Ecological Archives A025-081-A3

Margot L. Hessing-Lewis, Sally D. Hacker, Bruce A. Menge, Sea-Oh McConville, and Jeremy Henderson. 2015. Are large macroalgal blooms necessarily bad? nutrient impacts on seagrass in upwelling-influenced estuaries. Ecological Applications 25:13301347. http://dx.doi.org/10.1890/14-0548.1

Appendix C. AIC values for all candidate models evaluated through model selection.

AICc (Akaike Information Criteria, second order) values for all candidate models used in model selection and averaging (using AICcmodavg package in R). Across response metrics, strength of evidence for potential candidate models were evaluated: N (nutrient effect alone), M (macroalgae effect alone), N + M (macroalgae additive with nutrients), N x M (macroalgae interactive with nutrients), Null (no nutrient, macroalgae or temporal effect). Interactions with time (x T) with all of the above models were evaluated for all variables with a temporal component, as well as time only (T). For the field experiment, the PAR response was only measureable in macroalgal treatments, so macroalgal effects alone were evaluated. For the tank experiment, macroalgal biomass was only present in ADDITION treatments, so models only considered nutrient and time effects in these treatments. Candidate models appear in rank order from model with the strongest support to model with the least support, based on delta AICc values and AICc weights. Best models (Table 2) have delta AICc values < 2 AIC values, suggesting substantial evidence for the model. AICc weights compare the ratio of a given model to all candidate models (1 = 100% chance of being the best model considered amongst candidate models). Models = candidate models for model selection, K = number of estimated parameters in candidate model, LL = Log-likelihood of the model given the data (used to compute AICc), AICc = selection criteria (AICc used instead of AIC when n/K < 40), Delta AIC = simple differences in AICc values, AICc weights = weighted differences in AICc values (sum to 1 across candidate models). Treatment manipulations were replicated 3 times at the plot level for the field experiment, and 3 times at the tank level for the mesocosm experiment (with buckets nested within tanks).

Table C1.

 

Response metric

Models

K

LL

AICc

Delta AICc

AICc Weights

A. Field experiment

Macroalgal volume
(mL rep-1)

N + M

N x M

M

M + N + T

M x T

M x N x T

N

Null

Time

17

20

16

22

20

25

14

13

14

-972.42

-972.26

-977.70

-969.51

-974.48

-969.36

-985.30

-986.60

-986.20

1984.17

1992.02

1992.09

1992.21

1996.46

2000.86

2002.17

2002.25

2003.96

0.00

7.85

7.92

8.04

12.29

16.69

17.99

18.09

19.79

0.94

0.02

0.02

0.02

0.00

0.00

0.00

0.00

0.00

Eelgrass density (% change in shoots rep-1) per central quadrat (0.25 m²)

N

Null

M

N + M

N x M

11

10

13

14

17

-106.42

-110.20

-103.84

-103.83

-103.64

256.84

247.33

270.08

282.32

342.29

0.00

0.48

13.24

25.48

86.45

0.56

0.44

0.00

0.00

0.00

Eelgrass density (% change in shoots rep-1) per haphazard quadrat (0.0625 m²)

Null

N

M

N + M

N x M

3

4

6

7

10

-129.83

-128.64

-127.78

-127.54

-123.75

266.87

269.38

272.49

276.08

284.43

0.00

2.52

5.63

9.21

17.56

0.74

0.21

0.04

0.00

0.00

Final eelgrass biomass
(g dry wt rep-1)

 

Null

N

M

N + M

N x M

10

11

13

14

17

-82.68

-82.67

-77.54

-77.38

-76.73

202.28

209.35

217.48

229.43

289.46

0.00

7.06

15.20

27.14

87.18

0.97

0.03

0.00

0.00

0.00

Eelgrass shoot length (% change in cm rep-1)

 

 

