Limnology(lentic = lakes and ponds; lotic = streams and rivers)

Properties of Lakes

• Origins

• Water Balance

• Light

• Heat and Stratification

• Oxygen

• Nutrients: Nitrogen and Phosphorous

Lake Zones

Generalizations of Lake Physical

Properties

Lakes evolve by succession

The more shoreline – the more mature the

lake

Lakes change from deep to shallow

Lakes become more biologically productive

with succession

The Maturing of a Lake

Chemical Factors of Trophic

Lakes

Origins of lakes

1. Tectonic

2. Volcanic

3. Landslides

4. Glacial action

5. Solution of rock

6. River activity

7. Shoreline activity

8. Biological (beavers)

9. Human

Spirit Lake

Bonneville ReservoirGlacier Bay

The distribution of reservoirs

Distribution of reservoirs over 500 acres in the United States, by surface

area, January 1970. One dot equals 10,000 acres. Total area, 90 million

acres (Jenkins, R.M. 1970. AFS Spec. Publ. No. 7).

Limnology: water balance

Water inputs:

Precipitation, surface runoff from basin, groundwater, diversion

Water losses:

Drainage, seepage, evaporation and evapo-transpiration (plants), diversion

Mono Lake, CA

Soap Lake, WA

Global water supply

Water body Volume (km3 * 1000)

% of total Renewal time (years)

Oceans 1,370,000 97.61% 37,000

Polar ice,

glaciers

29,000 02.08% 16,000

Groundwater 4,000 00.29% 300

Freshwater

lakes

125 00.009% 1-100

Saline lakes 104 00.008% 10-1,000

Atmospheric

water vapor

14 00.0009% 9 days

Rivers 1.2 00.00009% 12-20 days

Adapted from Wetzel 1975

Limnology: light

http://www.ucar.edu/learn/images/spectrum.gif

Limnology: light

Absorbance of different colors

of light on a log scale in a clear

unproductive lake.

Note the rapid loss in the

quantity, and change in the

quality of light. Pattern vary

among lakes, depending on the

nature of material in the water

such as glacial flour, tannin,

phytoplankton, etc.

Clear, relatively unproductive lake

Limnology 1994

Depth

(m

)

Percent surface light0.1 1.0 10 100

15

10

5

0 0

5

10

Limnology: light

0.1 1.0 10 100

Absorbance of different colors

of light on a log scale by a clear

unproductive lake and a highly

productive, shallow reservoir.

Clear, relatively unproductive lakeShallow, productive reservoir

Limnology 1994

Depth

(m

)

Percent surface light0.1 1.0 10 100

15

10

5

0 0

5

10

Heating and cooling

Sources of heat:

1. Direct solar radiation (most important)

2. Groundwater and springs

3. Ground (minor)

Losses of heat:

1. Thermal radiation (primary)

2. Conduction

3. Evaporation

4. Outflow

Heat and the density of water

Temperature (C)

Density g

/cm

3

The maximum density

of water is at 3.94 C.

Ice at 0 C is 8.5%

lighter than liquid

water at 0 , so it floats.

Above 3.94 water

gets lighter as it

warms up, so the

surface water is also

warmer than deep

water in summer.

x

Distribution of heat

Hypolimnion

Metalimnion

Epilimnion

Temperature (C)

Depth

(m

)

Horizontal distribution is

primarily driven by wind

Vertical stratification is

seasonal, driven by the

relationship between

density and temperature

Mixing and Satratification

Limnology: heatD

epth

(m

)

Time (month)

Ice Ice

Dimictic Lake (turns over twice a year)

Limnology: heat

Time (month)

Depth

(m

)Monomictic lake (turns over once each year)

Limnology: heatThe distribution of heat within a

lake depends on water movement

1. Surface waves

2. Langmuir circulation waves

3. River Influents

Clear Lake, California

Dissolved Oxygen

Dissolved Oxygen

•Air contains 300 mg O2/L; the

rest is mostly nitrogen

•Water contains 14.6 mg O2/L

•Gasses diffuse slowly in water,

so distribution is governed by

circulation, not diffusion

Eutrophic Lakes: hypolimnion

depleted by decomposition

(biotic processes)

Oligotrophic Lakes:

Distribution governed by

physical processes

In warm water, the metabolic

demands of fishes tend to increase,

and the capacity of the water to hold

oxygen decreases.

Dissolved Oxygen

Winter Kill:

Occurs when a shallow lake is ice-covered and hence dark for a long period. The DO demand of plants can drive levels below the 2 mg/l required by most fish.

Summer Kill:

Occurs when dense concentrations of macrophytes die at the end of their growing season. Decomposition can drive DO levels down. If the lake is shallow and macrophytes are found over the whole surface, a “squeeze” between warm surface temperatures and low DO levels on the bottom in late summer can kill fish.

Depth (cm)

Oxyg

en

(m

g/l)

0 50 100 150 200 250 300 350

05

1

0

1

5

2

0

Relationship between dissolved

oxygen level and depth below the ice

in Black Lake, Alaska.

G. Ruggerone

8 mg/l is needed to

maintain healthy salmon

050

100

150

Oxygen (

% o

f satu

ration)

Pe

rce

nt

su

rviv

al

Oxygen (% saturation)

0 25 50 75 100

0 2

0

4

0 6

0

8

0 1

00

Survival of juvenile sockeye salmon in Black Lake

at different dissolved oxygen concentrations (Ruggerone 1999)

Development of temperature – dissolved oxygen “squeeze”

from summer-kill conditions in Lake Sammamish

Data: Hans Berge, Metro – King County

Limnology:

Nitrogen and Phosphorous

Nitrogen and Phosphorous are

essential elements for living

organisms, and one, the other,

or both in concert may limit

primary and secondary

production. In lakes, nitrogen

comes primarily from microbial

action or terrestrial runoff and

phosphorous primarily from local

geology. However, both can be

greatly affected by human

inputs.

Limnology:

Nitrogen and Phosphorous

Simplified Nitrogen cycle

Primary and secondary production may be

limited by Nitrogen or Phosphorus

Total phosphorous

Fis

h b

iom

ass (

kg/h

a)

Fis

h b

iom

ass (

kg/h

a)

Macro-benthos biomass

Natural and human sources for Nitrogen and

Phosphorous