Flow Structure Of A Heterogeneous Seagrass Canopy

Abstract

Seagrass canopies are widely recognized for their ecosystem services (Barbier et al., 2011) including flow and wave attenuation (Ondiviela et al., 2014), sediment stabilization (De Boer, 2007), carbon sequestration (Duarte & Krause-Jensen, 2017) and nutrient deposition (Gacia et al., 2002). Over the past decades, various studies have delved into the modifications imparted by a seagrass canopy under both unidirectional and oscillatory flow at various scales. However, until recently, the majority of studies have either reported on or modeled seagrass canopies without considering the heterogeneity of species within a single canopy. While simplified prototype models offer valuable insights into system dynamics, they can introduce biases, potentially leading to the reduction or amplification of relevant physical processes (Tinoco et al., 2020). For instance, the study by Weitzman et al. (2015) emphasized the significance of considering vertical heterogeneity in a canopy. They noted that the presence of an understory can modulate near-bed flow processes differently, with flow attenuation significantly increased due to the understory's presence. However, embedded physical mechanisms and quantitative limitations in ecosystem functioning and services are only little understood. Such a knowledge gap is pointed out in the recent review by Risandi et al. (2023) regarding field studies of seagrass meadows in Indonesia. Only few studies explore the interaction between such a heterogeneous canopy (Short et al., 2011) and hydrodynamics despite the abundance of seagrass species in the region (McKenzie et al., 2020). Through physical modeling of four different species of seagrass this study aims to improve the understanding of flow structure modulated by a heterogeneous canopy under unidirectional currents at full scale.