Abstract:

Historical database of dissolved (<0.45 µm) and truly dissolved (<0.02 µm) trace metals (Mo, Ba, U, Re, V, Fe, Cs, Cr, Mn), nutrients (NH4+, NO2-, NO3-, PO4, Si), chlorophyll-a, and hydrographic data (temperature, salinity, density, dissolved oxygen) in surface and bottom waters at eight fixed stations within the Mississippi Sound and Bight. Samples were collected as part of the University of Southern Mississippi project Monitoring and Assessment of Coastal and Marine Ecosystems in the Northern Gulf, which was funded by NOAA through the Northern Gulf Institute. Sampling was almost once every month from October 2007 to November 2011.

Suggested Citation:

Kjell Gundersen, Stephan Howden, Kevin Martin, Donald Redalje, Alan Shiller. 2017. Monitoring and Assessment of Coastal and Marine Ecosystems in the Northern Gulf: historical database of trace metal, nutrients, chlorophyll-a and hydrographic data in the Mississippi Bight and Sound from October 2007 to November 2011. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N77M06C6

Publications:

Soto, I. M., Cambazoglu, M. K., Boyette, A. D., Broussard, K., Sheehan, D., Howden, S. D., … Cressman, K. (2018). Advection of Karenia brevis blooms from the Florida Panhandle towards Mississippi coastal waters. Harmful Algae, 72, 46–64. doi:10.1016/j.hal.2017.12.008

Ho, P., Shim, M. J., Howden, S. D., & Shiller, A. M. (2019). Temporal and spatial distributions of nutrients and trace elements (Ba, Cs, Cr, Fe, Mn, Mo, U, V and Re) in Mississippi coastal waters: Influence of hypoxia, submarine groundwater discharge, and episodic events. Continental Shelf Research, 175, 53–69. doi:10.1016/j.csr.2019.01.013

Purpose:

To investigate the causes of hypoxia and the factors controlling the distribution of various trace elements in the Mississippi Sound and Bight.

Data Parameters and Units:

Sample_ID, Station, Day, Month, Year, Surface (S) or Bottom (B), Mo [nM], Ba [nM], Re [nM], Cs [nM], V [nM]-dilution, Fe [nM]-dilution, Mn [nM]-dilution, V [nM]-magIC, Fe [nM]-magIC, Mn [nM]-magIC, U [nM], Cr [nM], Filter_size, NH4+ [µM], NO2- [µM], NO3- [µM], PO4 [µM], Si [µM], Chlorophyll-a [mg/m3], Depth [m], Temperature [°C], Salinity [psu], Density (kg/m3), O2 (mg/L) Sampling Site: Coordinates Site 1: 30.313 -89.307 Site 2: 30.291 -89.285 Site 3: 30.237 -89.224 Site 4: 30.198 -89.183 Site 5: 30.161 -89.046 Site 6: 30.133 -88.907 Site 7: 30.092 -88.769 Site 8: 30.042 -88.647

Methods:

