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Titolo:
THE FATE OF NITROGEN AND PHOSPHORUS AT THE LAND SEA MARGIN OF THE NORTH-ATLANTIC OCEAN
Autore:
NIXON SW; AMMERMAN JW; ATKINSON LP; BEROUNSKY VM; BILLEN G; BOICOURT WC; BOYNTON WR; CHURCH TM; DITORO DM; ELMGREN R; GARBER JH; GIBLIN AE; JAHNKE RA; OWENS NJP; PILSON MEQ; SEITZINGER SP;
Indirizzi:
UNIV RHODE ISL KINGSTON RI 02881 TEXAS A&M UNIV COLLEGE STN TX 77843 OLD DOMINION UNIV NORFOLK VA 23529 FREE UNIV BRUSSELS B-1050 BRUSSELS BELGIUM UNIV MARYLAND COLLEGE PK MD 20742 UNIV DELAWARE NEWARK DE 19716 MANHATTAN COLL BRONX NY 00000 UNIV STOCKHOLM S-10691 STOCKHOLM SWEDEN US EPA WASHINGTON DC 20460 BIOL MARINE LAB WOODS HOLE MA 00000 SKIDAWAY INST OCEANOG SAVANNAH GA 31406 UNIV NEWCASTLE NEWCASTLE NSW 2308 AUSTRALIA RUTGERS STATE UNIV,NOAA,CMER PROGRAM PISCATAWAY NJ 08855
Titolo Testata:
Biogeochemistry
fascicolo: 1, volume: 35, anno: 1996,
pagine: 141 - 180
SICI:
0168-2563(1996)35:1<141:TFONAP>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
ORGANIC-CARBON ACCUMULATION; AMAZON CONTINENTAL-SHELF; MARINE ECOSYSTEMS; SEDIMENT ACCUMULATION; MISSISSIPPI RIVER; NUTRIENT INPUTS; SCOTIAN SHELF; MASS-BALANCE; FRESH-WATER; NEW-ENGLAND;
Keywords:
CONTINENTAL SHELF; ESTUARIES; MASS BALANCE; NITROGEN; NORTH ATLANTIC; NUTRIENT BUDGET; PHOSPHORUS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
128
Recensione:
Indirizzi per estratti:
Citazione:
S.W. Nixon et al., "THE FATE OF NITROGEN AND PHOSPHORUS AT THE LAND SEA MARGIN OF THE NORTH-ATLANTIC OCEAN", Biogeochemistry, 35(1), 1996, pp. 141-180

Abstract

Five large rivers that discharge on the western North Atlantic continental shelf carry about 45% of the nitrogen (N) and 70% of the phosphorus (P) that others estimate to be the total flux of these elements from the entire North Atlantic watershed, including North, Central and South America, Europe, and Northwest Africa. We estimate that 61 . 10(9) moles y(-1) of N and 20 . 10(9) moles y(-1) of P from the large rivers are buried with sediments in their deltas, and that an equal amountof N and P from the large rivers is lost to the shelf through burial of river sediments that are deposited directly on the continental slope. The effective transport of active N and P from land to the shelf through the very large rivers is thus reduced to 292 . 10(9) moles y(-1)of N and 13 . 10(9) moles y(-1) of P. The remaining riverine fluxes from land must pass through estuaries. An analysis of annual total N and total P budgets for various estuaries around the North Atlantic revealed that the net fractional transport of these nutrients through estuaries to the continental shelf is inversely correlated with the log mean residence time of water in the system. This is consistent with numerous observations of nutrient retention and loss in temperate lakes. Denitrification is the major process responsible for removing N in mostestuaries, and the fraction of total N input that is denitrified appears to be directly proportional to the log mean water residence time. In general, we estimate that estuarine processes retain and remove 30-65% of the total N and 10-55% of the total P that would otherwise passinto the coastal ocean. The resulting transport through estuaries to the shelf amounts to 172-335 . 10(9) moles y(-1) of N and 11-19 . 10(9) moles y(-1) of P. These values are similar to the effective contribution from the large rivers that discharge directly on the shelf. For the North Atlantic shelf as a whole, N fluxes from major rivers and estuaries exceed atmospheric deposition by a factor of 3.5-4.7, but this varies widely among regions of the shelf. For example, on the U.S. Atlantic shelf and on the northwest European shelf, atmospheric deposition of N may exceed estuarine exports. Denitrification in shelf sediments exceeds the combined N input from land and atmosphere by a factor of1.4-2.2. This deficit must be met by a flux of N from the deeper ocean. Burial of organic matter fixed on the shelf removes only a small fraction of the total N and P input (2-12% of N from land and atmosphere; 1-17% of P), but it may be a significant loss for P in the North Seaand some other regions. The removal of N and P in fisheries landings is very small. The gross exchange of N and P between the shelf and theopen ocean is much lager than inputs from land and, for the North Atlantic shelf as a whole, it may be much larger than the N and P removedthrough denitrification, burial, and fisheries. Overall, the North Atlantic continental shelf appears to remove some 700-950 . 10(9) moles of N each year from the deep ocean and to transport somewhere between 18 and 30 . 10(9) moles of P to the open sea. If the N and P associated with riverine sediments deposited on the continental slope are included in the total balance, the net flux of N to the shelf is reduced by60 . 10(9) moles y(-1) and the P flux to the ocean is increased by 20. 10(9) moles y(-1). These conclusions are quite tentative. however, because of large uncertainties in our estimates of some important terms in the shelf mass balance.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 30/11/20 alle ore 19:57:57