TY - JOUR
T1 - Nutrient Limitation and the Stoichiometry of Nutrient Uptake in a Tropical Rain Forest Stream
AU - Tromboni, Flavia
AU - Thomas, Steven A.
AU - Gücker, Björn
AU - Neres-Lima, Vinicius
AU - Lourenço-Amorim, Christine
AU - Moulton, Timothy P.
AU - Silva-Junior, Eduardo F.
AU - Feijó-Lima, Rafael
AU - Boëchat, Iola G.
AU - Zandonà, Eugenia
N1 - Funding Information:
We thank B. Moreira Ferreira, B. S. Da Silva and J. Ribeiro, for their help in the field and in the lab. We are grateful to Centro de Estudos Ambientais e Desenvolvimento Sustentavel (CEADS) for logistic support at Ilha Grande. We thank W.K. Dodds and two anonymous reviewers for comments and suggestions that improved the quality of the manuscript. This research was supported by the Brazilian Government funding agency CAPES with a grant from Science without Borders (Project 166/2012). The first author was supported by the CAPES/FAPERJ scholarship E-26/100.018/2015 and by NSF Macrosystems, Award 1442562. I. G. Boëchat and B. Gücker were supported through productivity grants by the Brazilian National Council for Scientific and Technological Development (CNPq) and the Foundation for Research Support of the State of Minas Gerais (FAPEMIG). Data used will be available at http://dataone.org.
Funding Information:
We thank B. Moreira Ferreira, B.?S. Da Silva and J. Ribeiro, for their help in the field and in the lab. We are grateful to Centro de Estudos Ambientais e Desenvolvimento Sustentavel (CEADS) for logistic support at Ilha Grande. We thank W.K. Dodds and two anonymous reviewers for comments and suggestions that improved the quality of the manuscript. This research was supported by the Brazilian Government funding agency CAPES with a grant from Science without Borders (Project 166/2012). The first author was supported by the CAPES/FAPERJ scholarship E-26/100.018/2015 and by NSF Macrosystems, Award 1442562. I.?G. Bo?chat and B. G?cker were supported through productivity grants by the Brazilian National Council for Scientific and Technological Development (CNPq) and the Foundation for Research Support of the State of Minas Gerais (FAPEMIG). Data used will be available at http://dataone.org.
Publisher Copyright:
©2018. American Geophysical Union. All Rights Reserved.
PY - 2018/7
Y1 - 2018/7
N2 - Nutrient limitation assessment is important to understand stream ecosystem functioning. Aquatic primary producers are often limited by nitrogen, phosphorus, or both, as assessed by nutrient diffusing substrata (NDS), a common method for assessing nutrient limitation in streams. But little is known regarding how this method relates to patterns of nutrient uptake at the whole-stream scale. We combined two techniques to examine nutrient limitation in a tropical stream. First, we conducted two NDS experiments using ammonium, nitrate, and phosphate alone and combined, to determine nutrient limitation at substrata scale over several weeks. Second, we conducted whole-stream nutrient addition experiments over the course of a year, using nutrients alone and in combination, to test theoretical predictions about uptake characteristics of limiting and nonlimiting nutrients. NDS results consistently indicated N limitation. Ambient uptake length (SW-amb) suggested either P limitation (shorter SW-amb for P than N) or colimitation (similar SW-amb for both nutrients). The relationship between N uptake and concentration when added alone or with P suggested P limitation, colimitation, or neither, depending on the date. We speculate that the different conclusions arise from differences in the spatial and temporal scale assessed by these techniques and the microbial processes involved, and the potential for physical processes influencing whole-stream uptake estimates. We conclude that nutrient limitation is not as categorical as NDS results often imply, rather habitat, resource, and biotic diversity result in nutrient uptake rates that do not necessarily conform to predictions drawn from fine scale, process-specific bioassays such as chlorophyll-a accrual on NDS.
AB - Nutrient limitation assessment is important to understand stream ecosystem functioning. Aquatic primary producers are often limited by nitrogen, phosphorus, or both, as assessed by nutrient diffusing substrata (NDS), a common method for assessing nutrient limitation in streams. But little is known regarding how this method relates to patterns of nutrient uptake at the whole-stream scale. We combined two techniques to examine nutrient limitation in a tropical stream. First, we conducted two NDS experiments using ammonium, nitrate, and phosphate alone and combined, to determine nutrient limitation at substrata scale over several weeks. Second, we conducted whole-stream nutrient addition experiments over the course of a year, using nutrients alone and in combination, to test theoretical predictions about uptake characteristics of limiting and nonlimiting nutrients. NDS results consistently indicated N limitation. Ambient uptake length (SW-amb) suggested either P limitation (shorter SW-amb for P than N) or colimitation (similar SW-amb for both nutrients). The relationship between N uptake and concentration when added alone or with P suggested P limitation, colimitation, or neither, depending on the date. We speculate that the different conclusions arise from differences in the spatial and temporal scale assessed by these techniques and the microbial processes involved, and the potential for physical processes influencing whole-stream uptake estimates. We conclude that nutrient limitation is not as categorical as NDS results often imply, rather habitat, resource, and biotic diversity result in nutrient uptake rates that do not necessarily conform to predictions drawn from fine scale, process-specific bioassays such as chlorophyll-a accrual on NDS.
KW - TASCC
KW - autotrophic
KW - heterotrophic
KW - nutrient diffusing substrata
KW - nutrient spiraling
KW - periphyton
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U2 - 10.1029/2018JG004538
DO - 10.1029/2018JG004538
M3 - Article
AN - SCOPUS:85050721368
VL - 123
SP - 2154
EP - 2167
JO - Journal of Geophysical Research G: Biogeosciences
JF - Journal of Geophysical Research G: Biogeosciences
SN - 2169-8953
IS - 7
ER -