Ecological Archives E085-002-A2

Kathryn L. Cottingham, Stephen Glaholt, and Ashley C. Brown. 2004. Zooplankton community structure affects how phytoplankton respond to nutrient pulses. Ecology 85:158–171.

Appendix B. Statistical tables for analyses described in the main text.

Table B1. Two-way ANOVA applied to the change in nutrient levels () from ~1 day before to 1 day after the nutrient pulse (see also Fig. 2 in the main text). 

Response
Variable
 
1999
2000

Source

df

F

P

df

F

P

total N

Zoop

3, 15

0.15

0.93

3, 24

0.85

0.48

 

Pulse

1, 15

29.01

<0.0001

1, 24

33.77

<0.0001

 

Zoop × Pulse

3, 15

0.29

0.83

3, 24

1.00

0.41

total P

Zoop

3, 16

1.14

0.36

3, 24

0.31

0.82

 

Pulse

1, 16

0.21

0.65

1, 24

38.56

<0.0001

 

Zoop × Pulse

3, 16

0.93

0.45

3, 24

1.46

0.25

   Notes: One mesocosm was not included in the 1999 TN analysis due to a lost sample. Effects for which P < 0.05 are indicated in bold font.


Table B2. Two-way analyses of zooplankton biomass variables sampled just prior to the nutrient pulse. 

A) Two-way MANOVA on Daphnia, small cladoceran, and copepod biomass for 1999 and 2000.  Rotifers were sufficiently rare that they were not included in this analysis.
 
1999
2000

Source

df

F

P

df

F

P

Zoopl.

9, 48

10.33

<0.0001

9, 72

5.69

<0.0001

Pulse

3, 14

 0.06

 0.98

3, 22

0.51

 0.68

Zoopl. × Pulse

9, 48

 0.71

 0.70

9, 72

0.33

 0.96

B) Univariate, two-way ANOVA for each component of the MANOVA, plus total biomass including rotifers.  There were 3 numerator df for the Zoop and Zoop × Pulse tests and 1 numerator df for the Pulse test, with 16 denominator df in 1999 and 24 in 2000. RV = response variable.
   
1999
2000

RV

Source

F

P

F

P

Daphnia
Zoop
72.30
<0.0001
92.20
<.0001
 
Pulse
0.21
0.65
0.26
0.62
 
Zoop × Pulse
0.07
0.97
0.02
0.99
Small cladocerans
Zoop
3.30
0.05
33.56
<.0001
Copepods
Zoop
12.63
0.0002
3.60
0.03
 
Pulse
0.04
0.85
0.88
0.36
 
Zoop × Pulse
1.77
0.19
0.73
0.55
Total biomass
Zoop
14.94
<.0001
82.60
<.0001
 
Pulse
0.27
0.61
0.47
0.50
 
Zoop × Pulse
1.34
0.30
0.25
0.86
C) Linear contrasts for the univariate ANOVAs in (B). There were two contrasts planned at the outset of the experiment:  (1) No Added Zooplankton vs. the three +Zooplankton treatments, and (2) Copepod vs. Daphnia treatments.  Degrees of freedom for the F test were (1,16) in 1999 and (1,24) in 2000.
 
1999
2000
RV
No Added vs. +Zooplankton
Copepod vs. Daphnia
No added vs. +Zooplankton
Copepod vs. Daphnia
Daphnia

F = 38.15

P < 0.0001

F = 159.41

P < 0.0001

F = 276.30

P < 0.0001

F = 0.72

P = 0.41

Small cladocerans

F = 2.61

P = 0.13

F = 2.09

P = 0.17

F = 100.32

P < 0.0001

F = 0.047

P = 0.83

Copepods

F = 28.65

P < 0.0001

F = 5.87

P = 0.028

F = 3.15

P = 0.089

F = 0.025

P = 0.88

Total zooplankton

F = 44.60

P < 0.0001

F = 0.23

P = 0.64

F = 243.84

P < 0.0001

F = 2.82

P = 0.11

   Notes: These analyses evaluate the effects of the zooplankton treatments and check that there was no difference between control and pulse mesocosms prior to the pulse. Response variables were log10(x + 0.01) transformed prior to analysis; 0.01 was the minimum biomass observed in any zooplankton functional group. Results were qualitatively similar for density variables, but are not presented here.


Table B3. Backwards indicator variable regressions predicting sensitivity and return time from a zooplankton variable, a year indicator, and their interaction.

