From “Natural” to Polluted Conditions in the Bunnefjord, Inner Oslofjord
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Master Thesis in Geosciences Environmental status: From “natural” to polluted conditions in the Bunnefjord, inner Oslofjord. A micropaleontological and geochemical study of a sediment core Jonas Hovd Enoksen Bildet kan ikke vises. Datamaskinen har kanskje ikke nok minne til å åpne bildet, eller bildet kan være skadet. Start datamaskinen på nytt, og åpne deretter filen på nytt. Hvis rød x fortsatt vises, må du kanskje slette bildet og deretter sette det inn på nytt. Environmental status: From “natural” to polluted conditions in the Bunnefjord, inner Oslofjord A micropaleontological and geochemical study of a sediment core Jonas Hovd Enoksen Bildet kan ikke vises. Datamaskinen har kanskje ikke nok minne til å åpne bildet, eller bildet kan være skadet. Start datamaskinen på nytt, og åpne deretter filen på nytt. Hvis rød x fortsatt vises, må du kanskje slette bildet og deretter sette det inn på nytt. Master Thesis in Geosciences Discipline: Environmental Geology - Micropaleontology Department of Geosciences Faculty of Mathematics and Natural Sciences UNIVERSITY OF OSLO 01.06.2010 © Jonas Hovd Enoksen, 2010 Tutor(s): Elisabeth Alve (UiO) and Aud Helland (Rambøll) This work is published digitally through DUO – Digitale Utgivelser ved UiO http://www.duo.uio.no It is also catalogued in BIBSYS ( http://www.bibsys.no/english ) All rights reserved. No part of this publication may be reproduced or transmitted, in any form or by any means, without permission . 4 Acknowledgements I would like to thank my supervisor Elisabeth Alve for making this project possible, supervising my thesis and always being helpful and available. My second supervisor, Aud Helland, deserves thanks for helpful sources and feedback, too. I am also grateful for all the people who helped me through this endeavour: the crew aboard R/V Trygve Braarud for assistance during the cruise; Mofak Naoroz for analyzing TOC and heavy metals, assistance and tutoring in the lab; Berit Kaasa for sample bottles and the use of autoclave; Jane Dolven, Vincent Bouchet and Silvia Hess for assistance and small-talk during microscope analyzes. “The Study desk gang” have contributed with constructive discussions and pleasant coffee- breaks, for which I am grateful and could not have coped without. Special thanks to Torill, my wife, for being supportive and understanding, and for graphical expertise. My encouraging family, deserve thanks as well. Last but not least, thanks to Primus for waking me up in the morning with a wagging tale, and crisp morning walks giving room for relaxation and reflection in hectic times. 5 Abstract The aim of this study was to assess the temporal development of the environment in Bunnefjord, the innermost part of Oslofjord (SE Norway), define its reference conditions, and link the results to other studies. A 55 cm long sediment core was collected from Bunnefjord (N59.84285, E10.72587), for micropaleontological and geochemical analyses. The core provided chronostratigraphical data for the past 300 years, dating back to the late 1600s. There was analyzed for heavy metals, total organic carbon (TOC), water content, and benthic foraminifera (protists) were picked and counted. Ecological status was determined and risk assessed using the Norwegian Pollution Control Authority’s guides. The natural conditions, around 1700 AD, were found to be of ecological class “Moderate”. Subsequently, the anthropogenic induced increase of organic carbon content and in turn deteriorating oxygen concentrations at the end of the 1800s worsened the ecological status. The pollution and organic-flux maxima were in the 1970s, and there has been some improvement ever since. However, the ecological status has been kept at “Very Bad”, due the slow remediation. There was established risk for ecological consequences and need for mitigating measures from 1925 until present. The present study displayed worse conditions than others nearby, due to the location within a small subbasin. Keywords: silled fjord; benthic foraminifera; natural conditions; environmental status; ecotoxicological risk assessment; Oslofjord. Nøkkelord: terskelfjord; benthiske foraminiferer; naturtilstanden; miljøstatus; økotoksikologisk risikoanalyse; Oslofjorden. 6 Table of Contents ACKNOWLEDGEMENTS ................................................................................................................. 5 ABSTRACT........................................................................................................................................... 6 TABLE OF CONTENTS ..................................................................................................................... 7 1. INTRODUCTION ...................................................................................................................... 9 2. LOCATION DESCRIPTION .................................................................................................. 12 2.1 GENERAL SETTING – GEOGRAPHY , HYDROGRAPHY AND GEOLOGY OF THE OSLOFJORD ......... 12 2.2 POLLUTION HISTORY .............................................................................................................. 15 2.3 PREVIOUS STUDIES IN BUNNEFJORD ....................................................................................... 18 2.4 MODERN FORAMINIFERA FAUNA IN OSLOFJORD .................................................................... 18 3. METHOD .................................................................................................................................. 21 3.1 SAMPLING PROCEDURES ......................................................................................................... 21 3.2 LABORATORY PROCEDURES ................................................................................................... 21 3.3 ENVIRONMENTAL QUALITY AND RISK ASSESSMENT ............................................................... 25 4. RESULTS .................................................................................................................................. 27 4.1 PHYSICAL AND GEOCHEMICAL PROPERTIES ............................................................................ 27 4.2 FORAMINIFERAL DATA ........................................................................................................... 35 4.3 RISK ASSESSMENT .................................................................................................................. 41 5. DISCUSSION ............................................................................................................................ 42 5.1 GEOCHEMICAL AND PHYSICAL FACTORS ................................................................................ 42 5.1.1 Dating and age model ................................................................................................. 42 5.1.2 Salt correction ............................................................................................................. 43 5.1.3 Heavy metals ............................................................................................................... 44 7 5.1.4 Water content ............................................................................................................. 45 5.1.5 Total Organic Carbon ................................................................................................ 46 5.2 MICROPALEONTOLOGICAL FACTORS ..................................................................................... 48 5.2.1 General micropaleontological factors ....................................................................... 48 5.2.2 Foraminiferal factors ................................................................................................. 50 5.3 CHRONOLOGICAL DEVELOPMENT .......................................................................................... 54 5.3.1 Period 1 (1680 – 1800 AD): “Natural conditions” ................................................... 54 5.3.2 Period 2 (1800 – 1885 AD): Transition fauna ........................................................... 55 5.3.3 Period 3 (1885 – 1940 AD): Anthropogenic impact .................................................. 55 5.3.4 Period 4 (1940 – 2000 AD): “All time low”, and time for mitigation ....................... 56 5.3.5 Period 5 (2000 AD – present): Amendment ............................................................... 56 5.4 A COMPARISON WITH RISDAL ’S (1963) BUNNEFJORD CORE .................................................. 57 5.5 ENVIRONMENTAL STATUS AND RISK ASSESSMENT ................................................................ 60 6. CONCLUSIONS ...................................................................................................................... 62 REFERENCES ................................................................................................................................... 64 APPENDIX A: FAUNAL REFERENCE LIST ............................................................................... 71 APPENDIX B: FORAMINIFERAL DATA .................................................................................... 74 8 1. Introduction The Water Framework Directive of the European Commission, which Norway has endorsed, claims reestablishment of near natural conditions for all manageable bodies of water (EuropeanCommunities 2003). This brings forth the question: What are the natural conditions? In the present study it is defined as pre-industrial conditions, seeing that they presumably are exposed to minor anthropogenic influence. That definition