, RTR to mixing is lessened○

Colder on top, warmer on bottom

Left & right ends = ice cover○

Limnology

Occur at latitudes 40-60

Cold temperate regions

Must be of moderate depth (10 meters or more)

Freeze in winter

Summer thermal density stratification□Winter inverse stratification□

Two stratifications

Fall□Spring□

Dimictic meaning two mixing cycles

Dimictic○

Latitude 25-40

Warm, temperate regions

Do not free in the winter

Stratify in the summer & circulate freely in the winter

No winter inverse stratification

Warm Monomictic○

Sub-arctic latitude 60-80

Ice free briefly

Water temperature never goes about 4C

One mixing cycle in the summer

Cold Monomictic○

Permanently frozen

Amictic = without mixing

Amictic○

Dependent on wind conditions & morphology◊

Can in some cases mix

Quite weakly stratified□Permanently stratified

Ogliomictic ○

High altitude, tropic regions

Mix often

Water temperature is typically in the range of 4-6C

As a consequence even minimal wind exposure can cause mixing□Low RTR

Polymictic○

Lake classification as per annual stratification and mixing cycles-

Limnology

Limnology

Water movements in lakes have a large influence on lake function because of their dispersive effects

-

Lake stratification - Epilimnion

Moving warm water of the epilimnion moving down gradient□Currents of the lake

Distribution of heat (and stratification)○

Lake water chemistry

Distribution of nutrients & chemicals○

Oxygen contributing to oxidation reduction potential (ORP)□Carbon Dioxide contributing to alkalinity & pH□

Oxygen and carbon dioxide

Distribution of gases○

Influenced by various water movements□Important factor in wastewater discharge

Influences where the contaminants will travel to

Stratified or not□Chemical Spills

Contaminant Transport○

Open water portion of the lake where plankton dominate

Passive organisms (plankton) in the pelagial zone□

Explains why large deep rooted plants dominate the littoral zone

Macrophytes occur in the littoral zone□

Directly

Distribution of nutrients□

When it comes to the distribution of aerobic organisms

Distribution of □

Indirectly

Lake water movements thereby affect all lake function, metabolism, and biological productivity

Distribution of organisms:○

Lake water moves largely as a result of the transfer of wind energy to the water○

Area/Shape□

Some water movements only occur in deep lakes or shallow lakes

Depth□

Volume□

Circular lakes vs. lakes with varying shoreline configurations

Shoreline configuration□

Lake morphology

Some movements only occur when lakes are thermally stratified□Lake stratification

Wind fetch□Climate and weather□

Wind exposure

The patterns of water movements and effects of water movements are lake specific:○

Various water movements affect:-

Lake Hydraulics-

An orderly flow pattern that occurs below a certain flow velocity□Laminar Flow

Turbulent Flow

Laminar vs. Turbulent Flow○

Water Movements in LakesFriday, October 23, 2015 3:11 PM

Limnology

As velocity increases, higher frictional shear results in chaotic/turbulent flow□Turbulent Flow

This is described by the Reynold's Number□Turbulence is predicted for a Reynold's Number greater than 2100□Given the large flow diameter in lakes, laminar flow is rare□

□

□ □

□

□

Water = 0.001

□

Ex.

V = 0.00001 m/s

Velocity required to create turbulent flow critical velocity = velocity that will take one from laminar to turbulent flow

This results in high dispersive effects in the water mass◊

In turbulent flow the pattern of flow is not straight

Turbulence is predicted for a Reynolds Number greater than 2100□

The velocity to induce turbulent flow is very low in lakes

Eddy Diffusion-

As two fluid layers of different density move relative to one another, a frictional shear stress occurs at the interface

○

Orderly (laminar) flow occurs below a certain relative speed○

The flow becomes chaotic/turbulent

As the relative velocity increases, higher frictional shear at the interface results in the development of vortices or eddies

○

Eddy Diffusion: The mixing of two fluid layers of different density perpendicular to the flow direction

○

Decreases markedly in the more stable metalimnion and hypolimnion

Mixing by Eddy Diffusion and turbulent flow is maximum in the epilimnion○

Wavelengths less than 6.3 cm

Ripples○

Frictional effects of the wind sets surface water into an oscillating motion

Water is displaced upwards and returns downward by gravity

Cycloid paths are established that diminish quickly with depth

(Travelling) Surface Waves○

Waves-

Limnology

Surface waves result in significant vertical mixing but little horizontal motion

In excess of 30 km/h

Apical water gets blown off to form white caps□

When the angle of the was profile becomes excessive, the peak becomes unstable and collapses

Wave velocity decreases corresponding to a reduction in wavelength and an increase in wave height

□

Waves become asymmetrical and unstable□They collapse forward to form breakers□

At the near-shore the oscillating motion of surface waves is transformed into a sloshing to and fro motion extending to the bottom of the lake

Breakers○

Waves crest curl over and collapse

Waves become asymmetrical quickly as a result of a steep shoreline or large waves

Plunging Breakers○

Collapse by spilling water forward

Surface waves become asymmetrical more slowly

Dissipate energy more slowly

Spilling Breakers○

Remove littoral sediments to deeper water

Deep rooted macrophytes in the littoral zone□Affects the distribution of organisms

Breakers impose high energy to shorelines○

Wind driven surface current

Non-linear beyond this□~2% of wind speed up to ~20 km/hr

Effect diminishes with depth

Affected by the Coriolis force of the earth's rotation

Wind Drift○

As thick as the epilimnion□Large currents of turbulent mixing in the lake surface water

Perpendicular to wind (surface wave) direction

Organized along cylinders that parallel wind direction

Vertical circular cells:□Flow is organized into vertical circular cells and helices

Parallel wind direction□Helices

Langmuir Circulations○

Currents-

Limnology

Generated by circular cells interacting with travelling surface waves□Lines of convergence of both circular cells and helices cause aggregate of particles called "streaks"

□

They reflect the pattern by which the turbulent energy of these waves is dissipated downward

Langmuir circulations are generated by travelling surface waves at wind speeds > 7 km/hr

