The design and evaluation of a measurement system for photosynthetically active quantum scalar irradiance1

Booth, Charles R.

doi:10.4319/lo.1976.21.2.0326

Cited by 86 publications

(23 citation statements)

References 2 publications

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“…The output from a photon scalar irradiance meter can be expressed as (modified from Spitzer and Wernand 1979;Booth 1976 By means of the detector system we could calibrate the spectral response. The relative spectral response and the absolute intensity response of the sensors depended on the coupling into the detector system.…”

Section: Methodsmentioning

confidence: 99%

Microalgal photosynthesis and spectral scalar irradiance in coastal marine sediments of Limfjorden, Denmark

1992

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Scalar irradiance and oxygenic photosynthesis were measured simultaneously at 100~pm spatial resolution by a fiber-optic scalar irradiance microsensor and an oxygen microelectrode spaced 120 pm apart. Marine microbial mats on sandy sediments along the coast of Limtjorden, Denmark, were dominated by cyanobacteria with a surface layer populated by pennate diatoms. In dim light Oscillatoria sp. migrated upward and a dense surface film of cyanobacteria developed. The spectral distribution of scalar irradiance showed absorption peaks at 430 and 675 nm (Chl a), 630 (phycocyanin), and 800 and 860 nm (bacteriochlorophyll cc). Infrared scalar irradiance reached 200% of incident light intensity at 0.0-0.3-mm depth and IR penetration was independent of the development of a cyanobacterial surface film. At high incident light intensity, 740 WEinst rnZ s-l, the photosynthetic efficiency at 1 .O-mm depth was lo-fold higher than in the uppermost 0.0-0.6 mm of the sediment. The lower boundary of the euphotic zone (detectable gross photosynthesis) was at a mean light level of ~7.5 FEinst rn+ s-l.

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Section: Methodsmentioning

confidence: 99%

Microalgal photosynthesis and spectral scalar irradiance in coastal marine sediments of Limfjorden, Denmark

1992

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“…Measuring the ratio of PAR in water to that in air works well for spherical sensors of scalar irradiance (Booth 1976) but the response of the much commoner flat plate (cosine-law) sensors of vector irradiance is highly sensitive to the direction of light. Immediately light enters water from air refraction very markedly changes the angular distribution of the light (Kirk 1977b).…”

Section: Development Of the Relative Methods Of Par Measurementmentioning

confidence: 99%

Optical characterisation of natural waters by PAR measurement under changeable light conditions

Davies‐Colley

Vant

Latimer

1984

New Zealand Journal of Marine and Freshwater Research

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Water bodies can be characterised optically by the euphotic depth, z eu (1% of surface light), the diffuse attenuation coefficients, K d for downwelling light and K u for upwelling light, and the reflectance coefficient, R (ratio of upwelling to downwelling light), all in terms of photosynthetically active radiation (PAR). The estimation of all of these quantities from underwater PAR measurements is simple in principle but very difficult in practice under changing ambient light conditions caused by drifting cloud patches. A method of PAR measurement using a two-channel instrument which records the ratio of the response of 2 PAR sensors and thus overcomes the problems of changeable ambient light is described. Relative PAR Q(z)/Q r, where Q(z) is PAR (either upwelling or downwelling) at depth z, and Q T is reference (downwelling) PAR, is much less dependent on ambient light when the reference sensor is located in water than when located in air (deck sensor). The profiles of relative PAR can be used to calculate z eu , K d , and K u . R can be measured directly as the ratio of upwelling to downwelling PAR.

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“…PAR is defined as the rate of electromagnetic radiation received on a surface with wavelengths from 400 to 700 nm, which corresponds to light energy absorbed by photosensitive pigments with units of µmol photons m -2 s -1 (Brooks 1964;Federer and Tanner 1966;Booth 1976). The measurement of PAR under water presents a number of challenges, such as light scattering and attenuation with depth, as well as differences among the spectral responses of different sensor types.…”

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confidence: 99%

“…The intercalibration of different light sensor types that may have dissimilar responses under variable light conditions has been suggested as a way to obtain comparable light measurements (Booth 1976;Jewson et al 1984;Meyercordt et al 1999). The comparison of sensor types is complicated by differences in light-collecting properties that may vary with environmental conditions such as depth, turbidity, and intense light-scattering (Jewson et al 1984;Arst et al 2000).…”

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confidence: 99%

A comparison and correction of light intensity loggers to photosynthetically active radiation sensors

Long

Rheuban

Berg

et al. 2012

Limnology & Ocean Methods

109

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Accurate light measurements are important in the analysis of photosynthetic systems. Many commercial instruments are available to determine light; however, the comparison of light estimates between studies is difficult due to the differences in sensor types and their calibrations. The measurement of underwater irradiance is also complicated by the scattering and attenuation of light due to interactions with particulates, molecules, and the bottom. Here, three sensor types are compared to evaluate the calibration of light intensity loggers to estimate photosynthetically active radiation (PAR). We present a simple calibration of light intensity loggers that agree within 3.8% to factory-calibrated scalar PAR sensors under a wide range of environmental conditions. Under the same range of conditions, two identical factory-calibrated PAR sensors showed a similar difference of 3.7%. The light intensity loggers were calibrated to a high-quality PAR sensor using an exponential fit (r 2 = 0.983) that accounts for differences in sensor types with respect to the angle of incoming light, scattering, and attenuation. The light loggers are small, robust, and simple to operate and install, and thus well-suited for typical subsurface research. They are also useful for small-scale measurements, when broad spatial coverage is needed, or in research requiring multiple sensors. Many studies have used these simple light intensity sensors to estimate PAR, yet their limitations and advantages in mimicking PAR have not been well defined previously. We present these small and user-friendly loggers as an excellent alternative to more sophisticated scalar PAR sensors.

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The design and evaluation of a measurement system for photosynthetically active quantum scalar irradiance1

Cited by 86 publications

References 2 publications

Microalgal photosynthesis and spectral scalar irradiance in coastal marine sediments of Limfjorden, Denmark

Microalgal photosynthesis and spectral scalar irradiance in coastal marine sediments of Limfjorden, Denmark

Optical characterisation of natural waters by PAR measurement under changeable light conditions

A comparison and correction of light intensity loggers to photosynthetically active radiation sensors

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