Export 7 results:
Sort by: Author [ Title  (Asc)] Type Year
A B C D E F G H I J K L M N O P Q R [S] T U V W X Y Z   [Show ALL]
Martz, TR, DeGrandpre MD, Strutton PG, McGillis WR, Drennan WM.  2009.  Sea surface pCO(2) and carbon export during the Labrador Sea spring-summer bloom: An in situ mass balance approach. Journal of Geophysical Research-Oceans. 114   10.1029/2008jc005060   AbstractWebsite

We report depth-resolved in situ time series of the partial pressure of CO(2) (pCO(2)) and other carbon-related parameters spanning the development and decline of a high-latitude phytoplankton bloom. A suite of sensors was deployed on a mooring in the Labrador Sea from June to August 2004. The study became quasi-Lagrangian when the mooring broke free in late June. Measured parameters included pCO(2), chlorophyll a fluorescence, beam c, optical backscatter, and photosynthetically active radiation. During the bloom, the pCO(2) was drawn down from 330 to 260 mu atm, corresponding to a 70 mu mol kg(-1) decrease of dissolved inorganic carbon (DIC). One-dimensional model results suggest that the observed drawdown was primarily driven by local processes and contributions from horizontal advection were minimal. A mass balance using the DIC and particulate organic carbon found that 47 mmol C m(-2) d(-1) of DIC was assimilated into biomass. The bloom biomass was not remineralized in the mixed layer but was rapidly exported below 35 m within 15 days of the bloom. As a consequence, the large air-sea pCO(2) gradient persisted, and approximately 30% of the DIC was regained through air-sea exchange by the end of the study. It is likely that all of the exported organic matter, corresponding to 5.4 +/- 1.9 Tg of carbon, was replaced by atmospheric CO(2) prior to the onset of deep convective mixing.

Nam, S, Takeshita Y, Frieder CA, Martz T, Ballard J.  2015.  Seasonal advection of Pacific Equatorial Water alters oxygen and pH in the Southern California Bight. Journal of Geophysical Research-Oceans. 120:5387-5399.   10.1002/2015jc010859   AbstractWebsite

Chemical properties of the California Undercurrent (CU) have been changing over the past several decades, yet the mechanisms responsible for the trend are still not fully understood. We present a survey of temperature, salinity, O-2, pH, and currents at intermediate depths (defined here as 50-500 m) in the summer (30 June to 10 July) and winter (8-15 December) of 2012 in the southern region of the Southern California Bight. Observations of temperature, salinity, and currents reveal that local bathymetry and small gyres play an important role in the flow path of the California Undercurrent (CU). Using spiciness (p) as a tracer, we observe a 10% increase of Pacific Equatorial Water (PEW) in the core of the CU during the summer versus the winter. This is associated with an increase in p of 0.2, and a decrease in O-2 and pH of 30 mu mol kg(-1) and 0.022, respectively; the change in pH is driven by increased CO2, while total alkalinity remains unchanged. The high-p, low-O-2, and low-pH waters during the summer are not distributed uniformly in the study region. Moreover, mooring observations at the edge of the continental shelf reveal intermittent intrusions of PEW onto the shelf with concomitant decreases in O-2 and pH. We estimate that increased advection of PEW in the CU could account for approximately 50% of the observed decrease in O-2, and between 49 and 73% of the decrease in pH, over the past three decades.

Bresnahan, PJ, Wirth T, Martz TR, Andersson AJ, Cyronak T, D’Angelo S, Pennise J, Melville KW, Lenain L, Statom N.  2016.  A sensor package for mapping pH and oxygen from mobile platforms. Methods in Oceanography. 17:1-13.   AbstractWebsite

A novel chemical sensor package named “WavepHOx” was developed in order to facilitate measurement of surface ocean pH, dissolved oxygen, and temperature from mobile platforms. The system comprises a Honeywell Durafet pH sensor, Aanderaa optode oxygen sensor, and chloride ion selective electrode, packaged into a hydrodynamic, lightweight housing. The WavepHOx has been deployed on a stand-up paddleboard and a Liquid Robotics Wave Glider in multiple near-shore settings in the Southern California Bight. Integration of the WavepHOx into these mobile platforms has enabled high spatiotemporal resolution pH and dissolved oxygen data collection. It is a particularly valuable tool for mapping shallow, fragile, or densely vegetated ecosystems which cannot be easily accessed by other platforms. Results from three surveys in San Diego, California, are reported. We show pH and dissolved oxygen variability >0.3 and >50% saturation, respectively, over tens to hundreds of meters to highlight the degree of natural spatial variability in these vegetated ecosystems. When deployed during an extensive discrete sampling program, the WavepHOx pH had a root mean squared error of 0.028 relative to pH calculated from fifty six measurements of total alkalinity and dissolved inorganic carbon, confirming its capacity for accurate, high spatiotemporal resolution data collection.

