The Baltic Sea

THE BALTIC SEA FURTHER TITLES I N THIS SERIES 1 J.L.MER0 THE MINERAL RESOURCES OF THE SEA 2 L.M. FOMIN THE DYNAMIC METHOD I N OCEANOGRAPHY 3 E.J.F. WOOD MICROBIOLOGY OF OCEANS A N D ESTUARIES 4 G.NEUMANN OCEAN CURRENTS 5 N.G.JERLOV OPTICAL OCEANOGRAPHY 6 V.VACQUIER GEOMAGNETISM IN MARINE GEOLOGY 7 W.J. WALLACE THE DEVELOPMENT OF THE CHLORINITY/SALINITY CONCEPT I N OCEANOGRAPHY 8 E. L l S l T Z l N SEA-LEVEL CHANGES 9 R.H.PARKER THE STUDY OF BENTHIC COMMUNITIES 10 J.C.J. NIHOUL (Editor) MODELLING OF MARINE SYSTEMS 11 0.1. MAMAYEV TEMPERATURE-SALINITY ANALYSIS OF WORLD OCEAN WATERS 12 E.J. FERGUSON WOOD and R.E. JOHANNES (Editors) TROPICAL MARINE POLLUTION 13 E. STEEMANN NIELSEN MAR1N E PHOTOSYNTH ESlS 14 N.G. JERLOV MARINE OPTICS 15 G.P. GLASBY (Editor) MARINE MANGANESE DEPOSITS 16 V.M. KAMENKOVICH FUNDAMENTAL OF OCEAN DYNAMICS 17 R.A. GEYER (Editor) SUBMERSIBLES A N D THEIR USE IN OCEANOGRAPHY AN D OCEAN ENGINEERING 18 J.W. CARUTHERS FUNDAMENTALS OF MARINE ACOUSTICS 19 J.C.J. NIHOUL (Editor) BOTTOM TURBULENCE 2 0 P.H. LEBLOND and L.A. MYSAK WAVES I N THE OCEAN 21 C.C. VON DER BORCH (Editor) SYNTHESIS OF DEEP-SEA DRILLING RESULTS IN THE IN D IAN OCEAN 22 P. DEHLINGER MARINE GRAVITY 23 J k J . NIHOUL (Editor) HYDRODYNAMICS OF ESTUARIES A N D FJORDS 24 F.T. BANNER, M.B. COLLINS and K.S. MASSIE (Editors) THE NORTH-WEST EUROPEAN SHELF SEAS: THE SEA BED AN D THE SEA I N MOTION 25 J.C.J. NIHOUL (Editor) MARINE FORECASTING 26 H.-G. RAMMING and Z. KOWALIK NUMERICAL MODELLING OF MARINE HYDRODYNAMICS 27 R.A. GEYER (Editor) MARINE ENVIRONMENTAL POLLUTION 28 J.C.J. NIHOUL (Editor) MARINE TURBULENCE 29 M. WALDICHUK, G.B. KULLENBERG and M.J. ORREN (Editors) MARINE POLLUTANT TRANSFER PROCESSES Elsevier Oceanography Series, 30 THE BALTIC SEA edited by AARNO VOlPlO Institute of Marine Research, Helsinki, Finland ELSEVIER SCIENTIFIC PUBLISHING COMPANY Amsterdam - Oxford - New York 1981 ELSEVIER SCIENTIFIC PUBLISHING COMPANY 1, Molenwerf 1014 AG Amsterdam P.O. Box 21 1, lo00 AE Amsterdam, The Netherlands Distributors for the United States and Canada: ELSEVIERINORTH-HOLLAND INC. 52, Vanderbilt Avenue New York, N.Y. 10017 Library of Congress Calsloging in Publicalion Data Main e n t r y under t i t l e : The B a l t i c Sea. ( E l s e v i e r oceanography s e r i e s ; 30) Includes b i b l i o g r a p h i e s end index. 1. Oceenopaphy--Baltic Sea. 2. Marine biology-Baltic Sea. 3. Fisheries-Baltic Sea. 4. Marine pollution--Baltic Sea. I. Voipio, Aarno, 1926- CC571.B24 551.46'134 0-444-41864-9 80-17385 ISBN ISBN 044441884-9(Vol. 30) ISBN 0444416234 (Series) 0 Elsevier Scientific Publishing Company, 1981 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic mechanical, photocopying, recording or otherwise, without the prior written permission of the publication, Elsevier Scientific Publishing Company, P.O. Box 330,1000 AH Amsterdam, The Netherlands Printed in The Netherlands V PREFACE The Baltic Sea is neither an ocean nor a lake, but a large brackish-water basin with very pronounced density stratification prevailing the whole year round. In addition to this, its recent geological history has been very complicated, resulting in profound changes in the hydrographic conditions and subsequently also in the biological features of this sea during the last ten thousand years. The above special features make it rather difficult for a deep-sea oceanographer to find the marked differences in physical properties between the shallow Baltic Sea and, for instance, the shelf seas with a similar mean depth. A limnologist, on the other hand, seems to have equal problems in remembering t