Soil Porewater Sulfide and Marsh Vegetation Vitality.

During the summer of 2006, extensive areas of coastal marshland in Delaware suffered from sudden wetland dieback (swd), which prompted a number of enquiries and broader discussions regarding a variety of possible soil-related and biological causes for the decline of Spartina alterniflora.  In many Mid-Atlantic marshes, substantial differences in vegetation vitality can be routinely observed over short distances which cannot be easily related to hydrological or geomorphological factors.  The accumulation of high levels of soluble sulfide in the marsh porewater has been postulated as one contributing cause of the phenomenon.  In an effort to evaluate this hypothesis, seven paired sites were identified among three Delaware coastal marshes where diminished stands of S. alterniflora were growing in close proximity to vigorous stands. IRIS technology was successfully utilized to rapidly assess the concentration of porewater  sulfide.  Sulfide levels up to 10 mmol were documented at sites, and dramatic differences between the paired sites were observed in over half the cases. The strengths and limitations of this new methodology also will be discussed.