, 1997). The Deepwater Horizon oil spill lasted almost 3 months (April 20 to July 15, 2010) and tides and storm surges brought oil from this largest accidental marine oil spill into coastal waters of the northern Gulf of Mexico. Estuaries of the central Louisiana coast were closest to the spill, and storm surges associated with Tropical Storm Alex in late June 2010 brought oil into some of these water bodies, including Barataria Bay and Terrebonne Bay. Oil stranded in northern and western Barataria Bay and in northern Terrebonne Bay, where the oil visibly coated marsh edges (
Fig. 1 in Whitehead et al., 2011). As part of the effort to assess CAL-101 possible ecosystem-level effects of this oil, we Maraviroc order collected barnacles and mussels from these two bays and from a third nearby estuarine system which received little oil, Breton Sound. We hypothesized that bacterial breakdown of oil was occurring where oil entered
estuaries, and previous work (Wright et al., 1982, Kirchman et al., 1984 and Peterson et al., 1985) has shown that mussels are capable of directly filtering such bacteria. Barnacles generally graze larger organisms, but could also use oil-derived carbon if they were grazing microzooplankton that ate bacteria (Head et al., 2006 and Graham et al., 2010). These microbial and grazing activities might also increase overall ecosystem respiration (Coffin et al., 1997). Our hypotheses were (1) enhanced ecosystem-level respiration would occur in Barataria Bay due to the presence
of oil substrates from the Deepwater Horizon spill, (2) oil would be strongly incorporated by mussels collected from visibly oiled marshes, and (3) barnacles collected near the mouth of Barataria estuary where tides most regularly advected oil into the estuary (Whitehead et al., 2011) would strongly show oil signals. We sampled barnacles widely in Barataria Bay to try to detect oil that might be entering food webs from visible deposits on marshes but also from less obvious deposits that can form Tyrosine-protein kinase BLK in bottom sediments by wave action (Macko and Parker, 1983). Barnacle data was used to screen larger areas for possible oil inputs to food webs, while mussel data were used to investigate hypothesized maximal oil uptake in marshes visibly coated with oil. Incorporation of oil carbon into food webs leading to barnacles and mussels, or into the respired CO2 pools of dissolved inorganic carbon from which barnacle and mussel shells are constructed, was expected to shift ambient isotope values towards those of oil. End member oil values for radiocarbon Δ14C are −1000‰ because no radioactive carbon remains in this ancient geological substance (White et al., 2005). For stable carbon isotopes, a -27‰ δ13C value has been determined previously for Deepwater Horizon oil (Graham et al., 2010).
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