Assessment of the benthic environment following offshore placer gold mining in Norton Sound, northeastern Bering Sea Item Type Thesis Authors Jewett, Stephen Carl Download date 04/10/2021 03:07:09 Link to Item http://hdl.handle.net/11122/9482 INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type o f computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. 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Further reproduction prohibited without permission. ASSESSMENT OF THE BENTHIC ENVIRONMENT FOLLOWING OFFSHORE PLACER GOLD MINING IN NORTON SOUND, NORTHEASTERN BERING SEA A THESIS Presented to the Faculty of the University of Alaska Fairbanks in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY By Stephen Carl Jewett, B.A., M.S. Fairbanks, Alaska December 1997 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 9816409 UMI Microform 9816409 Copyright 1998, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 i Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ASSESSMENT OF THE BENTHIC ENVIRONMENT FOLLOWING OFFSHORE PLACER GOLD MINING IN NORTON SOUND, NORTHEASTERN BERING SEA By Stephen Carl Jewett RECOMMENDED: A/i-- \ W^> < *r*Q3 d / l ___J OaamA ■ ^?a^>{vsAA< ^rrroBjt ‘^vrvvtXW- ________ nhiittee Chair jrector^bivision of Fisheries APPROVED: Dean, Schoo \{ d i Fisheries & Ocean Sciences _________ Deap^Pfhe Graduate School / ,9 ' ■ / - n ________________ Date / Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT The effects of placer gold mining on the benthic environment of Norton Sound in the northeastern Bering Sea were assessed. Research focused on red king crab Paralithodes camtschaticus, a species with commercial and subsistence importance in the Sound and seasonal occurrence in the mining area. The study addressed mining effects on: 1) benthic macroinvertebrates, many serving as food for this crab, 2) crab relative abundance, distribution, and food, and 3) heavy metal concentrations in crabs. Mining on variable substrates in < 20 m water depths occurred between 1986-90 during ice-free months when crabs were further offshore. Sampling nearly a year subsequent to mining revealed moderate substrate alteration. Benthic community parameters and abundance of numerically predominant families (e.g., owenid, spionid, and capitellid polychaetes and echinarachniid sand dollars) were reduced in mined areas. Many reduced taxa are known crab prey. Although young individuals of opportunistic taxa predominated, taxa were generally smaller at mined areas. Multi-year surveys of a once-mined area showed continued smoothing of bottom relief. Ordination of taxon abundance from mined (1 yr after mining), recolonizing (2-7 yrs after mining), and unmined stations reflected decreasing station disturbance. At least four years were required for benthos to recover from mining. Mining had a negligible effect on crabs. Crab catches, size, sex, and most prey groups in stomachs were similar between mined and unmined areas. Concentrations of eight heavy metals in muscle and hepatopancreas tissues were generally not different in mined areas. Furthermore, these metals were not different in sediments upcurrent and downcurrent of mining. Concentrations of most metals in tissues showed no temporal trend. Elemental concentrations in muscle tissues were below or within the range of iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. concentrations in red king crabs from other North Pacific locations. Most metals from Norton Sound crabs were well below federal guidance levels for human consumption. Effects from mining were apparent for benthic macrofauna with virtually no effects observed for king crabs. Absence of any demonstrable effects of mining on this crab is primarily a result of the high natural dynamics of the Sound and opportunistic feeding behavior and high mobility of the crab. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS Page ABSTRACT ....................................................................................................... iii TABLE OF CONTENTS .................................................................................... v LIST OF FIGURES........................................................................................... ix LIST OF TABLES.............................................................................................. xi ACKNOWLEDGMENTS.............................................................................. xiv INTRODUCTION.............................................................................................. I CHAPTER I : ASSESSMENT OF THE BENTHIC ENVIRONMENT FOLLOWING OFFSHORE PLACER GOLD MINING IN NORTON SOUND, NORTHEASTERN BERING SEA - 1. BENTHOS......................... 28 Introduction ................................................................................................ 29 Mining overview ................................................................................... 30 Study area .............................................................................................. 30 Methods .................................................................................................... 33 Field and laboratory ................................................................................. 33 Bathymetry and side-scan sonar .................................................... 33 Sediment ........................................................................................... 34 Macrobenthos ................................................................................... 34 Data analyses ..................................................................................... 36 Univariate analyses ........................................................................... 36 Multivariate analyses ........................................................................ 37 Results ......................................................................................................... 38 Bathymetric survey ................................................................................. 38 v .} Reproduced with permission of the copyright owner. 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TABLE OF CONTENTS (continued) Page Side-scan sonar surveys ............................................................. 38 Comparison between mined and unmined stations .................... 41 Sand substrate ........................................................................ 41 Cobble substrate .................................................................. 52 Recolonization .............................................................................. 55 Sand substrate ........................................................................ 55 Cobble substrate .................................................................. 57 Multivariate analysis .................................................................. 58 Sand substrate ........................................................................ 58 Cobble substrate .................................................................. 60 Discussion ......................................................................................... 60 Natural disturbances .................................................................. 61 Mining disturbances .............................................................. 65 Recolonization .............................................................................. 70 Conclusions ...................................................................................... 74 CHAPTER 2: ASSESSMENT OF THE BENTHIC ENVIRONMENT FOLLOWING OFFSHORE PLACER GOLD MINING IN NORTON SOUND, NORTHEASTERN