1A). These 31 sites represented our best judgment of conditions before the find more oil entered the estuaries. We were prevented from accessing most marshes until the fall 2010. Various agency and satellite image analyses at that time indicated that the most prominent oiling was in east and west Barataria Bay and eastern Terrebonne Bay. We focused on these three areas and chose the target areas before the field trip began, and then made our final selection while in the field and before landing the boat. Subsequent sampling included these three general areas, but the same exact sites were not always re-sampled because of landowner

permission, erosion, or logistical issues (principally the shallow water depth that hindered Enzalutamide nmr boat access). A core set of 12–13 site locations were sampled on each trip. Thirty sites were established on the northern edge of Bay Batiste in February 2011 (Fig. 1C). These were clusters of 3 stations 10 m apart and are the same sites used by McClenachan et al. (2013) for a marsh erosion study. Sites were marked

with a plastic 0.25 m2 quadrat to facilitate repeated sampling at the same location. We had no access to data on oil concentration to assist in site selection for any site until late summer 2011. We collected 405 surface-sediment samples from Louisiana coastal wetlands during May 2010 (n = 31), September 2010 (n = 64), February 2011 (n = 30), May 2011 (n = 87), September 2011 (n = 66), June 2012 (n = 22), August 2012 (n = 30), September 2012 (n = 30), October 2012 (n = 15), and June 2013 (n = 30) ( Fig. 1). The majority of the samples were collected within 10 m of the shoreline. Others were collected every 20 m along eight 90 m transects in June 2011, and five 100 m transects PRKACG in September 2011. These transects were perpendicular to the wetland/water interface. Sampling in February 2011, August 2012, September 2012, and June 2013 were within 1 m of each other. The primary emergent vegetation was Spartina alterniflora

and Juncus sp. with minor amounts of Schneoplectus americanus. The wetland type is commonly known as a ‘salt marsh’. All sediment samples were collected as a composite sample of the upper 5 cm, stored on ice until delivery to the laboratory, and either immediately extracted or refrigerated at 4 °C for no more than 14 days until extraction, as recommended by the US EPA (2007). The samples were analyzed using GC/MS-SIM that targeted 28 alkanes, 18 parent PAHs, and 25 alkyl homolog groups (Table 2). The target petrogenic compounds were extracted from the sediment samples using EPA SW-846 method 3540C (US EPA, 2000). Reagent grade or pesticide grade solvents were used in all the extractions and analyses. Samples were homogenized and a 15–20 g subsample was weighed, spiked with surrogate recovery standards (5-alpha androstane and phenanthrene-d10, AccuStandard, Inc.