□

Thickening of the epilimnion, deterioration of the metalimnion

Significant shear causes eddy diffusion once again, causing more vertical mixing

□

This excess water causes downward flow by gravity until it encounters the dense water of the mixing barrier

Flow continues upwind along the interface

Considerable wind drift can cause water of the epilimnion to pile up on the downwind end of the lake

○

Tilting of the metalimnion (mixing barrier) along with its entrainment by Eddy Diffusion

Thickening of the epilimnion

Result:○

Internal Water Currents-

When the wind stops, these tilted surfaces want to equilibrate

Momentum causes a sloshing/rocking action that generate waves as big as the lake basin itself

A persistent wind (wind drift) causes tilting of the lake water surface and (more so) of the mixing barrier

○

Occur in stratified lakes when the mixing barrier is caused to oscillate

Causes shear/eddy diffusion at the interface with major dispersive effects vertically and horizontally

Internal Seiche○

The lake surface oscillates when the wind stops whether the lake is stratified or not

Millimeters in small lakes, ~couple meters in large lakes□Periodicity of several minutes to several hours□Lake Erie: 2 m, 14 hours (end to end)□

Amplitude of surface seiches are much smaller than internal seiches

Surface Seiche○

Once seiches are set in motion, friction and gravity dampen the oscillations and the water mass returns to equilibrium

○

Seiches (pronounced Saysh)-

Springtime: water heats up more quickly near shoreline○

A wall of water at maximum density that prohibits mixing between in-and offshore zones until the whole lake is stratified

Thermal bars are eroded with steady circulation downward along the bar as it moves outward into the lake

A thermal bar forms○

Thermal Bars-

Overflow

Underflow

Interflow

Inflow tends to enter strata having density similar to its own○

Currents generated by River Influents-

Occur in shallow lakes that do not stratify○

Slow, thermally-induced currents generated by heat released from sediments

Convection currents under ice-

Limnology

Slow, thermally-induced currents generated by heat released from sediments○

Limnology

Nitrate, nitric acid from acid rain

Ex. Is mining projects in Western Canada

Positively charged cations adsorbed to the clay particle surfaces◊

Clay & dust particles

Acid rain can influence nutrient input◊

Can increase the toxic element input by dissolving mineral content

◊

Acid rain

Ex. Lakes like Pockwock Lake are low in alkalinity and thus have a low buffering capacity when dealing with acid rain

◊

Drop in pH

Nutrients Deposited□

Lake basins receive inorganic nutrients and dissolved and suspended organic matter from the entire drainage area

Aquatic ecosystems include the entire watershed (and airshed)○

Lake Ecosystem Concept-

Terrestrial, stream, Pelagial (open water), Wetland-littoral (transitional between the pelagial and terrestrial zones)

○

Lake Ecosystem Zonation-

Dominated by plankton□Pelagial zone

Dominated by macrophytes□Can be further subdivided as per figure□

Not effected by spray (related to breakers)

"Above littoral"

Epilittoral□

Effected by spray

Supralittoral□

Range of water levels between seasonal high & low

Eulittoral□

Emergent macrophytes

Upper Littoral□

Floating leaved plants

Middle Littoral□

Submergent macrophytes

Lower Littoral□

Wetland-littoral

That zone below the pelagial zone that is free of vegetation□Dominated by benthic algae □

Profundal

Characterized by dominating organisms○

Lake Basin Zonation-

Limited = Zooplankton□Limited = Nekton□No = Phytoplankton □

Microscopic with no/limited powers of locomotion

Subject to dispersal by water

Phytoplankton = plant plankton

Nekton = plankton having good powers of locomotion□Zooplankton = animal plankton

Plankton○

Groups of Organisms as per Lake Zone-

Structure & Productivity of Aquatic EcosystemsOctober 26, 2015 8:40 PM

Limnology

Nekton = plankton having good powers of locomotion□

Water motions of the epilimnion keep them in suspension

Turbulent mixing and the higher density and viscosity of the mixing barrier helps maintain suspension

□Denser than water and tend to sink

Photosynthetic bacteria

Cyanobacteria - Blue green algae□

Heterotrophic Bacteria - Oxidize organics□Detritus - Dead organic matter□

Bacteria and microscopic algae attached to substrates

Epilithic Periphyton living on rock substrate

Epipelic Periphyton living on sediment & organic 'muck' at the bottom of the lakeEpiphytic Periphyton living on plants-

Lower littoral zone-

Episammic Living on a sand

Metaphyton

Not Periphyton-

Aggregates of floating algae-

Accumulated in upper & middle littoral zones by water movements

•Accumulated by water motions-

□

Grouped according to substrate type

Influxes of nutrients for example

Very susceptible to environment changes□Food source and indicators of water quality

Periphyton○

Algae living in the transitional zone, Profundal/Littoral□Plants and animals living at or near the sediment-water interface

Benthos○

Limnology

Algae living in the transitional zone, Profundal/Littoral□

Micro - Bacteria □Both micro & macro invertebrates

Algae, worms, mussels, and other invertebrates

Adapted to air-water interface

Mostly microflora (Neuston)

Epineustic - Above□Hyponeustic - Below□

Surface tension is made use of as a substrate

Ex. Water Bug

Pleuston○

Neuston

Limnology

Organisms that live underneath the water surface film

Ex. Janthia (photo below)

Neuston ○

Large, 'rooted' plants of the littoral zone

Macrophytes○

Biological Productivity of Lake Ecosystems-

Where plankton dominate

Lowest in the pelagial zone○

Intermediate in the terrestrial setting○

Macrophytes

Highest in the littoral zone○

Indicator of pollution of some sort

In response to eutrophication you get metaphyton algae bloom

Lots of blue green algae

Eutrophication - Nutrient rich; over supply which produces algo-blooms with thick algalmats

○

Most is dead□

Living organisms make up only a very small portion of the total organic content of a lake ecosystem

All dead particulate and dissolved organic matter□

Provides a buffering effect from seasonal swings in ecosystem functioning

◊

Provides fundamental stability to ecosystems

Provides a large reserve of energy and food for living components□

Detritus

Dead Organic Matter○

Limnology

The net amount of new biomass formed over a time period including losses□Production

