Lighting for Algae Cultures

Understanding Light and Photosynthesis

Discussing illumination for photosynthesis essentially revolves around Photosynthetically Active Radiation (PAR). PAR encompasses light photons ranging in wavelength from 400 to 700nM, vital for the photosynthetic process.

To select the appropriate lighting for your algae culture, consider the following guidelines:

First Step: Identify the primary pigments present in your selected algae strain.
Second Step: Opt for a light source emitting radiation within the range absorbable by your algae’s pigments, which is a feature of almost all types of lights.
Third Step: Strategically place your chosen light adjacent to your culture tank, ensuring optimal exposure and absorption.

Wavelengths of light and the pigments that catch them

Image 1: Focusing on the Electromagnetic Spectrum’s 400-700nM Range

This range represents the PAR—Photosynthetically Active Radiation essential for algae and plant growth.

Within the confines of PAR, both algae and plants can absorb diverse light wavelengths. This absorption capability is dependent on the specific pigments they contain. Below are some of the crucial pigments:

Chlorophyll-a: Universally found in all plants, algae, and cyanobacteria.
Chlorophyll-b: Present in Chlorophytes and terrestrial plants.
Carotenoids: Incorporated in all plants and algae for photosynthesis and protection.
Phycoerythrin: Identified in Red Algae like Porphyridium and Rhodomonas, playing a role in capturing light for energy.
Phycocyanin: This pigment is prominent in Cyanobacteria, including Spirulina and Arthrospira, assisting in the light-absorption process for photosynthesis.

Figure 2: Relative absorbance of photosynthetic pigments as a function of wavelength of light.

Selecting the Proper Light for Algae Growth

Choosing the right light to foster algae growth requires ensuring the light source emits energy at the appropriate wavelengths. Typically, ‘green’ lights are not employed as grow lamps because they emit wavelengths that are not effectively absorbed by key pigments like Chlorophyll-a, Chlorophyll-b, and Carotenoids. However, ‘green’ light does get absorbed by the red pigment, Phycoerythrin, which is crucial for some algae strains. Understanding these nuances in light absorption is vital for successful algae cultivation.

Diverse Light Sources for Algae Cultivation

For effective algae growth, various light sources can be utilized, each offering distinct advantages:

1. LED Lights:

LEDs are energy-efficient options that provide a spectrum of light necessary for algae growth.

2. Fluorescent Bulbs:

These lights offer suitable wavelengths for algae without excessive energy consumption, making them a popular choice for many cultivators.

3. Incandescent Bulbs:

Though not as energy-efficient as LEDs or fluorescents, incandescent bulbs can still support algae growth if they’re what’s available or affordable.

4. Natural Sunlight:

Sunlight is a cost-effective and efficient light source for algae growth, provided you have a setup that allows for adequate sunlight exposure.

Each light source has its own set of pros and cons, and your selection should align with both the specific needs of the algae being cultivated and the operational and initial costs associated with your algae growing project.

LED lights for photosynthesis of algae

LEDs (Light Emitting Diodes) have garnered significant attention and preference in the algae cultivation community due to their efficient conversion of electrical energy to light with minimal energy loss in the form of heat.

Why Opt for White LEDs?

At ARS, we have a penchant for white LEDs. Despite emitting light at multiple wavelengths, white LEDs are particularly beneficial for photosynthesis as they provide a spectrum of useful energy. It is crucial to acknowledge, however, that green light, abundant in white LEDs, isn’t predominantly absorbed by algae.

One primary reason we lean towards white LEDs is the visibility it offers to our scientists during culture inspections. The wide spectrum allows a clear visual evaluation of the cultures’ health and condition, providing vital information at a glance.

The Aesthetic Pleasure of Green Light

Using LEDs that exclusively emit red and blue light – the spectra crucial for photosynthesis – would indeed facilitate the growth process but at the cost of visual information regarding the culture’s health. Moreover, there’s undeniable aesthetic value in the vibrant colors reflected by the green light in the cultures, adding a visually pleasing aspect to the meticulous process of algae cultivation. At ARS, we believe in not just doing what we do but loving it – and the delightful play of colors under white LEDs contributes significantly to that enjoyment.

Fluorescent lamps for growing micro-algae LED’s

Figure-5: T-12 Fluorescent shop lamp | Lighting For Algae Cultures — Figure-5: T-12 Fluorescent shop lamp

Figure 6: T-12 Full spectrum and not-full spectrum lamps. Showing little difference in actual spectral output.

Fluorescent lamps are another viable option for algae growth, and they are favored at ARS for various reasons.

Affordable and Accessible Lighting for Algae Cultures

First and foremost, fluorescent lamps are cost-effective and widely available in the market, making them an easily accessible choice for enthusiasts and researchers alike. While LEDs are steadily becoming more affordable and prevalent, they still are somewhat of a premium option compared to their fluorescent counterparts.

Wide Spectrum Emission

Fluorescent lamps are known for emitting light across a broad spectrum. This characteristic is vital as it provides the diverse energy required for the photosynthesis process in algae cultures.

