|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, firstname.lastname@example.org|
|Kyle, M, , Arizona State University, Tempe, USA, email@example.com|
|Schampel, J, H, Arizona State University, Tempe, USA, firstname.lastname@example.org|
|Watts, J, M, Arizona State University, Tempe, USA, email@example.com|
|STOICHIOMETRIC RESPONSE OF CYANOBACTERIA AND DIATOM MATS TO NUTRIENT ADDITIONS IN A SHALLOW SALINE POND, CUATROCIENEGAS MEXICO|
|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.