Summary of Abstract Submission

Abstract Submission No. IO50-09-0022PresentationPoster

DISTRIBUTION AND DIVERSITY OF GENES RESPONSIBLE FOR NITROGEN TRANSFORMATIONS IN THE ARABIAN SEA

Amal Jayakumar*1, S.W.A.Naqvi2, Bess B Ward1

1 Princeton University, USA
2 NIO, Goa, India

ABSTRACT :

One of the world┐s intense water column Oxygen Deficient Zones (ODZ) exists in the Arabian Sea. Thus the Arabian Sea is important as a region of intense anoxic Nitrogen (N) and Carbon (C) cycling. Due to the high primary productivity, the mid-depth water column becomes depleted in dissolved oxygen during microbial decomposition of the sinking organic matter (OM). Further decomposition of OM is carried out by anaerobic microbes that use oxidized forms of N as the oxidant. During the process of anaerobic organic matter decomposition, respiration using alternative oxidants sequentially transforms nitrate to nitrite, nitric oxide, nitrous oxide and molecular N. Bacteria capable of oxidizing the ammonia produced by such OM decomposition, also function in these anoxic depths. Thus, several different C and N transforming microbial processes are carried out in the oxic, suboxic and anoxic zones in the water column of this region. Over the past decade and a half we have collected data from this region to characterize and quantify the microbes responsible for such transformations. By targeting key genes in microbes that are responsible for several of these N transformation processes, we have explored the diversity, abundance and community composition of denitrifiers, anammox bacteria, nitrifiers and nitrogen fixing microbes. For example, we described a denitrifier bloom scenario and identified dominant genotypes, showed that the microbial assemblages exhibit significant biogeographic patterns, and linked the microbes to the N transformation rates. A synthesis of these data will be presented.