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The Role of Dissolved Organic Material in Regulating Primary Production in Prairie Saline Lakes

Personnel

Principal Investigators: Jasmine Saros, Christopher Osburn (Naval Research Laboratory), Sheri Fritz (University of Nebraska - Lincoln)

Undergraduates: Jarvis Erickson, Margaret Henke, Callie Martin, Courtney Wigdahl, Jessica Czubakowski, Erin Wilcox, Carmen Daggett, Eric Earle.

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Project Summary

Lake ecosystems are often defined in terms of a trophic paradigm, in which lake productivity is considered a direct function of nutrient loading. This paradigm has been modified to include the role of dissolved organic matter (DOM) in regulating this process, based on the effects of this material in forest-dominated aquatic ecosystems. However, the role of DOM in lakes situated in other types of ecosystems, such as grasslands, is presently unclear. Grasslands and converted grasslands (i.e. agricultural land) cover extensive areas in arid and semi-arid regions of the world. Lakes situated in grasslands are usually saline or sub-saline and have high concentrations of uncolored DOM. Due to the different nature of DOM in prairie lakes, the role of this material in these systems may be quite different from that in forest dominated aquatic ecosystems, and here we investigated the role that DOM plays in regulating primary production in prairie saline lakes via its effect on nutrient dynamics. 

         Using a combination of comparative lake sampling and nutrient enrichment experiments, we found widespread nitrogen limitation across these lakes in both spring and summer. Many of the typical metrics used to assess nutrient limitation, such as seston stoichiometry, were not able to reveal limitation patterns in these lakes, possibly due to contributions from DOC colloids.

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