Assessment of the benthic environment following offshore placer gold mining in the northeastern Bering Sea

The effects of offshore placer gold mining on benthic invertebrates were as sessed on 'sand' and 'cobble' substrates in Norton Sound, northeastern Beri ng Sea. Mining with a bucket-line dredge occurred nearshore in 9-20 m durin g June to November 1986-90. Sampling nearly a year subsequent to mining dem onstrated minor alteration of substrate granulometry with no clear trends. However, benthic macrofaunal community parameters (total abundance, biomass , diversity) and abundance of dominant families were significantly reduced ar mined stations. Many of the dominant taxa are known prey of the locally important red king crab (Paralithodes camtschaticus). Dominance of opportun istic species and small sizes at unmined and mined sites represents faunal responses to the natural dynamics of the region where establishment of popu lations of large, sexually-mature individuals is typically precluded. Multi -year bathymetric surveys of an area only mined in 1986 showed a continued smoothing of ocean bottom relief, decreasing size of tailing footprint, and shoaling of depressions left by mining. An ordination (multidimensional sc aling) of taxon abundance data from mined (1 year after mining), recolonizi ng(2-7 years after mining) and unmined stations shows configurations that r eflect disturbance. Recovery of the biota was underway in both substrates a fter 4 years, but this process was interrupted in the fall of the fourth ye ar (1990) by several severe storms. Mining effects are contrasted with loca l natural disturbances. (C) 1999 Elsevier Science Ltd. All rights reserved.