Fluxes of Methyl Halides in Subtropical Salt Marshes
Abstract
Atmospheric methyl halides have both natural and anthropogenic origins and play a role in stratospheric ozone depletion. Sources and sinks of methyl chloride and methyl bromide have been measured in a limited number of terrestrial biomes. In addition, the within-biome variability of fluxes is not well quantified, necessitating a wider spatial distribution of sampling sites from different climatic zones. Here we report measurements of methyl halide fluxes from subtropical barrier island salt marshes in Texas (27.8°N, 97.1°W) as a comparison to temperate salt marshes that have been previously studied. Between April 2006 and May 2008, static flux chamber experiments were performed at several salt marsh sites near Port Aransas, Texas. Of the 4 prevalent species of higher plants studied, Batis maritima showed the greatest production of methyl halides, similar to results from southern California. Fluxes from plots of B. maritima were then sampled over the course of a day to investigate how environmental factors affect the magnitude of fluxes. In the May 2008 outing, the highest reported net fluxes for methyl chloride (700μmol/m2d) and methyl bromide (40μmol/m2d) from any salt marsh was observed in association with this species. These high emission rates when compared to more temperate salt marshes may reflect the effect of a warmer climate on the metabolic activity of the plant. Methyl bromide and methyl chloride fluxes are well correlated, suggesting that the same mechanism controls them both. Fluxes normalized by biomass increased with time of day. There was also a weak correlation between net flux and solar insolation averaged over the previous hour and between net flux and internal chamber temperature. These results offer some insight into estimating the global contributions of salt marshes to the methyl halides budgets and provide an important counterpoint to studies from higher latitudes, which have significantly lower fluxes overall.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.A44B..07W
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0793;
- 1615;
- 4805;
- 4912);
- 0426 Biosphere/atmosphere interactions (0315);
- 0490 Trace gases