Ecological impacts of large-scale disposal of mining waste in the deep sea.

David J Hughes,John A Howe,Tracy M Shimmield,Kenneth D Black

doi:10.1038/srep09985

Abstract

Deep-Sea Tailings Placement (DSTP) from terrestrial mines is one of several large-scale industrial activities now taking place in the deep sea. The scale and persistence of its impacts on seabed biota are unknown. We sampled around the Lihir and Misima island mines in Papua New Guinea to measure the impacts of ongoing DSTP and assess the state of benthic infaunal communities after its conclusion. At Lihir, where DSTP has operated continuously since 1996, abundance of sediment infauna was substantially reduced across the sampled depth range (800–2020 m), accompanied by changes in higher-taxon community structure, in comparison with unimpacted reference stations. At Misima, where DSTP took place for 15 years, ending in 2004, effects on community composition persisted 3.5 years after its conclusion. Active tailings deposition has severe impacts on deep-sea infaunal communities and these impacts are detectable at a coarse level of taxonomic resolution.

Highlights

Its ecological consequences is a significant gap in our knowledge of anthropogenic impacts in the deep sea
The content of several tailings-derived trace metals was much higher in cores from L1-L3 with, for example, solid-phase lead ranging from 3.8–6.5 g m−2 at L1-L3 versus 0.6–0.7 g m−2 at L4-L6
Impact assessment using a formal “BACI” (Before-After-Control-Impact) or “Beyond BACI” sampling design[25] was not possible in this study owing to the lack of pre-Deep-Sea Tailings Placement (DSTP) benthic community data

Summary

Introduction

Its ecological consequences is a significant gap in our knowledge of anthropogenic impacts in the deep sea. The Lihir gold mine discharges ~100,000 ML tailings slurry year−1 (containing ~2.5 Mt solids) from an outfall at 128 m depth on the east coast of the island[12,13] (Fig. 1b). There are no published data for trace metal content in tailings-affected sediments off Lihir, but dispersal models ground-truthed by sediment sampling indicate a depositional “footprint” extending across a broad plain up to 20 km east of the outfall and to depths of at least 2000 m19. Available bathymetric data for the Misima area were very poor and with no accurate estimate of the total tailings “footprint”, reference stations were more difficult to define a priori. Location data for all sampling stations are listed in Supplementary Table S1

Methods

Results

Conclusion