Oceanography and Marine Biology: An Annual Review Volume 42 (Oceanography and Marine Biology)

442 Pages·2001·10.53 MB·English

by  R. N. Gibson

OCEANOGRAPHY
and
MARINE BIOLOGY
AN ANNUAL REVIEW
Volume 42
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OCEANOGRAPHY
and
MARINE BIOLOGY
AN ANNUAL REVIEW
Volume 42
Editors
R.N. Gibson
Scottish Association for Marine Science
The Dunstaffnage Marine Laboratory
Oban, Argyll, Scotland
[email protected]
R.J.A. Atkinson
University Marine Biology Station Millport
University of London
Isle of Cumbrae, Scotland
[email protected]
J.D.M. Gordon
Scottish Association for Marine Science
The Dunstaffnage Marine Laboratory
Oban, Argyll, Scotland
[email protected]
Founded by Harold Barnes
CRC PR ESS
Boca Raton London New York Washington, D.C.
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Library of Congress Cataloging-in-Publication Data
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Contents
Preface vii
Convective Chimneys in the Greenland Sea: A Review of Recent Observations 1
Peter Wadhams
The Role of Dimethylsulphoxide in the Marine Biogeochemical Cycle
of Dimethylsulphide 29
Angela D. Hatton, Louise Darroch & Gill Malin
The Essential Role of Exopolymers (EPS) in Aquatic Systems 57
Roger S. Wotton
Marine Microbial Thiotrophic Ectosymbioses 95
J. Ott, M. Bright & S. Bulgheresi
The Marine Insect Halobates (Heteroptera: Gerridae): Biology, Adaptations,
Distribution, and Phylogeny 119
Nils Møller Andersen & Lanna Cheng
The Ecology of Rafting in the Marine Environment. I. The Floating Substrata 181
Martin Thiel & Lars Gutow
Spawning Aggregations of Coral Reef Fishes: Characteristics, Hypotheses, Threats
and Management 265
John Claydon
Impacts of Human Activities on Marine Animal Life in the Benguela: A Historical
Overview 303
C.L. Griffiths, L. van Sittert, P.B. Best, A.C. Brown, B.M. Clark, P.A. Cook, R.J.M. Crawford,
J.H.M. David, B.R. Davies, M.H. Griffiths, K. Hutchings, A. Jerardino, N. Kruger,
S. Lamberth, R.W. Leslie, R. Melville-Smith, R. Tarr & C.D. van der Lingen
Author Index 393
Systematic Index 421
Subject Index 428
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Preface
The 42nd volume of this series contains eight reviews written by an international array of authors
that, as usual, range widely in subject and taxonomic and geographic coverage. The majority of
articles were solicited, but the editors always welcome suggestions from potential authors for topics
they consider could form the basis of appropriate contributions. Because an annual publication
schedule necessarily places constraints on the timetable for submission, evaluation, and acceptance
of manuscripts, potential contributors are advised to make contact with the editors at an early stage
of preparation so that the delay between submission and publication is minimised.
The editors gratefully acknowledge the willingness and speed with which authors complied
with the editors’ suggestions, requests, and questions. This year has also seen further changes in
publisher (CRC Press) and in the editorial team and it is a pleasure to welcome Dr. J.D.M. Gordon
as a co-editor for the series.
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CONVECTIVE CHIMNEYS IN THE GREENLAND SEA:
A REVIEW OF RECENT OBSERVATIONS
PETER WADHAMS
Scottish Association for Marine Science, Dunstaffnage Marine Laboratory,
Oban PA37 1QA, Scotland, and
Department of Applied Mathematics and Theoretical Physics,
University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, England
E-mail: [email protected]
[email protected]
Abstract The nature and role of chimneys as a mode of open-ocean winter convection in the
Greenland Sea are reviewed, beginning with a brief summary of Greenland Sea circulation and of
observations of convection and of the resulting water structure. Then recent observations of long-
lived chimneys in the Greenland Sea are described, setting them within the context of earlier
observations and models. The longest-lived chimney yet seen in the world ocean was discovered
in March 2001 at about 75˚N 0˚W, and subsequent observations have shown that it has survived
for a further 26 months, having been remapped in summer 2001, winter 2002, summer 2002, and
April–May 2003. The chimney has an anticyclonically rotating core with a uniform rotation rate
of f/2 to a diameter of 9 km; it passes through an annual cycle in which it is uniform in properties
from the surface to 2500 m in winter, while being capped by lower-density water in summer
(primarily a 50-m-thick near-surface layer of low salinity and a 500-m-thick layer of higher salinity).
The most recent cruise also discovered a second chimney some 70 km NW of the first, and
accomplished a tightly gridded survey of 15,000 km2 of the gyre centre, effectively excluding the
possibility of further chimneys. The conclusion is that the 75˚/0˚chimney is not a unique feature,
but that Greenland Sea chimneys are rare and are probably rarer than in 1997, when at least four
rotating features were discovered by a float survey. This has important implications for ideas about
chimney formation, for deepwater renewal in the Greenland Sea, and for the role of Greenland Sea
convection in the North Atlantic circulation.
Convection in the world ocean
Open-ocean deep convection is a process of ventilation, not associated with coastal processes, that
feeds the global thermohaline circulation. It occurs in winter at only three main Northern Hemi-
sphere sites (Greenland, Labrador, and Mediterranean Seas) as well as in the Weddell Sea and a
small number of other locations in Antarctica. These sites are of small geographical extent, occu-
pying only a few thousandths of the area of the world ocean, yet they are of great importance for
climate, because it is only through deep ventilation that a complete vertical circulation of the ocean
can take place, with dissolved gases and nutrients cycling back into the depths. In some cases
intense atmospheric cooling alone increases the surface water density to the point where the
overturning and sinking can occur. In others, sea ice is involved. The modes of convection at the
various key sites have been reviewed by Marshall & Schott (1999).
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Oceanography and Marine Biology: An Annual Review 2004 42, 29–56 1
© R. N. Gibson, R. J. A. Atkinson, and J. D. M. Gordon, Editors