Physics, Chemistry, and Biology in Ponds and Lakes

Ponds and Lakes Dominated by Heterotrophic Processes

• Example. A well‐mixed lake with V = 5x108 L is fed by a stream flowing at Q=2.4x107 L/d that contains 8 mg/L DO and has L = 10 mg/L. Waste from a small municipality (L = 95 mg/L, DO = 0 mg/L) enters the lake at 4.8 x 106 L/d. kd, kr, and DO* in the lake are 0.10 d−1, 0.05 d−1, and 11.2 mg/L, respectively. Assuming that the lake is at steady‐state:

a) Determine L and DO in the lake.b) Compute the rates (kg/d) at which advection, 

reaeration, and biological reaction, each acting alone, increase or decrease DO and L in the lake.

• Q1 = 2.4 x 107 L/d Q3 = Q1 + Q2 = 2.88 x 107 L/d• DO1 = 8 mg/L DO3 = ?• L1 = 10 mg/L L3 = ?• Q2 = 4.8 x 106 L/d• DO2 = 0 mg/L• L2 = 95 mg/L• kr = 0.05 d−1• kd = 0.10 d−1• DO* = 11.2 mg/L

V, kd Lin lake

DOin lake, kr Q3, L3, DO3

Q1 (stream),L1, DO1

Q2 (waste), L2, DO2

V, kd Lin lake

DOin lake, kr Q3, L3, DO3

Q1 (stream),L1, DO1

Q2 (waste), L2, DO2

MB on L: 1 1 2 2 3 3 in lake0 dQ L Q L Q L k VL= + − −

( )( )

7 6

7 1 83 3

L mg L mg0 2.4 10 10 4.8 10 95d L d L

L 2.88 10 0.10 d 5 10 Ld

L L−

⎛ ⎞⎛ ⎞ ⎛ ⎞⎛ ⎞= +⎜ ⎟⎜ ⎟ ⎜ ⎟⎜ ⎟⎝ ⎠⎝ ⎠ ⎝ ⎠⎝ ⎠

⎛ ⎞− −⎜ ⎟⎝ ⎠

x x

x x

L3 = Lin lake = 8.83 mg/L

V, kd Lin lake

DOin lake, kr Q3, L3, DO3

Q1 (stream),L1, DO1

Q2 (waste), L2, DO2

MB on DO:

DO3 = DOin lake = 0.57 mg/L

( ) ( ) ( ) ( ) ( ) ( )in lake 1 1 2 2 3 3 in lake in lakeDO DO DO DO DO* DOd rd V Q Q Q k L V k Vdt

= + − − + −⎡ ⎤⎣ ⎦

( ) ( ) ( ) ( ) ( )1 1 2 2 3 3 3 30 DO DO DO DO* DOd rQ Q Q k L V k V= + − − + −

( )

( ) ( ) ( ) ( )

7 6 73

1 8 1 83

L mg L mg L0 2.4 10 8 4.8 10 0 2.88 10 DOd L d L d

mg mg 0.1 d 8.83 5 10 L 0.05 d 11.2 DO 5 10 LL L

− −

⎛ ⎞⎛ ⎞ ⎛ ⎞⎛ ⎞ ⎛ ⎞= + −⎜ ⎟⎜ ⎟ ⎜ ⎟⎜ ⎟ ⎜ ⎟⎝ ⎠⎝ ⎠ ⎝ ⎠⎝ ⎠ ⎝ ⎠

⎛ ⎞ ⎛ ⎞− + −⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠

x x x

x x

V, kd Lin lake

DOin lake, kr Q3, L3, DO3

Q1 (stream),L1, DO1

Q2 (waste), L2, DO2

Advective outflow of biochemical oxygen demand:(2.88 x 107 L/d)(8.83 mg/L) (10‐6 kg/mg) = 254 kg/d

Rate of L utilization (i.e., the rate of DO utilization by biochemical reactions):

−rLV = kd (Lin lake) V= (0.10 d−1) (8.83 mg/L) (5 x 108 L)= 4.42 x 108 mg/d = 442 kg/d