The average rate of production of new biomass□Productivity

Lake Productivity○

Set up a grid and physically count them

Problem: organisms vary significantly in size and age

Enumeration□

Oven dry @ 105C

Problem: organisms vary as to water content

Organic carbon is burned off - ◊

Can be determined by loss in dry weight by ignition @550C

Dry Weight□

For phytoplankton and periphyton analysis

Measure of biomass

Chlorophyll a analysis□

Least variable parameter

Titrate with potassium dichromate◊

Amount of oxidant consumed is a measure of organic carbon content

◊

Sparging (with a gas)–

Acidic environment–

Rids the sample of inorganic carbon–

In an acidic environment you rid the sample of inorganic carbon as

–

Rids the sample of carbonic acid, releases –

–

Pre-treat the sample

TOC Analyzers◊

Rids the sample of inorganic carbon–

Sparge in an acidic environment

Measures the drop in pH through the use of colour indicators

–

Digest the sample to convert OC to

Hach Method◊

~40-60% by oven dry weight depending on species and state of decomposition

Total Organic Carbon (TOC) analysis□

The approach depends on objectives and organism type

Biomass Measurement○

O2 deficits in the hypolimnion□Follow changes in levels of O2/CO2 over time

Productivity○

Limnology

O2 deficits in the hypolimnion□

Higher pH due to more ◊

Lakes are often anaerobic in the hypolimnion

CO2 production in the hypolimnion □

Respiration uses O2 and photosynthesis uses □

Lower O2 and Higher

Dark bottles = respiration□

Lower and Higher O2

Light bottles = photosynthesis□

Assess results according to rates of change in the Co2/O2 ratio□

Light/Dark (BOD) Bottle Technique

Incorporation of tracer in the form of □

Rough

Estimation of change in biomass over time per area (or volume)□

Measuring inorganic carbon assimilation

Relates to the nutrition stages in lakes○

Secchi disk

Trophic State Index (TSI)○

Lake Trophic (Productivity) Status-

Limnology

Direct requirement of all aerobic organisms○

All are influenced by redox reactions□C, Fe, Mn, S, N, various micronutrients

Strongly affects the solubility, form, and availability of many elements and nutrients○

Oxygen is fundamental to lake function-

The distribution and availability of oxygen affects lake productivity by influencing the distribution, behaviour, and growth of organisms

-

Distribution and availability of oxygen is controlled by:-

Travelling surface waves

Langmuir circulation

Epilimnion @ equilibrium□

Turbulent mixing of water is needed for oxygen to be distributed at depth such that it is in equilibrium with the atmosphere

@20C 9.092mg/L□

@20C 1689mg/L

is 200x as soluble as oxygen□

Not very soluble in water

Diffusion from the atmosphere○

Plankton in the pelagial zone

Macrophytes in the littoral zone (better oxygen producers than plankton)

Photosynthetic inputs○

Turnover cycles & spring/winter mixing□Mixing processes and stratification

Hydromechanics○

Lithotrophs respiration□

Lithotrophs take things and oxidize them

□

Process of nitrification

Organic and inorganic oxidation reactions○

Increase in temperature = reduced solubility

Water Temperature□

Increase in pressure = increased solubility

Atmospheric

HP - Surface conditions (temperature & pressure)◊

Hydrostatic

Cold water in hypolimnion with hydrostatic pressure can hold more water than the warm epilimnion

Pressure acting on the oxygen□

Solubility decreases exponentially with salinity

~20% lower in seawater relative to 'pure' water

Hydrostatic pressure at depth (coupled with cooler temperatures) can result in supersaturation with respect to oxygen relative to surface water conditions

Supersaturation can also result from photosynthetic inputs at depth

Water salinity□

Oxygen (gas) solubility is a function of

Factors controlling oxygen solubility○

Oxygen in LakesTuesday, November 03, 2015 4:58 PM

Limnology

Results in bubble formation◊

Rise and break or accumulate as foam◊

Supersaturation can also result from photosynthetic inputs at depth

Stratification□Vertically

At sundown the macrophytes stop producing and levels drop dramatically (in littoral)

◊

Phytoplankton are much less proficient at producing as macrophytes which results in the difference in pelagic vs littoral production

◊

Littoral vs Pelagial

Littoral vs. pelagial zones□Horizontally

Photosynthesis in daylight□Respiration at night□

Daily

Organisms die off in the fall starting biodegradation

Variations in productivity□

Lake stratification and mixing cycles□

Organic loading - > consumes oxygen

Do loading -> how much oxygen water can hold varies by season

Influent waters (organic loading, DO loading)□

Temperature effects□

12-14 mg/L

Saturated with top to bottom◊

High pressure and low temperature–

Very little biomass being produced therefore very little consumption of

Very little consumption of –

Elevated

Ogliotrophic◊

Organisms consume and use up –

Large biomass production

Eutrophic◊

Spring Turnover

Complete mixing, colder temperatures mean more oxygen intake

◊

Fall Turnover

Clear colourless ice can allow photosynthesis to continue which allows more creation

◊

Winter

Seasons:□

Seasonally

Distribution varies in time and space○

Distribution of Dissolved Oxygen-

Common○

generation greater than consumption

Higher temperature in the epilimnion

consumption in the hypolimnion

DO in the metalimnion is greater than/often supersaturated relative to the epilimnion and hypolimnion

○

Metalimnetic Oxygen Maximum-

Respiration oxidation by zooplankton exceeds oxygen input○

Enhanced by organic matter sedimentation from the epilimnion onto the colder, denser metalimnion

○

Colder hypolimnion

Metalimnetic Oxygen Minimum-

Limnology

Colder hypolimnion○

Graph 1: Biologically productive lake, oxygen deficient hypolimnion

Graph 2: Not as productive as lake in graph 1

Areas of Karst topography□

Graph 3: Saline lakes, streams bring in less dense fresh water on top of saline water

Graphs:○

generation in the littoral zone (macrophytes) is greater than in the pelagial zone (phytoplankton)

○

Horizontal Variations in DO-

Rapid decay of massive littoral flora or plankton○

Aggravated by warmer water○

Summerkill-

Below ice with limited photosynthetic input of DO and lessened diffusion of from the atmosphere combined with continued consumption

○

Winterkill-

Rough index of productivity

Biomass production in the epilimnion is reflected in DO consumption in the hypolimnion

Reduction in the amount of DO present between the beginning and end of summertime stratification in the hypolimnion

○

Measure oxygen at the beginning of summertime stratification and again at the end of summertime stratification. The difference between the two is an indicator of lake productivity. A high use of O2 means that the lake is biologically productive.

