Body size, trophic position, and the coupling of different energy pathways across a saltmarsh landscape

Friedrich W Keppeler,Linda M Hooper‐Bùi,Nancy N Rabalais,Michael J Polito,R Eugene Turner,Brian J Roberts,Olaf P Jensen,F Joel Fodrie,Charles W Martin,Jill A Olin,Sabrina S Taylor,Paola C López‐Duarte

doi:10.1002/lol2.10212

Abstract

AbstractBody size is considered an important structuring mechanism of food webs because consumers are usually larger and more mobile than their prey and may couple energy among habitats. We explored the links among trophic position (TP), body size, and the coupling of different energy channels (phytoplankton and C4‐marsh plants) in a saltmarsh landscape in the northern Gulf of Mexico—a dynamic system considered weakly shaped by biotic interactions. Body size was positively associated with TP, and this relationship was stronger in the phytoplankton pathway vs. the C4‐marsh pathway. There was a gradual increase in the coupling of phytoplankton and C4‐marsh plants at larger body sizes and higher TP. Phytoplankton supported longer food chains and larger body sizes than C4‐marsh plants. Results support predictions of the landscape theory for food web architecture and indicate that the role of body size in determining trophic interactions may vary across food web compartments.

Highlights

Trophic interactions vary in space and time, leading to changes in the structure and dynamics of food webs (Winemiller 1990)
We explored the links among trophic position (TP), body size, and the coupling of different energy channels in a saltmarsh landscape in the northern Gulf of Mexico—a dynamic system considered weakly shaped by biotic interactions
TP was positively correlated with body size corroborating previous studies conducted in estuaries (Akin and Winemiller 2008) and marine ecosystems (e.g., RomeroRomero et al 2016)

Summary

Introduction

Trophic interactions vary in space and time, leading to changes in the structure and dynamics of food webs (Winemiller 1990). A landscape theory for food web architecture (LTFWA) was proposed (Rooney et al 2008). This theory is based on empirical evidence from macroecology and behavioral ecology, mainly associated with body size and foraging behavior. Consumers are typically larger than their prey and, food webs are expected to be size-structured, with larger consumers occupying higher trophic positions (TPs) (Riede et al 2011). Evidence indicates that small consumers from lower TP occupy smaller activity spaces and are often supported by a single basal resource, whereas large consumers from a high TP explore space at larger scales, relying on multiple energy channels to support their higher energetic costs (e.g., Arim et al 2010)

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Results

Conclusion