THIN LAYER DREDGE MATERIAL DISPOSAL IMPACTS ON TIDAL MARSH PROCESSES

Coastal marshes are critical natural resources that provide economic and social benefits. Continued existence of marsh habitat depends on its ability to maintain elevation relative to sea level. Currently several anthropogenic practices are disrupting the natural processes of marsh accretion by limiting sediment inputs. This study investigates if the addition of dredged material to sediment-starved marshes can offset submergence without negatively impacting function. The experiment takes place on marshes behind Masonboro Island and consists of four sites (2 deteriorated and 2 non-deteriorated) each of which has been covered by a wedge of dredged-fill sands ranging in thickness from 0 to 10 cm. Sediment traps deployed indicate that deposition rates in non-deteriorated sites (48.8 g/m2) are less then deteriorated sites (131.25 g/m2). Vascular plant biomass measured in the non-deteriorated sites (236.5 g/m2) exceeds the deteriorated sites (135.5 g/m2). Through winter 2001, both non-deteriorated and deteriorated soils have shown an increase in oxygen levels. Thus far, sediment placement has had little effect on sediment deposition rates and vascular plant biomass. Preliminary data suggest that the oxygen levels of sediment in all the sites are increasing. Additional data collected in summer and fall 2001 are expected to provide critical information to this study.