کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4551603 1328307 2008 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Anoxia over the western continental shelf of India: Bacterial indications of intrinsic nitrification feeding denitrification
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات اقیانوس شناسی
پیش نمایش صفحه اول مقاله
Anoxia over the western continental shelf of India: Bacterial indications of intrinsic nitrification feeding denitrification
چکیده انگلیسی

Studies on the Arabian Sea coastal anoxia have been of immense interest, but despite its ecological significance there is sparse understanding of the microbes involved. Hence, observations were carried out off Goa (15°30′N, 72°40′E to 15°30′N, 72°59′E) to understand the processes that mediate the changes in various inorganic nitrogen species in the water column during anoxia. Water column chemistry showed a clear distinct oxic environment in the month of April and anoxic condition in October. Our study based on microbial signatures indicated that oxygen deficit appeared as a well-defined nucleus almost 40 km away from the coast during the oxic period (April) and spreads there after to the entire water column synchronizing with the water chemistry. Striking results of net changes in inorganic nitrogen species in nitrification blocked and unblocked experimental systems show that denitrification is the predominant process in the water column consuming available nitrate (∼0.5 μM) to near zero levels within ∼72  h of incubation. These observations have been supported by concomitant increase in nitrite concentration (∼4 μM). Similar studies on denitrification-blocked incubations, demonstrate the potential of nitrification to feed denitrification. Nitrification could contribute almost 4.5 μM to the total nitrate pool. It was found that the relation between ammonium and total dissolved inorganic nitrogen (DIN) pool (r = 0.98, p < 0.001, n = 122) was significant compared to the latter with nitrite and nitrate. The occurrence of high ammonium under low phosphate conditions corroborates our observations that ammonium does not appear to be locked under low oxygen regimes. It is suggested that ammonium actively produced by detrital breakdown (ammonification) is efficiently consumed through nitrification process. The three processes in concert viz. ammonification, nitrification and denitrification appear to operate in more temporal and spatial proximity than hitherto appreciated in these systems and this gives additional cues on the absence of measurable nitrate at surface waters, which was earlier attributed only to efficient algal uptake. Hence we hypothesize that the alarming nitrous oxide input into the atmosphere could be due to high productivity driven tighter nitrification–denitrification coupling, rather than denitrification driven by extraneous nitrate.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Marine Environmental Research - Volume 65, Issue 5, June 2008, Pages 445–455
نویسندگان
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