Saltcorner
By Bob Goemans
By Bob Goemans
When I first utilized Light-Emitting Diodes (LEDs) in coral experiments in 2001, I never envisioned how these lights would revolutionize the aquarium hobby. The advantages of LEDs are many, including long life, relatively low heat generation, dimming capability, spectral tuning, potential low energy consumption, and so on.
There are many LED luminaires on the market today, with spectral qualities tuned for freshwater and marine environments. For many, these lights have become the luminaire of choice. With as many choices available, it is attention to detail that could influence the purchase decision.
This article will examine Orphek's new Atlantik iCon LED luminaire. This light differs from the Atlantik V4 in connectivity (via Android or iOS devices) and spectral quality.
This article will be slightly different than other reviews I've written (and one I've wanted to write for quite a while).
This luminaire, along with many others on the market, is more than capable of producing enough light, hence, instead of looking at light distribution, we'll examine the importance of spectral qualities. Reef2Reef.com member hart24601 has posted PPFD (PAR) values of the iCon do a search there for his posts.
Length x Width x Height: 24 ¼" x 9 3/8" x 2"
Cord Length (total): ~16'
Plug to Rectifier: 5'8"
Rectifier to Luminaire: 10'
Lens: 120° standard
Channels: 6
Important Note: Orphek uses glass lenses on UV and Violet LEDs, which will not degrade as plastic lenses will.
Channel 1: Sunrise and Sunset Mode, 13 LEDs - 590nm, 740nm, and 18,000K
Channel 2: Noon Mode, 13 LEDs - 490nm and 18,000K
Channel 3: Cyan and Blue Mode, 13 LEDs - 470nm and 490nm
Channel 4: Blue Mode, 13 LEDs - 450nm
Channel 5: Violet Mode, 13 LEDs - 430nm and 450nm
Channel 6: Ultraviolet and Violet Mode, 13 LEDs - 400nm and 415nm
Spectral Presets: Cloudy, Acclimation, Jellyfish, Lunar, and Custom
What's Included
The LED luminaire, rectifier (power supply) and electrical cords, and hanging kit.
Options
Lens: 5°, 15°, 45°, 60°, or 90°
Mounting arm
Before examining the spectral qualities of LEDs used in the Orphek iCon, we should first examine why their bandwidths are important.
We'll look at an action spectrum of a stony coral. An action spectrum examines biological responses (such as oxygen production via photosynthesis versus wavelength) as a result of spectral quality.
It is determined through use of a device called a monochromator, which splits white light into wavelength and an element-specific sensor (such as oxygen). See Figures 1 and 2.
Figure 1. Oxygen production by zooxanthellae isolated from the stony coral Favia by wavelength. The 'bump' at ~510 to 560nm is due to the accessory pigment peridinin, which gathers light energy and directs it to chlorophyll a. Aher Halldal, 1968.
Figure 2. Action Spectrum by bandwidth.
Since there are gradual transitions between colors in the spectrum, it should not be surprising that definitions of bandwidths vary among reference sources. These are the bandwidths used in this article.
LED Bandwidths
The Orphek iCon contains 78 LEDs emitting radiation at approximate peaks of 400, 415, 420, 430, 450 470, lime, amber, 'white' and far-red (infra-red) at 740nm.
Overall, Photosynthetically Usable Radiation (PUR) is a respectable 77%. See Figures 3, 4 and 5.
Figure 3. Spectral Power Distribution of the Orphek Atlantik iCon.
Figure 4. Breakout of the iCon spectrum. All channels at full power.
Figure 5. Breakout of full spectrum at 10nm bandwidths.
Fluorescence is described as the absorption by a substance of light and emission at a lower energy level. The absorbed light is called 'excitation' and the emitted light 'emission'.
The peak wavelength is at 400nm, with some radiation into the ultraviolet-A range. See Figure 6.
Figure 6. Spectral quality of the 400nm Ultraviolet-A and Violet
Emissions are almost entirely in the green-blue, blue-green portions of the spectrum, with an outlier at 593 (orange): Acropora nobilis (384/486), Condylactis gigantea (394/496), Acropora millepora (405/490), Heteractis crispa (405/500), Acropora millepora (405/504), Acropora millepora (405/593)
These LEDs blend in with the 400 and 420nm diodes. See Figure 7.