254Outlet

456Waste

240Stream

442Bioactivity

Lake

(a)

0Waste

16Outlet

442Bioactivity

Lake

192Stream

266Reaeration

(b)

Mass Balance Terms for L (kg/d)

Mass Balance Terms for DO (kg/d)

Cladocerans

Copepods

Cyclopoid

Calanoid

nauplii

Limiting Nutrients for Algal Growth and Lake Productivity:Nitrogen, Phosphorus & Carbon

Nutrient Source Cycling

Nitrogen [Atmosphere], BiologicalGeologic

Phosphorus Geologic Physical, Chemical

Carbon Atmosphere Chemical, Biological

Redfield RatioC: N : P P limited N limited106 : 16: 1 N:P >20 N:P < 10

Carbon: rarely limiting due to ready availability from the atmosphere

Nitrogen: can be limiting especially at very high phosphorus loading rates

Phosphorus: most common limiting nutrient and best predictor of algal biomass

Colimitation: very common for both nitrogen and phosphorus in combination to be limiting in short term (3-5 day) bioassays

Phosphorus vs. Phytoplankton Biomass

0.1

1

10

100

1000C

hlor

ophy

ll (µg

L-1

)

1 10 100 1000Total Phosphorus (µg L-1)

y = 0.08x1.5

r2 = 0.91

Jones and Bachmann (1976)

Common Threats to Lake and Stream Water Quality

• Point Sources: sewage and industrial effluent

• Non-Point Sources: fertilizers, animal wastes,erosion, failing septic systems, Canada geese

• Point sources have for the most part been controlled

• A key area for future research in limnology and lake management is the development of methods for quantifying and controlling non-point source nutrients

CAFOs = Factory Farms

0.997

0.998

0.999

1.000D

ensi

ty (g

ram

s/cm

3 )

0 5 10 15 20 25

Temperature (C°)

Max. Density @ 4 C°

The Impact of Temperature on Water Density

0 5 10 15 20 25

Temperature (C°)

0

5

10

15

20

25

Dep

th (m

)

Summer Stratification

Epilimnion

Hypolimnion

Metalimnion

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

0

10

20

30

40

50

60

Time of Year

Depth (m)

8 10 12 14 16 18 20Temperature (°C)

Temperate Lakes

Deep = usually Dimictic

Shallow = often Polymictic

0 5 10 15 20 25Temperature (C°)

0

5

10

15

20

25

Dep

th (m

)

Summer Stratification

0 5 10 15 20 25Temperature (C°)

0

5

10

15

20

25

Dep

th (m

)

Fall Mixing

0 5 10 15 20 25Temperature (C°)

0

5

10

15

20

25

Dep

th (m

)

Spring Mixing

0 5 10 15 20 25Temperature (C°)

0

5

10

15

20

25

Dep

th (m

)

Winter Inverse Stratification

Thermal Stratification in a Dimictic Lake

0

5

10

15

20

25

Dep

th (m

)Temperature

0

5

10

15

20

25

Dep

th (m

)

Light

0

5

10

15

20

25

Dep

th (m

)

Dissolved Oxygen0

5

10

15

20

25

Dep

th (m

)

Nutrients

A Eutrophic Dimictic Lake During the Summer

Eutrophication and Nuisance algal blooms

0

2

4

6

8

Secc

hi d

epth

(m)

0 10 20 30 40

Chlorophyll a (µg L−1)

Chlorophyll vs. Water Clarity

0.00 0.20 0.40 0.60 0.80 1.00

0

10

20

30

40

50

60

Time of Year

Depth (m)

2 4 6 8 10Chlorophyll concentration (µg/L)

0

1

2

3

4

5

6

7

Vol

. Wt.

Chlo

roph

yll C

onc.

(µg/

L)

6

7

8

9

10

11

12

13

Vol

. Wt.

