Introduction

The goal of this study was to investigate diatoms as a paleoecological indicator for identifying sediments deposited by storm surge and examining sea-level history in the coastal marshes of southwest Louisiana. The influence of storm sedimentation on vertical accretion is a critical research question in southern Louisiana because marsh loss is increasing under relative sea level rise and a sediment deficit is considered one of the primary causes (Hatton and others, 1983; Boesch and others, 1994; Turner, 1997). In southwest Louisiana, three primary processes deliver sediments to the marsh: freshwater inflow from upland areas, tidal flooding, and wind-driven currents from storms (Gosselink and others, 1979). Storm-derived sedimentation may be the dominant source of mineral sediments for some marsh areas, particularly the interior marsh (Stumpf, 1983; Delaune and others, 1986; Rejmánek and others, 1988). Storm sediments positively influence marsh elevation and slow submergence by delivering sediments and stimulating root matter production (McKee and Cherry, 2009); however, tropical storms can also negatively influence marsh elevations through erosion and saltwater intrusion (Guntenspergen and others, 1995; Stone and others, 1997; Morton and Barras, 2011). Paleoecological methods can provide a substantial tool for understanding the contribution of storm-related sedimentation on marsh elevation and the influence of rising sea levels on marsh ecology. Paleoecological analyses of these data can be found in Smith (2012).

Left: Example of the core collection device (photo credit: G. Steyer); Top: An air boat was used to access marsh sites (photo credit: K. Smith); Right: X-radiograph image of a sediment core (image credit: K. Smith); Bottom: Image specimens for four species of diatoms extracted from sediment samples (photo credit: K. Smith).