Toward Citizen Science-Based Ocean Acidification Observations Using Smartphone Devices.

pH is a key parameter in many chemical, biological, and biogeochemical processes, making it a fundamental aspect of environmental monitoring. Rapid and accurate seawater pH measurements are essential for effective ocean observation and acidification investigations, resulting in the need for novel solutions that allow robust, precise, and affordable pH monitoring. In this study, a versatile smartphone-based environmental analyzer (vSEA) was used for the rapid measurement of seawater pH in a field study.

Isotopic Insights into Organic Composition Differences between Supermicron and Submicron Sea Spray Aerosol.

To elucidate the seawater biological and physicochemical factors driving differences in organic composition between supermicron and submicron sea spray aerosol (SSA and SSA), carbon isotopic composition (δC) measurements were performed on size-segregated, nascent SSA collected during a phytoplankton bloom mesocosm experiment. The δC measurements indicate that SSA contains a mixture of particulate and dissolved organic material in the bulk seawater. After phytoplankton growth, a greater amount of freshly produced carbon was observed in SSA with the proportional contribution being modulated by bacterial activity, emphasizing the importance of the microbial loop in controlling the organic composition of SSA.

The Sea Spray Chemistry and Particle Evolution study (SeaSCAPE): overview and experimental methods.

Marine aerosols strongly influence climate through their interactions with solar radiation and clouds. However, significant questions remain regarding the influences of biological activity and seawater chemistry on the flux, chemical composition, and climate-relevant properties of marine aerosols and gases. Wave channels, a traditional tool of physical oceanography, have been adapted for large-scale ocean-atmosphere mesocosm experiments in the laboratory.

Acidity across the interface from the ocean surface to sea spray aerosol.

Aerosols impact climate, human health, and the chemistry of the atmosphere, and aerosol pH plays a major role in the physicochemical properties of the aerosol. However, there remains uncertainty as to whether aerosols are acidic, neutral, or basic. In this research, we show that the pH of freshly emitted (nascent) sea spray aerosols is significantly lower than that of sea water (approximately four pH units, with pH being a log scale value) and that smaller aerosol particles below 1 μm in diameter have pH values that are even lower.

Simultaneous quantum yield measurements of carbon uptake and oxygen evolution in microalgal cultures.

The photosynthetic quantum yield (Φ), defined as carbon fixed or oxygen evolved per unit of light absorbed, is a fundamental but rarely determined biophysical parameter. A method to estimate Φ 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.

Solid State Sensor for Simultaneous Measurement of Total Alkalinity and pH of Seawater.

A novel design is demonstrated for a solid state, reagent-less sensor capable of rapid and simultaneous measurement of pH and Total Alkalinity (A) 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. ISFET-based pH sensors that achieve 0.001 precision are widely used in various oceanographic applications.

Deep-Sea DuraFET: A Pressure Tolerant pH Sensor Designed for Global Sensor Networks.

Increasing atmospheric carbon dioxide is driving a long-term decrease in ocean pH which is superimposed on daily to seasonal variability. These changes impact ecosystem processes, and they serve as a record of ecosystem metabolism. However, the temporal variability in pH is observed at only a few locations in the ocean because a ship is required to support pH observations of sufficient precision and accuracy.

Characterization of an ion sensitive field effect transistor and chloride ion selective electrodes for pH measurements in seawater.

Characterization of several potentiometric cells without a liquid junction has been carried out in universal buffer, aqueous HCl, and artificial seawater media. The electrodes studied include Ion Sensitive Field Effect Transistor (ISFET) pH electrodes, and Chloride-Ion Selective Electrodes (Cl-ISE) directly exposed to the solution. These electrodes were compared directly to the conventional hydrogen electrode and silver-silver chloride electrode in order to report the degree to which they obey ideal Nernstian laws.

Abiotic versus biotic drivers of ocean pH variation under fast sea ice in McMurdo Sound, Antarctica.

Ocean acidification is expected to have a major effect on the marine carbonate system over the next century, particularly in high latitude seas. Less appreciated is natural environmental variation within these systems, particularly in terms of pH, and how this natural variation may inform laboratory experiments. In this study, we deployed sensor-equipped moorings at 20 m depths at three locations in McMurdo Sound, comprising deep (bottom depth>200 m: Hut Point Peninsula) and shallow environments (bottom depth ∼25 m: Cape Evans and New Harbor).

Diel variability in seawater pH relates to calcification and benthic community structure on coral reefs.

Community structure and assembly are determined in part by environmental heterogeneity. While reef-building corals respond negatively to warming (i.e.

High-frequency dynamics of ocean pH: a multi-ecosystem comparison.

The effect of Ocean Acidification (OA) on marine biota is quasi-predictable at best. While perturbation studies, in the form of incubations under elevated pCO(2), reveal sensitivities and responses of individual species, one missing link in the OA story results from a chronic lack of pH data specific to a given species' natural habitat. Here, we present a compilation of continuous, high-resolution time series of upper ocean pH, collected using autonomous sensors, over a variety of ecosystems ranging from polar to tropical, open-ocean to coastal, kelp forest to coral reef.

Tracer monitored titrations: measurement of dissolved oxygen.

The tracer monitored titration (TMT) technique is evaluated for measurement of dissolved oxygen. The TMT developed in this work uses a simple apparatus consisting of a low-precision pump for titrant delivery and an optical detector based on a white LED and two photodiodes with interference filters. It is shown that the classic Winkler method can be made free of routine volumetric and gravimetric measurements by application of TMT theory, which allows tracking the amounts of titrant and sample using a chemical tracer.

Universal tracer monitored titrations.

Titrations, while primarily known as the chemical rite of passage for fledgling science students, are still widely used for chemical analysis. With its many years of existence and improvement, the method would seem an unlikely candidate for innovation, yet it is desirable, in this age of autonomous sensing where analyzers may be sent into space or to the bottom of the ocean, to have a simplified titrimetric method that does not rely upon volumetric or gravimetric measurement of sample and titrant. In previous work on the measurement of seawater alkalinity, we found that use of a tracer in the titrant eliminates the need to measure mass or volume.

Divergent ecosystem responses within a benthic marine community to ocean acidification.

Ocean acidification is predicted to impact all areas of the oceans and affect a diversity of marine organisms. However, the diversity of responses among species prevents clear predictions about the impact of acidification at the ecosystem level. Here, we used shallow water CO(2) vents in the Mediterranean Sea as a model system to examine emergent ecosystem responses to ocean acidification in rocky reef communities.

Tracer monitored titrations: measurement of total alkalinity.

We introduce a new titration methodology, tracer monitored titration (TMT), in which analyses are free of volumetric and gravimetric measurements and insensitive to pump precision and reproducibility. Spectrophotometric monitoring of titrant dilution, rather than volume increment, lays the burden of analytical performance solely on the spectrophotometer. In the method described here, the titrant is a standardized mixture of acid-base indicator and strong acid.

A submersible autonomous sensor for spectrophotometric pH measurements of natural waters.

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.