Figure 7. Spectral quality of the 415nm Violet
The peak wavelength is 420nm, and is almost entirely in the violet bandwidth. See Figure 8.
Figure 8. Spectral quality of the 420nm Violet
Emissions are entirely in the green-blue portion of the spectrum and Emissions are almost entirely in the orange and red portions of the spectrum: Montipora calculata (420/485), Porites murrayensis (420/485), Acropora digitifera (425/490), Agaricia sp. (426/486), and Acropora nastua (427/483), and Acropora horrida (420/485).
Spectrum of these LEDs peak at about 430nm (violet) with some emission in the blue bandwidth. See Figure 9.
Figure 9. Spectral quality of the 430nm LED.
The iCon contains 13 of these Royal Blue LEDs. See Figure 10 for spectral quality.
Figure 10. Spectral quality of the 450nm LED.
Emissions are almost en,rely in the green-blue, blue-green and green/yellow-green portions of the spectrum: Montastraea faveolata (440/486), Montastraea cavernosa (440/486), Pocillopora damicornis (440/508), Montastraea cavernosa (440,510), Montipora sp. (440/620), Discosoma striata (450/484), Acropora secale (450/484), Porites astreoides (450/530), Acropora nastua (451/482), Acropora secale (green band - 452/482 ), and Clavularia sp. (456/484).
The 470nm LED is considered the universal bandwidth for showcasing coral fluorescence (Chalkie and Kain, 2006). See Figure 11 for spectral quality.
Figure 11. Spectral quality of the 470nm LED.
Emissions are almost entirely in the green-blue and blue-green portions of the spectrum: Anemonia majano (458/486), Acropora tenuis (465/485), Acropora tenuis (green band - 470/480), Acropora sp. (472/495), Discosoma sp. (475/500), Anemonia aspera (480/490), Anemonia sculata (480/499), Acropora aspera (480/500), and Acropora aspera (green band - 484/499).
These LEDs have a rela,vely narrow bandwidth, peaking at 495nm. See Figure X. These LED's emissions can be gathered by the accessory (or antenna) pigment peridinin. Peridinin molecules (as many as a dozen, per chlorophyll a molecule depending upon reference) absorb green light and transfer it to chlorophyll a molecules. Since green light is harvested, many corals do not appear green, but brown instead. See Figures 12, 13, and 14.
Figure 12. Spectral quality of the 490 nm 'Cyan' LED
Figure 13. Spectral Characteristics of the Cyan LED 490nm
Figure 14. Peridinin, an accessory pigment, transfers energy to chlorophyll a molecules, Since it absorbs green light, it makes many corals appear brown.
Emissions are almost entirely in the green-blue, blue-green, yellow-green and orange portions of the spectrum: Pocillopora damicornis (486/515), Goniopora tenuidens (488/520), Agaricia humilis(490/565), Porites astreoides (490/620), Plesiastrea verispora (492/505), Galaxea fascicularis (492/505), Zoanthus sp. (494/508), Scolymia cubensis (497/506), Scolymia cubensis (497/507), Renilla muelleri (498/510), Anemonia sculata var. rufescens (499/522), Acropora aspera (orange band I - 499/522), Acropora aspera (orange band II - 501/575), Ptilosarcus sp. (500/508), Acropora aspera (500/575), Discosoma sp. #3 (503/512), 'Pectiniidae' (503/518), Montastraea annularis (505/515), Acropora tenuis (505/555), Montastraea cavernosa (506/515), Ricordea florida (506/517), Ricordea florida (506/574), Ricordea florida (506/517), Montipora digitifera/angulata (506/574), Favia favus (507/517), Ricordea florida (508/515), Montastraea cavernosa (508/580), and Montastraea cavernosa (506/582).
This LED emits broad band light and appears amber, although much is in the orange and red spectrum. See Figure 15.
Figure 15. Spectral quality of the 590 nm 'Amber' LED
Emissions are almost entirely in the orange and red portions of the spectrum: Acropora digitifera (570/590), Montipora monasteriata (570/610), Pocillopora damicornis (570/625), Porites murrayensis (570/625), Discosoma (573/593), Anemonia sculata (574/595), Acropora horrida (574/625), Acropora aspera (575/625), and Favia favus (583/593).
