Ethylene and methane in the upper water column of the subtropical Atlantic

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The vertical distributions of ethylene and methane in the upper water column ofthe subtropical Atlantic were measured along a transect from Madeira to the Caribbean andcompared with temperature, salinity, oxygen, nutrients, chlorophyll-a, and dissolved organiccarbon (DOC).Methane concentrations between 41.6 and 60.7 nL L<sup>&#8722;1</sup> were found in the upper 20 m ofthe water column giving a calculated average flux of methane into the atmosphere of 0.82 µgm<sup>&#8722;2</sup> h<sup>&#8722;1</sup>. Methane profiles reveal several distinct maxima in the upper 500 m of the watercolumn and short-time variations which are presumably partly related to the vertical migrationof zooplankton.Ethylene concentrations in near surface waters varied in the range of 1.8 to 8.2 nL L<sup>&#8722;1</sup>.Calculated flux rates for ethylene into the atmosphere were in the range of 0.41 to 1.35 µgm<sup>&#8722;2</sup> h<sup>&#8722;1</sup> with a mean of 0.83 µg m<sup>&#8722;2</sup> h<sup>&#8722;1</sup>. Maximum concentrations of up to 39.2 nL L<sup>&#8722;1</sup>were detected directly below the pycnocline in the western Atlantic. The vertical distributionsof ethylene generally showed one maximum at the pycnocline (about 100 m depth) whereelevated concentrations of chlorophyll-a, dissolved oxygen, and nutrients were also found;no ethylene was detected below 270 m depth. This suggests that ethylene release is mainlyrelated to one, probably phytoplankton associated, source, while for methane, enhanced netproduction occurs at various depth horizons. For surface waters, a simple correlation betweenethylene and chlorophyll-a or DOC concentrations could not be observed. No considerablediurnal variation was observed for the distribution and concentration of ethylene in the upperwater column.

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Seifert, R. , Delling, N. , Richnow, H. H. , Kempe, S. , Hefter, J. and Michaelis, W. (1999): Ethylene and methane in the upper water column of the subtropical Atlantic , Biogeochemistry, 44 , pp. 73-91 .

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