Farris, C. N. National Park Service, charles_farris@nps.gov
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Tidal restrictions, such as dikes and causeways, are common to many salt marshes in New England and lead to alterations of tidal range, hydroperiod and as a consequence, nutrient transport. Because of the resultant differences in transport, these impounded marshes may have significantly different elemental retention cycling. As a part of comprehensive monitoring that is being conducted during a National Park Service salt marsh restoration project, water transport rates and nitrogen and phosphorus concentrations were measured during a number of tidal cycles in a impounded marsh and in the unrestricted marsh just outside the restriction. Preliminary results indicate differences in tidal range, inundation, salinity range and nutrient concentrations above and below the dike. Outside of the dike, the tidal range was 1.0 m; the sediments were sandy salt marsh peats that readily dewatered with the ebb tide. Inside of the dike, the tidal range was 0.25 m and pore water measurements showed that restricted marsh sediments dewater very poorly during spring tides. Outside the dike, nutrient concentrations reflected a water column that is regularly flushed by unimpeded tidal exchange. Inside of the dike, nutrient concentrations were more variable and reflected the influence of restricted water exchange, precipitation events changing the composition of the standing water and the incomplete dewatering in this marsh. These findings can help evaluate how differences in nutrients could contribute to observed differences in primary production, faunal communities and vegetative cover. Such findings can aid understanding of the pace and processes associated with the salt marsh restoration.
Day: Wednesday, Feb. 3
Time: 09:30 - 09:45am
Location: Sweeney Center
Code: CS59WE0930S