A) Sensitivity (Before/After metric)
Predictor Intercept
(95% CI)
Slope
(95% CI)
Change in Int.
(95% CI)
Change in slope
(95% CI)
R2 MSE F P
Total biomass 20.66
(17.23, 24.09)
-12.39
(-15.48, -9.31)
16.67 (9.72, 23.62) 0.75 26.7 37.94 0.0001
Cladoceran length 17.60
(12.61, 22.59)
-3.84
(-10.07, 2.39)
16.35 (6.64, 26.07) -26.82
(-38.47, -15.18)
0.67 35.8 16.07 0.0001
Daphnia biomass 9.73
(5.20, 14.25)
-4.74
(-6.42, -3.07)
7.64 (0.57, 14.70)   0.61 42.3 19.28 0.0001
Small cladoceran biomass 11.37
(8.15, 14.59)
-3.98
(-5.94, -2.02)
    0.40 64.4 17.44 0.0003
Copepod biomass 17.65
(12.24, 23.06)
-7.91
(-13.99, -1.84)
    0.22 84.4 7.17 0.0127
B) Sensitivity (Control/Pulse metric)
Predictor Intercept
(95% CI)
Slope
(95% CI)
Change in Int.
(95% CI)
Change in Slope
(95% CI)
R2 MSE F P
Total biomass 18.02
(14.81, 21.23)
-10.15
(-13.03, -7.27)
13.47
(6.97, 19.97)
  0.70 23.3 29.38 0.0001
Cladoceran length 16.17
(11.87, 20.46)
-4.39
(-9.75, 0.96)
12.89
(4.54, 21.24)
-21.16
(-31.17, -11.15)
0.66 26.4 15.62 0.0001
Daphnia 8.99
(5.02, 12.97)
-3.94
(-5.41, -2.47)
6.22
(0.00, 12.43)
  0.58 32.7 17.31 0.0001
Small cladocerans 10.28
(7.51, 13.05)
-3.33
(-5.02, -1.64)
    0.39 47.8 16.49 0.0004
Copepods 15.46
(10.80, 20.11)
-6.50
(-11.72, -1.27)
    0.20 62.4 6.54 0.0167
C) Return time (Before/After metric)
Predictor Intercept
(95% CI)
Slope
(95% CI)
Change in Int.
(95% CI)
Change in Slope
(95% CI)
R2 MSE F P
Total biomass 23.73
(18.71, 28.75)
-11.36
(-15.88, -6.85)
12.96
(2.78, 23.14)
  0.57 57.2 16.48 0.0001
Cladoceran length 22.44
(15.54, 29.33)
-6.40
(-15.00, 2.196)
9.39
(-4.03, 22.80)
-19.44
(-35.51, -3.36)
0.49 68.2 7.56 0.0010
Daphnia 16.12
(12.68, 19.57)
-3.61
(-5.24, -1.99)
    0.44 73.65 20.80 0.0001
Small cladocerans 13.83
(9.99, 17.67)
-3.87
(-6.20, -1.53)
    0.31 91.74 11.57 0.0022
Copepods 19.73
(13.48, 25.97)
-7.38
(-14.39, -0.37)
    0.15 112.32 4.69 0.0398
D) Return time (Control/Pulse metric)
Predictor Intercept
(95% CI)
Slope
(95% CI)
Change in Int.
(95% CI)
Change in Slope
(95% CI)
R2 MSE F P
Total biomass 27.01
(21.38, 32.64)
-5.34
(-8.44, -2.24)
    0.33 76.43 12.53 0.0015
Cladoceran length 25.07
(18.41, 31.74)
-0.62
(-8.93, 7.70)
6.01
(-6.96, 18.98)
-19.62
(-35.16, -4.08)
0.44 63.74 6.22 0.0028
Daphnia 20.30
(16.69, 23.90)
-2.69
(-4.39, -0.98)
    0.29 80.68 10.50 0.0033
Small cladocerans 18.53
(14.79, 22.27)
-3.12
(-5.39, -0.84)
    0.23 86.77 7.94 0.0091
Copepods 25.51
(20.20, 30.81)
-9.32
(-15.27, -3.37)
    0.28 81.02 10.35 0.0035

Notes: Biomass variables were log10(x + 0.01)-transformed to linearize relationships. Degrees of freedom for the F statistic were determined as P – 1 and 28 – P, where P is the number of parameters listed in each row of the table.



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