292
gradually raising the temperature by 5 K/min. Degradation products are swept from
the reaction chamber in flowing He gas and introduced to an oxidative chamber
(~10% O 2 and CuO wire) for conversion to CO 2 . The evolved CO 2 , which happens
over ~500 K between 200 °C and 700 °C, can be trapped cryogenically and purified
on a standard gas separation line (Rosenheim et al. 2008). Ultimately, this method
can provide an isotope composition spectrum of carbon released at different finite
temperature intervals on a continuous temperature ramp. Thus it is a powerful tool in
recognizing and quantifying petrocarbon in non- extractable and non-GC-amenable
portions of the bulk sample (Pendergraft et al. 2013; Pendergraft and Rosenheim
2014; Adhikari et al. 2016). These studies have shown that immediately after the oil
spill, compounds such as PAHs were negatively correlated with the amount of radiocarbon (Pendergraft et al. 2013). Several years after the spill and at deep-sea sites far
afield from the wellhead, PAHs returned to background levels as radiocarbon levels
approached natural abundance (Adhikari et al. 2016). However, in coastal sites, a
significant portion of radiocarbon-depleted petrocarbon was observed through time
shifting to higher temperature intervals of RPO analysis (Pendergraft and Rosenheim
2014), indicating that weathering was increasing the stability of the compounds and
compound classes containing petrocarbon.
17.2.4 Foraminifera δ
13
C
Foraminifera are single-celled protists that are globally abundant in both planktonic
and benthic habitats (Sen Gupta 1999). Many produce a calcite shell (test), while
others produce a calcite matrix to which they adhere sediment grains (agglutinate)
(Sen Gupta 1999). Benthic foraminifera density and diversity indices have proven
to be valuable indicators of benthic impact and habitat suitability (Romero et al.
2015; Schwing et al. 2015, 2017). Benthic foraminifera are of particular interest in
the context of marine oil spills considering the potential impact that the marine oilsnow sedimentation and flocculent accumulations (MOSSFA) had on the seafloor
after the DWH oil spill (Brooks et al. 2015; Romero et al. 2015; Hastings et al.
2016). MOSSFA is the combination of biological, lithic, and oil residues, which
caused rapid settling of flocculent material and deposition on the seafloor during
and following the DWH (Passow et al. 2012; Brooks et al. 2015; Daly et al. 2016;
Romero et al. 2017; Chap. 12 this volume). On the seafloor, it is likely that the
deposited marine oil snow (MOS) rich in organic matter changed the quality of the
organic carbon, increased microbial respiration, and produced lower pore-water
oxygen concentrations (Hastings et al. 2016).
The stable carbon isotopic composition of benthic foraminiferal calcite
(δ
13
C CaCO3 ) has been shown previously to predominantly reflect the isotopic composition of dissolved inorganic carbon (DIC) in bottom or pore waters and changes in
food sources (e.g., microbial biomass) and organic matter fluxes (TOC) in sediments (Torres et al. 2003; Hill et al. 2004; Nomaki et al. 2006; Zarriess and
MacKensen 2011; Theodor et al. 2016). The stable isotope composition of benthic
foraminifera tests (δ
13
C CaCO3 ) in sediment cores collected in the DeSoto Canyon
I. C. Romero et al.
gradually raising the temperature by 5 K/min. Degradation products are swept from
the reaction chamber in flowing He gas and introduced to an oxidative chamber
(~10% O 2 and CuO wire) for conversion to CO 2 . The evolved CO 2 , which happens
over ~500 K between 200 °C and 700 °C, can be trapped cryogenically and purified
on a standard gas separation line (Rosenheim et al. 2008). Ultimately, this method
can provide an isotope composition spectrum of carbon released at different finite
temperature intervals on a continuous temperature ramp. Thus it is a powerful tool in
recognizing and quantifying petrocarbon in non- extractable and non-GC-amenable
portions of the bulk sample (Pendergraft et al. 2013; Pendergraft and Rosenheim
2014; Adhikari et al. 2016). These studies have shown that immediately after the oil
spill, compounds such as PAHs were negatively correlated with the amount of radiocarbon (Pendergraft et al. 2013). Several years after the spill and at deep-sea sites far
afield from the wellhead, PAHs returned to background levels as radiocarbon levels
approached natural abundance (Adhikari et al. 2016). However, in coastal sites, a
significant portion of radiocarbon-depleted petrocarbon was observed through time
shifting to higher temperature intervals of RPO analysis (Pendergraft and Rosenheim
2014), indicating that weathering was increasing the stability of the compounds and
compound classes containing petrocarbon.
17.2.4 Foraminifera δ
13
C
Foraminifera are single-celled protists that are globally abundant in both planktonic
and benthic habitats (Sen Gupta 1999). Many produce a calcite shell (test), while
others produce a calcite matrix to which they adhere sediment grains (agglutinate)
(Sen Gupta 1999). Benthic foraminifera density and diversity indices have proven
to be valuable indicators of benthic impact and habitat suitability (Romero et al.
2015; Schwing et al. 2015, 2017). Benthic foraminifera are of particular interest in
the context of marine oil spills considering the potential impact that the marine oilsnow sedimentation and flocculent accumulations (MOSSFA) had on the seafloor
after the DWH oil spill (Brooks et al. 2015; Romero et al. 2015; Hastings et al.
2016). MOSSFA is the combination of biological, lithic, and oil residues, which
caused rapid settling of flocculent material and deposition on the seafloor during
and following the DWH (Passow et al. 2012; Brooks et al. 2015; Daly et al. 2016;
Romero et al. 2017; Chap. 12 this volume). On the seafloor, it is likely that the
deposited marine oil snow (MOS) rich in organic matter changed the quality of the
organic carbon, increased microbial respiration, and produced lower pore-water
oxygen concentrations (Hastings et al. 2016).
The stable carbon isotopic composition of benthic foraminiferal calcite
(δ
13
C CaCO3 ) has been shown previously to predominantly reflect the isotopic composition of dissolved inorganic carbon (DIC) in bottom or pore waters and changes in
food sources (e.g., microbial biomass) and organic matter fluxes (TOC) in sediments (Torres et al. 2003; Hill et al. 2004; Nomaki et al. 2006; Zarriess and
MacKensen 2011; Theodor et al. 2016). The stable isotope composition of benthic
foraminifera tests (δ
13
C CaCO3 ) in sediment cores collected in the DeSoto Canyon
I. C. Romero et al.