Nitrogen transformations differentially affect nutrient‐limited primary production in lakes of varying trophic state

• Main Authors: J. Thad Scott, Mark J. McCarthy, Hans W. Paerl
• Format: Article
• Language: English
• Published: Wiley 2019-08-01
• Series: Limnology and Oceanography Letters
• Online Access: https://doi.org/10.1002/lol2.10109

Abstract The concept of lakes “evolving” phosphorus (P) limitation has persisted in limnology despite limited direct evidence. Here, we developed a simple model to broadly characterize nitrogen (N) surpluses and deficits, relative to P, in lakes and compared the magnitude of this imbalance to estimates of N gains and losses through biological N transformations. The model suggested that approximately half of oligotrophic lakes in the U.S.A. had a stoichiometric N deficit, but 72–89% of eutrophic and hypereutrophic lakes, respectively, had a similar N deficit. Although reactive N appeared to accumulate in the most oligotrophic lakes, net denitrification perpetuated the N deficit in more productive lakes. Productive lakes exported reactive N via biological N transformations regardless of their N deficit. The lack of N accumulation through N fixation underscores the need for a modern eutrophication management approach focused on reducing total external nutrient loads, including both N and P.