Depth (m) Neutral filter
0
100
0,1
94,05
1
73,81
2
50,00
3
33,04
4
25,00
5
17,86
6
13,10
7
9,82
8
5,33
9
4,02
10
2,83
11
1,96
12
1,19
13
0,52
14
0,33
15
0,22
16
0,15
17
0,10
18
0,07
19
0,05
20
0,04
21
0,03
22
0,02
23
0,01
AVG
K
0,30
0,35
0,37
0,35
0,34
0,34
0,33
0,37
0,36
0,36
0,36
0,37
0,40
0,41
0,41
0,41
0,41
0,40
0,40
0,39
0,39
0,39
0,40
0,37
blue filter (460-500 nm)
100
94,74
70,53
55,79
44,21
35,79
28,42
19,37
14,21
10,16
6,84
4,84
3,47
1,84
1,16
0,74
0,47
0,33
0,21
0,15
0,12
0,09
0,02
0,01
0,00
K
0,35
0,29
0,27
0,26
0,25
0,27
0,28
0,29
0,30
0,30
0,31
0,33
0,34
0,35
0,36
0,36
0,36
0,36
0,35
0,35
0,41
0,42
0,33
green filter (500-580 nm)
100
87,32
63,38
53,52
32,25
27,46
22,68
18,73
13,24
7,75
5,92
3,66
1,72
1,11
0,63
0,44
0,24
0,17
0,13
0,08
0,02
0,00
0,00
0,00
0,00
K
0,46
0,31
0,38
0,32
0,30
0,28
0,29
0,32
0,31
0,33
0,37
0,38
0,39
0,39
0,40
0,40
0,39
0,40
0,45
0,36
yellow filter (580-590 nm)
100
88,42
50,00
35,26
19,74
16,58
12,37
7,89
6,58
5,39
3,95
2,32
1,56
1,00
0,66
0,42
0,21
0,14
0,10
0,07
0,05
0,04
0,02
0,01
0,00
0
0
5
10
15
20
40
60
20
25
0
5
10
15
20
25
0,01
0,1
1
K
0,69
0,52
0,54
0,45
0,42
0,42
0,39
0,37
0,36
0,38
0,38
0,38
0,39
0,39
0,41
0,41
0,41
0,40
0,40
0,39
0,41
0,42
0,42
red filter (640-720 nm)
100
87,50
60,00
35,50
22,50
15,00
8,75
6,15
4,50
3,55
2,50
1,60
0,70
0,44
0,26
0,17
0,12
0,08
0,06
0,04
0,03
0,01
0,00
0,00
0,00
K
0,51
0,52
0,50
0,47
0,49
0,46
0,44
0,42
0,41
0,41
0,45
0,45
0,46
0,46
0,45
0,45
0,44
0,43
0,43
0,46
0,46
80
100
120
Neutral
Blue
Green
Yellow
Red
Neutral
Blue
Green
Yellow
Red
10
100
9-Apr 9-Apr
9-Apr
23-Apr 23-Apr
23-Apr 7-May 7-May
7-May 21-May 21-May 21-May 4-Jun 4-Jun
Depth Temp Incident Reflected Temp Incident Reflected Temp Incident Reflected Temp Incident Reflected Temp Incident
0
4,9
100
100
10,9
100
100
12,2
100
100
16,9
100
100
20,8
100
1
4,9
28,2
75
10,9
32,2
65,6
12,1
35,2
12,1
16,9
31,4
9,4
20,5
35,3
2
4,9
16,8
42
10,8
25,6
56,1
12
20,9
9,3
15,2
22,1
7,1
19,6
23,5
3
4,9
10,5
31
10,8
18,9
43,9
11,9
15,4
5,9
13,1
18,4
4,8
17,4
15,3
4
4,9
6,6
20,5
10,8
13,3
32,2
11,8
13,6
3,8
12,7
13,5
3,5
14,9
13,8
5
4,9
3,5
13,5
10,7
8,9
22,2
11,1
10,1
2,4
12,2
9,8
2,3
13,1
8,9
6
4,9
2,6
8,8
9,4
6,1
13,3
9,8
7,3
1,8
12
6,5
1,8
12,1
6
7
4,9
1,8
5
7,8
4,4
7,8
8,7
4,5
1,4
10,5
5,1
1,2
10,8
4,6
8
4,9
1,2
3
6,9
3,2
5
7,4
3
1
8,3
3,4
0,9
8,7
2,9
9
4,9
0,8
2
6,1
2,3
3,3
6,3
2,1
0,7
7,1
2,4
0,7
7
2,1
10
4,9
0,5
1,3
5,2
1,6
2,8
5,7
1,4
0,6
6,2
1,7
0,6
6,2
1,5
11
4,9
0,3
0,8
4,9
1,1
2,2
5,1
1,2
0,5
5,8
1,3
0,6
5,9
1,2
12
4,8
0,2
0,3
4,8
0,7
1,7
5
1
0,5
5,5
1
0,6
5,5
0,9
Temperature
0
5
10
Incident Light
15
20
25
0
0
0
2
4
4
23-Apr
7-May
6
21-May
8
4-Jun
Depth
Depth
2
9-Apr
6
8
10
10
12
12
14
14
Reflected Light
0
0
20
40
60
80
100
120
20
40
60
80
100
0
20
40
60
80
100
120
0
2
Depth
4
6
9-Apr
23-Apr
7-May
21-May
8
10
12
14
4-Jun
4-Jun
Reflected
100
16,3
11,7
8,3
5,4
3
2,4
1,8
1,2
0,8
0,7
0,7
0,7
120
9-Apr
23-Apr
7-May
21-May
4-Jun
Depth (m) Neutral filter
0
