German Environmental Risk Assessments in the Southeastern Pacific Peru Basin: DISCOL Revisited*
Authors: Foell E.J. , Bluhm H. , Borowski C. , Thiel H. , Ahnert A. , Schriever G. 
Published: October 2008

The DISCOL (disturbance-recolonization) project started in 1989 on the abyssal sea floor of the Peru Basin in the southeastern tropical Pacific Ocean with financial support from the German government. Conceived as a long-term, large-scale, in situ experiment to assess some of the key environmental impacts expected to be associated with future deep seabed mining operations, this pioneering effort has obtained results that are of interest from a basic as well as applied science perspective. Fundamental data have been and are continuing to be obtained on the rate, sequence, and direction of benthic community recolonization after severe anthropogenic disturbance.

Increasing incursion upon the deep seabed and exploitation of its abundant natural resources are inevitable, if not immediately imminent. The DISCOL project is currently part of an expandedresearch program in the Peru Basin region organized by the TUSCH (Tiefsee-Umweltschutz or Deep-sea Environment Protection) Research Group. Consisting of scientists and engineers from a number of universities and research institutions, this group is taking amulti-disciplinary approach to evaluating the potential risks and effects of human activities within the deep-sea ecosystem.

INTRODUCTION

In response to the then anticipated rapid development of a nascent manganese nodule mining industry and impending at-sea test campaigns of scaled-down mining system components, the German government in the mid-1980s requested suggestions for environmental studies to accompany planned mining technology field trials. From an environmental point of view, a key element of uncertainty is the temporal and spatial effect of an extensive deep seabed disturbance upon the sea floor biota.' Some damage in the immediate mining area is to be expected and must be accepted as a trade-off if seabed mining is ever to occur. Concerns were voiced, however, that near-bottom currents may greatly enlarge the affected region by distributing stirred up sediment materials, possibly including released toxic components, over a much wider area in the form of benthic plumes. Relatively little is known about the capacity of the deep-sea fauna to survive such impacts or recolonized a disturbed area. The range beyond the immediate impact site over which effects would still be detectable is also unknown.

After considerable deliberation and delays in realization of planned commercial mining tests, a long-term, large-scale, in situ experiment was designed and special equipment was developed to allow creation of a seabed disturbance that would in some ways mimic the impacts expected from industrial test mining. It was decided to carry out the experiment in abyssal depths of the Peru Basin near an existing German nodule mining claim area (Fig. 1). During a two-month initial cruise of the RV SONNE in February- March, 1989, (SO-61, DISCOL 1/1 and 1/2), a suitable study site was selected, pre-impact baseline samples were acquired, a severe seabed disturbance was created, and a first series of post-impact samples was obtained