Wetland plant growth in recycled glass sand versus dredged river sand: evaluating a new resource for coastal restoration

Sand made from recycled glass cullet could supplement limited dredged river sand (dredge) in coastal wetland restorations; however, its suitability for wetland plants is unknown. In two experiments, we compared the biomass of several wetland plants in recycled glass sand to growth in dredge. First, we grew Salix nigra , Zizaniopsis miliacea , and Sporobolus alterniflorus in fine‐ and coarse‐glass sands, dredge, and a coarse‐glass/dredge mixture. Second, we grew Taxodium distichum and Schoenoplectus californicus in a revised coarse‐glass blend, dredge, and a mix. We characterized the substrate porosity, particle density, and bulk density for both experiments and tested how substrate nutrients, metals, and pH impacted S. californicus leaf contents. We found species‐specific responses to substrates: herbaceous species grew better in the mix and dredge than in glass alone, whereas trees grew equally well in the coarse glass, mix, and dredge. Glass sand was less dense than dredge. When saturated and compressed, finer‐grained glass sand and mixes had lower estimated porosities than coarser glass sand and dredge. S. californicus leaf chemistry resembled that of the plant's substrate. This study demonstrated that wetland plants can grow in glass sand, that mixtures of glass and dredge have species‐specific effects, and that substrate structure and chemistry could help explain these differences. Thus, it opens the door for broader field studies on how glass sand can best be used in coastal restoration efforts.