Early oxidation of organic matter in pelagic sediments of the eastern equatorial Atlantic: suboxic diagenesis

The transformations of nitrogenous compounds by soil bacteria have beenstudied for over a century. In terms of the global fluxes between aerial and terrestrial-aquatic systems, the simplified nitrogen cycle can be envisioned as a triangle where the only biologically reversible reaction occurs between ammonium and nitrate. The reverse reactions of dinitrogen fixation or denitrification by biological means do not occur in nature. Hence, the reductive process of denitrification, defined as the reduction of nitrate or nitrite to gaseous nitrogen (usually N2), is intimately associated with the oxidative process of nitrification.

Biochemical Ecology of Nitrification and Denitrification

Over 400 California sea lions (Zalophus californianus) died and many others displayed signs of neurological dysfunction along the central California coast during May and June 1998. A bloom of Pseudo-nitzschia australis (diatom) was observed in the Monterey Bay region during the same period. This bloom was associated with production of domoic acid (DA), a neurotoxin1 that was also detected in planktivorous fish, including the northern anchovy (Engraulis mordax), and in sea lion body fluids. These and other concurrent observations demonstrate the trophic transfer of DA resulting in marine mammal mortality. In contrast to fish, blue mussels (Mytilus edulus) collected during the DA outbreak contained no DA or only trace amounts. Such findings reveal that monitoring of mussel toxicity alone does not necessarily provide adequate warning of DA entering the food web at levels sufficient to harm marine wildlife and perhaps humans.

Mortality of sea lions along the central California coast linked to a toxic diatom bloom

New data force us to raise previous estimates of oceanic denitrification. Our revised estimate of ~ 450 Tg N yr -1 (Tg = 10 12 g) produces an oceanic fixed N budget with a large deficit (~ 200 Tg N yr -1 ) that can be explained only by positing an ocean that has deviated far from a steady-state, the need for a major upwards revision of fixed N inputs, particularly nitrogen fixation, or both. Oceanic denitrification can be significantly altered by small re-distributions of carbon and dissolved oxygen. Since fixed N is a limiting nutrient, uncompensated changes in denitrification affect the ocean´s ability to sequester atmospheric CO 2 via the "biological pump". We have also had to modify our concepts of the oceanic N 2 O regime to take better account of the extremely high N 2 O saturations that can arise in productive, low oxygen waters. Recent results from the western Indian Shelf during a period when hypoxic, suboxic and anoxic waters were present produced a maximum surface N 2 O saturation of > 8000%, a likely consequence of "stop and go" denitrification. The sensitivity of N 2 O production and consumption to small changes in the oceanic dissolved oxygen distribution and to the "spin-up" phase of denitrification suggests that the oceanic source term for N 2 O could change rapidly.

/pdf/the-oceanic-fixed-nitrogen-and-nitrous-oxide-budgets-moving-2urhkbnmw3.pdf

The oceanic fixed nitrogen and nitrous oxide budgets: Moving targets as we enter the anthropocene?*

Reduction of nitrogenous oxides by microorganisms.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1969.14.3.0450

Colorimetric determination of dissolved oxygen at low concentrations1

Observations in Lake Nitinat, an anoxic fjord on Vancouver Island, British Columbia, indicate that the large accumulations of ammonia, carbonates, phosphates, silicates, and sulfides in the deep water are the result of oxidative and fermentative decomposition of organic matter of planktonic origin, the reduction of sulfate ions, hydrolytic or other non-oxidative release (in the case of silicates), and the solution of carbonates (which also increases the alkalinity). Ammonia, sulfides, and silicates accumulate in the sulfide zone in direct proportion to each other, but some of the phosphate is probably released from the organic matter earlier than the other components, and some of the phosphate may be precipitated onto the bottom. Methane was observed in the anoxic waters, suggesting that some decomposition takes place by anaerobic fermentation. The concentrations of ferrous and sulfide ions are probably controlled by the solubility of ferrous sulfide. The vertical distribution of sulfides can be described by a mathematical model that can be simplified to one dimension because horizontal advective and diffusive terms can be neglected.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1965.10.suppl2.r185

Some consequences of the decomposition of organic matter in lake nitinat, an anoxic fjord1

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1971.16.5.0758

Chemical Changes, Including Nitrate Reduction, in DARWIN Bay, Galapagos Archipelago, Over a 2-MONTH Period, 19691

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1969.14.2.0288

William W. Broenkow

Papers

Colorimetric determination of dissolved oxygen at low concentrations1

Some consequences of the decomposition of organic matter in lake nitinat, an anoxic fjord1

Chemical Changes, Including Nitrate Reduction, in DARWIN Bay, Galapagos Archipelago, Over a 2-MONTH Period, 19691

An interface sampler using spring-actuated syringes1