Environmental factors influencing nitrogen fixation and diazotroph distribution in the Atlantic Ocean.

LaRoche, Julie, Baustian, Tina, Grefe, Imke and Schunck, Harald (2011) Environmental factors influencing nitrogen fixation and diazotroph distribution in the Atlantic Ocean. [Talk] In: ASLO Aquatic Sciences Meeting. , 13.-18.02.2011, San Juan, Puerto Rico, USA .

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Abstract

Nitrogen fixation is an important process that supplies new fixed nitrogen to N-depleted regions of the ocean. The distribution and relative abundance of diazotrophs were evaluated along two meridional transects in the Atlantic ocean in April 2008 and October 2009, using phylotype-specific qPCR assays. Broad distribution patterns could be identified for most phylotypes, who tracked specific temperature ranges. Trichodesmium and the unculturable unicellular cyanobacterial diazotroph (UCYN-A) dominated the surface waters reaching over 1 million nifH copies L-1. However, the Trichodesmium and UCYN-A phylotypes were mutually exclusive, with Trichodesmium dominating at temperatures greater than 26°C, while UCYN-A was most abundant at 22°C. During the October 2009 transect, nitrogen fixation rates, measured with the 15N2 tracer technique, showed high peaks in activity in both the North and South Atlantic. Nitrogen fixation rates were however highest in the South Atlantic and were strongly correlated with the nifH copy numbers of the UCYN-A phylotype. The distribution patterns of both Trichodesmium and UCYN-A are explained in terms of the Saharan dust input and physiological temperature range.

Document Type: Conference or Workshop Item (Talk)
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
Date Deposited: 09 Apr 2013 09:08
Last Modified: 09 Apr 2013 09:08
URI: http://oceanrep.geomar.de/id/eprint/20952

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