Sedimentation and drag in drifting macrophytes and plastic objects: A model

Abstract

Predicting macroalgal sedimentation and drag sensitivity is essential for ecological and geochemical modeling, and for optimizing seaweed cultivation. However, despite the diversity of macrophyte forms, models incorporating their specific morphology and hydrodynamic effects are largely lacking. To develop a broadly applicable model, we tested whether the drag response of diverse macrophyte morphologies and plastic objects can be accurately predicted by approximating them as ellipsoids and accounting for their specific shapes. A set of simple shape descriptors (wet weight, volume, thallus thickness, thallus projection area) and an empirical solution for the drag equation, enabled relative accurate predictions of the sinking velocity for 26 morphologically diverse macroalgae species, as well as the eelgrass Zostera marina, another major source of drifting biomass in many shallow seas. Additionally, we identified a second simpler empirical solution that incorporates shape and, while slightly less accurate, can be applied to a broader range of particles, including plastics. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=145 SRC="FIGDIR/small/651208v1_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@184bf04org.highwire.dtl.DTLVardef@18dce9org.highwire.dtl.DTLVardef@4f5b9dorg.highwire.dtl.DTLVardef@7aad5_HPS_FORMAT_FIGEXP M_FIG Graphical abstract C_FIG