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Tim Jickells is a marine biogeochemist with over publications. He has been based at the University of East Anglia for more than 25 years and before that worked in Bermuda and Scotland.
His main research interests are in atmospheric inputs to the oceans and coastal nutrient cycling and his field work has included tropical, temperate and polar environments. He was awarded the Challenger medal in If you do not receive an email within 10 minutes, your email address may not be registered, and you may need to create a new Wiley Online Library account. If the address matches an existing account you will receive an email with instructions to retrieve your username.
Skip to Main Content. First published: 28 August About this book Marine Geochemistry offers a fully comprehensive and integrated treatment of the chemistry of the oceans, their sediments and biota. During his career he wrote over scientific publications, and in was awarded the Hans Pettersson Bronze Medal by the Royal Swedish Academy of Sciences. Free Access.
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Summary PDF Request permissions. Tools Get online access For authors. Diffusion of methane from the middepth maximum is probably adequate to maintain the surface methane excess against loss across the air-sea interface.
Coastal waters are frequently enriched in methane, and it has been shown that advective supply of these methane-rich waters may be a significant source of methane for the mixed layer near the coast. However, a study of the western subtropical Atlantic shows that advective transport can probably supply only a fraction of the methane present in the maximum.
Also the loss of methane across the air-sea interface was observed to be twenty times greater than the flux from the maximum. Thus in situ methane production must be very important to the open ocean methane distribution. A series of phytoplankton culture experiments demonstrated that cultures of both Coccolithus huxleyi and Thalassiosira pseudonana produce trace amounts of methane during logarithmic growth. Because the cultures are highly oxygenated, anaerobic methane bacteria can be neglected as methane sources.
However heterotrophic bacteria cannot be excluded as possible sources of methane to the cultures. After three algal generations, the rate of methane increase closely parallels the growth curve suggesting that the methane is in fact coming from the algae.
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This rate is three to four orders of magnitude slower than the rates of oxygen consumption and glutamate and glucose uptake measured by other workers. The methane production rate calculated from the culture experiments is the correct order of magnitude to account for the methane production occurring in the open ocean.
Marine geochemistry Research Papers - memymoqaqusy.ga
Methane is present in quite low concentrations in the deep ocean. Methane consumption is rapid at first probably greater than 0. At depth consumption appears extremely slow. This may be due to the fact that the methane concentrations in the deep sea are so low that methane oxidizing bacteria cannot use methane as a substrate, or due to reduced metabolic activity in the bacteria at the high pressures and low temperatures of the sea floor.
Methane is present in very high concentrations in anoxic basins, indicating that methanogenic bacteria are active.
However, near the anoxic-oxic interface in both the Black Sea and the Cariaco Trench a one dimensional advection diffusion model predicts that methane consumption is occurring in the anoxic zone. In the Black Sea the methane depletion may be indicative of the presence of rapid methane oxidation near the Bosporus overflow. However in the Cariaco Trench the validity of such an explanation is difficult to evaluate since the overflow process is so poorly understood.
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A box model for the Trench has been developed which incorporates time dependence and supply of chemical species to the water from the sediments at all depths in the Trench. This model can explain the silica and sulfide data quite well, but methane depletion near the interface, relative to the model predictions, still occurs. Thus either anaerobic methane oxidation or decreased methane production in the sediments must be hypothesized. Description Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August,