Consideration of Heat and Lamp Life

While these lamps are generally efficient, it’s essential to consider that they emit a degree of heat and require replacement approximately annually. This recurrent replacement can incur additional costs over time. However, innovative and mindful cultivators can turn the heat emission to their advantage. For cultures that thrive in warmth, the heat generated by fluorescent lamps can be harnessed to maintain the culture’s temperature, thereby creating an optimal environment for growth.

By understanding and weighing the various factors, users can make an informed decision on whether fluorescent lamps are the ideal choice for their specific algae cultivation needs and conditions.

Harnessing Sunlight for Micro-Algae Growth

Sunlight, being the most natural and abundant source of light, is a logical choice for cultivating algae.

The Ideal Sunlight Exposure

While sunlight is a fantastic resource, the amount and type of exposure are crucial factors. Indirect sunlight proves to be effective for many algae growers, with a north-facing window providing an optimal environment for most algae types. However, the impact of direct sunlight on algae cultures varies depending on the volume of the culture. Large cultures can benefit from direct sunlight, whereas smaller ones, especially those under 40 liters, may face challenges such as overheating and excessive light exposure.

Managing Overheated Cultures

If cultures accidentally overheat due to direct sunlight exposure, it’s imperative to immediately move them to dim light. Thankfully, most algae strains can dissipate excess light energy through photoprotective mechanisms (refer to xanthophyll cycle and carotenoids in the glossary for more details). However, excessive heat and light can swiftly destroy a culture. For instance, a temperature of 39°C for just five minutes under sunlight can be lethal to the algae culture.

The Perfect Spectrum with Sunlight

Sunlight offers a spectrum that is remarkably suitable for growing various algae strains. This spectrum includes ultraviolet (UV) light, which can be detrimental as it may damage algae’s genetic material, akin to how sunburn affects human skin. Additionally, sunlight contains infrared (IR) light, or heat. The visible light spectrum from sunlight, as illustrated in Figure-7, perfectly aligns with the Photosynthetically Active Radiation (PAR) range of 400-700nM, making it an ideal, natural light source for algae growth. However, being mindful of the potential risks and managing exposure is crucial for successful cultivation using sunlight.

Figure 7: Sunlight intensity as a function of wavelength

Determining Optimal Light Levels for Algae

Understanding the right amount of light for algae cultures is crucial for successful growth.

Decoding Light Quantities for Photosynthesis

When discussing light requirements for photosynthesis, the term often used is “Einsteins”. An Einstein refers to a mole (6.02×10^23) of photons and is used to measure light in terms of photons per unit time (seconds) over a specific area (square centimeters). Photosynthetically Active Radiation (PAR) was previously expressed in micro-einsteins per second per square meter (μE m−2 s−1).

Direct sunlight at noon in the summertime: 2,500 μE m−2 s−1
Intensity at a distance of 1cm from a t-12 fluorescent lamp: 130 μE m−2 s−1
Saturating intensity for most marine microalgae: 120 μE m−2 s−1

Avoiding Overexposure: Striking a Balance

These figures indicate that direct sunlight provides up to 20 times more light than most marine microalgae need, leading to the risk of overexposure. Excessive light can be harmful to algae, akin to how too much sunlight can damage our skin. It is essential to monitor and adjust the light exposure for your algae culture carefully to prevent any damage, ensuring a healthy and thriving culture. Remember, balancing light exposure is key to preventing undue stress or harm to your algae, fostering a more sustainable and healthy growth environment.

Figure 8: Photosynthesis vs Irradiance curve.

Understanding Photosynthesis Rate Equations

Common equations actively outline the relationship between the rate of photosynthesis and light intensity in the realm of photosynthesis. One fundamental equation to understand is:

$P = K ^{I} + [ I ] P ^{max} [ I ]$

Here’s a breakdown of the terms:

Understanding the Variables:

$P$ : The rate of photosynthesis at a given light intensity, typically expressed in units like $m g C m^{-3} h^{-1}$ or $μg C μg C h l - a^{-1} h^{-1}$ .
$P_{max}$ : The maximum potential rate of photosynthesis per individual.
$[I]$ : The intensity of light at a given point, often noted in units such as $μ M o l p h o t o n s m^{-2} s^{-1}$ or $Wa tt s m^{-2} h^{-1}$ .
$K_{I}$ : The half-saturation constant, representing the light intensity where the photosynthetic rate is half of $P_{max}$ . The units for $K_{I}$ correspond to those used for $[I]$ .

Deciphering the Equation:

This equation illustrates how photosynthesis rate increases with light intensity, reaching a maximum at $P_{max}$ , and maintaining this rate thereafter. In simple terms, it represents a hyperbolic curve where the rate of photosynthesis accelerates with light intensity until it hits its peak. Understanding this equation is fundamental for anyone working with plants or algae, providing a scientific basis for analyzing and optimizing their growth under various light conditions.

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