Past and Present Water Column Anoxia

Life on Earth emerged under anaerobic conditions. Many fundamental b- chemical and metabolic pathways evolved before the atmosphere contained oxygen. Today, anaerobic (anoxic) conditions in marine milieus are generally restricted to sediments and to basins isolated from oxygenated deep-sea cir- lation. Oxygen-de?cientorhypoxicconditionsarede?nedinoperationalterms. In speaking of the degree of O -de?ciency, the term hypoxic is usually de?ned 2 as ranging between 22 and 64?MofO , while suboxic refers to a range below 2 10?M, and anoxic is the complete absence of oxygen. Biologists commonly use the term hypoxia to describe the point at which animals suffocate. But the papers presented in this book deal with the whole range of oxygen-de?cient conditions, and the de?nitions some authors have used here may vary. Enhanced oxygen consumption by decomposition of organic matter and slow downward mixing and diffusion of dissolved oxygen from the surface waters can lead to oxygen de?ciency in the water column in highly productive waters, forming the Oxygen Minimum Zone (OMZ). Bottom waters of coastal upwelling regions are frequently exposed to hypoxic (suboxic) or anaerobic conditions owing to extremely high primary productivity. The development of these conditions represents an acute perturbation to ecological dynamics and ?sheries. Inthepast,anoxicconditionsinthewatercolumnmayhavedeveloped morereadily. Oceanicanoxicevents(OAE)wereepisodesofgloballyenhanced organic carbon burial that signi?cantly affected global climate by reducing atmospheric CO . An excess of nutrient loading leads to eutrophication of 2 coastal areas and enclosed seas, a wide-spread global problem.

Covers biogeochemical features of anoxic conditions in the past and present world ocean Discusses most significant issues related to oxic/anoxic environments and transformations Strongly interdisciplinary including issues from various disciplines such as marine geology and paleoceanography, physical, chemical and biological oceanography, marine ecology, molecular ecology and microbiology Most contributions in the book are review-type contributions, which would be interesting for both, specialists in the field and students of environmental subjects

Résumé
Proceedings of the NATO Advanced Research Workshop, held in Yalta, Crimea, Ukraine, 4-8 October 2003

Contenu
MARINE ANOXIA DURING EARTH HISTORY.- ANOXIA THROUGH TIME.- THE PALEOME: LETTERS FROM ANCIENT EARTH.- SULFUR AND METHANE CYCLING DURING THE HOLOCENE IN ACE LAKE (ANTARCTICA) REVEALED BY LIPID AND DNA STRATIGRAPHY.- ANOXIA AND OXYGEN DEFICIENCY OF THE PRESENT WORLD OCEAN.- BIOGEOCHEMISTRY OF THE BLACK SEA ANOXIC ZONE WITH A REFERENCE TO SULPHUR CYCLE.- THE SUBOXIC TRANSITION ZONE IN THE BLACK SEA.- TEMPORAL VARIABILITY IN THE NUTRIENT CHEMISTRY OF THE CARIACO BASIN.- BIOGEOCHEMICAL AND PHYSICAL CONTROL ON SHELF ANOXIA AND WATER COLUMN HYDROGEN SULPHIDE IN THE BENGUEL A COASTAL UPWELLING SYSTEM OFF NAMIBIA.- SEASONAL OXYGEN DEFICIENCY OVER THE WESTERN CONTINENTAL SHELF OF INDIA.- OXYGEN DEPLETION IN THE GULF OF MEXICO ADJACENT TO THE MISSISSIPPI RIVER.- ECOLOGICAL CONSEQUENCES OF ANOXIC EVENTS AT THE NORTH-WESTERN BLACK SEA SHELF.- BIOGEOCHEMISTRY AND MICROBIOLOGY OF THE NITROGEN CYCLE.- NITROGEN CYCLING IN SUBOXICWATERS: ISOTOPIC SIGNATURES OF NITROGEN TRANSFORMATION IN THE ARABIAN SEA OXYGEN MINIMUM ZONE.- NITROGEN CYCLING IN THE SUBOXIC WATERS OF THE ARABIAN SEA.- ANAEROBIC AMMONIUM OXIDATION IN THE MARINE ENVIRONMENT.- DIVERSITY, DISTRIBUTION AND BIOGEOCHEMICAL SIGNIFICANCE OF NITROGEN-FIXING MICROORGANISMS IN ANOXIC AND SUBOXIC OCEAN ENVIRONMENTS.- BIOGEOCHEMISTRY OF CARBON AND SULFUR CYCLES. MICROBIAL METAL REDUCTION.- FRACTIONATION OF STABLE ISOTOPES OF CARBON AND SULFUR DURING BIOLOGICAL PROCESSES IN THE BLACK SEA.- RECENT STUDIES ON SOURCES AND SINKS OF METHANE IN THE BLACK SEA.- SHEWANELLA: NOVEL STRATEGIES FOR ANAEROBIC RESPIRATION.- MICROBIAL ECOLOGY OF THE OXIC/ANOXIC INTERFACE.- MICROBIAL ECOLOGY OF THE CARIACO BASIN'S REDOXCLINE: THE U.S.-VENEZUELA CARIACO TIMES SERIES PROGRAM.- COMPOSITION AND ACTIVITIES OF MICROBIAL COMMUNITIES INVOLVED IN CARBON,SULFUR, NITROGEN AND MANGANESE CYCLING IN THE OXIC/ANOXIC INTERFACE OF THE BLACK SEA.- ANOXYGENIC PHOTOTROPHIC BACTERIA IN THE BLACK SEA CHEMOCLINE.