POSITIVE GROWTH OF PHYTOPLANKTON UNDER CONDITIONS ENRICHED WITH STEEL-MAKING SLAG SOLUTION

The growth ability of 12 species of phytoplankton was examined in cult ure media enriched with steel-making slag solution at various concentr ations. Since a highly significant linear regression of the in vivo fl uorescence (IVF) of cell suspension against absolute chlorophyll a con centration 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 orga nisms could be divided into four groups: (I) the organisms which grow best under the highest enrichment (100%), (II) those which grow best w ith intermediate enrichment, but not in 100% enrichment, (III) those w hich grow best under enrichment lower than 60%, and (IV) those which r espond inconsistently to enrichment but often grow better under enrich ment. These results indicate that the slag solution has positive effec ts 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 a ll the four groups enhanced by the enrichment with the slag solution n ever exceeded the growth enhanced in an ideal culture medium, indicati ng that the enrichment with the slag solution can hardly be a cause of the red tide, if the enrichment is done in natural seawater.