Null

N

Time

N x T

M

M + N

M x N

M x T

M + N + T

M x N x T

5

6

6

8

8

9

12

12

14

20

-446.96

-446.11

-446.17

-445.25

-445.58

-444.77

-444.39

-444.57

-443.71

-443.19

904.58

905.17

905.29

908.16

908.81

909.63

916.54

916.90

920.60

937.59

0.00

0.59

0.71

3.57

4.23

5.05

11.95

12.32

16.02

33.00

0.35

0.26

0.25

0.06

0.04

0.02

0.00

0.00

0.00

0.00

Eelgrass sheath length (% change in cm rep-1)

 

 

 

Time

M x T

N x T

M + N + T

Null

N

M

M + N

M x N x T

M x N

12

18

14

20

11

12

14

15

26

18

-216.61

-205.28

-215.71

-204.64

-237.60

-237.5640

-234.8257

-234.1693

-203.0804

-233.0560

466.14

470.14

472.15

480.39

504.54

508.04

510.38

513.34

525.02

525.70

0.00

4.00

6.01

14.25

38.39

41.90

44.24

47.20

58.88

59.56

0.84

0.11

0.04

0.00

0.00

0.00

0.00

0.00

0.00

0.00

Redox potential

(mV rep-1)

 

Time

N x T

M x T

N + M + T

N x M x T

Null

N

M

N + M

N x M

5

7

11

13

19

4

5

7

8

11

-584.65

-582.64

-579.86

-577.72

-575.45

-614.18

-613.18

-612.21

-611.16

-610.34

1179.96

1180.56

1184.86

1185.89

1198.90

1236.80

1236.81

1237.00

1239.97

1245.82

0.00

0.60

4.90

5.92

18.94

56.84

57.04

59.73

60.01

65.86

0.53

0.39

0.05

0.03

0.00

0.00

0.00

0.00

0.00

0.00

PPFD

(μmol photon m-2 s-1 rep-1)

Null

M

 

6

9

-170.40

-169.57

356.46

366.14

 

0.00

9.68

0.99

0.01

B. Mesocosm experiment

 

Macroalgal volume (mL rep-1)

Time

Null

N

5

4

5

-145.10

-152.68   

-152.66

   305.21 

   316.43

 320.32

0.00

11.22

15.11

1.00

  0.00

0.00

Eelgrass density (% change in shoots bucket-1 rep-1)

 

N + M

M

N x M

N

Null

8

7

10

6

5

-547.31

-549.36

-546.44

-562.11

-564.14

1111.84

1113.68

1114.80

1136.93

1138.79

0.00

1.84

2.95

25.09

26.95

0.61

0.25

0.14

0.00

0.00

Final eelgrass biomass (g dry wt shoot-1 rep-1)

N x M

N + M

M

N

Null

9

7

6

5

4

485.44

481.49

473.56

368.57

364.88

-952.52

-948.76

-934.94

-727.02

-721.69

0.00

3.76

17.57

225.49

230.83

0.87

0.13

0.00

0.00

0.00

Eelgrass shoot length (% change in cm rep-1 bucket-1)

M x T

M + N + T

M x N x T

M + N

M

M x N

Null

N

Time

N x T

10

12

16

8

7

10

5

6

6

8

-967.02

-965.56

-962.68

-978.89

-980.09

-977.07

-1039.12

-1038.23

-1039.09

-1038.06

1954.97

1956.46

1959.72

1974.39

1974.65

1975.07

2088.48

2088.80

2090.53

2092.73

0.00

1.49

4.76

19.42

19.68

20.10

133.52

133.83

135.56

137.76

0.64

0.30

0.06

0.00

0.00

0.00

0.00

0.00

0.00

0.00

Eelgrass sheath length (% change in cm rep-1 bucket-1)

M + N + T

M x T

M x N x T

Time

N x T

M + N

M

M x N

Null

N  

15

13

19

9

11

11

10

13

8

9

-1030.87

-1033.75

-1029.32

1082.87

-1082.37

-1099.41

-1101.37

-1098.65

-1127.77

-1126.93

2093.81

2095.06

2100.00

2184.50

2187.86

2221.95

2223.67

2224.86

2272.15

2272.61

0.00

1.25

6.18

90.69

94.05

128.13

129.86

131.05

178.33178.80

0.63

0.34

0.03

0.00

0.00

0.00

0.00

0.00

0.00

0.00

Trimmed eelgrass biomass (g dry wt rep-1)

