Gulf of America non-spinose planktic foraminifera culture study from 2020-2022: LA-ICPMS

Thirty-nine live individuals of Globorotalia truncatulinoides specimen were collected from a vertical plankton tow in the surface mixed layer (0–80 meters) of the northern Gulf of America on February 8, 2020. The plankton tow was taken at the site of our long-term sediment trap time series (27.533833 degrees North [°N], 90.340433 degrees West [°W]) during peak annual flux of G. truncatulinoides. The upper 80 m of the water column were fully mixed with an average temperature of 21.1 degrees Celsius (ºC) and salinity of 36.3 practical salinity units (PSU). The G. truncatulinoides specimens were immediately collected and identified under a dissecting microscope, picked out using small brushes, and rinsed with filtered seawater (0.45-micrometer [µm] nitrocellulose membrane filters). The foraminifera were individually added to 70 milliliter (ml) polystyrene Falcon® culture flasks containing ambient filtered seawater. The flasks were stored in the dark at ambient temperature (20 ºC). Upon returning to the laboratory at the USGS SPCMSC in St. Petersburg, Florida, the samples were stored in a VWR International Incubator (Model 1575R) set to 20 ºC.

Seventeen Globorotalia menardii, one Neogloboquadrina dutertrei, one Globorotalia crassaformis, and one Pulleniatina obliquiloculata live specimens were collected December 6, 2021, from a vertical plankton tow in the upper 200 m of the water column at 28.231933°N, 89.099333°W. Averages for temperature and salinity throughout the tow collection were 22.5°C and 36.5 PSU respectively. Ten additional G. menardii live specimen were collected the following year on November 30, 2022 (28.213617°N, 89.131600°W) in the same manner. The upper 200 m had an average temperature of 20.4°C and salinity of 36.4 PSU. Species were selected based on their availability in the tow material. Individual foraminifera from both collections were identified under a dissecting microscope, rinsed with filtered seawater (0.45-µm nitrocellulose membrane filters), and stored in Strontium-87 (87Sr)-labeled seawater (strontium carbonate [SrCO3], Series LH, Batch 136990, 91.26%) inside 70 ml polystyrene Falcon® culture flasks. The 87Sr label has an 87Sr/88Sr ratio four times greater than the natural isotopic abundance ratios and was chosen to geochemically observe growth in culture (Fehrenbacher and others, 2018). The flasks were stored in the dark at ambient temperature (20 ºC). Once back in the laboratory, the samples were stored in a VWR International Incubator (Model 1575R) set to 20 ºC.

Eighteen individual foraminifera were prepared for elemental analysis via LA-ICPMS (6 of those are included in this data release). Individual specimens were oxidatively cleaned in a solution of hydrogen peroxide (H2O2) and sodium hydroxide (NaOH) (1:1 solution 30% H2O2:0.1N NaOH) and rinsed 3 times with Milli-Q water to remove organic residue according to previously published methods for cultured foraminifera (Fehrenbacher and others, 2017). Once cleaned, each foraminifera specimen was weighed on a Mettler Toledo UMXZ Microbalance and sent to the University of Oregon for analysis.

The University of Oregon completed the following analyses (as part of the LA-ICPMS) on the 18 foraminifera specimen: Barium/Calcium ratio (Ba/Ca), Magnesium/Calcium ratio (Mg/Ca), 88 Strontium/Calcium ratio (88Sr/Ca), 87 Strontium/Calcium (87Sr/Ca), Manganese/Calcium ratio (Mn/Ca), and 87 Strontium/88 Strontium (87Sr/88Sr). The results from these analyses for 6 specimen were compiled into Microsoft Excel (.xlsx) and comma-separated values (.csv) files and are included in this release (Foraminifera_LA-ICPMS_data.zip).