The combined influence of body size and density on cohesive sediment resuspension by bioturbators

Francesco Cozzoli,Tom Ysebaert,Pauline Ottolander,Tjeerd J Bouma,Peter M J Herman,Maria Salvador Lluch

doi:10.1038/s41598-018-22190-3

Abstract

We propose an empirical framework to scale the effects of bioturbation on sediment resuspension to population bioturbation activity, approximated as population metabolic rate. Individual metabolic rates have been estimated as functions of body size and extrapolated to population level. We used experimental flumes to test this approach across different types of marine, soft-sediment bioturbators. We observed that a large part of the variance in biota-mediated sediment resuspension can be explained by a positive relationship with population metabolic rate. Other mechanisms can strongly influence the outcome, such as bioturbation of deep sediment strata, biotic interactions with hydrodynamic stress and overlapping areas of influence must be further investigated. By relating the biota-mediated changes in resuspended sediment to metabolism, we can place our observations within the broader context of the metabolic theory of ecology and to formulate general expectations about changes in biota-mediated sediment resuspension in response to changes in population structure and climate change.

Highlights

Macrobenthic infauna may act as ecosystem engineers[1,2] by decreasing sediment stability and increasing sediment erodability with their bioturbating activities[3,4,5]
We developed a general approach to scale the effects of bioturbation on sediment erodability across a broad range of functional groups
By following the general predictions from body size effects on the energy expenditure of individual activities[33,62,97], and scaling up the energetic budget from the individual to population level[55], we showed that the effect of bioturbators on cohesive sediment resuspension can be described in terms of bioturbators’ population metabolic rate

Summary

Introduction

Macrobenthic infauna may act as ecosystem engineers[1,2] by decreasing sediment stability and increasing sediment erodability with their bioturbating activities[3,4,5]. Significant and positive power laws have been commonly observed between the size of macrozoobenthic organisms, their standard metabolic rate[45,46,47] and other activities affecting stability, such as sediment ingestion/egestion (e.g.48 for A. marina[49], for benthic detritivores[50], for C. edule), burial and transport (e.g. bioturbation potential[12], burying depth of A. marina,[48]; burying depth of L. balthica[51]). If macrozoobenthos rework sediment proportionally to their individual energetic requirements, the amount of sediment loosened by a bioturbator and made available for resuspension (R, g) should change with the bioturbator size proportionally to the metabolic rate I: R~I (2)

Methods

Results

Discussion

Conclusion