100
0.1
94.05
1
73.81
2
50.00
3
33.04
4
25.00
5
17.86
6
13.10
7
9.82
8
5.33
9
4.02
10
2.83
11
1.96
12
1.19
13
0.52
14
0.33
15
0.22
16
0.15
17
0.10
18
0.07
19
0.05
20
0.04
21
0.03
22
0.02
23
0.01
AVG
K
0.30
0.35
0.37
0.35
0.34
0.34
0.33
0.37
0.36
0.36
0.36
0.37
0.40
0.41
0.41
0.41
0.41
0.40
0.40
0.39
0.39
0.39
0.40
0.37
blue filter (460-500 nm)
100
94.74
70.53
55.79
44.21
35.79
28.42
19.37
14.21
10.16
6.84
4.84
3.47
1.84
1.16
0.74
0.47
0.33
0.21
0.15
0.12
0.09
0.02
0.01
0.00
K
0.35
0.29
0.27
0.26
0.25
0.27
0.28
0.29
0.30
0.30
0.31
0.33
0.34
0.35
0.36
0.36
0.36
0.36
0.35
0.35
0.41
0.42
0.33
green filter (500-580 nm)
100
87.32
63.38
53.52
32.25
27.46
22.68
18.73
13.24
7.75
5.92
3.66
1.72
1.11
0.63
0.44
0.24
0.17
0.13
0.08
0.02
0.00
0.00
0.00
0.00
K
0.46
0.31
0.38
0.32
0.30
0.28
0.29
0.32
0.31
0.33
0.37
0.38
0.39
0.39
0.40
0.40
0.39
0.40
0.45
0.36
yellow filter (580-590 nm)
100
88.42
50.00
35.26
19.74
16.58
12.37
7.89
6.58
5.39
3.95
2.32
1.56
1.00
0.66
0.42
0.21
0.14
0.10
0.07
0.05
0.04
0.02
0.01
0.00
0
0
5
10
15
20
40
60
20
25
0
5
10
15
20
25
0.01
0.1
1
K
0.69
0.52
0.54
0.45
0.42
0.42
0.39
0.37
0.36
0.38
0.38
0.38
0.39
0.39
0.41
0.41
0.41
0.40
0.40
0.39
0.41
0.42
0.42
red filter (640-720 nm)
100
87.50
60.00
35.50
22.50
15.00
8.75
6.15
4.50
3.55
2.50
1.60
0.70
0.44
0.26
0.17
0.12
0.08
0.06
0.04
0.03
0.01
0.00
0.00
0.00
K
0.51
0.52
0.50
0.47
0.49
0.46
0.44
0.42
0.41
0.41
0.45
0.45
0.46
0.46
0.45
0.45
0.44
0.43
0.43
0.46
0.46
80
100
120
Neutral
Blue
Green
Yellow
Red
Neutral
Blue
Green
Yellow
Red
10
100
9-Apr 9-Apr
9-Apr
23-Apr 23-Apr
23-Apr 7-May 7-May
7-May 21-May 21-May 21-May 4-Jun 4-Jun
Depth Temp Incident Reflected Temp Incident Reflected Temp Incident Reflected Temp Incident Reflected Temp Incident
0
4.9
100
100
10.9
100
100
12.2
100
100
16.9
100
100
20.8
100
1
4.9
28.2
75
10.9
32.2
65.6
12.1
35.2
12.1
16.9
31.4
9.4
20.5
35.3
2
4.9
16.8
42
10.8
25.6
56.1
12
20.9
9.3
15.2
22.1
7.1
19.6
23.5
3
4.9
10.5
31
10.8
18.9
43.9
11.9
15.4
5.9
13.1
18.4
4.8
17.4
15.3
4
4.9
6.6
20.5
10.8
13.3
32.2
11.8
13.6
3.8
12.7
13.5
3.5
14.9
13.8
5
4.9
3.5
13.5
10.7
8.9
22.2
11.1
10.1
2.4
12.2
9.8
2.3
13.1
8.9
6
4.9
2.6
8.8
9.4
6.1
13.3
9.8
7.3
1.8
12
6.5
1.8
12.1
6
7
4.9
1.8
5
7.8
4.4
7.8
8.7
4.5
1.4
10.5
5.1
1.2
10.8
4.6
8
4.9
1.2
3
6.9
3.2
5
7.4
3
1
8.3
3.4
0.9
8.7
2.9
9
4.9
0.8
2
6.1
2.3
3.3
6.3
2.1
0.7
7.1
2.4
0.7
7
2.1
10
4.9
0.5
1.3
5.2
1.6
2.8
5.7
1.4
0.6
6.2
1.7
0.6
6.2
1.5
11
4.9
0.3
0.8
4.9
1.1
2.2
5.1
1.2
0.5
5.8
1.3
0.6
5.9
1.2
12
4.8
0.2
0.3
4.8
0.7
1.7
5
1
0.5
5.5
1
0.6
5.5
0.9
Temperature
0
5
10
Incident Light
15
20
25
0
0
0
2
4
4
23-Apr
7-May
6
21-May
8
4-Jun
Depth
Depth
2
9-Apr
6
8
10
10
12
12
14
14
Reflected Light
0
0
20
40
60
80
100
120
20
40
60
80
100
0
20
40
60
80
100
120
0
2
Depth
4
6
9-Apr
23-Apr
7-May
21-May
8
10
12
14
4-Jun
4-Jun
Reflected
100
16.3
11.7
8.3
5.4
3
2.4
1.8
1.2
0.8
0.7
0.7
0.7
120
9-Apr
23-Apr
7-May
21-May
4-Jun
BIO L413 – LIMNOLOGY LAB
Lab 2a. Light and temperature.
