Data from: Watershed versus within-lake drivers of nitrogen: phosphorus dynamics in shallow lakes
Ginger, Luke J., University of St. Thomas
Zimmer, Kyle D., University of St. Thomas
Herwig, Brian R., Minnesota Department of Natural Resources
Hanson, Mark A., Minnesota Department of Natural Resources
Hobbs, William O., Science Museum of Minnesota
Small, Gaston E., University of St. Thomas
Cotner, James B., University of Minnesota
Published Jun 28, 2017 on Dryad.
Cite this dataset
Ginger, Luke J. et al. (2017). Data from: Watershed versus within-lake drivers of nitrogen: phosphorus dynamics in shallow lakes [Dataset]. Dryad. https://doi.org/10.5061/dryad.6b650
Research on lake eutrophication often identifies variables affecting amounts of phosphorus (P) and nitrogen (N) in lakes, but understanding factors influencing N:P ratios is important given its influence on species composition and toxin production by cyanobacteria. We sampled 80 shallow lakes in Minnesota (USA) for three years to assess effects of watershed size, proportion of watershed as both row crop and natural area, fish biomass, and lake alternative state (turbid versus clear) on total N: total P (TN:TP), ammonium, total dissolved phosphorus (TDP), and seston stoichiometry. We also examined N:P stoichiometry in 20 additional lakes that shifted states during the study. Lastly, we assessed importance of denitrification by measuring denitrification rates in sediment cores from a subset of 34 lakes, and by measuring seston δ15N in four additional experimental lakes before and after they were experimentally manipulated from turbid to clear states. Results showed alternative state had the largest influence on overall N:P stoichiometry in these systems, as it had the strongest relationship with TN:TP, seston C:N:P, ammonium, and TDP. Turbid lakes had higher N at given levels of P than clear lakes, with TN and ammonium two-fold and 1.4-fold higher in turbid lakes, respectively. In lakes that shifted states, TN was three-fold higher in turbid lakes, while TP was only two-fold higher, supporting the notion N is more responsive to state shifts than is P. Seston δ15N increased after lakes shifted to clear states, suggesting higher denitrification rates may be important for reducing N levels in clear states, and potential denitrification rates in sediment cores were among the highest recorded in the literature. Overall, our results indicate lake state was a primary driver of N:P dynamics in shallow lakes, and lakes in clear states had much lower N at a given level of P relative to turbid lakes, likely due to higher denitrification rates. Shallow lakes are often managed for the clear-water state due to increased value as wildlife habitat. However, our results indicate lake state also influences N biogeochemistry, such that managing shallow lakes for the clear-water state may also mitigate excess N levels at a landscape scale.
15N seston data
Data used to test for changes in 15N in seston as lakes shifted.
chla macro all lakes three years
Data used to classify lakes as clear, shifting, or turbid all 3 years.
Data used to assess denitrifcation rates in subset of lakes.
effects of changing fish mass on lakes
Data used to test whether changes in fish biomass caused changes in lakes.
effects of changing TP on NP
Data used to test whether changes in TP changed NP.
N and P data lakes that shifted states
N and P data for lakes that shifted states.
seston isotope data two years
Seston CNP data for 2 years.
stable lakes data 3 years
Data for stable lakes that didnt shift over three years.
National Science Foundation, Award: DEB-0919095; DEB-0919070; DEB-0918753