We are looking for a postdoc to join our lab

POSTDOCTORAL ASSOCIATE – UNIVERSITY OF OKLAHOMA

Shifting hotspots: How do consumer aggregations interact to influence resource heterogeneity and fluxes in streams?

We are seeking a Postdoctoral Associate to work on an NSF funded project examining how interacting groups of consumers influence resource heterogeneity in streams. This is a collaborative project between Caryn Vaughn at the University of Oklahoma and Keith Gido at Kansas State University. The postdoc would be based at the University of Oklahoma in Norman. Start date is flexible, but we would like someone to start as soon as possible. Caryn is here at the meeting and can be reached at cvaughn@ou.edu. The project is described below.

Aggregations of consumers create hotspots of nutrient regeneration and material flux that promote resource heterogeneity, increasing biodiversity. Understanding how different types of aggregations interact to influence resource distribution and fluxes is a key knowledge gap, particularly in how these dynamics change across spatial and temporal scales and environmental gradients. Stream fish and mussel assemblages are known to generate biogeochemical hotspots, but have very different characteristics based on species life history and behavior. Long-lived mussels are localized, stable, immobile, long-term hotspots that provide relatively constant nutrient subsidies. Shorter-lived fishes are mobile, widespread, short-term hotspots that provide nutrient subsidies more dependent on hydrologic conditions.

Our project asks: (1) Where and when do fish and mussel hotspots overlap? and (2) How does overlap between these groups influence nutrient recycling and the distribution of resources throughout a stream network? We are using an integrative approach that incorporates species distribution mapping, correlative field studies and a mechanistic mesocosm experiment. To determine the spatial and temporal overlap of mussel and fish hotspots, a biomass distribution model will be generated for mussels and fishes under different hydrologic conditions in two rivers. To determine where and when each group’s function is strongest, path analysis will be used to characterize associations between nutrient dynamics and resource distribution when mussels and fish overlap (summer low flows) and when fish are more dispersed (fall higher flows). To explore mechanistic contributions of mussel and fish assemblages to nutrient and food web dynamics, experiments will be performed in large, replicated, flow-through experimental streams where the movement of nutrients from consumer aggregates (mussel and fish excreta) through the rest of the food web will be tracked with stable isotopes. Lastly, ecosystem dynamics will be scaled to whole rivers using fish and mussel distribution and hydrologic data generated in the field study.

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