Coastal salt marshes as global methyl halide sources from determinations of intrinsic production by marsh plants
Abstract
Emissions of CH3Cl, CH3Br and CH3I were measured biweekly for 12- to 24-month periods between March 2002 and March 2005 from monospecific stands of four dominant southern California coastal salt marsh plants. These measurements revealed large inherent differences between species and more detailed patterns of seasonal production than previously reported. Marsh plants displayed intrinsic abilities to produce methyl halides. Salt marsh plants produced 92% of CH3Cl and 90% of CH3Br emitted and only 41% of the emitted CH3I. Unvegetated areas emitted 7.9% of CH3Cl, 9.9% CH3Br, and 59% of the emitted CH3I. The accuracy of the estimated methyl halide emissions from a coastal marsh and probably other ecosystems can be dramatically improved with increasing the number of species being measured and including emission from barren (mudflats and soil) areas. Estimates of global salt marsh emissions based on vegetated and barren area are 130, 21, 5.5 (mg m-2 yr-1) for CH 3Cl, CH3Br, and CH3I, respectively, or 1.2, 3.9, and 0.8% of total global fluxes of these gases. Copyright 2006 by the American Geophysical Union.
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