Centennial scale denitrification variability based on isotopic and geochemical proxies from the Arabian Sea since the last glacial period

Isotopic (nitrogen and carbon isotope ratio of sedimentary organic matter), geochemical (total organic carbon and total nitrogen content of sediment), and micropaleontological (Globigerina bulloides abundance) analyses were done in samples from a marine sediment core. This gravity-core was collected during the 274th cruise of the ORV Sagar Kanya from the Southeastern Arabian Sea. The chronology of the core is based on nine radiocarbon dates obtained using two species of planktic foraminifera (Globigerinoides ruber, Globigerinoides sacculifer; size range: 250–420 μm). It spans the last ~ 43 thousand years and the average resolution is ~150 years. For total organic carbon concentration and carbon isotope ratio estimation, carbonate was removed by treating the sample with 2N hydrochloric acid for 16 hours followed by centrifuging. Given the known problems of loss of nitrogen compounds from the sedimentary organic matter on acidification of samples, resulting in a bias in nitrogen content and nitrogen isotope ratios, untreated samples were used for their analysis. This data was used to study centennial-scale denitrification and productivity variability from the Southeastern Arabian Sea.