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Algae Production, Biology and Species
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Biology
Microalgae: microscopic single-celled eukaryotic planktonic algae To be magnified 100 – 400X in order to recognize
family Reproduction by cell division Some species have own movements by flagella,
other drift passively Divided in 9 divisions according to pigment types
etc. Photoautotrophic (also heterotrophic) organisms
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As with all plants, algae photosynthesise, i.e. they convert carbon into organic matter. Light is the source of energy, which drives this reaction with wavelength and photoperiod the main factors.
Photosynthesis: 6CO2 + 6H2O = C6H12O6 + 6O2
In the dark, algae shifts from photosynthesis to respiration, and the equation is reversed and glucose is needed for energy
Photosynthesis
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Growth dynamics
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Growth dynamics1. Lag or induction phaseThis phase during which little increase in cell density occurs is relatively long when an algal culture is transferred from a plate to liquid culture. 2. Log or exponential phase: the cell density increases as a function of time according to a logarithmic function.
3. Phase of declining growth rate; cell division slows down when nutrients, light, pH, carbon dioxide or other physical and chemical factors begin to limit growth.
4. Stationary plateau phase: the limiting factors and the growth rate are balanced, which results in a relatively constant cell density.
5. Death or "crash" phase: water quality deteriorates and nutrients are depleted to a level incapable of sustaining growth. Cell density decreases rapidly and the culture eventually collapses.
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Light
Fluorescent tubes emitting either in the blue or the red light spectrum are preferred, as these are the most active wavelengths for photosynthesis.
Energy source Intensity; not to low, not to high (photo-inhibition)
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Nutrients as nitrate and phosphate are important for synthesis of DNA
Minerals, trace elements and vitamins are important for synthesis of pigments, enzymes etc.
NutrientsAs the concentrations of cells in phytoplankton cultures are generally higher than those found in nature, algal cultures must therefore be enriched with additional nutrients and mineral to make up for the deficiencies in the seawater.
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Criteria for choosing the right species
Sufficient nutritional requirements for both the fish larvae and rotifers
Not poisonous for the predators Sufficient cell size and digestibility in order to be
filtered and digested by the rotifers High reproduction rate, reliable and sustainable
in standardized commercial growing systems
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Information about species
Different algal species are grown for different species of fish or shrimp depending on the culture technique. The typical species cultured are as follows;
Shrimp culture
Fish culture
Tetraselmis chuii Tetraselmis suesica
Nannochloropsis sp.
Isochrysis galbana Isochrysis galbana
Chlamydamonas sp.
Chaetoceros gracilis Monochrysis lutheri
Nannochloris atomus
Skeletonema sp Chrorella sp. Nannochloropsis oculata
Spirulina platensis Spirulina platensis
Pavlova lutheri
Dunaliella sp. Pseudochrysis galbana
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Information about some microalgae species
Tetraselmis chuii Large green flagellate, often
used in larval rearing of shrimp, fish and shellfish
Optimal salinity 15 - 36 0/00
Optimal temperature 15 - 33C
Typical densities in mass culture 300-450 celles/ml
Very high lipid content
Prasinophyceae – greenish coloured algae
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Prynesiophyceae – golden brown flagellate
Isochrysis sp. Used especially as a primary algae
in shellfish hatcheries Size: 3-5 um Spherical to pear shaped
Isochrysis galbana tahition Size: 5-6 um Prefer temperatures up to 30 C and
high light intensities High DHA level and is therefore
used for growing rotifers
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Eustigatophyceae – greenish yellow algae
Nannochloropsis Small green flagellate Size: 2-4 um Used in rotifer production Popular as greenwater Keeps suspended in the
water column High total lipid content
and EPA level.
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Bacillariophyceae - Diatoms
Chaetoceros sp.•non-chainforming marine diatoms •golden brown, rectangular in shape •Size:4-6 um•Optimal temperature: 25 and 30 C •Optimal salinity: 17 and 25 ppt •Light intensity: 500 to 10,000 lux
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Nutritional value in some species
Microalgae
Vit C
(Ascorbic
Acid)
Chlorophyl
A Protein
Carbo-
hydrate Lipid
EPA (20:5)
(% of Lipid)
DHA (22:6)
(% of Lipid)
Tetraselmis 0.25% 1.42% 54.66 % 18.31 % 14.27 % 9.3% 0%
Nannochloropsis 0.85% 0.89% 52.11 % 12.32 % 27.64 % 10.1% 0%
CHGRA 1.60% 1.04% 27.68 % 23.20 % 9.29 % 5.0% 0.5%
T-ISO 0.4% 0.98% 46.69 % 24.15 % 17.07 % 0.25% 8.5%
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Summary algae speciesMicroalgae Culture Type Cell Size Animals
Nannochloropsis Green Flagellate 1.5-3
microns Zooplankton, Marine Fish Larvae
CHGRA
(Chaetoceros gracilis) Diatom
6-9
microns
Zooplankton, Shellfish, Penaeid
Shrimp
T-ISO
(Isochrysis galbana) Yellow Flagellate
5-6
microns Zooplankton, Shellfish, Shrimp
Pavlova
(Pavlova pinguis) Brown Flagellate 5-6 micros Zooplankton, Shellfish
Tetraselmis Green Flagellate 14-23
microns
Zooplankton, Shellfish, Penaeid
Shrimp, Abalone Larvae
Culture
Paste
Concentration
(cells / ml)
Typical Culture
Density
(cells / ml)
Tetraselmis 1.0 Billion 400,000
Nannochloropsis 51 Billion 20 Million
CHGRA 3.2 Billion 1.5 Million
T-ISO 6.2 Billion