Table S1: Effects of fertilization on salt marsh ecology at PIE (Plum Island Ecosystem LTER) and GSM (Great Sippewissett Marsh). nd (no data) + (positive response) – (negative response) ~ (neutral response).

Ecological measurement / PIE fertilization / GSM fertilization
Sediment effects / Response / Reference / Response / Reference
Sediment density / nd / + / 1
Sediment elevation (above MSL) / nd / + / 2
% carbon content§ / + / Table S2 / + / 1
% nitrogen content§ / ~ / Table S2 / + / 1
Porewater NH4 concentration / nd / + / 1
Porewater H2S concentration / nd / - / 1
Redox potential / nd / + / 1
Trophic level effects
Aboveground plant growth / + / 1 / + / 4
Belowground plant growth / nd / ~ / 4
Tissue N content / + / 5 / + / 7
Species composition change / ~ / 6 / + / 7
Benthic microalgal biomass / + / 6 / + / 8
Oligochaete abundance / ~ / 9 / + / 10
Ostracod abundance / + / 11 / nd
Insect herbivores / nd / + / 12
Biogeochemical effects
Bacterial production rates / + / 4 / ~ / Table S3
Nitrogen fixation rates / ~ / Table S4 / - / 13
Denitrification rates / + / 14 / + / 1

1. M. R. Hamersley, B. L. Howes, Coupled nitrification-denitrification measured in situ in a Spartina alterniflora marsh with a 15NH4+ tracer.Mar. Ecol. Prog. Ser. 299, 123 (2005).

2. L. D. Brin, I. Valiela, D. Goehringer, B. Howes, Nitrogen interception and export in Great Sippewissett salt marsh plots exposed to chronic long-term experimental nutrient addition.Mar. Ecol. Prog. Ser. Submitted.

3. I. Valiela, J. M. Teal, N. Y. Persson, Production and dynamics of experimentally enriched salt marsh vegetation: Belowground biomassLimnol. Oceanogr. 21, 245 (1976).

4. I. Valiela, J. M. Teal, W. J. Sass,Production and dynamics of salt marsh vegetation and the effects of experimental treatment with sewage sludge. J. Appl. Ecol. 12, 973 (1975).

5. D. C. Drake, et al.,Plant nitrogen dynamics in fertilized and natural New England salt marshes: a paired 15N tracer study Mar. Ecol. Prog. Ser. 354, 35 (2008).

6. L. A. Deegan, et al., Susceptibility of salt marshes to nutrient enrichment and predator removal.Ecol. Appl. 17, S42 (2007).

7. I. Valiela, et al., in Ecological Considerations in Wetlands Treatment of Municipal Wastewaters, P. J. Godfrey et al., Eds. (Van Nostrand Reinhold Co., N.Y, 1985), pp. 301-316.

8. C. D. Van Raalte, et al., Estuar. Coast Shelf Sci. 2, 301 (1974).

9. D. S. Johnson, J. W. Fleeger, J. Exper. Weak response of salt marsh infauna to ecosystem-wide nutrient enrichment and fish predator reduction: a four year study Mar. Biol. Ecol. 373, 35-44 (2009).

10. R. Sarda, I. Valiela, K. Foreman,. Decadal shifts in a salt marsh macroinfaunal community in response to sustained long-term experimental nutrient enrichment J. Exper. Mar. Biol. Ecol. 205, 63 (1996).

11. J. W. Fleeger, D. S. Johnson, K. A. Galvin, L. A. Deegan, Top-down and bottom-up control of infauna varies across the salt marsh landscape.J. Exper. Mar. Biol. Ecol. 357, 20 (2008).

12. S. W. Vince, I. Valiela, J. M. Teal, An experimental study of the structure of herbivorous insect communities in a salt marsh.Ecology 62, 1662 (1981)

13. C. D. Van Raalte, I. Valiela, J. M. TealProduction of epibenthic salt marsh algae: Light and nutrient limitation Limnol. Oceanogr. 21, 862 (1976).

14. K. Koop-Jakobsen, A. E. Giblin, Anammox in tidal marsh sediments: the role of salinity, nitrogen loading, and marsh vegetationEstuar. Coasts 32, 238 (2009).

Table S2: Percent carbon, % nitrogen and C:N ratios in fertilized and control marsh sediments at the Plum Island Estuary fertilization experiment. Values are for dried sediments from each marsh habitat and represent the mean  standard error of samples (n = 5) taken monthly throughout the 2005 growing season. ANOVA results indicate significant differences between control and fertilized marshes only for % carbon (F = 5.584, p = 0.021).

% carbon / % nitrogen / C:N
Habitat / Fertilized / Control / Fertilized / Control / Fertilized / Control
Mudflat / 6.50.8 / 6.30.4 / 0.530.04 / 0.520.04 / 14.10.48 / 13.90.25
Filamentous algae / 7.10.4 / 5.00.5 / 0.660.04 / 0.420.04 / 12.70.70 / 13.10.16
Tall S. alterniflora / 7.10.3 / 6.30.7 / 0.600.08 / 0.540.03 / 13.10.41 / 13.50.20
Short S. alterniflora / 14.62.5 / 8.73.8 / 1.20.37 / 0.650.09 / 15.41.6 / 15.50.67
S. patens / 17.21.8 / 17.40.7 / 1.20.08 / 1.30.04 / 16.80.9 / 15.60.65

Table S3. Leucine incorporation rates measured in control and fertilized sediments of the Great Sippewissett Salt Marsh. Incorporation rates were measured monthly through the growing season of 2005 following the method of Buesing and Gessner (28) as modified by Bowen et al. (4). ANOVA results indicate no significant differences between the control and the fertilized plots. Data are means  standard error (n=6).

Leucine incorporation rate (pmol mL-1 h-1)
Control / Low dose / High dose / Very high dose
June / 30  6 / 31  2 / 9  1 / 18  2
July / 101  34 / 162  51 / 55  10 / 64  5
August / 178  31 / 171  28 / 115  29 / 100  24
September / 52  17 / 88  25 / 98  41 / 46  10
October / 65  20 / 76  27 / 36  9 / 27  7

Table S4. Seasonally averaged nitrogen fixation rates (mg N m-2 d-1 ± standard error) for each of the four PIE marshes measured from May to October 2005. MF = creek mudflat, FA = filamentous algal covered creek bank wall, TSA= tall form of Spartina alterniflora, SP = S. patens, SSA = short form of S. alterniflora.

Marsh pair one / Marsh pair two
Habitat / Fertilized / Reference / Fertilized / Reference
MF / 2.92 ± 1.12 / 0.42 ± 0.19 / 0.76 ± 0.35 / 1.58 ± 1.29
FA / 4.79 ± 2.61 / 1.26 ± 0.55 / 0.49 ± 0.29 / 2.58 ± 1.98
TSA / 2.47 ± 1.44 / 2.04 ± 0.95 / 7.40 ± 3.58 / 8.54 ± 6.05
SP / 8.96 ± 6.96 / 2.06 ± 0.73 / 0.71 ± 0.17 / 4.09 ± 2.99
SSA / 27.88 ± 19.37 / 42.5 ± 27.02 / 6.94 ±3.72 / 68.81 ± 63.28

Fig. S1. Relative fluorescence ratio of the two nirS probes that showed a significant response to fertilizer additions in Great Sippewissett Marsh (CB3-S-15: F=7.88, p=0.03; CB3-S-102: F=31.4; p=0.003).