To date findings demonstrate that the Microdictyon umbilicatum bloom biomass can be effectively composted with terrestrial greenwaste to provide a soil conditioner with a useful macronutrient and trace element profile, and with no evidence of metal contamination of concern. As expected with an unwashed marine algal source, the sodium concentrations were elevated and dosing of % seaweed biomass in compost should be controlled accordingly. Native plant growth responses to Microdictyon umbilicatum enhanced compost were positive up to 5% compost content in a 1:1 mix with potting mix (total 2.5% seaweed biomass), with increased growth rates for both species; saltbush (Rhagodia candoleana) and Coastal Banksia (Banksia integrifolia). Salt bush maintained enhanced growth rates for the 10% and 20% compost additions as well, but showed most benefit at 5% as an increase in leaf abundance as well. Banksia did not respond as well to higher seaweed concentration composts.