Sampling Methods: Trace Metal/Nutrients/Chlorophyll-a Surface waters were collected in an acid-cleaned sample bottle (PE) attached to a metal-free submerged rod. Bottom samples were collected by pumping bottom waters to the surface and filling an acid cleaned sample bottles (PE). The pump consisted of C-flex tubing which was attached to a peristaltic pump and other sections were connected with Teflon-lined polyethylene tubing. Discrete samples were collected at the surface (~0.5m) and bottom (~0.5m from bottom). Hydrographic Data Collection Ancillary data (salinity, temperature, pressure, density, and dissolved oxygen) were acquired from horizontally oriented cage with a SeaBird SBE49 CTD, and a SeaBird43 DO sensor. The dissolved oxygen sensor was calibrated by the Winkler titration. The hydrographic data was matched as close as possible to the surface and bottom discrete sample depth. Analytical Method: Dissolved trace metal concentrations For dissolve trace metal samples collection and processing, samples were filtered through pre-cleaned 0.45 and 0.02 µm pore size syringe filters (Shiller, 2003). Total dissolved and truly dissolved trace elements were present in the <0.45 and <0.02 µm samples, respectively. Filtered samples were acidified to pH <2 with the addition of 70 µL of 6 N ultra clean HCl to 15 mL of samples. Samples were stored at room temperature until analysis. Dissolved (<0.45 µm) and truly dissolved (<0.02 µm) trace metals (Mo, Ba, U, Re, V, Fe, Cs, Cr, Mn) in surface and bottom waters were determined using sector-field inductively coupled plasma-mass spectrometer (ICP-MS, Thermo-Fisher Element 2). Two methods were used in V, Fe and Mn analysis, a simple dilution method and a covariant of Magnesium-Induced Co-precipitation method (MagIC) (Wu and Boyle, 1997; Shim et al., 2012) for the samples collected prior to October 2008. Samples collected after October 2008 were prepared by a simple dilution method for trace metal analysis (Mo, Ba, U, Re, V, Fe, Cs, Cr, Mn) on the ICP-MS. Both methods were calibrated by isotope dilution, which is to add a known amount of a solution containing enriched minor isotopes. For the dilution method, samples were diluted 20-fold with 0.3 M HNO3 (Seastar Baseline) diluent which contains a known amount of In and isotopically-enriched 50V, 57Fe, 95Mo, 115In, 135Ba, and 185Re. Indium dilution was used for the initial instrumental drift correction and the sensitivity check. The concentration of V, Fe, Mo, Ba and Re were calculated from the isotope ratios. For Cs, U, determined in low resolution, the instrumental drift was corrected by the response factor which was derived from the instrumental response (cps/nM) of 95Mo and 135Ba (low resolution). The response factor derived from the instrumental response (cps/nM) of 57Fe (medium resolution) were applied in the instrumental drift correction for Cr and Mn. In the MagIC method, a small amount of 7 M NH4OH was added into the equilibrated mixture of enriched isotope (50V, 53Cr and 57Fe) and sample to form precipitates which contains the target elements. Before trace metal analysis on ICP-MS, the precipitates were dissolved in a small amount of 0.3 M HNO3 (Seastar Baseline. The concentration of Mn in this method was derived from the intensity factor of 57Fe which was described in the dilution method. The NGI_ID is a unique identification number associated to the trace metal sample. Analytical Method: Nutrients Samples were filtered through pre-rinsed glass fiber filters (GF/F) into 125 mL acid-washed brown polyethylene bottles and stored in a freezer until analysis. All nutrients were measured using fluorometric (N species) and spectrophotometric (Phosphate (PO4) and Silica (SiO3)) methods on the Astoria-Pacific A2+2 nutrient auto-analyzer (Method #A179, A027, A205, and A221; Astoria-Pacific International, Oregon USA). Analytical Method: Chlorophyll-a Three samples were collected at each station/depth. Samples were filtered using a GF/F filter pad and stored in liquid nitrogen until processing. Pigments were extracted following the Methanol extraction method and chlorophyll-a was measured fluorometrically using a Turner 10AU Fluorometer.

Provenance and Historical References:

Shiller, A.M., 2003. Syringe filtration methods for examining dissolved and colloidal trace element distributions in remote field locations. Environmental Science & Technology, 37(17): 3953-3957. Shim, M.J., Swarzenski, P.W. and Shiller, A.M., 2012. Dissolved and colloidal trace elements in the Mississippi River delta outflow after Hurricanes Katrina and Rita. Continental Shelf Research, 42: 1-9. Wu, J.F. and Boyle, E.A., 1997. Low blank preconcentration technique for the determination of lead, copper, and cadmium in small-volume seawater samples by isotope dilution ICPMS. Analytical Chemistry, 69(13): 2464-2470.

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