○

Hypolimnion Oxygen Deficits-

Limnology

Salinity refers to the total dissolved mineral (ionized) solids content of a water-

Expressed as the sum of all constituents contributing to the electrolyte solution-

Units: mg/L, ppm, meq/L, parts per thousand = %˳-

>95% of total○

Cations: ○

Anions:

○

In order of predominance○

Salinity is dominated by the six major ions-

Weight residue of filtrate (@ 0.45 microns) after vapourizing known volume @ 180C

But this includes Dissolved Organic Matter

DOM can be removed by ignition at 550C in a muffle furnace

□But this results in weight loss ( from carbonates

Gravimetric Method○

= ~mg/L

Provides a good approximation at lower salinities (<~100 micromhos/cm)

Biased low re salinity□The crowding of ions causes the salting out effect□

'Salting Out' increasingly disrupts accuracy at higher salinities

Specific Conductance○

Add things up for salinity

Most accurate method

Perform a 'complete' chemical analysis○

Methods for Salinity Determination-

Not very soluble

Low salinity, soft water having a low pH and alkalinity

Silicate rock mineral□

High salinity, hard water having higher pH and alkalinity

Calcareous rocks and evaporite deposits□

Mineralogy and soil zone processes

Derived from oceanic, terrestrial, and human sources□

Pine forest - turpentine–

Bioturbation–

VOCs from plant metabolism

Ex. Dimethyl sulfide –

Plankton gives off DMS–

Sulfate aerosol–

DMS

Seasalt crystals, dust, VOCs, DMS◊

Atmospheric aerosols server as raindrop nuclei (cloud condensation nuclei = CCN)

Primary Aerosols - are emitted into the atmosphere as solids◊

Atmospheric Aerosol - Small particle of liquid or solid with a size range of a few molecules to 40 microns which serve as cloud condensation nuclei

Rainwater□

Atmospheric Contributions

Weathering effects (climate) combined with bedrock and surficial geology and watershed soils

○

Controls on Salinity-

Salinity of Inland WatersTuesday, November 17, 2015 5:43 PM

Limnology

Seasalt crystals, dust etc (Solids)

Primary Aerosols - are emitted into the atmosphere as solids◊

VOCs, DMS (plankton) (Gases)

Secondary Aerosols - released into the atmosphere as gases and then condense into a liquid. They oxidize in the atmosphere.

◊

Arid and semiarid regions

40 micron diameter◊

Not in the air long enough to serve as CCN

Dust and clays carried down wind

Dry dust landing on surface water bodies

Western Canada◊

Tilled land

Dry fallout of mineral crystals and dust□

Sulfate and nitrate from acid rain

◊

Nitric acid from vehicle emissions

◊

◊

Sulfuric acid from burning of pyritic coal and crude oil

pH @ 5.6-5.7 is NOT an indication of acid rain effects◊

Especially an issue in lakes with very low alkalinity

Also in soils with low pH

pH of rain as low as 4-5 from acid rain effects◊

Fish @ pH of less than 5

Direct effect on organism metabolism and reproduction◊

Fish toxicity

Al3+ -> Soluble @pH less than 4.7-4.8

Trace elements–

Increased weathering

Increased nutrient and toxic input from acidity and dissolution◊

Acid rain can change the entire watershed

Woody material accumulates mercury◊

Linked to the declining loon population

Burning of coal◊

Mercury deposition

Human Sources□

Arid and semi-arid regions

Their outflow is only through evaporation

Caspian Sea & Aral Sea are two examples of this. □Closed lakes have higher salinities

Spring has a dilution effect from all of the runoff entering the waterways□

More surface water input as well

In the summer there is more groundwater input into water bodies□

Late summer

Balance between evaporation and precipitation○

In epilimnion the calcium concentration can be reduced

Calcium is in demand by organisms□

Diatom makeup

Silica□

Changes in metals (importantly Fe & Mn)

Epilimnion

Higher pH and higher ORP◊

-> Photosynthesis

Changes in redox potential & pH□

Nutrient uptake

Biota○

Limnology

Epilimnion

Fe, Mn will precipitate out as oxides and hydroxides◊

Hypolimnion

Lower pH and lower ORP◊

Rains down on hypolimnion and goes back into solution◊

Respiration

Changes in redox potential and pH

□

Carbonic acid is lessened, calcium carbonate will precipitate out

- Marl - Tiny colloidal particles that sink

In the hypolimnion lower temperatures and higher pressure will allow high concentration of in solution

◊

As the rains down on the hypolimnion, it will precipitate out

□

Calcareous hardwater lakes

Controlled by redox conditions and lake turnover

Lots of Fe & Mn in the sediments with a tendency to diffuse out. The oxidized microzone will cause them to not be able to. The Fe & Mn are immobilized

□Ex 1 - Anaerobic sediments (increased reducing conditions)

As summer progresses the oxidized microzone disappears □This allows Fe & Mn to diffuse out into the lake□

Can happen at water treatment plants

In the fall Fe & Mn will be taken up into the whole water column□

Can spur on algal blooms

Iron is a major nutrient for plankton□

Ex 2 - Anaerobic Hypolimnion

Exchange with the sediments at the bottom of the lake○

Examples: Na, Mg, K, & Cl □Tend not to react much and aren't in demand as nutrients□

Form soluble salts

In little demand as a nutrient◊

Ie. By Photosynthesis and respiration

Not affected by changing redox potential and pH◊

Minor biotic influence

Uniform distribution in space and time□

In minor demand only (for chlorophyll)

