Field experiments on bioturbation in salt marshes (Bombay Hook National Wildlife Refuge, Smyrna, DE, USA): implications for sea-level studies

The suitability of marsh sites for sea-level studies was examined based on field experiments along a transect from low to high marsh. Bead distributions were determined both seasonally and after 7 years. Seasonal sediment mixing was greatest in the low marsh and in the late spring and early summer, when biological activity is greatest. However, after an initial interval of relatively intense reworking, the bead concentrations reached an approximate equilibrium profile characteristic of each marsh environment as reflected by the profiles obtained after 7 years. Mixed-layer thickness is greatest (>10cm) in the intermediate and low marsh, and burial rates are rapid (3.7-11.1 mm yr (1)). Moreover, burial rates are comparable to or even Surpass longer-term (30 to >150 yr) radiotracer-derived sediment accumulation rates and rates of local and regional sea-level rise (similar to 4 mm yr (1)). Therefore, sediment accumulation rates appear to reflect primarily sediment resuspension/redeposition within the system due to bioturbation. Thus, bioturbation may be critical to the ability of marshes to keep pace with sea level, while seemingly precluding the use Of low marsh for high-resolution sea-level Studies. Copyright (C) 2008 John Wiley & Sons, Ltd.