The Impact of Coastal and Marine Mines on Seabed Biological Resources: Engineering Needs for Sustainable Recovery and for Use of the Resources after Mining Ceases

2002

Coastal and marine mines affect the seabed's biological resources when large volume wastes such as tailings and waste rock are placed in the sea, and by the extraction processes from marine mining. The biological resources are seabed fisheries, such as crabs and halibut, and the feedstock for the fisheries, i.e. benthic organisms. There are now thirty years of detailed monitoring data for assessing tailings impact, and biodiversity recovery of the fisheries feedstock from that impact, largely from the Island Copper mine and Kitsault molybdenum mine, both in Canada, but also from about 20 other sites scattered around the world. There is corresponding data available on the impact of extraction processes especially from marine mining for gold, diamonds, construction aggregate and borrow sand. Under current best environmental practices for submarine tailings placement, the seabed fishery feedstock will be temporarily reduced by action of the tailings density current flow, and by smothering where the tailings are most rapidly depositing (approximately >20cm/yr). However, the feedstock will recover on seabed stabilization to a sustainable ecological succession supporting bottom-feeding fishery stocks within approximately 1-3 years depending on the particle size of the tailings deposits. This can be readily documented as a sustaining ecological succession is easily measured. Further engineering developments are needed to ensure minimum destabilization of the deposited materials by slumping or other erosional forces. These generate setbacks to the ecological succession, and it is important for seabed biodiversity recovery to develop engineering procedures to predict and minimize potential destabilization of deposited tailings. The paper will present the data from the Island Copper mine and elsewhere to support these statements.

Keywords: Marine benthos, Coastal mines, Sustainable recovery, Ecological succession, Primary opportunist species, Tailings stability, Island mines, Equilibirum community, Marine mining, Submarine Tailings Disposal