phytoplankton culture help

[donkey77]

so i have to keep my f2 in the fridge , and why does everybody say 16hrs light and 8 h darkness iam confuzed

[Myka]

Originally Posted by donkey77

why does everybody say 16hrs light and 8 h darkness iam confuzed

I always get best results 16 hours on, 8 hours off.

[donkey77]

myka do you keep yours in the fridge too

[Myka]

Originally Posted by donkey77

myka do you keep yours in the fridge too

The f/2? Yes. I haven't had any luck with f/2 though, I think I got a bad batch. I've been using Miracle Grow and Kent Essential Elements, but I worry that f/2 might make the phyto more nutritious, so I'm going to order new f/2 and try it...eventually.

I don't put any phyto in the fridge.

[Jakegr]

Originally Posted by Myka

I always get best results 16 hours on, 8 hours off.

You are likely using too intense of light then. From a physiological standpoint there is no reason to give microalgae 8 hours of darkness. The dark reactions occur on the order of milliseconds and the light reactions occur pretty much instantaneously. The cells get their "dark" period on the inside of the reactor, when they are not illuminated. If you give the algae 8 hours of darkness, they are likely switching to respiration, which will lower growth rates. Try reducing light intensity to 30 umol on a 24/7 schedule, and then slowly ramping up the light intensity over time.

[mameroo2000]

As a plant to grow properly you need to provided the right habitat, which depends of the species they need usually a light intensity of 2500-5000 lux (250-500 footcandles) Conversion of foot candles to lux or lumens is: one ft. c = 10.8 lumens or lux, for nannochloropsis oculta (the mos common phyto to culture) you need 2,500-8,000 lux...You would get that intensity in a led warm white light on a 16 hours on that will allow the micro algae to breething co2 and you need 8 hours in full darkness for breething oxygene...like this system you will have a balance with your PH level inside the reactor chamber. Light shading by algae cells would become limiting as density increase, at high densities incoming light is shade from all but the cells currently at the outer surface of the reactor, that is mean is time to harvest the culture.

[Jakegr]

Originally Posted by mameroo2000

As a plant to grow properly you need to provided the right habitat, which depends of the species they need usually a light intensity of 2500-5000 lux (250-500 footcandles) Conversion of foot candles to lux or lumens is: one ft. c = 10.8 lumens or lux, for nannochloropsis oculta (the mos common phyto to culture) you need 2,500-8,000 lux...You would get that intensity in a led warm white light on a 16 hours on that will allow the micro algae to breething co2 and you need 8 hours in full darkness for breething oxygene...like this system you will have a balance with your PH level inside the reactor chamber. Light shading by algae cells would become limiting as density increase, at high densities incoming light is shade from all but the cells currently at the outer surface of the reactor, that is mean is time to harvest the culture.

Microalgae do not require a prolonged period of darkness to "breath oxygen". Microalgae require ATP to fix CO2. They produce ATP only when illuminated, and therefore will not fix CO2 in darkness. As soon as CO2 fixation ceases, growth will also cease. I'm not saying you can't grow microalgae if you give them a dark period, I'm saying growth is maximized if they are illuminated 24/7.

Here are a few references that explain the reasoning, which is firmly based on the well established physiology of plant cells and photosynthesis.

"..long dark periods (i.e., of the order of magnitude of several hours) generally result in biomass loss, as well as decline in growth rates, because microalgae switch to respiration processes; several authors have indeed suggested that a suitable dark period should be of the order of miliseconds (Kommareddy and Anderson 2004)—which would be more appropriately seen as an intermittent cycle"

From - Carvalho et al. 2011. Light requirements in microalgae photobioreactors: an overview of biophotonic aspects. Applied Microbiology and Biotechnology, 89, 1275 - 1288.

