, Volume 20, Issue 3, pp 195–212

Nitrogen mass balances and denitrification rates in central Ontario Lakes

  • Lewis A. Molot
  • Peter J. Dillon

DOI: 10.1007/BF00000787

Cite this article as:
Molot, L.A. & Dillon, P.J. Biogeochemistry (1993) 20: 195. doi:10.1007/BF00000787


Nitrogen mass balances for seven unproductive lakes and 20 forested catchments in central Ontario were measured between 1977 and 1989. Average annual lake denitrification rates calculated with the N/P ratio method were strongly correlated with summer anoxic factor (extent of surficial sediment anoxia) whereas denitrification rates calculated with a210Pb sediment N accumulation method were poorly correlated with the anoxic factor suggesting that the N/P method is superior. Substantial denitrification occurred in all lakes — an average of 36% of TN inputs or 75% of the net gain. On a regional area-weighted basis, 67% of bulk atmospheric TN deposition was stored or denitrified terrestrially, 12% was denitrified in lakes, 4% was stored in lake sediments, and 17% was exported from lakes. N/P ratios were generally less in streams than in precipitation suggesting preferential N retention in catchments, whereas the N/P ratios in lake outputs were slightly higher than lake input ratios, suggesting preferential P retention in lakes. This is consistent with the notion that P-limited lakes can exist adjacent to N-limited forests.

Key words

denitrificationlakemass balancenitrogen

Copyright information

© Kluwer Academic Publishers 1993

Authors and Affiliations

  • Lewis A. Molot
    • 1
  • Peter J. Dillon
    • 2
  1. 1.Faculty of Environmental StudiesYork UniversityTorontoCanada
  2. 2.Dorset Research CentreOntario Ministry of Environment and EnergyDorsetCanada