MEGABENTHIC RECOLONIZATION IN AN EXPERIMENTALLY DISTURBED ABYSSAL MANGANESE-NODULE AREA

The near total removal of manganese nodules during commercial deep-sea mining will destroy the habitat of the benthic hard-bottom fauna with in the mined areas and result in the formation of a soft-bottom commun ity of lower diversity In 1989 the first large-scale and long-term exp eriment, DISCOL, was initiated in the abyssal tropical southeastern Pa cific Ocean to study the impact of disturbances similar to ocean minin g on the deep-sea fauna. The megabenthic assemblage and the recoloniza tion of the disturbed area were monitored during three cruises of the German research vessel SONNE by use of an Ocean Floor Observation Syst em with real-time TV and ''photo-on-command'' capabilities. The result s of the image analyses of the baseline and three postimpact studies d emonstrate not only a direct impact within the disturber tracks, but a lso an apparent impact on areas that were not primarily disturbed. Com mercial mining will create a sediment plume, which will drift away wit h near-bottom currents and also affect animals outside the mined areas . Reduction of environmental effects remains an important objective du ring development of future nodule collector systems.