Response of a stoichiometrically imbalanced ecosystem to manipulation of nutrient supplies and ratios

Zarraz M. Lee, Laura Steger, Jessica R. Corman, Marc Neveu, Amisha T. Poret-Peterson, Valeria Souza, James Elser

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Cuatro Ciénegas Basin (CCB) is a desert ecosystem that hosts a large diversity of water bodies. Many surface waters in this basin have imbalanced nitrogen (N) to phosphorus (P) stoichiometry (total N:P > 100 by atoms), where P is likely to be a limiting nutrient. To investigate the effects of nutrient stoichiometry on planktonic and sediment ecosystem components and processes, we conducted a replicated in situ mesocosm experiment in Lagunita, a shallow pond located in the southwest region of the basin. Inorganic N and P were periodically added to mesocosms under three different N:P regimes (P only, N:P = 16 and N:P = 75) while the control mesocosms were left unamended. After three weeks of fertilization, more than two thirds of the applied P was immobilized into seston or sediment. The rapid uptake of P significantly decreased biomass C:P and N:P ratios, supporting the hypothesis that Lagunita is P-limited. Meanwhile, simultaneous N and P enrichment significantly enhanced planktonic growth, increasing total planktonic biomass by more than 2-fold compared to the unenriched control. With up to 76% of added N sequestered into the seston, it is suspected that the Lagunita microbial community also experienced strong N-limitation. However, when N and P were applied at N:P = 75, the microbes remained in a P-limitation state as in the untreated control. Two weeks after the last fertilizer application, seston C:P and N:P ratios returned to initial levels but chlorophyll a and seston C concentrations remained elevated. Additionally, no P release from the sediment was observed in the fertilized mesocosms. Overall, this study provides evidence that Lagunita is highly sensitive to nutrient perturbation because the biota is primarily P-limited and experiences a secondary N-limitation despite its high TN:TP ratio. This study serves as a strong basis to justify the need for protection of CCB ecosystems and other low-nutrient microbedominated systems from anthropogenic inputs of both N and P.

Original languageEnglish (US)
Article numbere0123949
JournalPloS one
Volume10
Issue number4
DOIs
StatePublished - Apr 16 2015

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General

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    Lee, Z. M., Steger, L., Corman, J. R., Neveu, M., Poret-Peterson, A. T., Souza, V., & Elser, J. (2015). Response of a stoichiometrically imbalanced ecosystem to manipulation of nutrient supplies and ratios. PloS one, 10(4), [e0123949]. https://doi.org/10.1371/journal.pone.0123949