Magnesium□

Biggest demand is for osmotic regulation

To prevent desiccation

Sodium and Potassium □

Road salt & seasalt ◊

Waste disposal; has elevated levels◊

Input from

Chloride□

Conservative Ions

Concentrations vary in space and time□

In demand as nutrients and/or

Photosynthesis & respiration◊

Affected by changing redox potential and pH from photosynthesis and respiration

Influenced by biota:□

Calcareous hard water lakesExamples: Ca, HCO3 (and CO3), SO4□

Dynamic Ions

Separable into 'conservative' and 'dynamic' ions○

Distribution of (Major) Ions-

Limnology

High demand for calcium in organisms◊

Calcareous hard water lakes

◊

Converted to reduced forms◊

Anaerobic conditions

Sulfate reducing bacteria make use of sulfate as an oxygen

Requirement for higher plants and algae

Requirement of animals with calcareous shells and plankton with calcareous skeletons

Eg. Calcareous hard water lakes◊

Affected by photosynthesis and respiration

Calcium□

Organisms needing calcareous shells/skeletons

Photosynthesis and respiration in calcareous hardwater lakes

Bicarbonate (and Carbonate) is affected by:□

Susceptible to changing redox conditions

Sulfate□

Little photosynthesis

Little respiration

As a consequence, calcium concentration varies little□Throughout the year very little variation in redox potential & pH occurs

Figure 10-3 (Ogliotrophic)○

Photosynthesis (Lower pH, Lower ORP, Higher solubility, Higher Specific Conductance)

Metals and carbonates

Things will precipitate out□

Lessened mineral solubility

Lower specific conductance □

Respiration (Higher pH, higher ORP)

Figure 10-4 (Ogliotrophic)○

Figures & Tables-

Limnology

Calcareous, productive, hard water lakes

Organic matter rains down on the hypolimnion□Carbonate compensation depth

Lower temperature, higher pressure @ the hypolimnion

Photosynthesis influences calcium

Figure 10-5 (Hypereutrophic)○

Sodium and potassium - Throughout the year, there is little demand on them as a nutrient

Not susceptible to changing pH, redox, etc

Figure 10-7○

Limnology

Chloride - very conservative - most conservative of all

Figure 10-8○

Limnology

Limnology

A relatively small amount of the TC is organic carbon in detritus ○

A very small amount of the TC is living matter○

By far most of the total carbon (TC) content in lake water is inorganic carbon associated with equilibrium relationships tied to carbonic acid

-

Henry's law - describes the proportion of free dissolved that can react with water to form carbonic acid

solubility @ 1689 mg/L @ sealevel & 20C

solubility @ 9.09 mg/L @ sealevel & 20C

is very soluble in water

The air/water barrier does not influence the diffusion

25% of produced by humans has dissolved into the ocean contributing to acidification

A water in equilibrium with the atmosphere will contain the same % by volume of as does the atmosphere itself

Equilibrium reactions○

Diffusion of from the atmosphere

Lower total inorganic carbon

Lower alkalinity

Photosynthesis

Higher inorganic carbon

Higher alkalinity (more

Respiration

Cannot predict pH of water based on in atmosphere, because of presence of carbonate minerals

Derived by weathering of carbonates in the presence of

Amount of

Carbonic on the inorganic carbon system○

Normal range of pH @ 6-9

Lethal effects @ pH < 5 and >9.5

Low alkalinity = high pH flocculants

Buffering capacity is of major importance

Water is acidic @ ◊

Water is basic @ ◊

There is still one hydrogen ion & one hydroxyl group

As you heat water up the pH will drop but it is not more acidic

If you boil deionized distilled water and then cool it down to 20C with a cover on it the pH will be 7.0. When the cover is removed, exposing it to atmospheric the pH will drop in response

pH of Neutrality

It dissociates in more than one step

Carbonic acid is a polyprotic acid

It is stable at a pH of over 11

OH can provide alkalinity but is not very stable in natural water (pH 5.5-9)

Provide alkalinity to water

P 1.

Determine the pH of a water in equilibrium with the atmosphere having a

content of 400ppm and sealevel:

The inorganic carbon system is of fundamental importance to lakes because it regulates lake pH and alkalinity

○

Carbonic Acid Equilibrium System-

Inorganic CarbonNovember 23, 2015 11:38 PM

Limnology

a)

P 1.

2.

a)

b)

pH = 5.66i) c)

3.

pH of ocean surface water in 1750 was 8.179

pH of ocean surface water in 2000 was 8.069

29% increase in H ion

Would wipe out many calcareous shelled organisms

By 2100 the pH is projected to be 7.8

Ocean (lake) acidification

Epilimnion water at or close to saturation with

Coupled with reduction in from photosynthesis

It sinks◊

This can be a major sink for inorganic carbon, organic carbon and nutrients (eg. P)

Affects lake metabolism and biological productivity

Adsorbs organic and inorganic matter:◊

Precipitated marl is colloidal and dense

Greater respiration rates at depth

Higher pressures

Cooler temperatures

Marl will dissolve corresponding to increased dissolved as a result of:

◊

Referred to as the 'carbonate compensation depth'◊

Loss to the sediments may not occur in stratified, productive lakes

A pocket of magma lies beneath the lake and leaks carbon dioxide (CO2) into the water, changing it into carbonic acid. Nyos is one of only three known exploding lakes to be saturated with carbon dioxide in this way, the others being Lake Monoun, also in Cameroon, and Lake Kivu in Democratic Republic of Congo. On August 21, 1986, possibly as the result of a landslide, Lake Nyos suddenly emitted a large cloud of CO2, which suffocated 1,700 people and 3,500 livestock in nearby towns and villages.

