SS2.04 Microbial Stoichiometry and Impacts on Biogeochemistry: From Genes to the Biosphere
Date: Friday, June 14, 2002
Time: 9:30:00 AM
Location: Carson C
 
Elser, J, J, Arizona State University, Tempe, USA, j.elser@asu.edu
Kyle, M, , Arizona State University, Tempe, USA, mkyle@asu.edu
Schampel, J, H, Arizona State University, Tempe, USA, john.schampel@asu.edu
WattsJM, Arizona State University, Tempe, USA, j.watts@asu.edu
 
STOICHIOMETRIC RESPONSE OF CYANOBACTERIA AND DIATOM MATS TO NUTRIENT ADDITIONS IN A SHALLOW SALINE POND, CUATROCIENEGAS MEXICO
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Laguna Intermedia is a shallow (<1 m depth), saline (~4 g/L), and phosphorus-deficient (TN:TP of 90:1) system dominated by spatially discrete Calothrix and diatom benthic mats having very high C:P and N:P ratios in biomass. To assess the affects of phosphorus enrichment on the matís C:N:P stoichiometry, a fully factorial nitrate and phosphorus addition experiment was conducted. For both mat types, 6 replicates of each nutrient treatment were enriched with 240 uM nitrate and/or 15 uM phosphorus (16:1 ratio) every 12 hours. Both mat types showed N and P uptake during the day, P uptake at night by the Calothrix mats, but a release of N at night by the diatom mats. After 4-weeks, mat biomass was analyzed for C, N, and P content. Calothrix mats had a decrease in C:P and N:P in both the +P and +NP addition treatments whereas diatom mats had a decrease in the C:P in P addition treatment only. For both mat types and all treatments, C:N did not significantly change during the experimental period. Implications for food-web dynamics will be discussed.