Live food aquaculture training course

1
Algae Production, Biology and Species
2
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

3
Photosynthesis
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
4
Growth dynamics
5
Growth dynamics
1. Lag or induction phase This 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.
6
Light
Energy source Intensity not to low, not to high
(photo-inhibition)
Fluorescent tubes emitting either in the blue or
the red light spectrum are preferred, as these
are the most active wavelengths for
photosynthesis.
7
Nutrients
As 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.

• Nutrients as nitrate and phosphate are important
  for synthesis of DNA
• Minerals, trace elements and vitamins are
  important for synthesis of pigments, enzymes etc.

8
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

9
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 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
10
Information about some microalgae species
Prasinophyceae greenish coloured algae

• Tetraselmis chuii
• Large green flagellate, often used in larval
  rearing of shrimp, fish and shellfish
• Optimal salinity 15 - 36 0/00
• Optimal temperature 15 - 33?C
• Typical densities in mass culture 300-450
  celles/ml
• Very high lipid content

11
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

12
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.

13
Bacillariophyceae - Diatoms

• Chaetoceros sp.
• non-chainforming marine diatoms
• golden brown, rectangular in shape
• Size4-6 um
• Optimal temperature 25 and 30 ?C
• Optimal salinity 17 and 25 ppt
• Light intensity 500 to 10,000 lux

14
Nutritional value in some species
15
Summary algae species