◊

Lake Nyos, Cameroon

Result: precipitation of marl ( )

Scenario:

Productive, calcareous, hardwater lakes illustrate the interaction of the controls on the inorganic carbon system

○

Limnology

Solution:

Limnology

Requirement for protein synthesis ○

Its distribution and form affects lake productivity ○

Nitrogen is a major nutrient affecting lake function-

The balance between input and losses○

Changes in form by biochemical processes○

The nitrogen cycle involves:-

Common valence states are +3, -3, & +5○

This allows nitrogen to occur in different combinations with other elements○

Nitrogen has many forms because of its susceptibility to redox process-

12.5mg/L @ 25C□Not very soluble

Lower concentrations in the epilimnion

Higher pressure□Cooler temperature□

Denitrification: □

Higher concentrations in an anaerobic hypolimnion

Molecular N2 (gas)○

N2 gas is converted to solid forms□

Genus Anaebaena (photosynthetic, filamentous blue green algae)

Limited to certain bacteria genera:□

G Clostridium (roots of legumes) □G Rhizobium (roots of alder)□

Nitrification

Organically bound nitrogen (in dissolved and particulate form)○

Generated by heterotrophic organisms (bacteria) as an end product of organic matter decay

NH4+ is the most readily utilizable form of N as a nutrient

Converted to organic N

Productivity levels□

NH4+ is released

Organic matter decay and pollution□

Nitrification vs. denitrification

Redox conditions□

The distribution of NH4+ is a function of:

Uptake by plants□

Nitrification: NH4+

□

NH4+ concentration is lower in aerobic, productive epilimnions

Denitrification:

□

Decay of organic matter□

Upon loss of the oxidized microzone

Loss of adsorbed NH4+ from sediments□

NH4+ concentration is higher in the hypolimnion of eutrophic lakes

Eutrophication□

Fish toxicity by its conversion to at higher pH□

NH4+ is a concern in wastewater treatment:

Ammonium (NH4+)○

Adsorbed NH4+○

Ammonia (NH3) (gas)

Common forms of nitrogen-

The Nitrogen CycleNovember 26, 2015 8:59 PM

Limnology

Ammonia (NH3) (gas)○

Nitrate (NO3-)○

Nitrite (NO2-)○

Nitric acid (HNO3)○

Ammonium hydroxide (NH4(OH))○

Hydroxyamine NH2OH○

Conversion of nitrogen from a reduced form to more of an oxidized form○

Performed by bacteria under aerobic conditions as an energy source○

Genus Nitrosomonas□Oxidation of ammonium to nitrite

Occurs readily such that rarely accumulates

Genus Nitrobacter□Oxidation of nitrite to nitrate

Nitrification occurs in two steps:○

Surface water flow, groundwater flow, acid precipitation

is the most common form of inorganic N entering lake basins from watersheds○

can be taken up by plants, reduced to

and assimilated into organic N

compounds○

25:1 in unpolluted lakes

1:1 with low, natural sources of

1:10 with slight to moderate sewage contamination

Ratios used to detect pollution (mg/L)○

Nitrification-

An anaerobic process in which bacteria reduce N anions (

by using them to

oxidize organic matter for energy○

Performed by many genera of facultative anaerobic bacteria○

Examples include E Coli & Salmonella

Facultative anaerobic bacteria us O2 for respiration. But, when it comes to becoming deficient, they have other options by using oxidizing agents.

○

Denitrification-

>50% of total dissolved N is DON○

Decreases as lakes become increasingly eutrophic

DON : PON @ 5:1 to 10:1○

Dissolved and Particulate organic Nitrogen-

Adsorbed

Live & dead plankton = higher particulate organic matter□That bound in humic and other organic compounds

Occurs as:○

Tied up and unavailable to organisms○

Adsorbed NH4+ - adsorbed on colloidal matter

Sediments are a sink for nitrogen and other nutrients such as C, S, and P○

Nitrogen in Sediments-

Fertilizer

Manure

Agriculture○

Sewage and industrial waste○

Acid precipitation ( )

Adsorbed

Atmospheric pollution○

Affects of Human Activity on Nitrogen Loading-

Limnology

Adsorbed

Limnology

In cells where the energy is needed, the ATP is hydrolyzed to ADP (adenosine diphosphate) with release of energy

Respiration releases energy that is incorporated into ATP molecules (high energy triple bonds)

□Involved in energy transfer as ATP

Important metabolic role○

Least abundant○

Phosphorous has major significance as a nutrient-

Typically the first nutrient to limit productivity-

Not susceptible to redox processes○

Only common valence is +5○

While there are many significant forms of nitrogen, less so for phosphorus-

Apatite group of minerals

Geology○

The majority comes from the bound up organic phosphorus

Terrestrial productivity and subsequent transport of organic matter to lakes○

Fertilizers - residential uses of fertilizers□Land use

Ammonium & phosphorus □Wastewater disposal

Reduction of the amount in base levels of phosphates

Phosphate based detergents□Detergents

Human influence○

Can stimulate algal blooms and lead to oxygen depletion in surface water bodies ○

Inputs of phosphorus-

Limiting factor - anything that when added, enables growth.○

Only readily utilizable form of P as a nutrient

Represents less than 5% of total P

Released upon decay of organic matter

In such high demand that it can be recycled in minutes

Above the ZPC can be adsorbed onto particles□Zero point of Charge:

Forms insoluble precipitates with □Factors limiting

availability

(reactive phosphorous = orthophosphate = soluble phosphate phosphorous)○

Forms of Phosphorous-

PhosphorusNovember 26, 2015 9:43 PM

Limnology

Acid hydrolysable phosphorous

Forms insoluble precipitates with □

Organic and inorganic colloids

Adsorption onto particulates□

Ligand exchange

Forms complexes with organics and inorganics□

Represents more than 90% of total P

Live/dead material□Dissolved/particulate organics□Adsorbed organic P (humic compounds)□

Includes:

Organically bound phosphorous○

Reactive phosphorus (

Precipitates of with □

Acid hydrolyzable phosphorus = acid soluble phosphorus

Soluble organic P

Particulate organic P

□

Humic compounds□

Adsorbed P

Complexed P

Summary of Phosphorous Forms○

Used to determine lake trophic status

<5 ug/L (oligotrophic) to >100 ug/L (highly eutrophic)□10-50 ug/L or unpolluted lakes□

Range of total P

Most important measure of phosphorus is the total phosphorus content of the unfiltered water of the epilimnion

