POTENTIAL ENVIRONMENTAL-IMPACT OF DEEP SEABED MANGANESE-NODULE MININGON THE SYNECHOCOCCUS (CYANOBACTERIA) IN THE NORTHEAST EQUATORIAL PACIFIC - EFFECT OF BOTTOM WATER-SEDIMENT SLURRY

Synechococcus (photoautotrophic cyanobacteria) are among the major pri mary producers in the oligotrophic open ocean. Potential environmental impacts of bottom water and sediment intrusion on the Synechococcus p opulation in the surface water column of the northeast equatorial Paci fic were investigated during the KODOS (Korea Deep Ocean Study) 95-2 c ruise. The growth of Synechococcus was limited primarily by Fe deficit and secondarily by nitrogenous nutrients. Since bottom water and sedi ment are abundant in both inorganic nutrients and trace metals, the ad dition of bottom water-sediment slurry to surface water samples stimul ated the growth of Synechococcus. Our results together with other expe rimental estimation suggest that certain impacts could occur on the ph otoautotrophic plankton biomass in the water column by the surface dis charge of bottom water and sediment during large-scale and long-term c ommercial mining of Mn nodules. More quantitative estimation for those environmental aspects in the water column is necessary for the constr uction of environmentally affiliated mining systems in the future.