The SAS Research Project Includes:
Integrated Science in the Gulf of Mexico (GoM): Sediments, Water Column, and the Benthic Ecosystem.
High-resolution studies of the GoM benthos and impacts of the Deepwater Horizon Oil Spill.
The research component of the education program will focus on sediment cores, but also include sediment trap collections, water column measurements and fish samples. A sediment trap (Richey) will be deployed for ~1 year to collect settling particles (sediment) at time intervals of 7-14 days for analysis of sinking particle flux and composition. Sediment cores, up to ~60 cm in length, will be collected using an Ocean Instruments MC800 multicore to preserve the sediment water interface, capture sedimentation over the past ~100 years to adequately assess sedimentation patterns, and allow for interdisciplinary studies (8 cores/deployment for sedimentology, biology, chemistry, etc.) to fully characterize the benthic response and evolution during and following events (Schwing et al., 2018; Schwing et al. 2020; Larson, 2020). Piston cores (up to 3m in length) will be collected to investigate patterns on longer time-scales, including the role and frequency of downslope processes in redistributing sediments in the NGoM. Demersal fish longlining will collect a variety of data on fish populations as well contamination exposure and uptake. The continuation of the time-series of collecting sediment cores, fishes, and sediment trap samples allows for the detection of the events in the sedimentary record, the evolution of the sedimentary deposit, the potential for biological exposure via sediments, and the eventual burial and preservation in the sedimentary system. This approach was critical for determining sedimentary and biological impacts of, and recovery from, the DwH event and can assist in determining the preservation potential of contaminated sediments including influences of burial, bioturbation/mixing, alteration, and resuspension/erosion (Schwing et al., 2018; Schwing et al., 2020A; Larson, 2020). Analytical activities with Teams will be specific to the senior personnel and collaborators expertise and objectives of the integrated project. These activities will also be integrated into the Post-Expedition course and the focus of the peer mentors throughout the project. Opportunities for students to work with collaborators (Murawski and Richey) at their respective institutions will be available, but the majority of opportunities, and course associated analyses/lab work, will be at EC focused on core samples collected on the research cruises.
Short-Lived Radioisotope Geochemistry and Sedimentology
At EC facilities, senior personnel will oversee student participation for short-lived radioisotope dating, sedimentology (texture and composition) and foraminifera analyses. Samples will be analyzed for short-lived radioisotopes by gamma spectrometry on Series HPGe (High-Purity Germanium) Coaxial Planar Photon Detectors for activities of total Lead-210 (210PbTot), Lead-214 (214Pb), Bismuth-214 (214Bi), Thorium-234 (234Th), Cesium-137 (137Cs), and Berilium-7 (7Be) to determine timing and rates of sedimentation and over the past ~100 years (Larson, 2018). Data acquisition and interpretations will be consistent with previous collections to continue utilizing 234Thxs for short (months) time-scale sedimentation and 210Pbxs for longer (years to decades for ~100 yrs.) time-scale accumulation. Sediment texture (grain size) and composition analyses will be conducted on core sub-samples. Sediment grain size will be determined by wet sieve and pipette method (Folk, 1965) to measure the relative percentage of %gravel, %sand, %silt, and %clay. Carbonate content will be determined by the acid leaching (Milliman 1974). Total organic matter (TOM) will be determined by loss on ignition (LOI) (Dean, 1974).
Benthic Foraminifera Ecology and Biogeochemistry
Benthic foraminifera (BF), which are single celled protists that primarily produce calcite shells, have been commonly used as bioindicators of anthropogenic and natural perturbations (Sen Gupta, 1999; Morvan et al., 2004; Denoyelle et al., 2010; Lei et al., 2015). There have been several advances in benthic faunal response to anthropogenic (DwH) and natural stressors based on the time series of sediment collections from 2010-2018 in the NGoM, which this project will extend. Results from collections funded by this proposal will have implications for determining the long-term preservation of oil spills, assessing petroleum carbon mineralization and burial, and contributing to overall oil spill budgets. BF assemblages, density and diversity will be characterized from each multicore deployment following standard procedures (Patterson & Fishbein, 1989; Sen Gupta et al. 1999; Osterman et al. 2003; Schönfeld et al. 2012). Multiple indices will be developed including: the foram-AMBI marine biotic index (Alve et al. 2016; Jorrissen et al. 2018) for assessment of benthic habitat suitability, the foraminiferal index of environmental impact (FIEI; Mojtahid et al. 2006; Lei et al. 2015) for organic contamination, the benthic foraminifera abnormality index (FAI; Frontalini & Coccioni 2009) for inorganic contamination, and the PEB index (Osterman et al. 2003) for hypoxia. BF shell (test) calcite stable isotopes (δ13C, δ18O) will be measured to provide tracers of nutrient loading, terrestrial carbon, temperature, salinity (Fontanier et al. 2006) and recorders of organic contamination events (Schwing et al. 2018; Schwing et al., 2020).
Planktic fluxes and Paleoceanography
Analysis of samples from sediment trap collections will be supervised by Richey at the USGS, including the calculation of flux rates and composition of sinking particles. Fluxes will be determined as well as geochemical parameters to further define the composition of sediment particles settling in the water column. The USGS sediment trap has been a valuable platform for calibrating and validating paleoenvironmental proxies in the GoM (Thirumalai et a., 2014; Richey and Tierney, 2016), as well as testing hypotheses regarding the ecology of foraminifera (Jonkers et al., 2014; Reynolds et al., 2018; Richey et al., 2019). Sediment trap time series data are a valuable asset in ecologically and economically significant marine locations such as the NGoM.
Fisheries and Ecotoxicology
Analysis of fish samples will be supervised by Murawski at USF/CMS including the calculation of spatial and temporal abundance and population patterns as well as sample analyses for multiple indicators of uptake and exposure to contamination using methods consistent with the on-going research project (Murawski et al. 2018; Snyder et al. 2015).