When cultivating algae, several factors must be considered, and different algae have different requirements. Essential factors include water, carbon dioxide, minerals and light .The algae basically consist of the plant-like organisms (particularly, they are chloroplast-containing eucaryotes) that for the most part live in the sea, but also in freshwater as well as moist terrestrial habitats and as lichen endosymbionts.
Size and Structure
A thallus is the body of the vegetative form of algae. For single-celled algae, the thallus is just the single cell. For multi-celled algae, the thallus consists of the entire, continuous organism.
There also exist complex algae that superficially appear to be macroscopic, multicellular organisms but, upon closer inspection, are found to actually consist of one giant, coenocytic (single celled) thallus.
The aquatic habitat is a relatively benign and unchanging place, and its properties helped shape the organisms that live there. Because water supports the algal plant body, most algae lack rigidity, and usually undulate gently with water currents and waves. Since water surrounds the plant on all sides, individual algal cells absorb moisture and minerals directly from the surrounding. Plant shape also reflects this direct contact with water: Most algae are quite flattened, which maximizes the surface area for absorbing water, minerals, and sunlight.
- Mostly photosynthetic
- Photosynthetic pigments- four different kinds of chlorophyll
- accessory pigments- a variety, including blue, red, brown, golden
- Require moist environments (lack a waxy cuticle found in terrestrial plants)
- May be microscopic and float in surface waters (phytoplankton) or macroscopic and live attached to rocky coasts (seaweeds)
- Size ranges from size of bacteria (0.5 um) to over 50 m long (1 um = 1/25,000th inch; 1 m = 39 inches)
The water must be in a temperature range that will support the specific algal species being grown. Temperature vary with the species and strain cultured. The optimal Temperature for phytoplankton cultures is generally between 20 and 30º C. Temperatures lower than 16 º C slow down growth; Temperatures higher than 35 º C are lethal for a number of species
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Light and Mixing
Light must not be too strong nor too weak. In most algal-cultivation systems, light only penetrates the top 3 inches (7.6 cm) to 4 inches (10 cm) of the water. This is because as the algae grow and multiply, they become so dense that they block light from reaching deeper into the pond or tank. Algae only need about 1/10th the amount of light they receive from direct sunlight. Direct sunlight is often too strong for algae.
In order to have ponds that are deeper than 4 inches algae growers use various methods to agitate the water in their ponds, thus circulating the algae so that it does not remain on the surface, which would cause it to be over-exposed. Paddle wheels can be used to circulate (stir) the water in a pond. Compressed air can be introduced into the bottom of a pond or tank to agitate the water, bringing algae from the lower levels up with it as it makes its way to the surface.
Apart from agitation, another means of supplying light to algae is to place the light in the system. Glow plates are sheets of plastic or glass that can be submerged into a tank, providing light directly to the algae at the right concentration.
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