Potential environmental impact of deep seabed manganese nodule mining on the Synechococcus (cyanobacteria) in the northeast equatorial Pacific: Effect of bottom water-sediment slurry

Abstract

Synechococcus (photoautotrophic cyanobacteria) are among the major primary producers in the oligotrophic open ocean. Potential environmental impacts of bottom water and sediment intrusion on the Synechococcus population in the surface water column of the northeast equatorial Pacific were investigated during the KODOS (Korea Deep Ocean Study) 95-2 cruise. The growth of Synechococcus was limited primarily by Fe deficit and secondarily by nitrogenous nutrients. Since bottom water and sediment are abundant in both inorganic nutrients and trace metals, the addition of bottom water-sediment slurry to surface water samples stimulated the growth of Synechococcus. Our results together with other experimental estimation suggest that certain impacts could occur on the photoautotrophic plankton biomass in the water column by the surface discharge of bottom water and sediment during large-scale and long-term commercial mining of Mn nodules. More quantitative estimation for those environmental aspects in the water column is necessary for the construction of environmentally affiliated mining systems in the future.