In this lab we will plot the percentage transmission of underwater light versus depth for
total light and for different colors of light. We will also calculate the mean absorption coefficients
of total light and the different colors of light. We will then plot temperature versus depth profiles
from data provided and then plot depth-time diagrams for temperature and light.
Underwater Irradiance
As solar radiation penetrates the water, portions are absorbed by the water itself and by
dissolved and suspended materials. A significant portion is also scattered, deflected by the
molecular components of water, its solutes, and suspended particulates. The extent of scattering
varies with the composition, quantity, and relative transparency of suspended materials. Therefore
it is anticipated that inorganic and organic suspended materials and sediments will influence the
scattering of light.
Light attenuation is the reduction of radiant energy with depth by both scattering and
absorption mechanisms. The measurement of transmission or absorption of light in water can be
made in several ways. The percentage absorption through a given depth of water may be expressed
in percent according to the relationship developed by Birge:
100(𝐼𝑜 − 𝐼𝑧 )
𝐼𝑜
Where Io = irradiance at the surface, Iz = irradiance at depth z, usually taken at 1m intervals
below Io.
The percentile absorption of pure water is very
high in the infrared portion of the spectrum and
results in rapid heating of the water by incident
light. About 53% of total light energy is
transformed into heat in the first meter of water.
Absorption by pure water decreases markedly in
the short wavelengths to a minimum absorption
in the blue and increases again in the violet and
UV spectral wavelengths. (Fig. 1).
Solar irradiance Iz at depth z is a function
of the intensity at the surface, Io, multiplied by
the antilog of the negative extinction coefficient
(k) at depth z in meters as given by the following
equations
Figure 1. Transmission of light by distilled
water at six wavelengths. Percentage of
incident light remaining expressed in linear
(upper) and logarithmic (lower) scales.
From Wetzel and Likens.
Iz = Ioe-kz
-orlnIo – lnIz = kz
Although the extinction coefficient (k) theoretically is constant for a given wavelength in
water, in nature underwater irradiance is a composite of many wavelengths. Therefore the
relationship is imperfect under natural conditions and represents a composite for multichromatic
light and the various characteristics of water that affect absorption and scattering.
The total extinction coefficient (kt) is a composite of absorption of the water itself (kw),
by particles suspended in the water (kp), and dissolved compounds or ‘colors’ (kc).
kt = kw + kp + kc
Laboratory exercise:
1. Using the data provided (Gull Lake), calculate the extinction coefficients and determine
the mean extinction coefficient (all depth intervals below 1m) for total light and that for
light absorption with blue, green, yellow, and red filters.
2. Using Gull Lake data, graph the vertical profiles of spectral attenuation as a percentage of
surface irradiance (0m = 100%) vs. depth using a) a linear scale and b) a log scale.
3. Using Lawrence Lake data, graph vertical depth profiles for
a. Temperature
b. Underwater incident light
c. Underwater scattered light
For your data in #3 plot the different dates on the same graph, thus for temperature you’ll
have 5 lines, for the incidental light graph you’ll have 5 lines, and for the scattered light graph
you’ll have 5 lines.
Questions
1. When the compensation point is defined where net photosynthesis is zero, and for a
particular algal population the compensation depth was determined to be 1% of surface
light, what is the maximum depth available for growth in both lakes?
2. Which wavelengths are most important for the heating of surface waters?
3. Why do clean, clear lakes appear blue in color? Why do aquatic plants appear green?
4. What accounts for any observed differences in your graphs for 3b and 3c?
Purchase answer to see full
attachment