○

Acid hydrolysable□That precipitated with

On colloidal material that rains down to the bottom of the lake□Adsorbed

Adsorbed humic compounds

Rain down to bottom of the lake□

Plankton

Or, brought into the water body

From either: □

Particulate organic P

Sediments can be a major sink for P○

O2 supply (redox potential) in the hypolimnion

Affects redox conditions□Decay and release of P□

Microbial activity

Turbulence□

Worms

Larvae

Benthic organisms□

Mixing

Phosphorus can be exchanged across the sediment-water interference as a function of:○

When the oxidized microzone is lost and can be released into an

anaerobic hypolimnion

Much of the precipitates during fall turnover and returns to the

bottom of the lake

An oxidized microzone at the sediment-water interface prevents upward diffusion of

,

○

Limnology

bottom of the lake

Limnology

They are, thereby, affected by respiration and photosynthesiso

The cycling of micronutrients is largely controlled by redox conditions and processes along with pH

It remains high (>300 mV) even at low levels @ ~1 mg/ Lo

For O2 – saturated water the ORP is > 500mV

It drops to zero and well below within a few mm of the sediment – water interfaceo

As O2 levels approach zero, the ORP drops quickly

Both are needed for photosynthesis

Idea to combat climate change is to seed the ocean with iron to increase the amount of plankton (decreasing the amount of CO2)

Fe and Mn are essential micronutrientso

Mn forms more soluble compounds

Fe and Mn behave similarly chemicallyo

Most is present as ferric iron (Fe+++) precipitated as Fe(OH)3

Ferrous iron (Fe++) is low in aerated watero

Chelated to form a ring structure

A lot of iron is taken out of solution through chelation

Chelation

That complexed with humic compounds

Acid hydrolysable

That bound with PO43-

Also:o

In lake sediments intensely reducing conditions and low pH cause dissolution of Fe and Mn compounds

o

When the oxidized microzone at the sediment – water interface is lost Fe++ and Mn++

diffuse from the sediments and accumulate in the anaerobic hypolimniono

Fall turnover brings on oxidizing conditions

Brings them back into solution

Water treatment plants can have issues with Fe & Mn during fall turnover

Can also cause Algal bloom

These precipitate out at Fall turnovero

Iron and Manganese

Sulfur

MicronutrientsTuesday, December 01, 2015 7:31 PM

Limnology

Stable over a wide range of Eh & pH conditionso

Gypsum, and anhydrite (SO4=), burning of coal and oil, organically bound S

Sulfur is in abundant supplyo

Sulfur is susceptible to redox processes such that it can assume different valence states (+/- 2, +4, +6)

o

The stable form of S under oxidizing conditions is SO4=o

Under intense reducing conditions (lake sediments) the stable form of sulfur is S=o

SO4= → S=

(Sulfur reducing bacteria work at increasingly reducing conditions:

2H+ + S= → H2S )

Sulfate (SO4=) reducing bacteria

Decay of organic matter

S= is derived from:o

Fe++ + S= → FeS (pyrrhotite)(black precipitate)

Deposited in intensely reducing conditions

Acid rock drainage (when bacteria oxidize it)

Dissolves readily in oxidizing conditions

(sulfur atoms in pyrite occur in pairs with S = S bonds)

Fe++ + 2 S-- → FeS2 (pyrite)

Iron has a close relationship with sulfur under these circumstanceso

Sulfur

Not used readily

Generally not limiting o

Burning of coal & oil is redistributing these micronutrientso

Other micronutrients (metals) that respond to redox conditions include Zn, Cu, Co, Mo, V, Se, Cr

Cycled at the sediment – water interface similar to Fe and Mno

Their concentrations have increased from pollution

Large requirement by diatom algaeo

Silicic acid (H4SiO4)

Particulate silica

In relative abundance as:o

Essential nutriento

Diatom algae use it in their shellso

Silica, regardless of the form it takes, is expressed as mg/L o

Silica

Limnology

Angle of Incidence - Angle changes at higher latitudes and at dawn/dusk in which case the light must pass through a greater distance of Earth's atmosphere (Page 23)

-

Autochthonous - Indigenous to the place it was formed (Page 22)-

Allochthonous - Transported into the area it was found (Page 22)-

Available Water - Measured in terms of the rate of water renewal (Page 1)-

Characteristics of Water - (Page 4-6)-

Continental Water - Evaporated/transpired, absorbed by soil, stored in the groundwater zone, moved by gravity to lakes and streams (Page 19)

-

Depth Time Diagram - (Page 30-31)-

Definition: The mixing of two fluid layers of different density perpendicular to the flow direction (Page 34)

○

Eddy Diffusion - As two fluid layers of different density move relative to one another, a frictional shear stress occurs at the interface (Page 34)

-

Flux - Amount of something transmitted per area per time (Page 22)○

Electromagnetic Spectrum - Solar radiation occurs as pulses or packets of electromagnetic energy called photons (Page 22)

-

Epilimnion - Upper zone of uniformly warm, less dense, turbulent (mixing) water (Page 30)-

Distribution of Accumulated Heat - is controlled by high heat capacity, physical work of the wind, currents, basin morphology, and water losses from the lake (Page 27-28)

○

Heat Income to Lakes - Direct absorption of radiant energy, conduction of heat from the atmosphere, condensation of water vapour at the lake surface, transfer of heat from sediments, and inflow from groundwater, surface water, and direct precipitation (Page 28)

Heat Losses from Lakes - Conduction of heat to the atmosphere, evaporation at the lake surface, & outflow from drainage lakes (Page 28)

Thermal Density Stratification & Turnover (Page 29)

Lakes Stratify into Three Zones - Epilimnion, Metalimnion, and Hypolimnion (Page 29-30)

Dimictic (21) - two mixing cycles□Warm Monomictic (31) - Occur in warm temperate regions, circulate freely in the winter

□

Cold Monomictic (31) - Sub-arctic latitude, one mixing cycle in the summer□Amictic (31) - Permanently frozen□Ogliomictic (31) - Permanently stratified □Polymictic (32) - Located in high altitude, tropic regions. Mix often.□

Lake Classification as per annual stratification and mixing cycles

Lake Heat Budgets - (Page 28)○

Fate of Heat - About 50% of the radiant energy impinging on lakes is in the red-infrared region of the electromagnetic spectrum (Page 27)

