Krause Jeffrey W.

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Jeffrey W.

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Biogeochemical responses to late-winter storms in the Sargasso Sea, I - Pulses of primary and new production

2008-09-17 , Lomas, Michael W. , Lipschultz, Fredric , Nelson, David M. , Krause, Jeffrey W. , Bates, Nicholas R.

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Biogeochemical responses to late-winter storms in the Sargasso Sea, III—Estimates of export production using 234Th:238U disequilibria and sediment traps

2009-01 , Maiti, Kanchan , Benitez-Nelson, Claudia R. , Lomas, Michael W. , Krause, Jeffrey W.

Direct measurements of new production and carbon export in the subtropical North Atlantic Ocean appear to be too low when compared to geochemical based estimates. It has been hypothesized that episodic inputs of new nutrients into surface water via the passage of mesoscale eddies or winter storms may resolve at least some of this discrepancy. Here, we investigated particulate organic carbon (POC), particulate organic nitrogen (PON), and biogenic silica (BSiO2) export using a combination of water column 234Th:238U disequilibria and free-floating sediment traps during and immediately following two weather systems encountered in February and March 2004. While these storms resulted in a 2-4 fold increase in mixed layer NO3 inventories, total chlorophyll a and an increase in diatom biomass, the systems was dominated by generally low 234Th:238U disequilibria, suggesting limited particle export. Several 234Th models were tested, with only those including non-steady state and vertical upwelling processes able to describe the observed 234Th activities. Although upwelling velocities were not measured directly in this study, the 234Th model suggests reasonable rates of 2.2 to 3.7 m d-1. Given the uncertainties associated with 234Th derived particle export rates and sediment traps, both were used to provide a range in sinking particle fluxes from the upper ocean during the study. 234Th particle fluxes were determined applying the more commonly used steady state, 1-dimensional model with element/234Th ratios measured in sediment traps. Export fluxes at 200 m ranged from 1.91 ± 0.20 to 4.92 ± 1.22 mmol C m-2 d-1, 0.25 ± 0.08 to 0.54 ± 0.09 mmol N m-2 d-1, and 0.22 ± 0.04 to 0.50 ± 0.06 mmol Si m-2 d-1. POC export efficiencies (Primary Production/Export) were not significantly different from the annual average or from time periods without storms, although absolute POC fluxes were elevated by 1-11%. This increase was not sufficient, however, to resolve the discrepancy between our observations and geochemical based estimates of particle export. Comparison of PON export rates with simultaneous measurements of NO3 - uptake derived new production rates, suggested that only a fraction, < 35%, of new production was exported as particles to deep waters during these events. Measured bSiO2 export rates were more than a factor of two higher (p < 0.01) than the annual average, with storm events contributing as much as 50% of annual bSiO2 export in the Sargasso Sea. Furthermore it appears that 65 - 95% (average 86 ± 14%) of the total POC export measured in this study was due to diatoms. Combined these results suggest that winter storms do not significantly increase POC and PON export to depth. Rather, these storms may play a role in the export of bSiO2 to deep waters. Given the slower remineralization rates of bSiO2 relative to POC and PON, this transport may, over time, slowly decrease water column silicate inventories, and further drive the Sargasso Sea towards increasing silica limitation. These storm events may further affect the quality of the POC and PON exported given the large association of this material with diatoms during these periods.

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Dataset

Silicon Uptake Kinetics sampled aboard the R/V Pelican during during PE17-04 and PE17-20 along the Northern Gulf of Mexico, specifically the Louisiana Shelf region dominated by the discharge of the Mississippi River plume.

2020-09-03 , Krause, Jeffrey W. , Acton, Sydney , Marquez Jr., Israel A. , Maiti, Kanchan

Silicon Uptake Kinetics sampled aboard the R/V Pelican during PE17-04 (August & September 2016) and PE17-20 (May 2017) in Northern Gulf of Mexico, specifically the Louisiana Shelf region dominated by the discharge of the Mississippi River plume. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/822037

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Dataset

Water column data sampled aboard the R/V Pelican during August and September 2016 and May 2017 in Northern Gulf of Mexico, specifically the Louisiana Shelf region dominated by the discharge of the Mississippi River plume.

2020-09-03 , Krause, Jeffrey W. , Acton, Sydney , Marquez Jr., Israel A. , Pickering, Rebecca A. , Maiti, Kanchan

Water column data sampled aboard the R/V Pelican during August and September 2016 and May 2017 in Northern Gulf of Mexico, specifically the Louisiana Shelf region dominated by the discharge of the Mississippi River plume. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/822048

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Dataset

An investigation into the characteristics of the reactive pools of Mississippi River plume sediments collected August to September of 2016 and May 2017 aboard the R/V Pelican.

2020-09-09 , Pickering, Rebecca A. , Krause, Jeffrey W. , Maiti, Kanchan

An investigation into the characteristics of the reactive pools of Mississippi River plume sediments collected August to September of 2016 and May 2017 aboard the R/V Pelican. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/823190

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Dataset

One meter binned CTD data collected aboard the R/V Pelican during PE17-04 and PE17-20 along the Northern Gulf of Mexico, specifically the Louisiana Shelf region dominated by the discharge of the Mississippi River plume.

2020-09-03 , Krause, Jeffrey W. , Maiti, Kanchan

Coastal LouisianA Silicon Cycling (CLASiC) 1-m binned CTD data collected aboard the R/V Pelican during PE17-04 (late summer 2016) and 17-20 (May 2017) along the Northern Gulf of Mexico, specifically the Louisiana Shelf region dominated by the discharge of the Mississippi River plume. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/822194

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Krause Jeffrey W.

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Biogeochemical responses to late-winter storms in the Sargasso Sea, I - Pulses of primary and new production

Biogeochemical responses to late-winter storms in the Sargasso Sea, III—Estimates of export production using 234Th:238U disequilibria and sediment traps

Silicon Uptake Kinetics sampled aboard the R/V Pelican during during PE17-04 and PE17-20 along the Northern Gulf of Mexico, specifically the Louisiana Shelf region dominated by the discharge of the Mississippi River plume.

Water column data sampled aboard the R/V Pelican during August and September 2016 and May 2017 in Northern Gulf of Mexico, specifically the Louisiana Shelf region dominated by the discharge of the Mississippi River plume.

An investigation into the characteristics of the reactive pools of Mississippi River plume sediments collected August to September of 2016 and May 2017 aboard the R/V Pelican.

One meter binned CTD data collected aboard the R/V Pelican during PE17-04 and PE17-20 along the Northern Gulf of Mexico, specifically the Louisiana Shelf region dominated by the discharge of the Mississippi River plume.