Tem

pera

ure

(°C)

0 0.2 0.4 0.6 0.8 1

Time of Year

Lake Washington ChlorophyllTemperature

Aquatic foodweb

phytoplankton

zooplankton

planktivores

top consumers

Clear Lake PeruvianUpwelling

Fish

Zooplankton

Phytoplankton

“The phytoplankton-zooplankton interrelationship appears to be particularly dependent on the species composition of the biota; hence, if the phytoplankton is composed primarily of species edible [and of nutritional value] for zooplankton, one may find a relatively low phytoplankton standing crop”

R.A. Vollenweider (1976)

Mem. Ist. Ital. Idrobiol. 33: 53-83.

Hypereutrophy and N limitation

• Anoxic hypolimnion (bottom layer)

• Denitrification (NO3 converted to N2)

• Reduced conditions in sediments (Fe3+ Fe2+)

• Supply of NO3 and PO43-

Cyanobacteria

• Competitive Advantages– Can fix atmospheric nitrogen– Buoyancy regulation– Luxury P uptake (polyphosphate crystals)– Poor food quality and edibility to zooplankton

• Competitive Disadvantages– Slow growers relative to other phytoplankton

"On May 2, 1878, George Francis of Adelaide, Australia, published the first scholarly description of the potentially lethal effects produced by cyanobacteria . . . in a letter to Nature . . . Symptoms--stupor and unconsciousness, falling and remaining quiet, as if asleep, unless touched, when convulsions come on, with head and neck drawn back by rigid spasm, which subsides before death. Time--sheep, from one to six or eight hours; horses, eight to twenty-four hours; dogs, four to five hours; pigs, three or four hours."

From the website for CellTech, the company harvesting and selling Super Blue Green® Algae.

1. Super Blue Green® Algae is over 60% high quality (complete) protein

2. and is the richest source of chlorophyll known to man.

3. It is a (vegetable) source of vitamin B-12, and in fact contains more B-12 than any other vegetable!

4. Super Blue Green® Algae is 100% vegetarian, 100% natural and 100% wild-grown.

5. It is enzyme active for super absorption by your body and, it contains over 60 minerals and trace minerals.

6. Are there any medically proven health benefits? Super Blue Green® is a food, not a drug or medicine. Therefore, we cannot promote it as having proven health consequences.

Lake Washington Story• Mean depth 32 m• Max depth 61 m• HRT = 2.4 yr-1

Case Study: Lake Washington

From: W.T. Edmondson (1994) Lake & Reservoir Management 10: 75-84.

0

25

50

75

100

125

Dis

solv

ed P

Inpu

ts (m

etri

c to

ns y

r.-1)

1965 1970 1975 1980 1985 1990

Year

Watershed Loading

Sewage Effluent

From: W.T. Edmondson (1994) Lake & Reservoir Management 10: 75-84.

Change in Lake Washington phytoplankton composition and biomass

0

1

2

3

Phyt

o. B

iovi

ol. (

mm

3L

-1)

1965 1970 1975 1980 1985 1990

Year

Other Phytoplankton

Cyanobacteria

0

25

50

75

100

125Pe

rcen

t of 1

964

Valu

e

1965 1970 1975

Year

Phytoplankton

Phosphate

Nitrate

Inorganic Carbon

From: W.T. Edmondson (1991) The Uses of Ecology.

Change in Lake Washington nutrient concentrations, and phytoplankton biomass after waste water diversion

05

101520 D

aphn

ia L

-1

0

2

4

6

8

10

Secc

hi (m

)

1965 1970 1975 1980 1985 1990

Year

Secchi Depth

Daphnia

Trophic Equilibrium

05

101520 D

aphn

ia L

-1

0

2

4

6

8

10

Secc

hi (m

)

1965 1970 1975 1980 1985 1990

Year

Secchi Depth

Daphnia

Trophic Equilibrium

05

101520 D

aphn

ia L

-1

0

2

4

6

8

10

Secc

hi (m

)

1965 1970 1975 1980 1985 1990

Year

Secchi Depth

Daphnia

Trophic Equilibrium

0

2

4

6

8

10

Biom

ass (

µg C

hla/

l)

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Time of Year

Lake Washington seasonal phytoplankton succession

Others

Cyanos

Greens

Cryptos

Diatoms