LEDs with peak output at 730nm are uncommon in luminaires designed for aquarium use, however, this should not discount their potential importance (See Figures 16 and 17). Perhaps most important, Pigment 700 (P700) in Photosystem I can absorb light at 730nm. Since Photosystem II is the electron donor, it is
important that Photosystem I (acting as the electron acceptor) is properly stimulated. At least some coral tissues (and likely all) preferentially transmit light at wavelengths around 700nm (the same can be said for human tissue, which can be proved by observing light from a flashlight transmitted through your hand). See Figures 16 and 17.
Figures 16. Spectral quality of the 730nm LED
Figures17. 730/740nm - 10nm Bandwidths
In addition, Chlorophyll f (recently discovered (2010) chlorophyll found in stromatolites, which are calcareous mounds made of lime layers secreted by cyanobacteria) and has been isolated from nitrogen-fixing bacteria found in some corals has a peak absorp,on at about 730nm. Nitrogen fixation is the conversion of nitrogen gas (N2) to ammonia (NH3) by the enzyme nitrogenase.
Now, before one freaks out and claims radiation at or about 730nm causes cyanobacteria outbreaks, let's examine some evidence. For example:
The cyanobacteria Fischerella thermalis contains chlorophyll f with a maximum absorption at 740nm, and it is an antenna pigment to Photosystem I. It requires very low light (PPFD, or PAR of roughly 10 to 20 microMol/square meter/second). The optimum growth temperature is 22°C or 71.6° F (Carolina Biological Supply Co.).
As for corals, the Caribbean coral Montastraea cavernosa has also been found to contain nitrogen-fixing cyanobacteria living in symbiosis with its host. This is most interesting, as the supply of ammonia provided by nitrogen-fixing by the cyanobacteria could (and likely is) an important supply of nitrogen to the symbiotic zooxanthellae. In addition, these cyanobacteria exhibit fluorescence at a peak of 578nm (orange-red). These cyanobacteria likely require little light since they are within coral tissues and competing for light with zooxanthellae. Indeed, M. cavernosa occurs in all reef environments especially lower slopes (Veron,1986).
I have seen what I believe to be fluorescence of these cyanobacteria in the stony coral Montipora digitata/angulata.
As noted, phycoerythrin is found in some cyanobacteria, as well as Rhodophyta (red algae), and cryptophytes (a form of algae).
As a footnote, years ago, I heard of a cyanobacterial outbreak in a marine aquarium disappearing when light intensity was increased. If lessons learned from experiments with Fischerella and Montastraea cavernosa are valid for more cyanobacteria species, it might be worthwhile experimenting, albeit slowly, for cyano control.
White - 18000K
These LEDs produce a crisp, full spectrum light. See Figures 18, 19, and 20.
Figure 18. Radiation generated by the 18,000K 'white' LEDs.
Figure 19. Further analysis of the 18,000K LED
Figure 20. a final anlaysis of the 18,000K LED.
Price
See Orphek.com for current pricing.
Methods and Materials
Spectral qualities were determined through use of an Ocean Optics USB2000 fiber optic spectrometer, with averaging of 5 measurements taken every 3 milliseconds, and boxcar averaging of 5 nm.. Data were downloaded into a proprietary Excel program for further analyses. Kelvin and Photosynthetically Useable Radiation were made by a Seneye device.
References
Carolina Biological Supply (www.carolina.com)
Chalkie, M. and S. Kain, 2006. Green Fluorescent Protein: Proper0es, Applica0ons and Protocols. John
Wiley and Sons, Hoboken, N.J. 443 pp.
Halldal, P., 1968. Photosynthe,c capaci,es and photosynthe,c ac,on spectra of endozoic algae of the massive coral Favia. Biol. Bull., 134:3.
Lesser, M., C. Mazel, M. Gorbunov and P. Falkowski, 2004. Discovery of symbio,c nitrogen-fixing cyanobacteria in corals. Science, 305, (5686): 997-1000.
Veron, J., 1986. Corals of Australia and the Indo-Pacific. University of Hawaii Press, Honolulu. 664 pp.
