Key Bioturbator Species Within Benthic Communities Determine Sediment Resuspension Thresholds

Abstract

Abundant research has shown that macrobenthic species are able to increase sediment erodibility through bioturbation. So far, however, this has been at the level of individual species. Consequently, we lack understanding on how such species effects act on the level of bioturbator communities. We assessed the isolated and combined effects of three behaviorally contrasting macrobenthic species, i.e., Corophium volutator, Hediste diversicolor, and Limecola balthica, at varying densities on the critical bed shear stress for sediment resuspension (τcr). Overall, the effect of a single species on sediment erodibility could be described by a power function, indicating a relatively large effect of small bioturbator densities which diminishes toward higher individual density. In contrast to previous studies, our results could not be generalized between species using total metabolic rate, indicating that metabolic rate may be only suitable to integrate bioturbation effects within and between closely related species; highly contrasting species require consideration of species-specific bioturbation strategies. Experiments at the benthic community level revealed that the ability of a benthic community to reduce τcr is mainly determined by the species that has the largest individual effect in reducing τcr, as opposed to the species that is dominant in terms of metabolic rate. Hence, to predict and accurately model the net effect of bioturbator communities on the evolution of tidal flats and estuaries, identification of the key bioturbating species with largest effects on τcr and their spatial distribution is imperative. Metabolic laws may be used to describe their actual activity.

Contrasting strategies to cope with storm‐induced erosion events: a flume study comparing a native vs. introduced bivalve

“…A high density of macrofauna may also reduce the transport rate of surfaced individuals (Anta et al 2013). The processes underpinning density‐dependent effects on sediment and macrofauna erodibility are complex and may change depending on the sediment properties (Li et al 2017), community composition (de Smit et al 2021), and season (De Backer et al 2010), which would certainly affect the surfacing and transport rate of macrofauna during an extreme storm. Furthermore, we can imagine that if the frequency of extreme storms increases, then surface sedimentary conditions and macrofaunal densities of animals may change between storms, thus affecting the vulnerability of remaining animals.…”

How bioturbators perturb the paleo record.

“…bioirrigation, a process describing the active pumping of bottom water through burrows by benthos and often leading to oxygenation of the surrounding volume (Aller 1982, Kristensen, Penha-Lopes et al 2012. Moreover, bioturbation may cause a change in the chemical composition of bulk sediment during the passage through the gut of the animals (Hammond 1982, Abele-Oeschger andTheede 1991), stimulate microbial biofilm formation in order to stabilize the walls of burrows (Meadows and Tait 1989), induce infaunal-microbial feedbacks Cochran 2019, Wyness, Fortune et al 2021) or increase resuspension of particles at the sediment water interface (Davis 1993, de Smit, Brückner et al 2021.…”

Biogeomorphology shaping coastal and estuarine systems

“…Competition, predation and facilitation add another level of complexity that would require an ecological model itself to predict a species distribution and interaction-dependent growth in the morphodynamic model, such as initiated in . Furthermore, the same group of species, for example benthic tube-builders, can have opposite effects depending on conditions (de Smit et al, 2021). On the one hand they promote more sediment erosion and resuspension via the increase in roughness with their tubes and because they convey mud from the substrate to the surface as they forage.…”