Evaluation of steelmaking slag as basal media for coastal primary producers

- Marine algae on dephosphorization slag mixed with dredged sediment was examined.
- The algal species composition and biomass were influenced by the sediment.
- Shear strength and pH of the sediment were higher than those of natural tidal flats.
- Dephosphorization slag contributes to changing algal composition and sediment environment.

The use of granular steelmaking slag as a substitute for natural sand in the construction of tidal flats was investigated. Using an intertidal flat simulator, we evaluated dephosphorization slag mixed with 8% by dry weight of dredged sediment (DPS + DS) as a basal medium for the growth of benthic macro- and microalgae in comparison with silica sand mixed with 8% dredged sediment (SS + DS). Species compositions of macro- and microalgae were distinctly different between DPS + DS and SS + DS. The mean dry weight of macroalgae on DPS + DS was three orders of magnitude higher than that on SS + DS. Sediment shear strength and pH were higher in DPS + DS than in SS + DS or in the sediment of natural tidal flats. These results suggest that DPS contributes to changing the sediment environment, thereby changing the algal composition compared to the composition on natural tidal flats.

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