Sediment properties, biota, and local habitat structure explain variation in the erodibility of coastal sediments

Abstract

Sediment resuspension is a frequent phenomenon in coastal areas and a key driver for many ecosystem functions. Sediment resuspension is often linked to biological and anthropogenic activities, which in combination with hydrodynamic forcing initiate sediment erosion and resuspension, if the erosion threshold (s c ) is exceeded. Despite its importance to ecosystem functions very few studies have provided measurements on natural assemblages for subtidal sediments. The aim of this study was to determinate key environmental variables regulating sediment resuspension potential across a sedimentary gradient in a subtidal coastal environment. In order to explore this, we sampled 16 sites encompassing a wide variety in environmental variables (e.g., grain size distribution, macrofaunal communities, vegetation) in the Gulf of Finland, Baltic Sea. A corebased erosion device (EROMES) was used to determine sediment resuspension potential measures of erosion threshold, erosion rate (ER), and erosion constant (m e ). Based on abiotic and biotic properties sampled, sediments diverged into two distinct groups; cohesive ("muddy") and noncohesive ("sandy") sediments. Results showed that abiotic sediment properties explained 38-53% and 15-36% of the total variation in resuspension potential measures in "muddy" and "sandy" sediments, respectively. In cumulative models, biota accounted for 12-26% and 6-24% to the total variation in "muddy" and "sandy" sediments, respectively. Sediment erodibility and resuspension potential of natural sediments is highly variable from local habitats to a larger seascape scale. Our results underline the importance of biota to resuspension potential measures in spatially variable environments.

The role of microphytobenthos in soft‐sediment ecological networks and their contribution to the delivery of multiple ecosystem services

“…Microphytobenthos such as diatoms and cyanobacteria secrete carbon‐rich EPS, which binds sediment particles together at the sediment‐water interface creating a ‘biofilm’ (Underwood & Paterson, ). Biofilm formation can increase the resistance of the sea bed to hydrodynamic stress and raise sediment erosion thresholds through the cohesion between particles (Black, Tolhurst, Paterson, & Hagerthey, ; Joensuu et al, ). Biofilm formation can also smooth the surface and reduce bed roughness.…”

A process based model of cohesive sediment resuspension under bioturbators' influence

“…Nevertheless, bioturbators generally make the sediment less resistant to erosion by loosening it with their activities (Willows, et al, 1998;Ciutat, et al, 2007;Montserrat, et al, 2008;Volkenborn, et al, 2009;van Prooijen, et al, 2011;Rakotomalala, et al, 2015;Cozzoli, et al, 2018a;Joensuu, et al, 2018). The effect of bioturbators on cohesive sediment resuspension impacts the short-and long-term development of coastal morphology (Le Hir, et al, 2007;Orvain, et al, 2012;Winterwerp, et al, 2018), and should hence be taken into account when forecasting the evolution of landscapes and ecosystems Orvain, 2005;Orvain, et al, 2012;Bouma, et al, 2014;Queirós, et al, 2015;Nasermoaddeli, et al, 2018).…”

Temporal Variation in Resuspension Potential and Associated Nutrient Dynamics in Shallow Coastal Environments

“…The study area is non-tidal and hydrodynamics are dominated by wind-driven waves and large-scale currents, such as upwelling events, which can initiate sediment resuspension events (Haapala 1994;Lehmann and Myrberg 2008;Valanko et al 2010). Based on a previous study focused on spatial variations in sediment resuspension potential from the same area (Joensuu et al 2018), we selected three sites to quantify temporal variability in sediment erodibility and resuspension related nutrient fluxes (Fig. 1).…”

“…vegetated patches) and the resident benthic flora and fauna whose activities can stabilize or destabilize the sediment (e.g. Black et al 2002;Harris et al 2015Harris et al , 2016Joensuu et al 2018). Despite growing insights into the variables that affect sediment resuspension, our understanding of spatial-temporal variability remains limited; for example, the relative importance of the different, site-specific and biophysical interactions that determine sediment stability are likely to vary seasonally with environmental conditions.…”

“…The main objectives of this study were to quantify spatialtemporal variation in sediment resuspension potential and associated nutrient fluxes across a sedimentary gradient and to identify environmental predictors of that variability. In a previous spatially structured study in the coastal Baltic Sea, we assessed resuspension potential across a mud-sand sedimentary gradient encompassing 18 sites (Joensuu et al 2018), from which we selected three sites to resolve the interactions between space and time. The three sites spanned the range of sedimentary properties (median grain size 58-271 μm; muddy, mixed and sandy sediment) and associated benthic communities sampled previously.…”