Low-cost modular chromatography column rack and vial holders.

Gravity-driven chromatography columns are used in scientific, engineering, medical, and industrial fields to separate desired compounds from solutions. Running multiple columns simultaneously saves time and improves procedural consistency. Though column chromatography is widely used, to meet their laboratory needs many investigators must resort to designing and fabricating custom racks for holding their chromatography columns. We have created a robust column rack design, with collection vial holders, that is easily made, inexpensive to build, and may be easily adapted to fit experimental needs. The column holder can be made to hold various sizes of columns (and can be interchanged as necessary); the height of columns above collection vials can be precisely set; and the design is modular, so the rack and vial holders can be expanded to accommodate the desired numbers of columns and the numbers and sizes of vials used to collect fractions eluted from each column. Importantly, the rack is made of inexpensive, readily-available materials and the fabrication is straightforward. Here we present details of the rack's features, a list of materials, and instructions for making it. We hope our design will help investigators who perform gravity-driven column chromatography.

Insights from barium variability in a Siderastrea siderea coral in the northwestern Gulf of Mexico.

Coral Ba/Ca is a proxy for seawater barium concentration that varies with upwelling, terrigenous input, and marine productivity whereas coral Sr/Ca varies with temperature. We examine monthly coral Ba/Ca and Sr/Ca before and during offshore oil exploration in a Siderastrea siderea coral from West Flower Garden Bank located on the continental shelf edge in the Gulf of Mexico. Coral Ba/Ca variations lack pulses driven by upwelling or river outflow and are not in sync with coral Sr/Ca that exhibit a different seasonal pattern. Seasonal variations in chlorophyll-a concentration negatively correlate with coral Ba/Ca explaining 25% of that variability. A significant increase in mean coral Ba/Ca of 1.76 µmol/mol between 1931-1944 and 1976-2004 corresponds to the increase in the United States barite production and consumption primarily used in offshore oil drilling, which escalated in the 1970s, suggesting oil drilling operations are increasing seawater Ba concentration in the Gulf of Mexico.

Salinity and stable isotope dataset for Guayas estuary waters.

The Guayas estuary is an ecologically and economically vital, large estuarine system located on the western coast of South America. A suite of ∼400 water samples was collected and analyzed to enable investigation of the sources of water types within this estuary, as well as environmental processes active within various portions of it. These samples were obtained at sites distributed across the major areas of the inner and outer portions of the estuary at the ends of consecutive dry (December/January) and rainy (May) seasons. At each site, Van Dorn bottles were lowered into the water from a boat (or bridge) and then triggered when they reached specified depths. When the Van Dorn bottles were brought back aboard the boat, aliquots of water from them were promptly sealed in glass containers for later analysis. These were transported to onshore laboratories where their salinities, and their oxygen (δ18O) and hydrogen (δ2H) isotopic compositions were measured. Established analytical procedures and standards were employed to obtain a robust set of resultant data. The samples, analyses, and data presented here support the associated research article, "Stable isotope evidence for the origins of waters in the Guayas estuary and Gulf of Guayaquil" [1], to which readers are referred for interpretation.

Surface Water CO2 variability in the Gulf of Mexico (1996-2017).

Approximately 380,000 underway measurements of sea surface salinity, temperature, and carbon dioxide (CO2) in the Gulf of Mexico (GoM) were compiled from the Surface Ocean CO2 Atlas (SOCAT) to provide a comprehensive observational analysis of spatiotemporal CO2 dynamics from 1996 to 2017. An empirical orthogonal function (EOF) was used to derive the main drivers of spatial and temporal variability in the dataset. In open and coastal waters, drivers were identified as a biological component linked to riverine water, and temperature seasonality. Air-sea flux estimates indicate the GoM open (- 0.06 ± 0.45 mol C m-2 year-1) and coastal (- 0.03 ± 1.83 mol C m-2 year-1) ocean are approximately neutral in terms of an annual source or sink for atmospheric CO2. Surface water pCO2 in the northwest and southeast GoM open ocean is increasing (1.63 ± 0.63 µatm  year-1 and 1.70 ± 0.14 µatm year-1, respectively) at rates comparable to those measured at long-term ocean time-series stations. The average annual increase in coastal CO2 was 3.20 ± 1.47 µatm year-1 for the northwestern GoM and 2.35 ± 0.82 µatm year-1 for the west Florida Shelf. However, surface CO2 in the central (coastal and open) GoM, which is influenced by Mississippi and Atchafalaya River outflow, remained fairly stable over this time period.