Ponds and Lakes Dominated by Heterotrophic...
Transcript of Ponds and Lakes Dominated by Heterotrophic...
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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
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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)
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Cladocerans
Copepods
Cyclopoid
Calanoid
nauplii
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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
1000
Chl
orop
hyll
(µg
L-1
)
1 10 100 1000Total Phosphorus (µg L-1)
y = 0.08x1.5
r2 = 0.91
Jones and Bachmann (1976)
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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
1.000
Den
sity
(gra
ms/
cm3 )
0 5 10 15 20 25
Temperature (C°)
Max. Density @ 4 C°
The Impact of Temperature on Water Density
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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
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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
)
Temperature0
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
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0
2
4
6
8
Secc
hi d
epth
(m)
0 10 20 30 40
Chlorophyll a (µg L−1)
Chlorophyll vs. Water Clarity
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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.
Chl
orop
hyll
Conc
. (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
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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-
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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."
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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
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Case Study: Lake Washington
From: W.T. Edmondson (1994) Lake & Reservoir Management 10: 75-84.
0
25
50
75
100
125D
isso
lved
P In
puts
(met
ric
tons
yr.-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
125
Perc
ent o
f 196
4 Va
lue
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
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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
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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