The influence of hydrodynamics and ecosystem engineers on eelgrass seed trapping
Fig 7
Conceptual diagram on interactions between habitat complexity, sediment scouring, flow velocity and seed trapping.
Red arrows indicate negative effect, blue arrows indicate positive effect. Solid arrows correspond to direct effect; dashed arrows correspond to indirect and potential effect. (1) Trapping of eelgrass seeds increases with epibenthic complexity provided by e.g. eelgrass canopy or bivalves (Fig 2; S1 Table; S2 Table); (2) Turbulent conditions increase with complexity of the system (Fig 5B); (3) An increase in turbulence can cause erosion processes [36, 48], increasing surface complexity; (4) Surface complexity increases seed trapping (Fig 4); (5) Epibenthic complexity negatively affects flow velocity (Fig 5A); (6) Flow velocity increases the effect of habitat complexity on turbulent flow (Fig 5B) and sediment scouring (Fig 2D–2F; S4 Table), thus contributing indirectly to seed trapping; (7) The direct effect of flow velocity on seed trapping is assumed negative (Fig 4, [38]); (8) As there is a density dependent effect of eelgrass shoots on seed trapping, while germination success of seeds is independent of density [56], we suggest the existence of a positive feedback over time, facilitating eelgrass patch emergence. Symbols from IAN Symbol Libraries.