Positive Growth of Phytoplankton under Conditions Enriched with Steel-making Slag Solution

Abstract

The growth ability of 12 species of phytoplankton was examined in culture media enriched with steel-making slag solution at various concentrations. Since a highly significant linear regression of the in vivo fluorescence (IVF) of cell suspension against absolute chlorophyll a concentration was established, the growth ability was determined quickly by IVF. Under the enriched conditions all the species examined showed positive growth, although in different manners. Based on the specific differences in the optimal concentration of the slag solution, 12 organisms could be divided into four groups: (I) the organisms which grow best under the highest enrichment (100%), (II) those which grow best with intermediate enrichment, but not in 100% enrichment, (III) those which grow best under enrichment lower than 60%, and (IV) those which respond inconsistently to enrichment but often grow better under enrichment. These results indicate that the slag solution has positive effects for the growth of phytoplankton, so that the slag will be utilized as nutrients in cultures for algae. On the other hand, the growth of all the four groups enhanced by the enrichment with the slag solution never exceeded the growth enhanced in an ideal culture medium, indicating that the enrichment with the slag solution can hardly be a cause of the red tide, if the enrichment is done in natural seawater.