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Optical sensing solutions for aquaculture
Aquaculture, fish farming and hydroponics are burgeoning industries that require careful monitoring of growing conditions to ensure healthy, sustainable production. Techniques including spectroscopy and optical oxygen sensing are useful analytical tools in aquaculture settings
A
quaponics is the combination of aquaculture and hydroponics to produce
crops. In an aquaponics system, fish or other aquatic organisms and plants share a symbiotic relationship that requires careful maintenance of critical parameters to keep the system in balance. If parameters including pH, dissolved oxygen, water temperature and nutrient concentration are not maintained, unhealthy fish will lead to poor crop production. Real-time monitoring of these criteria enables aquaponics farmers to react quickly to changes, ensuring best results. Similar environmental
parameters are monitored in fish farming, where water quality and growing conditions can affect fish health, harvest, and sustainability. With their small footprint, great portability and integration readiness, optical sensing devices are well suited for such applications.
Aquaponics systems
In a benchtop-sized aquaponics setup, we tested the viability of Ocean Insight spectrometers, chemical sensors and accessories to monitor pH, nutrient level and lighting conditions. To further simulate an aquaponics operation,
we used the Schematic View in OceanView spectroscopy software – a feature that generates, edits and exports spectral process flow diagrams – to create a system dashboard to monitor conditions in real time (Figure 1). For pH measurements, we used
an STS-VIS microspectrometer (350-800 nm), a tungsten halogen light source, and a transmissive dip probe used with a pH indicator patch. The patch comprises a pH indicator dye in a matrix, which changes color in response to the analytes in its environment. The spectrometer measures the colorimetric (absorbance) response. Nutrient concentration—in this,
of nitrates—was measured using a Flame-UV-VIS spectrometer (200-850 nm), a deuterium-halogen light source and transmission dip probe. Nitrates fertilise plants and help remove the harmful build-up of ammonia from fish waste but need to be kept at healthy levels. A similar setup could be integrated into larger-scale aquaponics processes at the component, subsystem, or turnkey system levels.
The other system element we
measured was lighting. Whether relying on sunlight for outdoor
Figure 2. Optical oxygen sensors have been used to monitor dissolved oxygen in fish farming operations
setups or high-pressure sodium lights or LEDs in greenhouse operations, growers are interested in the total optical power of illumination sources and the effects of their color spectra on crops. These criteria can be measured using Ocean Insight radiometrically calibrated spectrometers.
Fish farming systems Aquaculture is big business. According to the National Oceanic and Atmospheric Administration (NOAA) Fisheries, aquaculture accounts for 50% of all seafood produced globally for human consumption. Maintaining water quality is
crucial for fish farming (Figure 2). This effort includes monitoring oxygen levels in real time, often in changing conditions. How can spectroscopy help streamline dissolved oxygen (DO) measurements, making measurements affordable and scalable?
It helps to first understand fiber optic chemical sensors. These sensors use robust indicator materials and optoelectronics for DO measurements in food and agriculture, marine sciences, life sciences and biotechnology. Compared with electrochemical sensing techniques, optical oxygen sensors can be made in small and customizable form factors, allow non-intrusive measurements, and do not consume the sample. In this case, the principle of
Figure 1. With spectroscopy software tools, users can create a customized interface like this dashboard showing different parameters of a simulated aquaponics system
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operation is to trap an oxygen- sensitive fluorophore in a sol-gel host matrix applied to an adhesive
membrane (patch). The indicator material changes optical properties in response to specific analytes and electronics measure the response. Ocean Insight offers complete
oxygen-sensing systems, but our proprietary sensing material also can be integrated into third-party electronics. In one recent fish farming operation, the customer used Ocean Insight disposable oxygen-sensitive patches in a system to measure DO and temperature.
Precision aquaculture and machine learning Aquaculture is a sophisticated business where managing data is vital to success. So, what happens to all the data customers collect using optical sensing techniques? One answer: the use of machine learning to translate spectral data into actionable answers. For example, Ocean Insight
offers robust machine learning tools for situations that can make a difference for the customer who does not want to interpret complex spectra but wants a simple yes-no answer, a determination of concentration, or some other criteria.
The combination of optical sensing technologies and sophisticated yet accessible machine learning promises to expand the reach and heighten the impact of optical sensing for aquaculture. These tools will uncover new, objective data that can be used to improve yield, streamline production, and maintain sustainability. EO
www.oceaninsight.com
July 2021 Electro Optics 21
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