Open AccessThe potential effect of nitrogen removal processes on the δ15N from different taxa in the mexican subtropical north eastern Pacific
Author(s) -
J. Camalich,
Alberto Sánchez,
Sergio Aguíñiga,
Eduardo F. Balart
Publication year - 2012
Publication title -
cicimar oceánides
Language(s) - English
Resource type - Journals
eISSN - 2448-9123
pISSN - 1870-0713
DOI - 10.37543/oceanides.v27i2.114
Subject(s) - trophic level , upwelling , abiotic component , food web , environmental science , oceanography , anoxic waters , plankton , ecology , water column , δ15n , subtropics , biology , δ13c , stable isotope ratio , geology , physics , quantum mechanics
The sub-tropical north eastern Pacific is one of the major zones in the ocean where nitrogen is removed by bacterial processes which are enhanced by low oxygen concentrations commonly found in the water column along the Pacific coast upwelling areas. It is well established that the nitrogen isotopic signal (δ15N) increases in relation to trophic levels but little is known about the transfer of this δ15N signal from the dissolvedfraction to higher trophic levels in oceanic regions with low oxygen. The objectives of this study are: 1) to report δ15N values from different abiotic and biotic components collected in the low-oxygen oceanic region in front of Bahía Magdalena (Mexican subtropical north-eastern Pacific); 2) to compare the δ15N of different trophic levelswith analogous organisms in regions where nitrogen fixation is the dominating process, which will allow us to evaluate the actual transfer of δ15N enriched in 15N through the trophic web up to top predators. The δ15N was higher in both abiotic and biological compared to those reported from zones where N fixation is the dominating process. Oxygen concentrations in the oceanic area in front of Bahía Magdalena are low (< 2ml/l) at shallow water depths (< 100m) but not anoxic. Despite this we found that the δ15N signal reflects denitrification and this signal is transferred up though the food web.