Abstract:
We proposed to assess the impact of the Deepwater Horizon oil and dispersants on sediments and benthic communities on the West Florida Shelf and Slope. In particular, we proposed the assessment of subsurface oil and dispersants to gauge the effects on benthic habitat critical to nearby fisheries and marine protected areas. We proposed to use a new Ocean Instruments MC-800 multicore system to sample sediments in two depth transects that intersect suspected layers of subsurface oil at approximately 400 m and 1400 m water depth. The transects were aligned with those identified in the College of Marine Science’s Initial Baseline Survey. One transect sampled areas influenced by the spill, and extended from offshore Pensacola (DSH) to approximately 1600 m in the Desoto Canyon. The second transect extended from just south of Panama City (PCB) to 1200 m. Core samples were dated using short-lived radioisotopes, analyzed for petroleum byproducts by organic and inorganic chemistry, including organic compounds and metals specific to Deepwater Horizon petroleum. In addition, benthic foraminifera abundance and their stable isotope geochemistry will be quantified to assess the impact on benthic communities. In this way, we documented the “bathtub rings” of sub-surface oil and their effects on benthic habitats.
Suggested Citation:
Schwing, Patrick, et al.. 2014. Sediment and Benthic Foraminifera Assessment, DeSoto Canyon, 2010-11-01 to 2011-02-28. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N70P0WZM
Purpose:
1. To quantify benthic foraminiferal assemblages and shell abnormalities from contaminated vs. non-contaminated sites and horizons to document any impact on benthic communities. -Benthic foraminifera were picked, identified to genus, and in some cases species, and counted. Samples from DSH08 (December and February), PCB06 (December and February), and DSH10 (February) were used for benthic assemblage/abundance analysis. Several other cores from the PCB transect were sampled to determine whether there was an increase in shell abnormalities at suspected intrusion depths (400 and 1400 m). 2. To assess potential uptake of hydrocarbons by benthic foraminifera based on stable and radiocarbon isotope geochemistry. -Benthic foraminifera (Uvigerina peregrina, Cibicidoides wuellerstorfi, Cibicidoides kullenbergi) and Planktonic foraminifera (Globigerinoides ruber) were isolated from the surface samples of DSH10 and PCB09 and analyzed for both stable and radio-carbon. 3. To establish pre-impact conditions for sediment geochemistry and benthic foraminiferal assemblages as a baseline for future monitoring studies of benthic habitats. -The down-core portions of each sediment record have provided an excellent background or baseline for sedimentology, accumulations rates, benthic foraminifera assemblages/abundance, and PAH concentrations/toxicity.
Data Parameters and Units:
foraminifera abundance (fcm-3, fg-1), δ13C (‰), D14C Sediment and Benthic Foraminifera Assessment -- 041611_EAB_proc_1.xls with Standards, PDB, Summary, Raw Data, NT export: Time (YYYY/MM/DD HH:MM:SS), sample identity 1, sample identity 2, position, line, SA Size, Pressure Balance at start, Pressure Balance at end, SA (mV), pre-reaction, leak rate, CO2 yield, Nr of Exp, d13C PDB, d18O PDB, standard deviations. 042911_Broun_Schwingproc_2.xls with Standards, PDB, Summary, Raw Data, NT export: Time (YYYY/MM/DD HH:MM:SS), sample identity 1, sample identity 2, position, line, SA Size, Pressure Balance at start, Pressure Balance at end, SA (mV), pre-reaction, leak rate, CO2 yield, Nr of Exp, d13C PDB, d18O PDB, standard deviations. BP Benthic Foram C14 data.xlsx: CAMS#, Sample Name, Other ID, fraction Modern, +/- standard deviation, D14C, +/- standard deviation, 14C age, +/- standard deviation. DSH08: 29.120916, -87.86545 DSH10: 28.97666, -87.89 PCB06: 29.099833, -87.2655 PCB09: 28.859116, -87.214683
Methods:
All benthic foraminifera were picked from every sample, identified to genus and counted. Benthic foraminifera (Uvigerina peregrina, Cibicidoides wuellerstorfi, Cibicidoides kullenbergi) and Planktonic foraminifera (Globigerinoides ruber) were isolated from the surface samples of DSH10 and PCB09 and analyzed for both stable and radio-carbon. Dataset for abundance of foraminifera has been submitted by the C-IMAGE project.
Instruments:
A spectrometer coupled to a GasBench-II peripheral in continuous-flow mode was used. This instrument was located at the University of South Florida College of Marine Science Stable Isotope Biogeochemistry Lab. Isotopic analyses were consistent with published procedures (REF 1). Briefly, samples were weighed into pre-cleaned and oven-dried Exetainers (Labco, LTD), purged with helium (99.999%) and reacted with 102% H3PO4 for >2hrs @ 60°C prior to analysis. CO2 evolved from the carbonate mineral-acid reaction was sampled into the GasBench-II peripheral by a double-holed sampling needle and passed through a permeable membrane (Nafion) water trap, a packed gas chromatographic column (Agilent PoraPLOT-Q 25m x 0.320), and a second permeable membrane water trap before entering a 100µl sampling loop injector (Valco), through an active open-split MS interface and into the mass spectrometer ionization source. Multiple measurements of NBS19 and NBS18 NIST Certified Reference Materials (CRMs) were used to normalize raw measurements to the VPBD scale. Analytical uncertainty, expressed as 1sd of n= 37 measurements of the NBS19 CRM, is ± 0.05‰ for δ13C. REF 1: Spötl, C. and Vennemann, T. W. (2003), Continuous-flow isotope ratio mass spectrometric analysis of carbonate minerals. Rapid Commun. Mass Spectrom., 17: 1004–1006. doi: 10.1002/rcm.1010 C-14 measurements were made by AMS at the Lawrence Livermore National Laboratory.
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