Bioavailability of Dissolved Organic Phosphorus in Temperate Lakes

Seth K. Thompson, James B. Cotner

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Freshwater aquatic systems are biogeochemical hotspots, with heterotrophic bacteria rapidly cycling the compounds that pass through them. P is a key nutrient that controls primary production in many freshwater ecosystems and is important for understanding eutrophication in lakes. Previous work has often focused on the dynamics of inorganic phosphorus and its impact on primary production, however, the role of nutrients bound in more complex organic forms (such as dissolved organic phosphorus, DOP) in supporting primary production and harmful algal blooms has been neglected. Here, we quantify the bioavailability of dissolved organic carbon (DOC) and DOP in 27 aquatic systems across the Upper Midwest United States. Using exponential decay models, long-term nutrient degradation assays revealed that decay constants for DOP ranged from −0.001 per day to −0.12 per day with a median value of −0.01 per day. These rates were geographically variable and were as high or higher than DOC decay constants, which ranged from −0.003 per day to −0.024 per day with a median value of −0.01 per day. Additionally, total bioavailability of DOP ranged from 0 to 100% with a median value of 78% of the DOP pool, demonstrating that DOP bioavailability was highly variable across systems. In contrast, bioavailable DOC was more tightly constrained with values ranging from 4.37 to 53.81% of the total DOC pool with a median value of 24.95%. DOP bioavailability was negatively correlated with the DOC:DOP of the organic matter pool, suggesting that bioavailable DOP is drawn down in systems that are more likely to be P limited. Finally, we show that including estimates of DOC and DOP bioavailability reduces estimates of elemental imbalance experienced by aquatic bacteria.

Original languageEnglish (US)
Article number62
JournalFrontiers in Environmental Science
Volume6
DOIs
StatePublished - Jun 28 2018

Bibliographical note

Funding Information:
This work was funded by the Itasca Graduate Student Fellowship and Moos Graduate Fellowship in the aquatic science awarded to ST by the College of Biological Sciences at the University of Minnesota and NSF award 1257571 to JC.

Publisher Copyright:
© Copyright © 2018 Thompson and Cotner.

Keywords

  • bioavailability
  • carbon
  • degradation
  • dissolved organic matter
  • phosphorus

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