Byrne, RH, DeGrandpre MD, Short T, Martz TR, Merlivat L, McNeil C, Sayles F, Bell R, Fietzek P.  2010.  Sensors and Systems for Observations of Marine CO2 System Variables. Proceedings of OceanObs’09: Sustained Ocean Observations and Information for Society . 2( Hall J, Harrison DE, Stammer D, Eds.)., Venice, Italy: ESA Publication WPP-306   10.5270/OceanObs09.cwp.13   Abstract
Du, N, Gholami P, Kline DI, Dupont CL, Dickson AG, Mendola D, Martz T, Allen AE, Mitchell BG.  2018.  Simultaneous quantum yield measurements of carbon uptake and oxygen evolution in microalgal cultures. Plos One. 13   10.1371/journal.pone.0199125   AbstractWebsite

The photosynthetic quantum yield (F), defined as carbon fixed or oxygen evolved per unit of light absorbed, is a fundamental but rarely determined biophysical parameter. A method to estimate Phi for both net carbon uptake and net oxygen evolution simultaneously can provide important insights into energy and mass fluxes. Here we present details for a novel system that allows quantification of carbon fluxes using pH oscillation and simultaneous oxygen fluxes by integration with a membrane inlet mass spectrometer. The pHOS system was validated using Phaeodactylum tricornutum cultured with continuous illumination of 110 mu mole quanta m(-2) s(-1) at 25 degrees C. Furthermore, simultaneous measurements of carbon and oxygen flux using the pHOS-MIMS and photon flux based on spectral absorption were carried out to explore the kinetics of F in P. tricornutum during its acclimation from low to high light (110 to 750 mu mole quanta m(-2) s(-1)). Comparing results at 0 and 24 hours, we observed strong decreases in cellular chlorophyll a (0.58 to 0.21 pg cell(-1)), Fv/Fm (0.71 to 0.59) and maximum Phi(CO2) (0.019 to 0.004) and Phi(O2) (0.028 to 0.007), confirming the transition toward high light acclimation. The Phi time-series indicated a non-synchronized acclimation response between carbon uptake and oxygen evolution, which has been previously inferred based on transcriptomic changes for a similar experimental design with the same diatom that lacked physiological data. The integrated pHOS-MIMS system can provide simultaneous carbon and oxygen measurements accurately, and at the time-resolution required to resolve highresolution carbon and oxygen physiological dynamics.

Briggs, EM, Sandoval S, Erten A, Takeshita Y, Kummel AC, Martz TR.  2017.  Solid State Sensor for Simultaneous Measurement of Total Alkalinity and pH of Seawater. Acs Sensors. 2:1302-1309.   10.1021/acssensors.7b00305   AbstractWebsite

A novel design is demonstrated for a solid state, reagent-less sensor capable of rapid and simultaneous measurement of pH and Total Alkalinity (A(T)) using ion sensitive field effect transistor (ISFET) technology to provide a simplified means of characterization of the aqueous carbon dioxide system through measurement of two "master variables": pH and A(T). ISFET-based pH sensors that achieve 0.001 precision are widely used in various oceanographic applications. A modified ISFET is demonstrated to perform a nanoliter-scale acid base titration of A(T) in under 40 s. This method of measuring A(T), a Coulometric Diffusion Titration, involves electrolytic generation of titrant, through the electrolysis of water on the surface of the chip via a microfabricated electrode eliminating the requirement of external reagents. Characterization has been performed in seawater as well as titrating individual components (i.e., OH-, HCO3-, B(OH)(4)(-), PO43-) of seawater A(T). The seawater measurements are consistent with the design in reaching the benchmark goal of 0.5% precision in A(T) over the range of seawater A(T) of similar to 2200-2500 mu mol kg(-1) which demonstrates great potential for autonomous sensing.

Martz, TR, Carr JJ, French CR, DeGrandpre MD.  2003.  A submersible autonomous sensor for spectrophotometric pH measurements of natural waters. Analytical Chemistry. 75:1844-1850.   10.1021/ac020568l   AbstractWebsite

An autonomous sensor for long-term in situ measurements of the pH of natural waters is described. The system is based upon spectrophotometric measurements of a mixture of sample and sulfonephthalein indicator. A simple plumbing design, using a small, low-power solenoid pump and valve, avoids the need for quantitative addition of indicator. A similar to50-muL slug of indicator is pulled into the sample stream by the pump, and subsequent pumping and mixing results in a section of indicator and sample where absorbance measurements can be made. The design also permits direct determination of the indicator pH perturbation. Absorbances are recorded at three wavelengths (439, 579, and 735 nm) using a custom-built 1.7-cm path length fiber-optic flow cell. Solution blanks are obtained by periodically flushing the cell with sample. Field tests were performed in a local river over an 8-day period. The in situ accuracy, based on comparison with laboratory spectrophotometric pH measurements, was -0.003 pH unit (n = 16), similar to the measurement precision. No drift was observed during the 8-day period. The absorbance ratio used to calculate pH, in combination with a simple and robust optical design, imparts an inherent stability not achievable with conventional potentiometric methods, making the design feasible for long-term autonomous pH measurements.