Dissolved organic matter in Chesapeake Bay sediment pore waters

Results of recent studies of dissolved organic matter (DOM) in Chesapeake Bay sediment pore waters are summarized here, to gain further insights into the controls on the composition and reactivity of estuarine pore water DOM. This analysis shows that much of the DOM accumulating in sediment pore waters appears to be refractory and of relatively low molecular weight (less than 3 kDa), consistent with recent water column DOM studies. Comparative analyses of pore water DOM data from bioturbated/bioirrigated sediments versus anoxic (i.e. non-bioturbated/bioirrigated) sediments indicate that differences in the physical and biogeochemical processes in these sediments lead to distinct differences in DOM concentrations and composition. The causative factors here appear to be both the presence/absence of macrofauna in the sediments, as well as differences in sediment redox conditions (more strictly anoxic vs. “mixed” redox conditions). These observations further suggest that differences in DOM composition and reactivity as a result of varying sediment redox conditions might also play a role in how sediment redox conditions affect overall sediment carbon preservation.