AUSTRALASIAN SOCIETY FORPHYCOLOGY AND AQUATIC
BOTANY

Novelinsights onsteroid
biosynthesis
in diatoms

Kelp Lady
travelling theworld withChurchillFellowship

OptoLeaf for
Photosynthetic
Photon Flux
Density

Shellfish
farmers
joining thelab bench

AUSTRALASIAN SOCIETY FOR PHYCOLOGY AND AQUATIC BOTANY

OptoLeaf: Measure Photosynthetic Photon Flux
Density using a Light Sensitive Film
Dr John W. Runcie1,2
1School of Biological Sciences, University of Sydney NSW 2006
2Aquation Pty Ltd, PO Box 3146 Umina Beach NSW 2256
john.runcie@aquation.com.au, john.runcie@sydney.edu.au
http://www.researchgate.net/profile/John_Runcie/
http://www.linkedin.com/profile/view?id=11715301

Photosynthetic photon flux density (PPFD) plays a pivotal
role in the growth and survival of photosyntheticorganisms. Light is often strongly attenuated in coastal
aquatic and marine environments where macroalgae,
seagrasses and corals are commonly found.
Understanding light availability in these submerged
environments is key in interpreting growth rates,
photosynthetic performance and determining thecapacity to tolerate stress.

OptoLeaf attached to Posidonia australis

Direct measurements of PPFD can be achieved using quantum sensors. However, this approach is expensive,obtrusive and impractical for simultaneously sampling multiple locations.
✓ A colour acetate film treated with azo dye offers a useful alternative where multiple unobtrusive
measurements need to be made, as the thin film can be easily attached to small leaves.
✓ The absorbance of the dye gradually fades with light exposure, and the rate of fading correlates wellwith PPFD. Ideally, multiple pieces of film are deployed in the field along with a few samples directly
adjacent to a logging quantum sensor.
✓ Fading rates of the reference samples can then be compared with measured quantum dose derived
from the quantum sensor. This relationship is then used to convert fading rates of all samples in thefield to total photon dose. The film is available as “OptoLeaf”.
Underwater applications
The film can be used underwater (e.g. Hirano et al. 1996). Small strips (1 x 2 cm) can be attached to seagrassblades or macroalgae with stainless steel staples or clips. As the film is thin (~0.1 mm), and light (<1 g perstrip) it has minimal impact on the movement and buoyancy of a seagrass blade or macroalgal thallus.
Therefore, samples can be placed in a multitude of orientations and depths within the canopy. By measuring
the absorbance of each sample prior and post deployment, one can determine the rate of change ofabsorbance. This rate of change can then be expressed in terms of total photon dose by use of a reference
curve. Reference curves can be generated independent of a field experiment as long as the temperatureand light conditions are similar. Systems where the film could be usefully used include:

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AUSTRALASIAN SOCIETY FOR PHYCOLOGY AND AQUATIC BOTANY••••••

Seagrass meadows
Macroalgae beds
Benthic microalgae mats
Coral reef systems
Suspended in the water column (downwelling and upwelling irradiance)
Horizontal and vertical surfaces, etc.

Case studies – terrestrial
Numerous studies have been conducted withterrestrial plants, for example:• A method for evaluating the interaction
between individuals competing for light ina monospecific stand (Hikosaka et al.
2001) – this method could be directly
relevant in assessing how seagrass blades
shade one another.
• An assessment of forest understory PPFD
over a 12-month period including changes
in ambient temperature over the year
(Kawamura et al. 2004) – the study
concluded that the accuracy and low costof the film made it a good option for Image from http://prometheuswiki.publish.csiro.au
estimating the integrated PPFD in a forest
understory.
• The detection of novel quantitative trait loci controlling photosynthesis by increasing leaf nitrogencontent and analysing its effect on leaf and canopy photosynthesis (Hirotsu et al. 2017)
Availability
Aquation Pty Ltd now distributes OptoLeaf for Taisei Fine
Chemical. Co., Ltd. (Japan). Three different films areavailable (1 to 3 days, 3 to 7 days, 1 to 3 weeks). While the
1-3 day tape is more accurate, some users prefer the 1-3week tape for longer integration intervals. Handheld
readers are available, or a spectrophotometer can beused. https://aquation.com.au/products/optoleaf/.
References
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Hikosaka, K., Nagashima, H., Harada, Y. and Hirose T. 2001. A simple formulation of interaction between individuals competing for lightin a monospecific stand. Functional Ecology 15, 642–646
Hirano, T.; Aiga, I.; Monji, N.; Hamotani, K.; Jintana, V.; Ishikawa, T.; Yabuki, K.; 1996. Radiation Environment of Mangrove
Pneumatophores in Brackish Water. Environ. Contr. Biol. 34, 87-90.
Hirotsu N., Ujiie K., Perera I., Iri A. Kashiwagi T. and Ishimaru K. 2017. Partial loss-of-function of NAL1 alters canopy photosynthesis bychanging the contribution of upper and lower canopy leaves in rice. Scientific Reports 7, 15958
Kawamura K., Cho M. and Takeda, H. 2005. The applicability of a color acetate film for estimating photosynthetic photon flux density
in a forest understory. J For Res 10, 247–249
Osada N., Onoda Y. and Hikosaka K. 2010. Effects of atmospheric CO 2 concentration, irradiance, and soil nitrogen availability on leaf
photosynthetic traits of Polygonum sachalinense around natural CO2 springs in northern Japan. Oecologia 164, 41–52

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