The Future of Advanced Optical Sensors for In-Situ Monitoring of pH and Oxygen

(Image credit: Discover Our Oceans LLC)
Founded in 2011, PyroScience GmbH is a prominent provider of advanced optical sensor technology for pH, oxygen, and temperature measurements that prides itself on delivering ultra-compact, plug-and-play, cost effective, flexible, and maintenance-free laboratory, underwater, and OEM devices. Available in a variety of sensor formats, including screw caps, fiber-based probes, and sensors with contactless read-out, all systems are developed and manufactured in-house (ISO 9001:2015 certified), with continuous development of new innovative sensor solutions.

Users leveraging PyroScience underwater sensor systems benefit from autonomous in-situ data collection capabilities, advanced optical sensing principles, and robust designs that withstand harsh underwater environments, all of which enable an array of marine research and industry applications.

With the rapid expansion of ocean industries, including offshore renewable energy, deep-sea exploration, mining, and aquaculture, the need for sophisticated technologies to monitor marine environments has increased significantly. Reliable real-time and long-term data is vital to boosting operational efficiencies and promoting sustainable practices.

COMPREHENSIVE PORTFOLIO

AquapHOx meters and PICO-OEM modules are designed for seamless integration with autonomous observation platforms like ADCPs, buoys, gliders, AUVs, and CTDs. The loggers can operate in stand-alone mode, while transmitters require an external data logger and power supply for real-time monitoring. AquapHOx meters equipped with oxygen or total scale pH sensor caps can also be used for flow-through monitoring in pumped systems such as FerryBox systems via the screw-on underwater flow cell APHOX-FTC.

The AquapHOx sensor series features plug-and-play simplicity and flexibility enabled by different sensor heads. Six versions are available for different applications in coastal and deep ocean waters to cover the needs for ocean sensing.

Shallow water devices—loggers, including the AquapHOx®-L-pH and AquapHOx®-L-O2, and transmitters, including the AquapHOx®-T-pH and AquapHOx®-T-O2—are rated for applications up to 100 m and are specific to either pH or oxygen, while deep-sea devices—the AquapHOx®-LX and AquapHOx®-TX—have a maximum depth rating of 4,000 m. Although only one sensor head can be attached at a time, the same deep-sea device can be used to alternate between oxygen or total scale pH measurements. All AquapHOx meters are equipped with a fast temperature sensor for automatic temperature compensation of the oxygen and pH measurements.

In addition to a plug-and-play sensor suite, PyroScience is home to the PICOOEM series, which includes two models: PICO-O2-SUB and PICOPH-SUB. The OEM meters require integration into custom-made underwater housing with subsequent custom pressure testing. Further, they require the use of third-party temperature sensors for temperature compensation of the chemo-optical sensor measurements. The PICOOEM series is compatible with a wide range of optical total scale pH and oxygen sensor head formats for different concentration ranges and response times.

ELECTRODELESS SEAWATER pH

The optical pH sensor cap, PHCAP-PK8TSUB, is designed for highly-resolved measurements of total scale ocean pH. Its robust design minimizes maintenance needs by allowing for easy cap replacements. The optical REDFLASH detection technology eliminates the need for a reference electrode, leading to a minimized effect of high ionic strength—making it an excellently suited sensor solution for measurements in seawater.

To combat biofouling challenges, PyroScience has recently launched a pH sensor cap sensor with a novel anti-fouling layer, the PHCAP-PK8TAF-SUB. Additional protective accessories based on copper alloy, like the APHOX-CAGE-AF and APHOX-CAP-AF, enhance durability for long-term measurements underwater.

OXYGEN SENSORS

Marine sensors can help supply defensible ocean data for environmental assessments and sustainable practices for operations. PyroScience’s technology supports diverse marine R&D in oceanography and the offshore industry, like monitoring operations of oxygen minimum zones (OMZs) or reporting environmental changes near offshore operations.

The broad portfolio of oxygen sensors available from PyroScience provides a variety of sensor formats, measuring ranges, and response times. Full-range oxygen sensor caps OXCAP-SUB with protective cages to ensure robustness against mechanical impact are intended for general oceanographic applications, long-term underwater deployments, and monitoring applications.

The ultra-trace oxygen sensor UTROXCAP-SUB is especially suited for trace oxygen detection in OMZs or during de-oxygenation events underwater, which are increasingly prevalent due to climate change and eutrophication.

(Image credit: PyroScience)

High-speed and ultra-high-speed sensors are ideal for water column profiling. Retractable fiber oxygen mini-sensors with ultra-fast response times allow micro-invasive rapid monitoring of oxygen concentration changes. This capability is crucial for assessing benthic oxygen flux dynamics, such as aquatic eddy covariance AEC.

The high and ultra-high-speed oxygen sensors are only compatible with the AquapHOx real-time transmitters (e.g., AquapHOx®-T-O2 and/or

AquapHOx®-TX). These transmitters integrate seamlessly with Nortek’s Acoustic Doppler Velocimeters (ADVs) via the APHOX-T-VECTOR cable, enabling synchronized high-frequency logging of oxygen and current velocities. Research studies have demonstrated the effectiveness of this technology in capturing oxygen fluxes in ecosystems like seagrass meadows and rocky coastal habitats, highlighting its role in advancing our understanding of carbon cycling and benthic ecosystem health.

A COLLABORATION FUTURE

PyroScience actively collaborates with universities, research institutions, and industry partners to enhance innovation and expand the product portfolio to support their applications in ocean waters. The suite of sensors, like the AquapHOx loggers and transmitters, have been effectively used in diverse ocean habitats. Soon, PyroScience will be expanding its portfolio of pH sensors to provide solutions with fast response time for water column profiling applications.

This feature appeared in ON&T Magazine’s 2025 Special Edition, The Future of Ocean Technology, Vol. 5, to read more access the magazine here.

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