Seasonal DOC accumulation in the Black Sea: a regional explanation for a general mechanism

During three cruises in the Black Sea, organised in July 1995 and April–May 1997, biological and chemical parameters that can influence the carbon budget were measured in the water column on the NW shelf, particularly in the mixing zone with Danube River waters. We observed in early spring (end of A...

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Bibliographic Details
Published in:	Marine chemistry Vol. 79; no. 3; pp. 193 - 205
Main Authors:	Cauwet, Gustave, Déliat, Gaëlle, Krastev, Anton, Shtereva, Galina, Becquevort, Sylvie, Lancelot, Christiane, Momzikoff, André, Saliot, Alain, Cociasu, Adriana, Popa, Lucia
Format:	Journal Article Conference Proceeding
Language:	English
Published:	Amsterdam Elsevier B.V 01-10-2002 Elsevier Science
Subjects:	Accumulation Black Sea Carbohydrates Carbon cycling Danube Dissolved organic carbon Earth sciences Earth, ocean, space Exact sciences and technology External geophysics Geochemistry Marine and continental quaternary Microbial loop Mineralogy Mixing zone Nutrients consumption Physical and chemical properties of sea water Physics of the oceans Productivity Silicates Surficial geology Water geochemistry Danube Delta Romania Eastern Europe East Mediterranean Black Sea Danube River MED, Black Sea Dissolved organic carbon Productivity Carbohydrates Danube Mixing zone Carbon cycling Nutrients consumption Black Sea Accumulation Microbial loop impact statements stream transport mixing ammonium nitrates sedimentation rates nutrients hydrochemistry productivity phytoplankton plankton dissolved materials Mediterranean Sea organic carbon phosphorus carbohydrates sea water salinity accumulation Europe nitrogen carbon cycle phosphates seasonal variations deltaic environment
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Summary:	During three cruises in the Black Sea, organised in July 1995 and April–May 1997, biological and chemical parameters that can influence the carbon budget were measured in the water column on the NW shelf, particularly in the mixing zone with Danube River waters. We observed in early spring (end of April–May) conditions an important input of freshwater organisms that enhanced the microbial activity in the low salinity range. High bacterial activity regenerates nitrogen in the form of nitrates, but is also responsible for an important consumption of ammonium and phosphate, leading to a high N/P ratio and a strong deficit in phosphorus. The consequence is a limitation of phytoplankton development but also a production of carbohydrates that accumulate all along the salinity gradient. These mechanisms are responsible for a seasonal accumulation of dissolved organic carbon (DOC) that increases from 210 μM in winter to about 280 μM in summer. All this excess DOC disappears during winter, probably degraded by bacterial activity. The degradation of carbon-rich organic matter increases the phosphorus demand by bacteria bringing limitation to phytoplankton primary production.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 ObjectType-Article-2 ObjectType-Feature-1
ISSN:	0304-4203 1872-7581
DOI:	10.1016/S0304-4203(02)00064-6