-

First Flush - Storm water is directed to surface water (Page 2)-

Flux: Amount of something transmitted per area per time (Page 22)-

Frequency - Number of wavelengths per distance (Page 22)-

East African rift, Lake Athabasca, Lake Baikal, Caspian Sea, Aral Sea, Owen's Lake (7-8)○

Great Lakes - ~4% of the Earth's total volume of fresh water is contained in the world's great lakes (Page 7)

-

Human Influences on the Hydrologic Cycle - Irrigation, industrial & domestic use, deforestation, changes in drainage patterns, reservoir development, exploitation of groundwater, climate change (Page 19-20)

-

Hypolimnion - Low zone of ~uniformly cool, more dense, quiet (non-mixing) water (Page 30)-

Lake Metabolism - All of the chemical reactions in a lake basin (Page 4)-

Tectonic Lake Basins - Rifting (Page 9)Lake Classification - Classified by origin (Page 7-17)-

Limnology GlossaryNovember 4, 2015 7:13 PM

Limnology

Tectonic Lake Basins - Rifting (Page 9)○

Volcanic Lakes - Maar Lakes, Caldera Lakes, Lava Flow Lakes (9-10)○

Landslide Lakes - (10)○

Glacial Lakes - Moraine Lakes (11), Kettle Lakes (11), Cirque Lakes (12), Cryogenic Lakes (12), Scouring of weak fractured zones (13), Solution Lakes (13-14)

○

River Action Lakes - Oxbow Lakes (14), Plunge Pool Lakes (14), Levee Lakes (15), Delta Lakes (15)

○

Wind Action Lakes - Dune Lakes (15), Playa Lakes (15)○

Coastal Lakes - (16)○

Biogenic Lakes - Bog Lakes (16), Beaver Dams (17)○

Reservoirs - (17)○

Lake Morphology - Lake morphology and the geomorphic setting of lakes has a large influence on lake function and is strongly related to lake origin (Page 17)

-

Laminar Flow - An orderly flow pattern that occurs below a certain flow velocity (Page 34)-

Langmuir Circulations - Large currents of turbulent mixing in the lake surface water (Page 35)-

Light Energy in Lakes - Transformed by photosynthesis & absorbed in the water column-

Limnology - The study of inland surface water including the structure, function, and interrelationship of physical, chemical, and biological components (Page 1)

-

Metalimnion - Transitional zone between the epilimnion and the hypolimnion (Page 30)-

Transformation of Radiant Energy to Heat - (Page 23)○

The Greenhouse Effect - (Page 23)○

Light Impinging on Lakes - (Page 23)○

Fate of Heat Impinging on Lakes - Reflected at the surface, scattered in the water column, absorbed in the water column (Page 24)

○

Light Attenuation in Lakes - (Page 24-25)○

Radiant Energy in the Water Column - In lakes this effects development of thermal-density stratification, lake hydraulics, all chemical cycles and lake metabolism, population dynamics (Page 22)

-

Relative Thermal Resistance (RTR) - Expressed as the ratio of the density difference between water at the top and bottom of each 0.5m column to the difference of water at 4-5C (Page 29)

-

Reservoirs of the Hydrologic Cycle - Oceans, atmosphere, ice caps and glaciers, continents (lakes & rivers, groundwater) (Page 19)

-

○

Reynolds Number - Turbulence is predicted for a Reynolds number greater than 2100 (Page 34)

-

Photosynthesis - Biochemical conversion of radiant energy to potential chemical energy (Page 22)

-

Secchi Disk - Measures water clarity and transparency (Page 25)-

Internal Seiche - Occur in stratified lakes when the mixing barrier is caused to oscillate. Causes shear/eddy diffusion at the interface with major dispersive effects vertically and horizontally (Page 36)

○

Surface Seiche - The lake surface oscillates when the wind stops whether the lake is stratified or not. The amplitude of surface seiches are much smaller than internal seiches (Page 36)

○

Seiche - A persistent (wind drift) causes tilting of the lake water surface and (more so) of the mixing barrier (Page 36)

-

Surface Tension - Surface tension will decrease with temperature, salinity, and dissolved organics (Page 6)

-

Thermocline - The plane of maximum change in temperature with depth (Page 30)-

Travelling Surface Waves - Frictional effects of the wind sets surface water into an oscillating motion. Water is displaced upwards and returns downward by gravity. Cycloid paths are established that diminish quickly with depth (Page 34)

-

Turbulent Flow - As velocity increases, higher friction shear results in chaotic/turbulent flow (Page 34)

-

Water Budgets in Lakes - (Page 20)-

Water Economy - Relates to the water balance of lakes and it is tied to the global hydrologic cycle (Page 19-21)

-

Limnology

cycle (Page 19-21)

Various water movements effect - (33)○

Lake Hydraulics - Laminar vs Turbulent Flow (34)○

Eddy Diffusion - (34)○

Waves - (34-35) - Ripples, surface waves, breakers, plunging breakers, spilling breakers○

Currents - (35-37) - Wind drift, Langmuir circulations○

Internal Water Currents - (36) - Considerable wind drift can cause water of the epilimnion to pile up on the downwind end of the lake

○

Internal Seiche

Surface Seiche

Seiches - (36) - A persistent wind causes tilting of the lake water surface and of the mixing barrier

○

Thermal Bars - (36) - A wall of water at maximum density that prohibits mixing between in-and offshore zones until the whole lake is stratified (springtime)

○

Currents Generated by River Influents - (36) - Inflow tends to enter strata having a density similar to its own

○

Convection Currents Under Ice - (37) - Occur in shallow lakes that do not stratify○

Water Movements in Lakes - Have a large influence on lake function because of their dispersive effects (Page 33-37)

-

Viscosity of Water - Viscosity will double between 20 & 4C (Page 5)-

Limnology

Secchi Disk Depth

Total Phosphorus

Epilimnion:

Hypolimnion:

Chlorophyll a

Trophic Status IndexSaturday, December 05, 2015 3:12 PM

Limnology

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