Role of eelgrass on bed‐load transport and sediment resuspension under oscillatory flow

Abstract

Coastal vegetation is widely attributed to stabilize sediment. While most studies focused on how canopy causes flow reduction and thereby affects sediment dynamics, the role of roots and rhizomes on stabilizing the surface sediment has been less well studied. This study aims to quantify interactions between above‐ and belowground biomass of eelgrass (i.e., living Zostera marina plants and mimics) with surface sediment erosion (i.e., bed load and suspended load), under different hydrodynamic forcing that was created using a wave flume. Belowground biomass played an important role preventing bed‐load erosion, by roughly halving the amount of sediment transported after being exposed to maximal orbital velocities of 27 cm s−1, with and without canopy. Surprisingly, for suspended sediment transport, we found opposite effects. In the presence of eelgrass, the critical erosion threshold started at lower velocities than on bare sediment, including sand and mud treatments. Moreover, in muddy systems, such resuspension reduced the light level below the minimum requirement of Z. marina. This surprising result for sediment resuspension was ascribed to a too small eelgrass patch for reducing waves but rather showing enhanced turbulence and scouring at meadow edges. Overall, we conclude that the conservation of the existent eelgrass meadows with developed roots and rhizomes is important for the sediment stabilization and the meadow scale should be taken into account to decrease sediment resuspension.

Effects of Sediments Phosphorus Inactivation on the Life Strategies of Myriophyllum spicatum: Implications for Lake Restoration

“…In our study, phosphorus inactivation by the addition of Phoslock ® reduces the total biomass of M. spicatum, which may increase the risk of sediment resuspension and nutrients released from the sediments. However, Marin-Diaz et al [74] showed that the effects of macrophytes on sediment resuspension were positively highly related to their underground biomass. In the present study, the number and biomass of roots of M. spicatum were significantly enhanced by the addition of Phoslock ® .…”

Metabarcoding of environmental samples suggest wide distribution of eelgrass (Zostera marina) pathogens in the north Pacific

“…In the north Pacific, the predominant seagrass species is eelgrass, Zostera marina, a widely distributed marine angiosperm adapted to the cold waters of northern high latitudes. Eelgrass meadows provide valuable habitat for diverse animal assemblages -including salmon (Salmonidae), Dungeness crab (Metacarcinus magister), herring (Clupeidae), and gunnels (Pholidae) to name a few -and function as an important primary producer and erosion stabilizer in coastal ecosystems (Asmala et al 2019;Olson et al 2019;Marin-Diaz et al 2020). In Alaska, eelgrass meadows also provide critical foraging habitat for migrating avian species, including most of the world's population of Pacific black brant (Branta bernicla nigricans) (Ward et al 2005).…”

Making realistic wave climates in low‐cost wave mesocosms: A new tool for experimental ecology and biogeomorphology

“…This wave mesocosm system is suitable to study long-term interactions between benthic organisms and wave exposure for a single organism or for a community of organisms. For example, interactions between wave exposure and coastal vegetation (Wolaver et al 1985;Koch et al 2010;Infantes et al 2011;La Nafie et al 2012), erosion of sediment (Lo et al 2017;Wang et al 2017;Marin-Diaz et al 2020), animal behavior (Stoll et al 2010), and animal plasticity and adaptations to flow (Trussell 1997;Trussell 2002;Le Pennec et al 2017). The wave mesocosms has also applications for freshwater ecosystems, for example, in water mixing in lakes and freshwater ecology (Blottière et al 2017;Hulot et al 2017).…”

“…(Cao et al 2020), how sediment motion is affected by plant canopies? (Wang et al 2017; Marin‐Diaz et al 2020), when plant roots reduce erosion? (Lo et al 2017).…”