Light exposure in seagrass meadows is modified by flow-driven plant reconfiguration

Seagrasses are foundation species in marine and estuarine ecosystems. They contribute biomass, provide habitat, and damp waves and currents. Globally, seagrass health and primary productivity are particularly threatened by factors that affect light availability, such as shading by algae, self-shading, and increased water column turbidity. This study focuses on how plant motion and reconfiguration lead to shading of an individual plant, and how flow conditions, plant flexibility, and plant density affect light availability along a seagrass blade. We use a simple ray-optics shading model with simulations of plant motion using the model of Zhu et al. (2020). Results show the effect of wave orbital excursion on plant shading, as well as the more complex dynamics that arise for blades with greater flexibility or asymmetry in their motion. We develop a parameterized model that can be used when field conditions, such as seagrass species characteristics and wave statistics, are known, in order to predict light exposure in seagrass meadows globally.