Open AccessGlacial/interglacial variations in production and nitrogen fixation in the Cariaco Basin during the last 580 kyr
Author(s) -
Haug Gerald H.,
Pedersen Thomas F.,
Sigman Daniel M.,
Calvert Stephen E.,
Nielsen Bente,
Peterson Larry C.
Publication year - 1998
Publication title -
paleoceanography
Language(s) - English
Resource type - Journals
eISSN - 1944-9186
pISSN - 0883-8305
DOI - 10.1029/98pa01976
Subject(s) - interglacial , geology , glacial period , oceanography , sediment , anoxic waters , nitrogen fixation , total organic carbon , paleontology , environmental chemistry , chemistry , bacteria
The effect of sea level change on nutrient supply to the anoxic Cariaco demonstrates the fundamental importance of nitrogen (N 2 ) fixation and phosphate to oceanic production. As N 2 fixation produces biomass of low δ 15 N and has been reported to be an important component of the nitrogen cycle in the modern Cariaco Basin, we propose that it contributes to the light interglacial δ 15 N (∼2‰–3‰) values observed in the Ocean Drilling Program (ODP) site 1002 sediment record. During the glacials the sediments are bioturbated (oxic conditions) with low total organic carbon (TOC) contents and sedimentary δ 15 N values of ∼5‰, suggesting that nitrogen (N 2 ) fixation contributed little to the N nutrition of Cariaco surface waters. The most plausible explanation for the inferred glacial/interglacial changes in N 2 fixation in the Cariaco is that they have occurred in response to variations in the N/P ratio of the nutrient supply, driven by changes in denitrification.