"This internal shading (clearly visible in that light does not pass through the culture’s optical path, being essentially fully absorbed in the outer surfaces), results in cells receiving light intermit- tently, a phenomenon augmented by the fact that light energy attenuates exponentially in passing through the culture column. The higher the cell density, the shorter the depth light penetrates into the culture. Two light zones are thereby established in the culture: the outer illuminated volume, in which light is sufficient to support photosynthesis (i.e. the photic zone); and the dark volume, in which net photosynthetic productivity cannot take place, since light intensity is below the compensation point (Fig. 8.1). The higher the population density (and the longer the optical path), the more complex it becomes to address the basic requirements for efficient utilization of strong light, i.e. an even distribution of the available light to all cells in the culture, at an optimal dose per cell (to be elucidated somewhat later).

Clearly then, when mutual shading prevails, cells are not exposed to continuous illumination but rather to cycles of light and darkness (L–D cycle), which may take scores of milliseconds to a few seconds to complete, depending on the optical path and the extent of turbulence in the culture. The endless combinations of light intermittency expressed in L–D cycles to which the individual cells are exposed at a given instant, relate to two basic para- meters: first, the ratio between the light and the dark period in the cycle and second, the frequency of the cycle. As shall be elucidated, the higher the frequency of the L–D cycle, the more efficient strong light may be used for photosynthesis."

From Richmond (2005) - page 127/128. "Handbook of Microalgae Culture".

[MitchM]

Jakegr,
Thanks for posting references.
It's helpful to see that.

[mameroo2000]

I am not say that you can't grow microalgae if they are illuminated 24/7. I just said that it would be unhealthy, the phyto required the most nature habitat you can provided. Lets start with a natural law "everything that is over used is bad from a carrot to exced of exercise" I am analizing what you said and the books part that you used, so if phytoplankton grow good and normally being under lights 24/7 of the 12 months of the year how is possibly that phytoplankton have declined in the world's oceans over the past century in response to ocean warming. When the phytoplankton have abundant sunlight, carbon dioxide and disolved nutrients an undergo explosive growth forming blooms, algal blooms, during these blooms most of the phyto die and sink to the bottom, where descomposes. This process deplets the dissolved oxygen at the water bottom which demaged the culture in no time, in the ocean time this occurs during the springtime.
For confirm what I just wrote you can check on wikipedia: algal bloom; earthobservatory.nasa.gov/NaturalHazards/
There is many reason you don't want to have a wrong amount of light for your phyto the cells will get dense and they would don't feed certains organism like tisbes or rotifers.
In bade the hyphotesis you used, you also can have a look at the following paragraphs on the same book, I just will writte a part!
Appl Microbiol Biotechnol (2011) page 1279; Kimmareddy and Anderson 2004:- In view of the relatives magnitude of aforementioned time scales, the turnover time of the photo-synthetic unit (PSU) or photosyntetic reaction center, is given by the dark reaction time for practical purposes. The light-dark cycle period, which is determined by the travel time of cells between the dark and lit portions along PBR, should accordingly be made AS SHORT AS POSSIBLE, this usually means an optical path of 0.5 to 1.0 cm (to make it clear if the dark time was not necessary then they would mentioned)

Appl Microbiol Biotechnol (2011) page 1279 "Effects of excessively low and high light supply"
"Althought light is required for photosynthesis, too low or high levels thereof will entertain serious disaventantages!! ..."
To who is interesting this pages could be read at http://www.hcmv.vn.refer.org/moodle/...ic-aspects.pdf

You can have more information on Plakton Culture Manual by Frank H. Hoff & Terry W. Snell.

http://en.m.wikipedia.org/wiki/Phytoplankton
Also you can read it all, but if you just want to be more secure about the light process, look on the last paragraph of Aquaculture.

Just to make it clear, it is always good to try or do different things, for some reason what you suggest didn't work for me on one of the Golden Brown Species of phyto which one required a strong illumination. I am just try to pass on all the information I learned and help any one who is interesting, I have six species of phyto and other live foods and I learn to don't expouse your culture to something that may don't work or you are not 100% sure, but I still respect all the opinion of other people. 16 hours on and 8 hours off it works for me since I start the cultired.

[Myka]

Originally Posted by Jakegr

You are likely using too intense of light then. From a physiological standpoint there is no reason to give microalgae 8 hours of darkness.

My method works very well for me. I use less electricity and get the same results as 24 hour lighting. Phyto doesn't need a dark period, but it also doesn't need 24 hour lighting. Thanks for the advice though.