N x M x T

N + M+ T

M x T

N x M

N + M

M

N x T

N

Time

Null

1713

11

11

9

8

9

7

7

6

-73.91

-84.19

-95.48

-103.34

-109.12

-117.56

-130.59

-135.44

-138.12

-142.84

184.25

195.81

213.98

229.66

236.94

251.68

279.87

285.31

290.68

298.00

0.00

11.55

29.73

45.41

52.68

67.43

96.61

101.06

106.43

113.75

0.99

0.01

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

Sloughed eelgrass biomass (g dry wt rep-1)

M x T

N + M + T

N x M x T

M

Time

N + M

N x T

N x M

Null

N

14

16

20

11

10

12

12

14

9

10

-53.50

-53.26

-50.92

-66.51

-67.69

-66.49

-67.63

-65.94

-75.55

-75.55

136.44

140.41

144.79

155.92

156.14

158.06

160.32

161.33

169.71

171.56

0.00

3.97

8.35

19.47

19.70

21.61

23.88

24.89

33.27

35.12

0.87

0.12

0.01

0.00

0.00

0.00

0.00

0.00

0.00

0.00

Redox potential (mV rep-1)

 

M x N x T

M x T

N + M + T

N + M

M

N x M

T

N x T

Null

N

22

16

18

14

13

16 12 14 11 12

-5195.26

-5204.30

-5203.56

-5251.62

-5252.89

-5250.07

-5279.20

-5278.65

-5284.94

-5284.82

  10435.66

  10441.20

  10443.88

  10531.70

  10532.19

  10532.74

  10582.75

  10585.76

  10592.16

  10593.98

0.00

5.54

8.22

96.04

96.53

97.08

147.09

150.10

156.50

158.32

  0.93

  0.06

  0.02

  0.00

  0.00

  0.00

  0.00

  0.00

  0.00

  0.00

Total light attenuation (μmol photon m−2 s−1 rep-1)

 

M x T

N + M + T

N x M x T

N + M

M

N x M

T

N x T

N

Null

11

13

17

9

8

11 7

9

7

6

-1846.89

-1844.98

-1843.70

-1863.62

-1865.08

-1862.67

-1878.19

-1877.04

-1881.84

-1883.27

   3716.87

   3717.49

   3724.03

   3746.00

   3746.74

   3748.44

   3770.84

   3772.83

   3778.14

   3778.88

0.00

0.62

7.15

29.12

29.97

31.57

53.97

55.96

61.27

62.01

0.57

0.42

0.02

0.00

0.00

0.00

0.00

0.00

0.00

0.00

Temperature (°C rep-1)

M

N + M

Null

N

N x M

10

11

8

9

13

-207.26

-206.45

-210.40

-209.70

-206.01

  435.50

  436.09

  437.44

  438.21

  439.68

0.00

0.59

1.94

2.71

4.17

0.40

0.30

0.15

0.10

0.05

Salinity (ppt rep-1)

Null

N

M

N + M

N x M

5

6

7

8

10

-254.97

-254.96

-254.68

-254.66

-254.65

  520.20

  522.27

  523.86

  525.96

  530.29

0.00

2.06

3.66

5.76

10.09

0.63

0.23

0.10

0.04

0.00

Dissolved Oxygen (mgL-1 rep-1)

M

N + M

N x M

Null

N

10

11

13

8

9

-366.43

-366.43

-366.11

-392.90

-392.88

  753.84

  756.04

  759.87

  802.43

  804.55

0.00

2.20

6.03

48.59

50.71

0.72

0.24

0.04

0.00

0.00

pH (rep-1)

M

N + M

N x M

Null

N

11

12

14

9

19

55.41

55.58

57.15

45.94

46.01

  -87.63

  -85.75

  -84.39

  -73.08

  -71.05

  0.00

  1.88

  3.24

  14.55

  16.58

0.63

0.25

0.12

0.00

0.00


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